Cell Structure Lecture 04 1 Objectives At the end of this series - - PDF document

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Cell Structure

Lecture 04

 At the end of this series of lectures you should be able to:

 Define terms.  Explain cell theory.  Describe the relative sizes of objects in biology.  Explain why most cells are small.  Distinguish between prokaryotic and eukaryotic cells.  Describe the structure and function of the parts of typical plant and animal cells.  Discuss the theory of endosymbiosis.

Objectives

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 1 meter (m)  1 centimeter = 0.01 m  1 millimeter = 0.001 m or 10‐3m  1 micrometer = 0.000001 m or 10‐6m  1 nanometer = 0.000000001 m 10‐9m

Relative Sizes

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http://htwins.net/scale2/ Cell Theory

 All organisms are made up of cells.  Cells are the smallest units of life  Cells come only from preexisting cells. Cells do things.

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 Have to be large enough to contain all of the materials that they need to do their job.  Need to be relatively small to have a large surface to volume ratio.

 Efficient transfer of materials into and out of the cell.

Most Cells are Small

Figure 4.7

Jeffrey Mahr, CC BY 3.0, http://cnx.org/contents/263caa9c‐31e1‐4c8a‐80ea‐afdc47b43228@2

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Prokaryotic vs. Eukaryotic Cells

 Prokaryotic cells

 Nucleoid – no membrane  Small  No internal compartments  DNA circular  Bacteria and Archea  Eukaryotic cells

 Membrane bound nucleus  Large  Internal compartments  DNA linear  Membranous organelles  Protozoa, Fungi, Plants and Animals.  The structures and organelles perform four basic functions.

 Genetic control of the cell

 Nucleus and ribosomes

 Manufacture, distribution, and breakdown of molecules

 Endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes

 Energy processing

 Mitochondria and chloroplasts

 Structural support, movement, and communication

 Cytoskeleton, plasma membrane, and cell wall

Eukaryotic

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Plant vs. Animal Cells

 Plant Cells

 Cell wall  Chloroplasts  Vacuole

 Animal Cells

 Lysosomes  Centrioles

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Plasma Membrane

 Function

 Keeps the cell intact.  Regulates what enters and exits the cell.  Is semipermeable – some things can enter the cell

• thers are blocked.

 Made of a phospholipid bilayer with embedded proteins (Fluid mosaic model) 13 14

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Cytoplasm

 The portion of the cell between the nucleus and the plasma membrane  A semifluid medium made mostly of water and dissolved or suspended molecules.

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 Contains the DNA  Controls the cell activities by directing protein synthesis.  A dark structure in the nucleus – nucleolus

 Synthesizes ribosomal RNA (rRNA)

 Enclosed in a double membrane – nuclear envelope.

 Perforated – nuclear pores

Nucleus

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 Site of protein synthesis  Made of rRNA and protein  Free in the cytoplasm or attached (bound) to the endoplasmic reticulum (rough ER).

Ribosome

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 Membranous tubules and sacs

 Two types

 Smooth ER – No attached/bound ribosomes

 Synthesis of many types of lipids

 Rough ER – Attached/bound ribosomes

 The ribosomes produce proteins that are embedded in the membrane, transported to other organelles, or secreted by the cell.

Endoplasmic Reticulum

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Golgi Apparatus

 Slightly curved stack of large flattened vesicles. (Stack

• f pancakes)

 The Golgi apparatus serves as storage and finishing facility for products from the ER.  Products travel in vesicles from the ER to the Golgi.  Contains enzymes that modify proteins and lipids.

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Lyososomes

 Lysosomes help digest food particles engulfed by a cell.

 A food vacuole binds with a lysosome.  The enzymes in the lysosome digest the food.  The nutrients are then released into the cell.

 Lysosomes also help remove or recycle damaged parts of a cell.  Large vesicles that have a variety of functions.

 Protists/Protozoa

 Contractile vacuoles that eliminate excess water.

 Plants

 Digestive functions  Contain pigments  Contain toxins for protection or storage

Vacuoles

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 Break down fatty acids to use as fuels  Detoxifiy materials

Peroxisomes

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Mitochondria

 Site of most ATP synthesis ‐‐ Converts energy from glucose to ATP (adenosine triphosphate).

 Aerobic cellular respiration

 Small peanut‐shaped organelles  Double membrane

 Outer membrane is smooth  Inner membrane is heavily folded – folds are called cristae.  The inner most portion is the matrix.

 Endosymbiosis

 DNA, ribosomes (type), double membrane, antibiotics

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Chloroplast

 Occurs in plants and some protists.  Where photosynthesis occurs ‐‐ convert solar energy to chemical energy .  Double membrane  Thylakoid – flattened sacs with chlorophyll  Granum – a stack of thylakoids  Stroma ‐‐ thickened fluid that surrounds the granum

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Cytoskeleton

 A network of filaments and microtubules  Similar to an animal’s skeleton

 Provides structure and movement.

 Can change shape and configuration.

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Movement

 Flagellum  Cilia (Cilium)  Psuedopodium

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