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AP BIOLOGY Membranes & Proteins

Slide 2 / 181 Membranes & Proteins

· Cell Membranes · Enzymatic Proteins · Transport Proteins · Signaling Proteins

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Cell Membranes

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Slide 4 / 181 Biological Membranes

The term membrane most commonly refers to a thin, film-like structure that separates two fluids. Membranes act as a container for biological systems, surrounding protobionts, cells, and organelles. The video below shows experiments done at a laboratory in France to study the properties of lipids. The only substances used in the making of this video are lipids, water and dye. The lipids and dye were mixed and then injected into aqueous solution. Try to figure out some of the properties that make lipids useful as membranes by watching the video. Click here for the video

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Phospholipids

The most important lipid that composes the majority of biological membranes is the phospholipid. The amphiphilic nature of these lipids cause them to naturally form a spherical bilayer.

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Lipids and the Membrane

Phospholipids form two parallel lines with their hydrophobic ends in between. The hydrophobic ends are protected from the water by the hydrophilic ends, creating a bilayer. In animals, cholesterol inserts itself into the membrane in the same

• rientation as the phospholipid. Cholesterol immobilizes the first few

hydrocarbons in the phospholipid, making the bilayer more stable, and impenetrable to water molecules.

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Selective Permeability

Membranes act as selectively permeable barriers, allowing some particles or chemicals to pass through, but not others. The properties of the phospholipid bilayer dictate what can pass through a membrane.

Slide 8 / 181 Selective Permeability

When phospholipids come together, they create a wall that is tightly packed with a core that is nonpolar. However, the individual molecules are not fixed and small gaps form as they fluidly move around in the membrane.

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Selective Permeability

So what molecules CAN pass through a membrane made of just phospholipids?

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1 Will O2 pass through?

Yes No Why?

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2 Will H2O pass through?

Yes No Why?

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3Will Na+ pass through?

Yes No Why?

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4Will C6H12O6 pass through?

Yes No Why?

Slide 14 / 181 Selective Permeability

To recap... Large molecules or charged molecules will not make it through a lipid bilayer. Some examples: sugars, ions, nucleic acids, proteins

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How do cells get what they need?

We know that cell membranes are made of lipid bilayers, and we know that cells require things like sugar and nucleic acids and proteins and sodium that can't pass through this barrier. So how do cells get the materials they need?

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Fluid Mosaic

Proteins embedded in the cell membrane facilitate the movement of large or charged molecules through the barrier. By doing this, the internal chemistry of the cell becomes far different than its surroundings. The pattern of lipids and proteins in the cell membrane is referred to as the fluid mosaic model.

Slide 17 / 181 Proteins Regulate What is in a Cell

Proteins are long chains of amino acids that fold up on each

• ther to form useful structures in biological systems. Below

is a ribbon diagram of an amino acid chain that forms a channel protein.

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Types of Membrane Proteins

Peripheral proteins stay on only one side of the membrane. Integral proteins pass through the hydrophobic core and often span the membrane from one end to the other. Proteins in the plasma membrane can drift within the bilayer. They are much larger than lipids and move more slowly throughout the fluid mosaic.

Slide 19 / 181 Carbohydrates and the Membrane

Glycoproteins have a carbohydrate attached to a protein and serve as points

• f attachment for other

cells, bacteria, hormones, and many other molecules. Glycolipids are lipids with a carbohydrate attached. Their purpose is to provide energy and to act in cellular recognition.

protein

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An integral protein forms a pore that allows specific substances to diffuse across the membrane, even if they are large or have charge.

Proteins Regulate What is in a Cell Slide 21 / 181

Review Membrane Transport

Watch this video to review the way in which membranes can regulate by transport.

Click here for a review of solute moving through membranes

If further review is needed please see NJCTL's first year biology course.

Membranes First Year Course

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5When diffusion has occurred until there is no longer a

concentration gradient, then _______________ has been reached.

A equilibrium B selective permeability

C phospholipid bilayer D homeostasis

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6In osmosis, water molecules diffuse from

A inside the plasma membrane to outside only B outside the plasma membrane to inside only C from areas of high solute concentration to areas of low solute concentration

D from areas of low solute concentration to areas of high solute concentration

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7What type of environment has a higher concentration of solutes

• utside the plasma membrane than inside the plasma membrane?

A hypertonic B isotonic

C normal D hypotonic

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8What type of solution has a greater flow of water to the inside of

the plasma membrane? A hypertonic

B isotonic

C normal D hypotonic

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9A red blood cell will lyse when placed in which of the

following kinds of solution?

A

hypertonic

B

hypotonic

C

isotonic

D

any of these

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10Dialysis tubing is permeable to monosaccharides only.

