The Study of Cells

Electron Microscopes Transmission EM

Internal features

Scanning EM Surface features

EM Drawbacks Expense B&W Images Dead specimens

VolumeThe need to exchange materials is the same with one large or many small cells.

Surface AreaThe ability to exchange materials is greater w/ small cells.

Why are cells so small?

Increasing exchange

Cells alter shape to increase surface area (ability to exchange materials).

SA = 6SA = 7

(same V)SA = LARGE

(same V)

½ 121

11

Cell Membrane Phospholipid Bi-Layer

Selectively permeable Small, nonpolar molecules pass easiest

Cell Membrane Membrane Proteins

Assist passage of materials Bind cells together Enable cell recognition

Cell types

Eukaryotes Animals, plants, fungi, protists DNA enclosed in nuclear envelope Membrane-bound organelles

Prokaryotes Bacteria and Archaea DNA not in nuclear envelope No membrane-bound organelles

Nucleus Nuclear Envelope

Membrane protects DNA Pores allow passage of RNA

Nucleolus Ribosome synthesis

Chromosomes DNA + Proteins

Visible during cell division Otherwise, indistinguishable

(chromatin)

Nucleus

Organelles Ribosome

Protein synthesis No membrane

Endoplasmic Reticulum Transport Alterations

Organelles Golgi Apparatus

Packaging and export of materials

Lysosome Digestive sacs Break down

food, invaders, dead organelles

Organelles Cytoskeleton

Protein cell framework Provides cell shape Cell movement Cell division

cilia flagellum

Plant Organelles Cell Wall

Support/protection Plants Cellulose Fungi Chitin Bacteria Peptidoglycan

Chloroplast Convert Light E Glucose

Vacuole Storage space

Contains water, waste, starch

Review QuestionsComplete these analogies1. Volume : surface area :: cytoplasm : _______________

2. Sundae : sprinkles :: rough endoplasmic reticulum : __

Which structure is dysfunctional?4. Desirable materials are not able to enter the cell.

5. Engulfed food is building up in the cell.

6. The cell is unable to power any functions despite an ample food supply.

Review QuestionsWhich structure?

1. Protein synthesis

2. Made of microtubules

3. Selectively permeable

4. Only found in plant cells

5. Makes ribosomes

6. Coiled up DNA