Membranes, Membranes Diffusion Membranes are an arrangement of - - PDF document

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Biology

Membranes

2015-10-28 www.njctl.org

Slide 3 / 74 Vocabulary

active transport integral protein carrier protein channel protein concentration gradient diffusion enzymatic activity facilitated diffusion fluid mosaic hypertonic hypotonic isotonic molarity

• smosis

passive transport peripheral protein phospholipid bilayer selectively permeable signal transduction

Slide 4 / 74 Membranes Unit Topics

· Membranes, Diffusion · Osmosis

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· Plasma Membranes Transport through Proteins

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Membranes, Diffusion

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Membranes are an arrangement of phospholipids that gather together to enclose a volume. Membranes act as a wall or a barrier separating the

• utside and the inside of that enclosed volume.

Membranes

Slide 7 / 74 Membranes

Remember we learned that a phospholipid has a hydrophilic and a hydrophobic end. When these phospholipids arrange to form a membrane that separates the inside and the outside of the shape, both the inside and the outside of the shape usually include water (think of a water balloon in a bathtub). So how can these phospholipids arrange themselves so that their hydrophobic ends are not near the water? Move them into a bilayer.

Slide 8 / 74 Phospholipid Bilayer

The phospholipids do not form a single line, but instead form two parallel lines with their hydrophobic ends in between. Now the hydrophobic ends are protected from the water by the hydrophilic ends. Phospholipids are amphiphilic molecules: meaning they contain both hydrophobic and hydrophilic regions. We call this a phospholipid bilayer.

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1 The section labelled A is: A amphiphilic B hydrophobic C hydrophilic

A

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2 The sections labelled B are: A amphiphilic B hydrophobic C hydrophilic

B B

Slide 11 / 74 Selective Permeability

Membranes allow for the intake of nutrients and the elimination of waste because they are selectively permeable. This means they can let some molecules pass through and not others.

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The formation of a membrane was

• ne of the first steps in evolution
• f cells.

The membrane separated the inside world and outside world but still allowed for the intake of nutrients and the elimination of waste. Regulating the amount of nutrients and waste passing through the membrane is called maintaining homeostasis.

Homeostasis

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3 The basic component of all membranes is A proteins B fats C starches D phospholipids

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4 How many layers do plasma membranes have? A

• ne

B two C three D four

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5 Phospholipids arrange themselves so that their A hydrophilic ends contact each other B hydrophobic ends ends contact each other C hydrophilic end of one layer meets the hydrophobic end of the other layer D hydrophobic ends contact the enclosed volume of fluid

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6 Plasma membranes allow all types of molecules to pass through. True False

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7 A cell's regulation of its internal environment is called A selective permeability B plasma membranes C phospholipids D maintaining homeostasis

Slide 18 / 74 Passive Transport

Some molecules pass through the membrane without the use of energy, this is called passive transport. These molecules always move from areas of high concentration to areas of low concentration. This is referred to as moving "with the concentration gradient." Which direction with the molecules move?

Slide 19 / 74 Solutions Review

Solutions are defined as homogeneous mixtures

• f two or more pure substances.

The _______________ is the substance present in the greatest abundance. All other substances are ____________. ___________ dissolves the ___________ . In biology, the solvent is almost always ___________ .

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Molarity (M) Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Molarity is one way to measure the concentration of a solution. Molarity (M) = moles of the solute volume of solution in liters

Expressing Concentrations of Solutions Slide 21 / 74

Mass of Solute Volume of Solvent Concentration 5g C 10g C 20g NaCl 20g NaCl 100ml 100ml 100ml 200ml ___________ ___________ ___________ ___________

Concentration Practice

Calculate the concentrations below.

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Diffusion Osmosis Facilitated Diffusion

Three Types of Passive Transport Slide 23 / 74

Diffusion is the process where solute molecules move from areas

• f high concentration to areas of low concentration. Membranes

act as the barrier between these two areas. Molecules will continue to diffuse across the membrane until an equilibrium is reached.

Diffusion Slide 24 / 74

Which way will the O 2 move? 8.3mM O2 9.5mM O2

Diffusion

No energy is required to move molecules with their concentration gradient.