Which solute(s) will exhibit a net diffusion out of the cell? A sucrose

B

glucose C fructose D sucrose, glucose, and fructose

E

sucrose and glucose

Cell: 0.05M sucrose 0.02M glucose environment 0.01M sucrose 0.01M glucose 0.01M fructose

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11Is the solution outside the cell isotonic, hypotonic, or

hypertonic? A Hypertonic

B

Hypotonic C Isotonic

Cell: 0.05M sucrose 0.02M glucose environment 0.01M sucrose 0.01M glucose 0.01M fructose

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12The process by which a cell ingests large solid particles,

therefore it is known as "cell eating".

A Pinocytosis B Phagocytosis

C Exocytosis D Osmoregulation

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13Antibodies are embedded in cell membranes and bind to antigens on the surface of foreign cells. What type of molecule is an antibody?

A

phospholipid

B

glycolipid

C

glycoprotein

D

enzyme

Slide 31 / 181 Osmosis

In animal cells, water moves from areas of low solute concentration to areas of high solute concentration during osmosis. In plants, bacteria, and fungi, however, the cell wall exerts a force on the internal environment of the cell and affects the net flow of water through the cell membrane. The effects of solute concentration and the pressure provided by the cell wall are incorporated into a quantity called water potential ( ). Osmosis moves water from areas of high water potential to areas

• f low water potential.

Slide 32 / 181 Water Potential

Water potential is calculated using the following equation: Note: Animal cells do not have cell walls so pressure potential = zero Water potential is measured in megapascals (MPa) or bar. 1 MPa = 10 bar

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14 An animal cell with a solute potential of -0.30 MPa (megapascals) is placed in a sucrose solution with a solute potential of -0.55 MPa. What is the net direction of

• smosis?

A into the cell B out of the cell C not enough information

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15 A fungal cell with a solute potential of -2.5 bar is place in a saline solution with a potential of -1.2 bar. What is the net direction of osmosis? A into the cell B out of the cell C not enough information

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16 In a given plant cell, the cell wall exerts 2.3 bar of pressure and the solute potential is -3.0 bar. Calculate the water potential.

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17 In a given animal cell, the solute potential is -0.25 MPa. Calculate the water potential.

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18 A turgid plant cell with a solute potential of -7.0 bar is placed in pure water. When the cell reaches osmotic equilibrium with its surroundings, what is the pressure potential of the cell?

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19 A bacterial cell with a solute potential of -9.0 bar is placed in a sucrose solution with a solute potential of -4.0 bar. No net movement of water occurs. What is the pressure potential of the cell?

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Solute Potential

Solute potential is dependent upon type and concentration of solute. Its value can be determine using the following equation:

= -iCRT

s

i =# of particles/ions in one molecule of solute after dissociation C = molar concentration (M) R = pressure constant (0.0831 L bar/mol K or 0.0083 L MPa/mol K) T = temperature (K)

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20 What does i equal for NaCl?

= -iCRT

s

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21 What does i equal for fructose?

= -iCRT

s

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22 What does T equal for a solution at 260C?

= -iCRT

s

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23 Calculate water potential (in bar) for a cell that contains 0.9M NaCl and is stored at 19oC.

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24 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.

0.4 M NaCl 0.5 M Sucrose 37oC

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25 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.

0.4 M NaCl 0.5 M Sucrose 37oC

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0.4 M NaCl 0.5 M Sucrose 37oC

26 In what direction will the net flow of water occur? A toward side A B toward side B C not enough information

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27 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.

0.2 M NaCl 0.2 M Sucrose 0.1 M NaCl 0.3 M Sucrose 25oC

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28 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.

0.2 M NaCl 0.2 M Sucrose 0.1 M NaCl 0.3 M Sucrose 25oC

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29 In what direction will the net flow of water occur? A toward side A B toward side B C not enough information

0.2 M NaCl 0.2 M Sucrose 0.1 M NaCl 0.3 M Sucrose 25oC

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Just as individual cells utilize their membranes to maintain homeostasis, so must multicellular organisms maintain a balance in their internal conditions. Let's look at the mammalian urinary system as an example. Its ability to conserve water is a key adaptation to terrestrial life. The fundamental unit of the kidney is a nephron. Nephrons rely on solute concentrations to power the reabsorption of water and other nutrients.

Homeostasis in Multicellular Organisms

Click here for an introduction to the urinary system

Slide 56 / 181 Nephrons

Loop of Henle

As the filtrate descends the loop of Henle, increasing osmolarity of the interstitial fluid (fluid between the cells) causes water to diffuse

• utward.

As the filtrate ascends back up the tubule, decreasing osmolarity enables the facilitated diffusion of NaCl from the filtrate. Some active transport of NaCl also occurs. The filtrate then enters the collecting ducts where more water is reabsorbed through osmosis. The water and nutrients are then passively transported back into the blood supply.

