Cell Structure

Chapter 4

http://learn.genetics.utah.edu/content/begin/cells/scale/

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Cell Theory

Cells were discovered in 1665 by Robert Hooke.

Early studies of cells were conducted by

- Mathias Schleiden (1838)

- Theodor Schwann (1839)

Schleiden and Schwann proposed the Cell Theory.

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Cell Theory

Cell Theory

1. All organisms are composed of cells.

2. Cells are the smallest living things.

3. Cells arise only from pre-existing cells.

All cells today represent a continuous line of descent from the first living cells.

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Cell Theory

Cell size is limited.

-As cell size increases, it takes longer for material to diffuse from the cell membrane to the interior of the cell.

Surface area-to-volume ratio: as a cell increases in size, the volume increases 10x faster than the surface area

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Cell Theory

Textbook pg. 60

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Prokaryotic Cells

Prokaryotic cells lack a membrane-bound nucleus.

Two types of prokaryotes:

-archaea

-bacteria

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Prokaryotic Cells

Prokaryotic cells possess

-DNA

-cytoplasm

-plasma (cell) membrane

-cell wall

-ribosomes

-no membrane-bound organelles

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Prokaryotic Cells

Textbook pg. 63

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Prokaryotic Cells

Flagella

-present in some prokaryotic cells

-used for locomotion

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Prokaryotic Cells

Textbook pg. 65

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Eukaryotic Cells

Eukaryotic cells

-membrane-bound nucleus

-cellular functions occur within organelles

-cytoskeleton for support

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Textbook pg. 66 Eukaryotic Cell

(animal)

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Eukaryotic Cell (plant)

Textbook pg. 67

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Eukaryotic Cell Organelles

Nucleus

-stores the genetic material (DNA)

-surrounded by a nuclear envelope composed of 2 phospholipid bilayers

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Eukaryotic Cell Nucleus

Textbook pg. 68

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Ribosomes

-the site of protein synthesis in the cell

-composed of RNA and proteins

-free-floating or attached to E.R.

Eukaryotic Cell Organelles

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Rough endoplasmic reticulum (RER)

-attachment of ribosomes to the membrane gives a rough appearance

-synthesis of proteins to be secreted, sent to lysosomes or plasma membrane

Eukaryotic Cell Organelles

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Smooth endoplasmic reticulum (SER)

-synthesis of membrane lipids

Eukaryotic Cell Organelles

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E.R.

Textbook pg. 70

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Golgi apparatus

-flattened stacks of membranes

-packaging and distribution of materials to different parts of the cell

-synthesis of cell wall components

Eukaryotic Cell Organelles

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Textbook pg. 71

Protein transport:

Ribosome

ER

Golgi apparatus

Cell membrane

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Lysosomes

-vesicles containing digestive enzymes

-digest food, destroy worn out organelles and wastes

Eukaryotic Cell Organelles

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Textbook pg. 72

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Vacuoles-membrane-bound structures

There are different types of vacuoles:-central vacuole in plant cells (stores H2O)-contractile vacuoles (rid waste)-vacuoles for storage

Eukaryotic Cell Organelles

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Mitochondria – Site of Cell Respiration

-contain enzymes for creating ATP (energy)

-contain their own DNA

Eukaryotic Cell Organelles

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Mitochondria

Textbook pg. 74

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Chloroplasts

-organelles present in green cells

-contain chlorophyll for photosynthesis

-double membrane

-chlorophyll contained in thylakoids/grana

Eukaryotic Cell Organelles

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Chloroplasts

Textbook pg. 75

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Chromoplast -organelles present in some Plant cells-contain color Pigments (Orange - Yellow - Red)- Fruits/Veggies – Fall Leaves

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Leucoplast- Colorless organelles present in Plant cells-Food storage – e.g. “Starch” in potato cells

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Cytoskeleton

Cytoskeleton

-network of protein fibers

-supports the shape of the cell

-keeps organelles in fixed locations

-helps move materials within the cell

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Cytoskeleton

Textbook pg. 77

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Extracellular Structures

Cell walls

-present surrounding the cells of plants, fungi, Bacteria, and some protists

-plant and protist cell walls - cellulose

-fungal cell walls - chitin

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Textbook pg. 79 & 82

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