The Cell

I. Cell Theory

1. If its alive, its made of cells.

2. Cells are basic unit of life.

3. Under current conditions, cells come from preexisting cells.

II.Limits on Cell Size

1. Surface Area is used by Cells to Obtain Nutrients (e.g. doors)

2.Volume Measures Biomass, or How Much Cells Need for Nutrients

II. Limits on Cell Size

3. As Cell Size Increases, Surface Area is squared while Volume is cubed.

4. So volume increases more quickly than surface area.

5. SA:V Ratio Limits Cell Size

III. Organelles and Cell Features

A.Cell Membrane : Selectively permeable membrane that limits what enters and exits a cell. Made of phospholipids bilayer with some channels (proteins).

Label Phosphate,

Lipid Tail,

Circle Hydrophobic area in Red,

Circle Hydrophilic area in Blue.

III. Organelles and Cell Features

B. Cell Wall Rigid structure that provides support. Found outside cells of plants, algae and some bacteria.

III. Organelles and Cell Features

C.Nucleus – A membrane

envelop that surrounds

DNA in Eukaryotic cells. Nucleus (because it holds the DNA) largely controls the cell.

III. Organelles and Cell Features

D. Cytoplasm – Liquid between cell membrane and nucleus (if the cell were a water balloon, this would be the water).

III. Organelles and Cell Features

E. Mitochonridion – Where sugar is converted into useful energy (ATP).

III. Organelles and Cell Features

F. Chloroplast – In plant cells, converts solar energy into stored chemical energy (sugars).

III. Organelles and Cell Features

G. Ribosomes – Put amino acids together

to form proteins. Assemble proteins.

III. Organelles and Cell Features

H. Endoplasmic Reticulum –

Rough – Where many proteins are

produced. “Rough” spots are ribosomes.

Smooth – many lipids produced; moves

products through cells.

III. Organelles and Cell Features

J. Vacuoles – Stores water and solutes.

Gives plants tugor support.

III. Organelles and Cell Features

K. Cytoskeleton – Framework/Skeleton of

the cell.

Analogy Assignment:

• Nucleus – (Brain of Cell)• Mitochondria (Power house)• Chloroplasts (Solar panel)• Ribosomes (protein factories)• Endoplasmic Reticulum (manufacturing

and shipping)• Vacuoles (Storage Locker)• Cytoskeleton (Scaffolding)

IV. Movement through Membrane

A. Cell Membrane: Lipid Bilayer with Channels.

Hydrophobic – ‘water fearing’

Hydrophilic - ‘water loving’

B. Cell Membrane is Semipermeable – Large and/or Charged particles can’t pass through membrane.

IV. Movement through Membrane

IV. Movement through Membrane

1. Diffusion – Molecules move from high concentration to low concentration due to random motion of molecules.

IV. Movement through Membrane

2. Osmosis – Special case of diffusion in which water molecules diffuse through a semipermeable membrane.

Osmosis

Osmosis Terms

• Hypotonic: Relatively high amounts of water (Hippos live in water)

• Hypertonic: Relatively lower amounts of water and higher amounts of solutes, such as sugar or salt. (Hyper means ‘lots’ so think of a sugar high causing hyperactivity)

• Water moves from Hypo to Hyper, or High Concentration (of water) to Low Concentration (of water).

Hyper, Hypo, or Iso (solution in the bag)?

Fig. 5.14, p. 88

2M sucrosesolution

1 liter ofdistilled water

10M sucrosesolution

2M sucrosesolution

HYPOTONICCONDITIONS

HYPERTONICCONDITIONS

ISOTONICCONDITIONS

Fig. 5.10, p. 86

open channelproteins

gated channelproteins transport protein

lipid bilayer

IV. Movement through Membrane

C. Membrane Proteins: Help move through items that are large and/or charged.

1. Facilitated Diffusion: Requires a specific protein but the cell doesn’t need to expend energy. Will still go from high to low concentration. Passive Transport

IV. Movement through Membrane

2. Active Transport: Proteins pump items

through membrane, requiring

expenditure of ATP.

Fig. 5.10, p. 86

open channelproteins

gated channelproteins transport protein

lipid bilayer

IV. Movement through MembraneD. Endocytosis and Exocytosis.

1. Endocytosis: Bulk movement of

materials into a cell.

ENDOCYTOSIS• Vesicle forms from a patch of inward-sinking• plasma membrane, enters cytoplasm

EXOCYTOSISVesicle in cytoplasm moves to plasma membrane,

fuses with it; contents released to the outsideFig. 5.17, p. 90

2. Exocytosis: Bulk movement of materials out of a cell.

IV. Movement through Membrane