Collecting Duct

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30 As the filtrate descends the loop of Henle, the extracellular solute potential ________________ causing the transport of ____________ across the membrane. A increases, salts B decreases, salts C increases, water D decreases, water

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31 Natural selection should favor the highest proportion of nephrons in which of the following species? A a mouse species living in a tropical rain forest B a mouse species living in a temperate rain forest C a mouse species living in a desert D they would all possess the same proportion of nephrons

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32 Antidiuretic hormone (ADH) is released to maintain homeostasis in response to low blood osmolarity. Which

• f the following is false regarding this hormone?

A It decreases the active transport of NaCl in the ascending tubule B It increases the collecting ducts' permeability to water C It results in a more concentrated urine D It is a response to increases in perspiration

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Transport Proteins

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Larger molecules and ions that cannot squeeze between the phospholipids need the help of a transport protein. This is called Facilitated Diffusion . In Facilitated Diffusion, particles move from an area of high to low concentration with the help of a transport protein. Since the substances are going with the natural concentration gradient, this is a type of Passive Transport: no energy is needed.

Facilitated Diffusion Slide 62 / 181 Examples of Transport Proteins

In facilitated diffusion, transport proteins speed the passive transport of molecules across the plasma membrane. Transport proteins allow passage of hydrophilic substances across the membrane. Channel proteins, are one type of transmembrane transport proteins that provide corridors that allow a specific molecule

• r ion to cross the membrane.

Carrier proteins, are another type of transmembrane transport proteins that change shape slightly when a specific molecule binds to it in order to help move that molecule across the membrane.

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Facilitated Diffusion Slide 64 / 181

33 Facilitated diffusion moves molecules _____.

A against their concentration gradients using energy B against their concentration gradients without the use of energy C with their concentration gradients using energy D with their concentration gradients without the use of energy

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34 Glucose and amino acids are transported into the cell through permases which change their shape during

• transport. These molecules are examples of...

A

channel proteins

B

carrier proteins

C

enzymes

D

both B and C

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Active Transport

Active Transport uses energy to move solutes through a transport protein against their gradients. Active transport requires energy. Active transport is performed by specific proteins embedded in the membranes. Carrier proteins can also be used in active transport when they are moving specific molecules against their concentration gradients.

energy

Slide 67 / 181 Comparing Passive and ActiveTransport

Passive Transport Active Transport (REQUIRES ENERGY)

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35 Active transport moves molecule _____.

A against their concentration gradients using energy B against their concentration gradients without the use of energy C with their concentration gradients using energy D with their concentration gradients without the use of energy

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36 Which protein can be used for both active and passive

transport? A carrier protein B channel protein C any integral protein D any transmembrane protein

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37 ATP synthase is an integral protein used to generate ATP, by allowing the flow of hydrogen ions across the

• membrane. This is an example of what type of

transport?

A

diffusion

B

facilitated diffusion

C

active transport

D

exocytosis

Slide 71 / 181 Sodium Potassium Pump

The sodium potassium pump is an example of the active transport

• mechanism. This system is utilized in every animal cell to transport

Na+ and K

+ maintaining a relatively high concentration of potassium

and relatively low concentration of sodium inside the cell.

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1) The pump, binds ATP, and then binds 3 intracellular Na+ ions. 2) ATP is hydrolyzed, leading to phosphorylation of the pump and subsequent release of ADP. 3) A conformational change in the pump exposes the Na+ ions to the outside. The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released. 4)The pump binds 2 extracellular K+ ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell. 5) The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released. ATP binds, and the process starts again.

Sodium Potassium Pump Slide 73 / 181

38 The sodium-potassium pump is a major contributor in

establishing the ________ of a cell.

A

pump direction

B

• smolarity

C

ATP

D

membrane potential

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39 In the sodium potassium pump, ___ sodium ions initially

bind to the transport protein.

A

1

B

2

C

3

D

4

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40 The binding of the sodium ions does not change the

shape of the protein until the potassium ions bind.

True False

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41 The sodium potassium pump passes:

A

more Na+ out than K+ in

B

K+ out and Na+ in on a one-for-one basis

C

Na+ out and K+ in on a one-for-one basis

D

K+ and Na+ in the same direction

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Neurons rely on the unequal distribution of sodium and potassium ions to transmit signals (known as action potentials ) throughout the nervous system. In a resting neuron (one not sending signals) the ionic gradient produced by the Na+/K+ pump generates a resting potential

• f -60

to -80 mV. A certain amount of Na+ and K+ is always leaking across the membrane through leakage channels, but Na+/K+ pumps in the membrane actively restore the ions to the appropriate side.

Neurons Slide 78 / 181

Nerve impulses are passed along neurons by a depolarization

• f the membrane. An action potential is triggered when the

membrane potential increases to between -40 and -55 mV. When this threshold value is reached Na+ gates open causing sodium ions to move into the cell. The influx of Na+ triggers K+ gated channels to open releasing potassium ions from the cell. This depolarization of the cell signals the next neuron in the pathway to depolarize. The neuron returns to its original state through the action of sodium/potassium pumps embedded in the membrane and the

• riginal concentration gradients are reestablished.

