Membranes

Question 1

What forms the basic structure of a membrane?

Answer 1

Phospholipid bilayer

The bilayer consists of hydrophilic heads facing water and hydrophobic tails avoiding water.

Question 2

What is membrane asymmetry?

Answer 2

The outer and inner leaflets differ in lipid, protein, and carbohydrate composition

This difference contributes to the unique functions of each leaflet.

Question 3

What model describes the fluid nature of membranes?

Answer 3

Fluid mosaic model

This model allows for flexibility and proper function of embedded proteins.

Question 4

What factors influence membrane fluidity?

Answer 4

Temperature, phospholipid composition, cholesterol

The degree of unsaturation and tail length of phospholipids also affect fluidity.

Question 5

What role does cholesterol play in membrane fluidity?

Answer 5

Acts as a fluidity buffer

It helps maintain membrane stability under temperature fluctuations.

Question 6

What are the two main types of membrane proteins?

Answer 6

Integral and peripheral proteins

Each type serves various roles in the membrane.

Question 7

What are transmembrane domains?

Answer 7

Stretches of non-polar amino acids that span the membrane

These are found in integral membrane proteins.

Question 8

What is passive transport?

Answer 8

Transport that requires no energy

Includes simple diffusion and facilitated diffusion.

Question 9

What is active transport?

Answer 9

Transport that requires energy (ATP)

This process moves molecules against concentration gradients.

Question 10

Fill in the blank: The phospholipid bilayer has _______ heads and _______ tails.

Answer 10

hydrophilic; hydrophobic

Question 11

True or False: Membrane proteins can function as signal receptors.

Answer 11

True

Question 12

What is passive transport?

Answer 12

Movement down concentration gradients (high to low)

Includes diffusion and facilitated diffusion.

Question 13

What is facilitated diffusion?

Answer 13

Requires transport proteins (channels, gated channels, carrier proteins) to help molecules cross the membrane

It is a type of passive transport.

Question 14

What is active transport?

Answer 14

Moves molecules against gradients using energy

Includes primary and secondary active transport.

Question 15

What is primary active transport?

Answer 15

Uses ATP to move molecules against a gradient (e.g., sodium-potassium pump)

It is a type of active transport.

Question 16

What is secondary active transport?

Answer 16

Uses energy from electrochemical gradients to move molecules

Example: sodium-glucose co-transporter.

Question 17

What is endocytosis?

Answer 17

Uptake of substances via vesicles

Includes receptor-mediated endocytosis, pinocytosis, and phagocytosis.

Question 18

What is exocytosis?

Answer 18

Release of substances from cells through vesicle fusion with the membrane

It is the opposite of endocytosis.

Question 19

What is osmosis?

Answer 19

The movement of water across a semi-permeable membrane toward regions of higher solute concentration.

Question 20

What happens to cells in a hypertonic solution?

Answer 20

Cells can shrink.

Question 21

What happens to cells in a hypotonic solution?

Answer 21

Cells can swell.

Question 22

What happens to cells in an isotonic solution?

Answer 22

Cells remain stable.

Question 23

What is primary active transport?

Answer 23

Uses ATP to maintain concentration gradients, e.g., proton pumps and sodium-potassium pumps.

Question 24

What is secondary active transport?

Answer 24

Utilizes ion gradients, e.g., sodium-glucose cotransport.

Question 25

What are the key roles in signal transduction?

Answer 25

Transporters, enzymes, and receptor proteins transmit signals across membranes.

Question 26

What do signaling pathways often involve?

Answer 26

Phosphorylation cascades that amplify faint extracellular signals.

Question 27

How is energy stored in gradients?

Answer 27

Concentration gradients across membranes store potential energy.

Question 28

What is the role of electrochemical gradients?

Answer 28

Generate voltage across membranes, important for nerve function.

Question 29

What do receptor proteins do in signal transduction pathways?

Answer 29

Activate intracellular pathways, e.g., phosphorylation cascades.

Question 30

Fill in the blank: Small signals can be _______ to produce larger responses.

Answer 30

[amplified]