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Concentration gradients are specific to each type of molecule meaning each type of molecule can diffuse in a different direction, some in and some out.

Diffusion

Which way will the O 2 move? Which way will the CO 2 move?

9 mM O2 6 mM CO2 7.2mM O2 7.2mM CO2

Diffusion is a spontaneous process and each type of molecule diffuses at its own rate.

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8 Diffusion is the movement of molecules A against their concentration gradient B with their concentration gradient C in their concentration gradient D

• utside their concentration gradient

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9 All molecules diffuse from the inside of the membrane to the outside of the membrane. True False

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10 Each type of molecule diffuses at a different rate. True False

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11 The membrane is permeable to water and to the simple sugars glucose and fructose but completely impermeable to the sucrose. Which solute(s) will exhibit a net diffusion into 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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12 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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13 When 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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14 When equilibrium is reached, what is the concentration

• f fructose outside the cell?

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

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Osmosis

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Slide 34 / 74 Osmosis

Osmosis is the diffusion of free water molecules across a selectively permeable membrane.

Slide 35 / 74 Two ways to Describe Osmosis

The water is moving with its concentration gradient from an area with lots of free water molecules to an area with fewer free water molecules. The water moves from areas of low solute concentration to areas of high solute concentration until the solute concentrations are in equilibrium. OR

Slide 36 / 74 Osmosis

If the solution on the outside of the membrane has a higher solute concentration than the solution inside, we say that the

• utside solution is hypertonic.

This means that water will diffuse from the inside solution to the outside solution.

solute molecule water molecule

H2 O

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If too much water leaves the cell, due to its being in a hypertonic solution, it can shrink or shrivel up.

solute molecule water molecule

H2 O

Osmosis Slide 38 / 74

If the solution on the outside of the membrane has a lower solute concentration than the solution inside the membrane we say that the

• utside solution is hypotonic. This means that water will diffuse from

the outside solution to the inside solution.

solute molecule water molecule

H2 O

Osmosis Slide 39 / 74

If too much water enters a cell due to its being in a hypotonic solution it can swell, and if it swells too much it can _________, or burst. H2 O

solute molecule water molecule

Osmosis Slide 40 / 74

If the solution on the outside of the membrane has an equal solute concentration to the solution inside the membrane we say that the outside solution is isotonic to the inside solution. This means that water will diffuse equally across the membrane in either direction.

H2 O

solute molecule water molecule

Osmosis Slide 41 / 74

15 The diffusion of water molecules across a selectively permeable membrane is called what? A diffusion B isotonic C

• smosis

D hypotonic

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16 Water molecules diffuse from A inside the plasma membrane to outside only B

• utside 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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17 Diffusion and osmosis are both types of active transport. True False

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18 What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane? A hypertonic B isotonic C normal D hypotonic

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19 What type of environment has an equal amount

• f solute on the inside and outside of the

plasma membrane? A hypertonic B isotonic C normal D hypotonic

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20 What 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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21 The membrane is permeable to water and to the simple sugars glucose and fructose but completely impermeable to the sucrose. Is the solution outside the cell isotonic, hypotonic, or hypertonic? A Hypertonic B Hypotonic C Isotonic Cell: 0.03M sucrose 0.03M glucose environment 0.02M sucrose 0.04M glucose 0.01M fructose

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22 In which direction will there be a net osmotic movement of water? A In B Out C No net osmosis

Cell: 0.05M sucrose 0.03M glucose environment 0.02M sucrose 0.04M glucose 0.01M fructose

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Plasma Membrane of Cells, Transport through Proteins

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Slide 50 / 74 Plasma Membrane of Cells

Early cells were simple lipid bilayers, relying only on passive transport. Later cells developed more complex membranes that included

• proteins. These proteins act as doorways to allow for more

molecules to enter and leave the cell. Most small molecules can diffuse without membrane proteins. Larger molecules need to be facilitated (helped) to diffuse across a membrane by these proteins.

Slide 51 / 74 Phospholipid Bilayer

Remember that membranes are made up mostly of phospholipids. Phospholipids are __________________ molecules, containing hydrophobic and hydrophilic regions.