Action Potential

Click here to see how an action potential travels

Slide 79 / 181 Action Potential Slide 80 / 181

Signaling Proteins

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Slide 81 / 181

Cellular signaling is a part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis

• f development, tissue repair, and immunity.

Cellular Signaling Slide 82 / 181

Cells within multicellular organisms must communicate with one another to coordinate all aspects of life. Single-celled organisms also communicate with one another to perform certain symbiotic tasks. Correct and appropriate signaling pathways are generally under strong selective pressure and show shared evolution among

• rganisms with shared pathways.

Evolution of Signaling Slide 83 / 181

42 Which of the following organisms would likely not show similar

communication pathways to the others?

A peacock B turtle C

butterfly

D

shark

E alligator

Slide 84 / 181

Transcription factors are cofactors regulating the initiation of gene transcription. They cause a cell to respond to a signal in the environment in a very specific way. This signal is anything that the cell has the ability to respond to. It could be light, a chemical, a hormone, heat, etc. A signal transduction pathway proceeds with reception of a signal, transduction of that signal through the cell to the DNA, and finally results in expression of a transcription factor.

Signal Transduction Slide 85 / 181 Signal Transduction Pathway

DNA Cell

Signal

The pathway starts when a new signal reaches a cell.

Reception

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Signal Transduction Pathway

DNA Cell

Receptor

External signal activates membrane-bound protein know as a receptor.

Signal

These receptors are like enzymes in that they will bind with only 1 kind of substrate (signal).

Reception

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Signal Transduction Pathway

DNA Cell

Activated Receptor

The activated receptor triggers a cascade reaction, a metabolic pathway .

Transduction

Slide 88 / 181

Signal Transduction Pathway

Activated Receptor

The metabolic pathway produces a specific transcription factor in response to signal. The product initiates transcription of a response gene. DNA

Transcription Factor

Cell

Transduction

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Signal Transduction Pathway

Activated Receptor

DNA

Transcription Factor

Cell Transcription factors initiate the transcription

• f additional genes,

which coordinate the cell's response to stimuli.

Response

Signal Transduction Video

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43 Which of the following is an example of a signal that can start a

signal transduction pathway?

A heat B

light

C

hormone

D

all of the above

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44 The activated metabolic process in a signal transduction pathway

produces A A transcription factor B Cell movement C A signal D Receptors on the cell membrane

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45 Which of the following correctly illustrates a signal transduction pathway?

A

Light is absorbed by chlorophyll molecules. Chlorophyll releases a transcription factor.

B

Antigens bind to the antibodies on the surface of a cell. Antibodies break down the foreign cell's membrane, causing cell death.

C

Glucose enters the cell via transport proteins. A metabolic pathway within the cell causes the synthesis and release of insulin

D

All of the above are correct

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When a receptor receives an external signal from another cell, the response can either be to increase or decrease the concentration of a specific molecule within the cell. Increasing the concentration is called upregulation and decreasing production of that molecule is called downregulation.

Regulation Slide 94 / 181 Upregulation

During upregulation , the number of receptors on the surface of target cells increase, making the cells more sensitive to a hormone or another agent. For example, there is an increase in uterine oxytocin receptors in the third trimester of pregnancy, promoting the contraction of the smooth muscle of the uterus.

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Alternatively, downregulation is a decrease in the number of receptors

• n the surface of target cells, making

the cells less sensitive to a hormone

• r another agent. Some receptors

can be rapidly downregulated. An example of downregulation

• ccurs in Type II diabetes. This form
• f the disease is characterized by

Downregulation

elevated levels of insulin in the bloodstream but a loss of insulin

• receptors. This downregulation can sometimes be reversed

through exercise, and occasionally, a change in diet can also resolve the issue.

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46 An increase of the number of receptors on a targeted cell's surface

is known as A upregulation B downregulation

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47 Which of the following is an example of downregulation?

A

control of blood sugar levels

B

milk production in lactating females

C

nicotine addiction

D

contractions during pregnancy

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In single-celled organisms, signal transduction pathways influence how the cell responds to its environment. Many single-celled organisms live in symbiotic relationships with other organisms, responding to signals released by adjacent cells.

Single-Celled Signaling Slide 99 / 181

Bacteria will produce and release signaling molecules. The same bacteria also have receptors for that molecule on their surface. When the signal binds to a receptor on another organism, it activates a system which typically causes another specific behavior in the group.

Quorum Sensing

Certain bacteria use chemical messengers to communicate to

• ther nearby cells and regulate specific reproductive pathways in

response to population density. This is known as quorum sensing.

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Pseudomonas aeruginosa use quorum sensing to coordinate cell aggregation. They grow within a host without harming it until they reach a certain concentration. Once that concentration is reached, they release a signal to aggressively replicate in order to overcome the host's immune

• system. The bacteria create a biofilm wherein they form a layer

that completely covers the host's tissue and then reproduce at a exponential rate. Research has shown that garlic inhibits the formation of these Pseudomonas biofilms by blocking the quorum sensing

• pathway. This is called quorum inhibition

.

