Eukaryotic Cell: Plasma Membrane

Question 1

What are the basic components of the plasma membrane?

Answer 1

Lipids (phospholipids)

Proteins

Question 2

What is the fluid mosaic model?

Answer 2

Protein rafts floating in a sea of lipids

Question 3

What are the basic functions of membrane proteins?

Answer 3

transport

enzymatic activity

signal transduction

cell-cell recognition

attachment (intracellular & ECM)

Question 4

What is passive transport?

Answer 4

Diffusion of a substance down a gradient and across the plasma membrane

Question 5

What is osmosis?

Answer 5

Diffusion of water across a permeable membrane

Question 6

What is an isotonic solution?

Answer 6

When the concentration of solute is the same on both sides of a membrane

Question 7

What is a hypertonic solution?

Answer 7

When the solution has higher concentration of solute than the cell.

Question 8

What happens to a cell in a hypertonic solution?

Answer 8

The cell loses water to the solution (shrinks)

Question 9

What is a hypotonic solution?

Answer 9

The concentration of solute is less than the inside of the cell.

Question 10

What happens to a cell in a hypotonic solution?

Answer 10

Water flows into the cell and it gets lysed (bursts)

Question 11

What is active transport?

Answer 11

A protein pump moves a solute across the membrane against a concentration gradient

This requires energy

Question 12

What are the structure and function of membrane channels?

Answer 12

Transmembrane channel proteins (basically corridors) allow solutes (usually ions) to move down a concentration gradients

Question 13

What are gated channels?

Answer 13

A type of transmembrane protein that open/close in response to stimuli (eg electrical or chemical)

Question 14

Describe the structure & function of the Na-K pump

Answer 14

This is a form of active transport

Goal is to increase K^- inside cell

Requires ATP

Na concentration is high outside of cell

K is high inside of cell

3 Na go OUT

2 K go IN

Result is a negative cell potential

Question 15

What is cotransport?

Answer 15

It is a form of active transport

One solute moves down a gradient

It’s movement allows a second solute to move UP a gradient (in the same direction as the first solute)

Question 16

What is exocytosis?

Answer 16

Transport vesicles inside cell

fuse with plasma membrane

Contents of vesicle spill OUT of cell

Question 17

What is endocytosis?

Answer 17

Movement of molecules/matter from OUTSIDE to INSIDE the cell

Question 18

What are the 3 main forms of endocytosis?

Answer 18

Phagocytosis (eating)

Pinocytosis (drinking)

Receptor-mediate endocytosis

Question 19

What are the main types of cell signaling pathways?

Answer 19

Contact signaling (physical)

Chemical signaling

Electrical signaling

Question 20

What are the stages of cell signaling?

Answer 20

Reception (signal molecule is detected)

Transduction (binding of signal converted to relay molecules inside of cell)

Response (intracellular activity)

Question 21

What is paracrine signaling?

Answer 21

LOCAL signaling (between nearby cells)

Question 22

What is endocrine signaling?

Answer 22

LONG-DISTANCE signaling

e.g hormones

Question 23

What is the resting potential of a typical cell?

Answer 23

Negative due to Na-K pumps

Question 24

What is a protein kinase?

Answer 24

An enzyme that transfers P from ATP to a protein

Can be part of a phosphorylation cascade

which is transduction

Question 25

What is a second messenger?

Answer 25

The first messenger is the signal molecule

The second messenger is WITHIN the cell

It diffuses & spreads

Question 26

What are gap junctions?

Answer 26

little holes connecting two cells, allow passage of stuff

Question 27

What are tight junctions?

Answer 27

Barriers between cells that prevent movement of stuff

Question 28

What are desmosomes?

Answer 28

They are links between the cytoskeletrons of cells, they provide strength/rigidity but do not provide a barrier