Slide 52 / 74 2 Types of Membrane Proteins

Peripheral proteins are not embedded in the membrane, but instead 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, also called transmembrane proteins. The plasma membrane also contains two types of proteins:

Slide 53 / 74 Fluid Mosaic

The plasma membrane is sometimes referred to as a fluid mosaic. Fluid because the phospholipids can move sideways within the membrane and do not stay in one stationary position. Proteins can also move around in the membrane but they are much larger than lipids and move more slowly.

Slide 54 / 74 Fluid Mosaic

The plasma membrane is sometimes referred to as a fluid mosaic. Mosaic means the membrane contains many different proteins spread throughout.

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23 Which of the following statements about the role of phospholipids in forming membranes is correct? A They are completely insoluble in water. B They form a single sheet in water. C They form a structure in which the hydrophobic portion faces outward. D They form a selectively permeable structure.

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24 Which best describes the structure of a cell's plasma membrane? A proteins sandwiched betweeen two layers of phospholipids B proteins embedded in two layers of phospholipids C phospholipids sandwiched between two layers of proteins D a layer of protein coating two layers of phospholipids

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25 The fluid-mosaic model of membrane structure refers to _____. A the fluidity of phospholipids and the pattern of proteins in the membrane B the fluidity of proteins and the pattern of phospholipids in the membrane C the ability of proteins to switch sides in the membranes D the fluidity of hydrophobic regions, proteins, and the mosaic pattern of hydrophillic regions

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Proteins serve several important functions in the cell membrane. Transport Signal transduction Cell-cell recognition Enzymatic activity

Membrane Protein Functions Slide 59 / 74 Transport

Proteins can act as doorways for nutrients and waste. There are two types of transport which require proteins: · Facilitated Diffusion (a type of passive transport) · Active Transport (requires energy)

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Small molecules like O2 and CO2 readily diffuse through all plasma membranes because they are small and non-polar; they can squeeze between the phospholipids. However......

Facilitated Diffusion

Larger molecules and ions, charged particles, cannot squeeze between the phospholipids, they need the help of a transport

• protein. This is called Facilitated Diffusion .

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Just like regular diffusion, particles in Facilitated Diffusion move from an area of high to low concentration. Unlike regular diffusion these particles move through the membrane with the help of a integral protein. Since the substances are going with their concentration gradient, this is a type of Passive Transport: no energy is needed.

Facilitated Diffusion Slide 62 / 74 Examples of Transport Proteins

Channel proteins are one type of transmembrane transport protein that provide corridors that allow a specific molecule or ion to cross the membrane. Carrier proteins are another type of transmembrane transport protein that change shape slightly when a specific molecule binds to it in order to help move that molecule across the membrane.

Slide 63 / 74 Examples of Transport Proteins Slide 64 / 74

26 Which of the following molecules is most likely to diffuse freely across the lipid bilayer of the plasma membrane without the involvement of a transport protein? A carbon dioxide B glucose C sodium ion D DNA E all of the above

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27 Which of the following processes includes all

• thers?

A

• smosis

B diffusion of a solute across a membrane C facilitated diffusion D passive transport

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28 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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29 Carrier proteins are an example of integral proteins. True False

Slide 68 / 74 Active Transport

Active Transport uses energy to move solutes through a transport protein against their concentration gradients. Carrier proteins can be used in active transport for specific molecules.

energy

Slide 69 / 74 Comparing Facilitated Diffusion and ActiveTransport

Passive Transport Active Transport

(REQUIRES ENERGY)

Click here for a comparison of the different forms of membrane transport

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30 Which one of the following is not in some way involved in facilitated diffusion? A a concentration gradient B a membrane C a protein D an energy source E all of the above are components of facilitated diffusion

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31 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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32 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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Transport

Membrane Protein Functions

Proteins serve several important functions in the cell membrane.

Click here for an animation about Membrane Proteins

Enzymatic activity Some proteins are used to catalyze (speed up) reactions. Cell-cell recognition Some proteins are used to recognize viruses, bacteria, or other cells that have attached to the cell they are in. Signal transduction Some proteins are used to gather information about the cell's surrounding environment.

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Diffusion Facilitated Diffusion Active Transport No Energy Energy Required Transmembrane Protein High Low Carrier Protein Channel Protein Low High