Example of Quorum Sensing: Pseudomonas aeruginosa Slide 101 / 181 Biofilm Development in Pseudomonas aeruginosa Slide 102 / 181

Quorum Sensing

Below is a longer video that ties in quorum sensing and antibiotic

• resistance. Teachers may want to pause and discuss for student

understanding.

Click here for a TED talk on Quorum Sensing Quorum Sensing Introduction Quorum Sensing Explanation

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48 Quorum sensing would most likely occur when: A an antibiotic attacks a bacterial infection B

bacteria reach a certain concentration

C

bacteria sense the presence of an antibiotic

D

a biofilm is broken down

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In animal cells these cell junctions are: Tight junctions: can bind cells together into leakproof sheets Adhering junctions: fasten cells together into strong sheets. They are somewhat leakproof.

Multicellular Signaling

Communicating (Gap) junctions: allow substances to flow from cell to cell. They are totally leaky. They are the equivalent of plasmodesmata in plants.

Examples of Animal Cell Junctions

Multicellular organisms have physical pathways between adjacent cells to aid in communication and transfer of substances.

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Plant cells connect using plasmodesmata which are channels that allow them to share water, food, and communicate via chemical messages.

Multicellular Signaling

Animal and plant cells have different types of cell junctions mainly because plants have cell walls and animal cells do not.

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49 Which type of cell junction is found in plants?

A Tight junctions B Gap junctions C Adhering junctions D Plasmodesmata

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50 Which type of junction allows substances to flow between animal

cells? A Tight junctions B Adhering junctions C Gap juctions D Plasmodesmata

Slide 108 / 181

Practice

Let us look at a few examples of different types of organisms adjusting to their surroundings.We will start with a protist. This protist is single celled, photosynthetic, and motile.

mitochondria chloroplasts flagella nucleus

Slide 109 / 181 Practice

The protist has the ability to move toward light by directing its flagella to oscillate in a particular direction, this is known as

• phototaxis. Moving closer to the light allows the cell to

produce more sugar by photosynthesis.

Slide 110 / 181 Practice

Write down a step by step explanation of how this cell will start moving toward the light in terms of a signal transduction pathway.

Slide 111 / 181

Practice

Lets look at a similar two-celled protist. Both cells must propel themselves together. If only one does, or one is slower than the other this organism will spin in circles.

Slide 112 / 181 Practice

Looking more closely, these 2 cells share gap junctions. These ensure that the amount of transcription factor and nuclear signaling is consistent in both cells.

Slide 113 / 181 Practice

Now lets look at a multi-celled version of a similar protist.

Slide 114 / 181

Practice

If we add a light source, what problems does this organism face? How could the organism overcome these problems. Discuss in a small group then suggest problems and solutions to the class.

Slide 115 / 181 Practice

Problem: Light only signals on the front cells, not the back and they are the ones that need to propel the cell. Solution: Cell-to-cell communication

Slide 116 / 181 Practice

There are several ways a cell can communicate with another cell. In this situation, receptor communication would be best. Lets look closely at 2 of these cells.

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Local Cell Communication

Unlike the single celled organism, cell 1 does not want to activate its flagella when contacted by light. That would cause it to move

• away. It would need to signal its partner, cell 2.

2 1

Slide 118 / 181 Local Cell Communication

2 1

A signal transduction pathway would still occur in cell 1, but the nucleus in 1 would produce proteins that become signals for cell 2.

Slide 119 / 181 Local Cell to Cell Communication

The signal produced by the nucleus of 1 would set off a second transduction pathway that would make cell 2 engage its flagella.

2 1

Slide 120 / 181

Local Cell to Cell Communication

The organism would move to the light. This system works well for smaller multi-celled organisms, and can be used for some systems in larger organisms.

Slide 121 / 181 Cell to Cell Communication

What about much larger organisms with lots of specialized cells and complex responses? When many systems have to respond simultaneously? Let us use Darwin as our example of a complex, multi- celled organism.

Slide 122 / 181 Cell to Cell Communication

When Darwin sees a cheeseburger he smiles. Why? What is happening at a cellular level? What is the signal? What cells respond?

Slide 123 / 181

Cell to Cell Communication

Cells To Brain Signal

What is the signal? Neurotransmitters Neurons are specialized cells. Neurotransmitters, protein signals, are released by neuron A in a certain pattern, based on the image

• f the bear. Neuron B receives them as a signal for a specific

transduction pathway. Neuron A is the signaling optic neuron, neuron B acts as the receptor for the brain.

Slide 124 / 181

These regulators attach to receptors embedded in the plasma membrane

• f nearby cells.

Short Distance Cell Communication

Neurotransmitters are an example of short distance communication between cells. In this type of communication, regulator chemicals are released into the small space between the cells, a synapse.

