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Cell StructureLecture 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 others are blocked.
Made of a phospholipid bilayer with embedded proteins (Fluid mosaic model)
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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 of 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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