Concept 4.1 Cells Provide Compartments for Biochemical Reactions

Cell size

Working in pairs, consider two cubes, one with a side that is 1 mm long and the other with a side that is 6 mm long. For each cube calculate:

1. Surface area (= height × width × number of sides)

2. Volume (= height × width × length)

3. Surface area-to-volume ratio (= surface area:volume)

What pattern do you observe as the size of the cube increases?

What inferences can you make regarding cell size?

Take a few minutes to discuss, and then present your conclusions to the class.

Concept 4.1 Cells Provide Compartments for Biochemical Reactions

The plasma membrane

a. acts as a selectively permeable barrier.

b. consists of a phospholipid bilayer and proteins.

c. functions in communication between cells.

d. contributes to cell shape.

e. All of the above

Concept 4.2 Prokaryotic Cells Do Not Have a Nucleus

Prokaryotic cells

Working individually, draw a prokaryotic cell and label the following structures and components:

• Plasma membrane

• Nucleoid

• DNA

• Cytoplasm

• Ribosomes

• Cell wall

Then compare your drawing with that of a classmate.

Concept 4.2 Prokaryotic Cells Do Not Have a Nucleus

Prokaryotic cells can have all of the following except

a. flagella.

b. internal membranes.

c. a nucleus.

d. a cytoskeleton.

e. a cell wall.

Concept 4.3 Eukaryotic Cells Have a Nucleus and Other Membrane-Bound Compartments

Comparing animal and plant cells

Working in pairs, compare and contrast animal and plant cells.

First, draw a representative animal cell with the following structures: nucleus, mitochondrion, rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, and plasma membrane. As you draw each structure, discuss its function.

Then draw a representative plant cell with these additional structures: cell wall, vacuole, and chloroplast. Discuss the functions of these structures.

Concept 4.3 Eukaryotic Cells Have a Nucleus and Other Membrane-Bound Compartments

Cell structure reflects cell function. Using your knowledge of the functions of particular organelles, select the incorrect match of a type of cell and the organelle that you might expect to be particularly abundant in that cell:

a. Pancreatic cell that secretes a digestive enzyme: Rough endoplasmic reticulum

b. Mammalian skin cell: Central vacuole

c. Skeletal muscle cell: Mitochondria

d. Liver cell that modifies toxins: Smooth endoplasmic reticulum

e. Leaf cell: Chloroplasts

Concept 4.4 The Cytoskeleton Provides Strength and Movement

The cytoskeleton

Working individually, characterize microfilaments, intermediate filaments, and microtubules with respect to:

• Protein component(s)

• Major functions

• Presence of dynamic instability

Then discuss your characterizations with those of your classmates.

Concept 4.4 The Cytoskeleton Provides Strength and Movement

Which of the following statements about cilia and flagella is false?

a. Intermediate filaments form the interior skeleton for cilia and flagella.

b. Cilia can either move a cell or move fluid over a stationary cell.

c. Cilia typically outnumber flagella on a cell.

d. Motor proteins drive the motion of cilia and flagella.

e. Cilia and flagella have a 9 + 2 arrangement of microtubules.

Concept 4.5 Extracellular Structures Allow Cells to Communicate with the External Environment

Junctions between animal cells

Working in pairs, discuss tight junctions, desmosomes, and gap junctions. Then determine which type of junction would most likely be found in the following locations in the human body:

1. Epithelial lining of the urinary bladder (functions to prevent urine from leaking out into the body)

2. Skin

3. Epithelial lining of the stomach (functions to prevent stomach contents from leaking out into the body)

4. Cardiac muscle (the rapid spread of electric current mediated by ions is critical for cardiac muscle cells to beat in unison)

Finally, which type of junction in animal cells is most similar to the plasmodesmata of plant cells?

Present your answers to the class.

Concept 4.5 Extracellular Structures Allow Cells to Communicate with the External Environment

The extracellular matrices of animal cells

a. contain the fibrous protein collagen.

b. contain the polysaccharide cellulose.

c. interact with cell membrane proteins to regulate cell attachment.

d. contain proteoglycans in a gel-like matrix.

e. a, c, and d