Slide 125 / 181 Hormone Response

When Darwin sees an angry bear... Let us take a look at the hormone response that is responsible for most of what Darwin is feeling right now.

Slide 126 / 181

Cells To Brain Signal

Cell to Cell Communication

What is the signal? The image of the bear (pattern of light waves) on the retinal cells in Darwin's eye use synaptic signaling to relay the image to the brain through the optic nerve.

Slide 127 / 181 Hormone Response

What is the signal? The brain begins a massive cascade of synaptic signals through millions of nerve cells. It calculates the proper response and releases hormones into the blood stream. In this case, the "fight

• r flight" molecule will be released: epinephrine (adrenalin)

Slide 128 / 181 Hormone Response

Epinephrine is released into the blood stream, where it is sent throughout the body. Each cell it contacts will have a different response to the molecule.

Slide 129 / 181

Hormone Response

Epinephrine

Since epinephrine is only a signal molecule it can have different effects on different cells. It all depends on what a particular cell is programed to do in the presence of epinephrine. Hair follicle muscle cell

• contract, hair stands up

Sweat gland muscle cell - contract, sweat is released Lung cells - relax, take in more air Heart cells - speed up, more oxygen to cells for respiration Liver cells - release glucose, to supply more energy to cells ...among other responses

Slide 130 / 181 Hormone Response

Click here for an animation of fight or flight signalling

Slide 131 / 181

The hormone response illustrates how cells can communicate

• ver long distances.

Hormones are produced within certain organs of the body and can travel long distances through the blood to reach different target cells in many regions of the body. For example, the hormone testosterone is produced by endocrine cells, and travels through the blood stream stimulating increases in muscle mass, bone growth, and the development of male secondary sex characteristics.

Long Distance Cell Communication Slide 132 / 181

51 Hormones, such as estrogen, act...

A

between adjacent cells

B

• n neurons

C

in prokaryotes only

D

• ver long distances within an organism

Slide 133 / 181

52 Why do liver cells and heart cells not have the same response to epinephrine?

A

Heart cells have receptors for epinephrine but liver cells do not

B

Heart cells and liver cells have variation in their genomes

C

Epinephrine does not enter heart cells, but it does diffuse across the liver cell membrane

D

Heart and liver cells initiate different transduction pathways in the presence of epinephrine

Slide 134 / 181

A feedback loop is the path that leads from the initial generation

• f a signal to the modification of an event. They are the cause-

and-effect sequence in biology. Feedback loops can either be positive or negative.

Feedback Loops Slide 135 / 181

When the thermostat senses it is too hot, it turns on the air conditioner to cool it off. If the house is too cool, it will send a signal to warm the house up.

Negative Feedback Loops

A negative feedback loop happens when the outcome of an action acts to reverse cause of the original signal. The thermostat in your house acts on a negative feedback circuit.

Slide 136 / 181 Negative Feedback Examples

Most control systems in the body involve negative feedback

• systems. Cells send signals to other cells to fix problems they

are sensing. This could involve the release of another signal to counteract a problem or more simply, the shut down of the

• riginal signal.

Examples include: body temperature control the regulation of pituitary hormones control of blood glucose levels

Slide 137 / 181 Positive Feedback Loops

A positive feedback loop is one which involves cells continually amplifying a signal until an outcome is reached. The key to positive feedback loops is that any small change will be amplified. A snowball rolling down an increasingly steep hill will continue to pick up speed until it gets to the bottom of the hill.

Slide 138 / 181

Positive Feedback Examples

Activities associated with childbirth offer two examples of positive feedback loops. As contractions happen during labor, the hormone oxytocin is released into the bloodstream. As oxytocin levels increase, more contractions occur, until the baby is born which stops the feedback loop. Another example involves lactation. The more a newborn baby suckles, the more milk is produced. This is due to a positive feedback loop involving the hormone prolactin.

Slide 139 / 181 Feedback Loop Explanation

click here for a video explanation of feed back loops

Slide 140 / 181

53 The "fight-or-flight" adrenalin response to an emergency

situation would be considered a: A Negative Feedback Loop B Positive Feedback Loop

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54 Calcitonin is a hormone released from cells in the thyroid gland

which controls circulating blood levels of calcium in conjunction with the parathyroid hormone. This would be an example of a: A Negative Feedback Loop B Positive Feedback Loop

Slide 142 / 181

Enzymatic Proteins

Return to Table of Contents

Slide 143 / 181

A metabolic pathway begins with a specific molecule and ends with a product. Each step is catalyzed by a specific enzyme. No enzyme = no reaction

Metabolic Pathways

enzyme 1 enzyme 2 enzyme 3

A

B C D

Starting Molecule Product Reaction 1 Reaction 3 Reaction 2

Slide 144 / 181

Enzymes are proteins that act as catalysts in biological systems. This video covers an example of enzymes that is frequently used

• n the AP tests and reviews the function of enzymes.

Review of Enzymes

Click here for a review of catalase

If further review is needed please see NJCTL's first year biology course.

