WEEK 6

Question 1

What are the basic components of a cell?

Answer 1

Plasma membrane, cytoplasm (cytosol + organelles), and genetic material (DNA).

Question 2

What is the ECF?

Answer 2

Extracellular fluid — includes interstitial fluid and plasma.

Question 3

List the functions of the plasma membrane.

Answer 3

• Acts as a barrier
• Regulates transport of substances in and out
• Facilitates communication and signaling
• Provides structural support
• Participates in cell recognition

Question 4

What three molecules comprise the plasma membrane?

Answer 4

• Phospholipids
• Proteins
• Carbohydrates

Question 5

98% of the plasma membrane is composed of which three molecules?

Answer 5

• Phospholipids
• Cholesterol
• Glycolipids

Question 6

What does it mean for a molecule to be amphipathic?

Answer 6

It has both hydrophobic (non-polar) and hydrophilic (polar) regions.

Question 7

How do amphipathic molecules affect membranes?

Answer 7

They cause phospholipids to form bilayers — tails in, heads out.

Question 8

How do unsaturated fatty acids affect membrane fluidity?

Answer 8

Their kinks prevent tight packing, increasing fluidity.

Question 9

How does cholesterol maintain fluidity in various temperatures?

Answer 9

• Prevents tight packing at cold temps
• Stabilizes membrane and reduces movement at warm temps

Question 10

What is a glycolipid?

Answer 10

A lipid with a carbohydrate attached.

Question 11

What role do glycolipids play in recognition?

Answer 11

They help the immune system recognize self-cells.

Question 12

What molecule constitutes ~2% of the membrane but ~50% of its weight?

Answer 12

Proteins.

Question 13

Describe a transmembrane (integral) protein.

Answer 13

Spans the entire lipid bilayer and functions in transport, signaling, and structural roles.

Question 14

What is a peripheral protein?

Answer 14

Attached to the inner or outer surface of the membrane; not embedded.

Question 15

List the functions of membrane proteins.

Answer 15

• Transport
• Enzymatic activity
• Signal transduction
• Cell recognition
• Attachment
• Intercellular joining

Question 16

What is the fluid mosaic model?

Answer 16

Membranes are fluid with proteins and other molecules floating in or on the fluid lipid bilayer like boats on a pond.

Question 17

What are microvilli?

Answer 17

Tiny extensions of the membrane that increase surface area for absorption (e.g., in intestines).

Question 18

What is a cilium?

Answer 18

A hair-like projection used for movement or sensing.

Question 19

What is the difference between primary and motile cilia?

Answer 19

• Primary (nonmotile) cilia are sensory
• Motile cilia move substances across the cell surface

Question 20

How does a cilium beat?

Answer 20

With a coordinated back-and-forth motion powered by ATP and motor proteins like dynein.

Question 21

What is a flagellum?

Answer 21

A long whip-like structure used for cell movement.

Question 22

Give an example of a flagellum.

Answer 22

Sperm cells.

Question 23

What are pseudopods?

Answer 23

Temporary projections of cytoplasm for movement or engulfing particles.

Question 24

Give an example of a cell using pseudopods.

Answer 24

White blood cells.

Question 25

What does it mean that the plasma membrane is selectively permeable?

Answer 25

Only certain substances can cross it freely.

Question 26

How can a cell adjust its permeability?

Answer 26

By adding/removing transport proteins or altering lipid composition.

Question 27

What is transmembrane transport?

Answer 27

Movement of substances across the membrane.

Question 28

What is the difference between passive and active transport?

Answer 28

Passive does not use energy; active does.

Question 29

What is diffusion?

Answer 29

Movement of molecules from high to low concentration.

Question 30

Is a membrane required for diffusion?

Answer 30

No, but it can occur across membranes.

Question 31

What is a concentration gradient?

Answer 31

Difference in concentration across a space.

Question 32

What is Brownian motion?

Answer 32

Random movement of particles due to kinetic energy.

Question 33

What is equilibrium?

Answer 33

Equal concentration throughout a space.

Question 34

Are particles still moving at equilibrium?

Answer 34

Yes, but no net movement.

Question 35

When might diffusion occur across a membrane?

Answer 35

When particles are small, nonpolar, or when channel/carrier proteins are present.

Question 36

Do diffusing solutes affect each other?

Answer 36

No, each diffuses independently.

Question 37

List the factors influencing diffusion rate.

Answer 37

* Temperature * Molecular size * Concentration gradient * Surface area * Membrane permeability

Question 38

What is simple diffusion?

Answer 38

Direct movement through the membrane.

Question 39

Give an example of simple diffusion.

Answer 39

Oxygen, CO₂.

Question 40

What is facilitated diffusion?

Answer 40

Uses a protein to cross membrane.

Question 41

Give an example of facilitated diffusion.

Answer 41

Glucose via GLUT transporter.

Question 42

What is the difference between channel and carrier proteins?

Answer 42

* Channels form pores * Carriers bind and change shape

Question 43

What is an aquaporin?

Answer 43

A protein channel for water.

Question 44

Can water diffuse without aquaporins?

Answer 44

Yes, but inefficiently.

Question 45

What is water balance?

Answer 45

Equal water movement in/out of cells; prevents cell lysis or shrinkage.

Question 46

What is osmosis?

Answer 46

Diffusion of water across a membrane.

Question 47

When does osmosis occur?

Answer 47

When there's a solute concentration difference across a membrane.

Question 48

How can cells influence osmosis?

Answer 48

By adjusting solute concentrations.

Question 49

What is tonicity?

Answer 49

Measure of solution’s ability to affect water movement.

Question 50

What happens in a hypotonic solution?

Answer 50

Lower solute outside cell → water in → cell swells, may burst.

Question 51

What happens in an isotonic solution?

Answer 51

Equal solute concentration → no net water movement → cell stable.

Question 52

What happens in a hypertonic solution?

Answer 52

Higher solute outside → water leaves → cell shrinks.

Question 53

What is the osmosis rule?

Answer 53

Water follows solutes.

Question 54

What are the two types of active transport?

Answer 54

* Primary * Secondary

Question 55

What is active transport by carrier protein?

Answer 55

Moves substances against gradient using ATP.

Question 56

What is vesicular/bulk transport?

Answer 56

Movement of large materials via vesicles.

Question 57

What is the difference between exocytosis and endocytosis?

Answer 57

* Exocytosis: expels substances * Endocytosis: brings substances in

Question 58

What is phagocytosis?

Answer 58

Cell engulfs solids.

Question 59

Give an example of phagocytosis.

Answer 59

Macrophages.

Question 60

What is pinocytosis?

Answer 60

Cell 'drinks' fluid.

Question 61

Give an example of pinocytosis.

Answer 61

All cells, especially immune cells.

Question 62

What is receptor-mediated endocytosis?

Answer 62

Selective uptake via receptors (e.g., cholesterol uptake).

Question 63

What are the three types of cell junctions?

Answer 63

* Tight junctions * Anchoring junctions * Gap junctions

Question 64

What are tight junctions?

Answer 64

Seal cells together; found in intestines.

Question 65

What are anchoring junctions?

Answer 65

Provide mechanical stability; found in skin, heart.

Question 66

What are gap junctions?

Answer 66

Channels for communication; found in heart, smooth muscle.

Question 67

What is the difference between active and passive studying?

Answer 67

* Active: retrieval, self-testing, teaching * Passive: rereading, highlighting