Enzymess First Year Course

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55 Which of the following is not part of allosteric regulation?

A

• ther substrate molecules compete for the active site

B regulatory molecules bind to a site separate from the active site C inhibitors and activators may compete with one another D a naturally occuring molecule stabilizes an active conformation

Slide 146 / 181

56 In allosteric regulation both an inhibitor and an activator can bind

to one substrate complex at the same time. True False

Slide 147 / 181

57 Feedback inhibition is a type of _____.

A competitive inhibition B product C allosteric regulation D enzyme

Slide 148 / 181

As complexity increases, the need to regulate digestion and optimize the food that is being ingested becomes greater. Human digestion is an example of a highly complex digestion system. Humans are capable of ingesting a wide range of food, absorbing many nutrients and adjusting absorption to match intake and need. Numerous enzymes are involved in this process.

Enzymes of Digestion: an example

Humans are

• mnivorous

bulk feeders.

Slide 149 / 181 Human Digestive System

The human digestive tract is composed of compartmentalized

• rgans. It is

regulated hormonally by the pancreas and the brain.

Slide 150 / 181

Cephalic Phase

This phase occurs before food enters the stomach and involves preparation of the body for eating and digestion. Sight, smell, taste and thought of food stimulate the brain. Salivary glands are activated by neural control. Amylase, an enzyme in saliva, hydrolyzes starch and glycogen into smaller polysaccharides. Saliva combined with chewing and movements of the pharynx and tongue turn the food into a bolus, a ball of partially digested food.

Slide 151 / 181 Gastric Phase

The bolus is passed into the esophagus from the mouth. Muscular contractions of the esophagus move the bolus to the stomach. There the bolus is mixed into the digestive "soup" of the

• stomach. The stomach is

muscular and it churns the food into a homogenized acid chyme.

Slide 152 / 181 Gastric Phase

The stomach produces an enzyme that becomes active in the presence

• f acid. To avoid destruction of stomach cells, the active enzyme

pepsin is released into the lumen of the stomach as inactive

• pepsinogen. Another cell releases HCl to make the lumen acidic. This

activates the hydrolytic enzyme pepsin.

Slide 153 / 181

Chief cells produce pepsinogen, parietal produce HCl and all cells produce mucous to ensure a lining in the stomach that will protect the cells from the products they release. Pepsin breaks down proteins.

Gastric Phase Slide 154 / 181 Intestinal Phase

The pyloric sphincter is the transition from the gastric phase to the intestinal phase. The major change that happens here is that mechanical breakdown is ending and absorption is beginning. pyloric sphincter duodenum lumen

Slide 155 / 181 Intestinal Phase

The duodenum is the central processing area for incoming food. The pancreas monitors the food entering the small intestine and releases hormones that engage multi organ responses. The liver and gallbladder release bile salts that help absorb fats, carbohydrates are given one last bath of hydrolytic enzymes and the brain is alerted to the influx of nutrients.

Slide 156 / 181

Intestinal Phase

The liver and gallbladder release bile salts that help absorb fats. The bile salts emulsify the fat and make it possible for cells to absorb them.

Slide 157 / 181 Intestinal Phase

The pancreas releases enzymes that breakdown proteins, lipids, and carbohydrates.

lipase -fats amylase- carbs trypsin- proteins chymotrypsin- proteins and many others

Slide 158 / 181 Intestinal Phase

Finally the mix of enzymes and food move through the intestines where nutrients are absorbed and undigestible material is released via the anus.

Slide 159 / 181

Human Digestive Hormones

As stated, the digestive system exhibits hormonal control over other systems in the body. This is largely accomplished through communication with the brain, pancreas and liver.

Slide 160 / 181 Human Digestive Hormones

Normal blood glucose level is 90mg per 100 ml of blood. This must be maintained for normal body function to proceed. When the pancreas recognizes an influx of glucose into the blood it releases insulin.

insulin insulin

Slide 161 / 181 Human Digestive Hormones

This hormone causes an uptake of sugar by the liver to store and convert to fat. At the same time it suppresses hunger in the brain.

insulin insulin Hunger Glucose Uptake

Slide 162 / 181

Human Digestive Hormones

If the pancreas recognizes a situation where blood glucose will drop too low, it releases a hormone called glucagon. This effect is the opposite

• f insulin.

glucagon glucagon Hunger Glucose Uptake

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58 Which of these enzymes operates in low PH

A Trypsin B Amylase C Lipase D Pepsin

Slide 164 / 181

59 Which of these enzymes digest proteins?

A Trypsin B Amylase C Lipase D All of the above

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60 Which of these enzymes is the first to start digestion?

A Trypsin B Amylase C Lipase D Pepsin

Slide 166 / 181

61 Which of these foods would cause the most insulin to be

released? A Ice Cream B Hamburger C Tomato D Salmon

Slide 167 / 181

"Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often referred to as an overactive thyroid."

• US department of Health and

Human Services

This disease effects more than 5% of woman in the United States (10x the rate in men).

Practicing Enzyme Metabolism Control

Swelling of the thyroid gland is a sign of hyperthyroidism.

Slide 168 / 181

The thyroid gland controls how much energy is being produced by the body, by increasing or decreasing the amount of Thyroid hormone (T3) that is circulating in the blood. The thyroid is controlled by the brain which monitors levels of thyroid hormone and adjusts its signal to the thyroid accordingly.

Practicing Enzyme Metabolism Control

lhttp://www.endocrine.niddk.nih.gov/pubs/ Hyperthyroidism/

Slide 169 / 181

Practicing Enzyme Metabolism Control

lhttp://www.endocrine.niddk.nih.gov/pubs/ Hyperthyroidism/

Increased TSH means more production of T3 Increased T3 means more production of energy in the body

This is known as a feedback loop . Thyroid stimulating hormone (TSH) acts as a co-enzyme in thyroid cells that activates the metabolic pathway for production of T3.

Slide 170 / 181

Practicing Enzyme Metabolism Control

lhttp://www.endocrine.niddk.nih.gov/pubs/ Hyperthyroidism/

When the brain has determined that there is sufficient T3 in the blood, it slows the release of TSH so the thyroid reduces the amount of T3 it is producing. In this way, the brain is exhibiting allosteric regulation

• f the enzymes

in the thyroid via release of a co-enzyme (TSH).

Brain monitors T3 and adjusts release of THS

Slide 171 / 181

62 Organic molecules that aid in the action of the enzyme are called

_____. A products B coenzymes C substrates D helpers

Slide 172 / 181

The enzyme at the start of the metabolic pathway that produces T3 requires TSH to work. TSH stabilizes the active site of the enzyme allowing it to bind with substrate A.

Allosteric Control

enzyme 1 enzyme 2 enzyme 3

A

B C

T3

Starting Molecule Product Reaction 1 Reaction 3 Reaction 2 Enzyme 1

TSH Active site only works when THS is present

Slide 173 / 181 Allosteric Control

enzyme 1

A

T3

Starting Molecule Product Reaction 1 Enzyme 1

TSH Active site deforms without TSH No T3 produced Without TSH, substrate B can not be produced and the pathway is shut down.

Slide 174 / 181

Remember that there are millions of enzymes so the amount

• f TSH dictates how much T3 the pathway will produce

Enzyme Concentration

enzyme 1 enzyme 2 enzyme 3

A

B C

T3

Starting Molecule Product Reaction 1 Reaction 3 Reaction 2

Excess TSH = Highest production

• f T3

Only a small amount = less production

Slide 175 / 181

Now that you understand the process of thyroid control, suggest ways in which this regulation may be lost, thus producing hyperthyroidism. Work with a partner or group to suggest at least 2 ways that this may happen.

Back to Hyperthyroid

enzyme 1 enzyme 2 enzyme 3

A

B C

T3

Starting Molecule Product Reaction 1 Reaction 3 Reaction 2

lhttp://www.endocrine.niddk.nih.gov/pubs/ Hyperthyroidism/

Slide 176 / 181

Some actual reasons for the disease...

• Enzyme 1 is defective and remains on even

if TSH is present.

• A substance similar to B or C is present in

the system so regulation of Enzyme 1 does nothing.

• The brain fails to recognize too much T3 is

present and makes TSH regardless.

• TSH molecule is defective and bonds too

strongly to enzyme causing increased activity (TSH does not breakdown normally).

Back to Hyperthyroid

enzyme 1 enzyme 2 enzyme 3

A

B C

T3

Starting Molecule Product Reaction 1 Reaction 3 Reaction 2

lhttp://www.endocrine.niddk.nih.gov/pubs/ Hyperthyroidism/

Slide 177 / 181

Enzymes in a Chloroplast

Chloroplast

C O O

C6H12O6

Below is a simple diagram of a chloroplast. Imagine it is part

• f a larger biological system that needs to control when

sugar is made.

Slide 178 / 181 Enzymes in a Chloroplast

Water used up and concentration decreases Carbon dioxide used up and concentration decreases Glucose formed so concentration increases

6

We will need to expand this simple diagram to understand how this biological system can control the reaction

Slide 179 / 181 Enzymes in a Chloroplast

enzyme 1 enzyme 2 enzyme 3 Reaction 1 Reaction 3 Reaction 2 O

H H

e-

C

O O

Work with a group to formulate a plan that would allow a system to monitor the amount of glucose present and adjust production accordingly. Draw a diagram and share with the class.

Slide 180 / 181

Enzymes in a Chloroplast

Though this is still simplified (we will see this expanded further soon), it is enough to pose a question: What would be a good way for a biological system to regulate sugar production?

enzyme 1 enzyme 2 enzyme 3 Reaction 1 Reaction 3 Reaction 2 O

H H

e-

C

O O

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