Unit 3.2 and 3.3: Membrane + traffic

Question 1

What are the three macromolecules that consists the membrane structure?

Answer 1

1) Lipids (usually phospholipids)
2) Sterol lipids
3) Proteins

Question 2

What are the two parts forming a phospholipid molecule

Answer 2

An hydrophobic tail and an hydrophilic head : form a bilayer

Question 3

What are sterol lipids in animals? In plants?

Answer 3

In animal: cholesterol

In plant: phytosterol

Question 4

What is the role of the sterol lipid?

Answer 4

Keeps membrane fluid and provides stability

Question 5

What are the three type of proteins in the membrane structure?

Answer 5

1) Integral
2) Transmembrane
3) Peripheral (membrane’s surface)

Question 6

What are the 7 functions of the membrane?

Answer 6

1) define cell - contains and seperates
2) selective transport
3) enzyme activity
4) signal transduction
5) cell adhesion
6) cell recognition
7) attachement to cytoskeleton

Question 7

From what are due these 6 membrane functions:

selective transport, enzyme activity, signal transduction, cell adhesion, cell recognition, attachement to cytoskeleton

Answer 7

Due to membrane proteins

Question 8

What are the three types of passive transport?

Answer 8

Diffusion, osmosis and facilitated diffusion

Question 9

Explain what diffusion is.

Answer 9

Movement of particles down concentration gradient

Question 10

Give exemples of molecules that can diffuse through membranes

Answer 10

O2, CO2, lipid-soluble molecules

Question 11

What is the difference between passive and active transport

Answer 11

Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input while active transport requires work/energy (ATP).

Question 12

Explain what osmosis is.

Answer 12

Transport of water through aquaporin channels through membrane

Question 13

Explain what is facilitated diffusion

Answer 13

Transport of solutes across membrane down concentration gradient via specific protein channels

Question 14

What is the goal of osmosis?

Answer 14

From hypotonic to hypertonic until isotonic

Question 15

Give example of facilitated diffusion

Answer 15

glucose transporter, gated ion channels ( Na+, K+) in membranes neurons

Question 16

Give exemple of osmosis

Answer 16

Turgor pressure, using salt and sugar as a perservative, water moving into stomach, contractile vacuoles

Question 17

Describe what is active transport

Answer 17

It move substance cross membrane against concentration gradient.

Question 18

What does active transport require?

Answer 18

Energy (ATP) and transmembrane protein

Question 19

Name the 4 types of active transport.

Answer 19

Ions pumps
Co-transport
Exocytosis
Endocytosis

Question 20

Describe ions pumps transport

Answer 20

It moves ions across membrane against their concentration gradient

Question 21

What does ions pumps maintain?

Answer 21

Maintain electrochemical gradient (membrane potential) and help maintain osmotic pressure.

Question 22

Give four exemples of ions pumps

Answer 22

Na+/K+ ions pump
Ca++ pump in sarcoplasmic reticulum
Proton pump
H+/K+ ATPase (in stomach pumps H+ into lumen)

Question 23

Proton pump’s roles?

Answer 23

In lysosome membranes maintain acid pH

In mitochondria use H+ gradient to make ATP

Question 24

Describe co-transport.

Answer 24

Movement of 2 ions : one moves down concentration gradient, one moves against concentration gradient. Both move through same transport protein

Question 25

Give two types of co-transport and one example for each of them.

Answer 25

symport : coupled molecule move in same direction (plant cells uptake of H+/sucrose)
antiport: coupled molecules move in opposite direction (cardiac muscle cells Na+ into cell/Ca++ out of cell)

Question 26

Describe exocytosis

Answer 26

Vesicles containing molecules are transported from within the cell to the cell membrane.
The vesicle membrane attaches to the cell membrane.
Fusion of the vesicle membrane with the cell membrane releases the vesicle contents outside the cell.

Question 27

Give examples of exocytosis

Answer 27

secretion of neurotransmitters by neuron
secretion of hormones and enzymes
insertion of plasma membrane
insertion of transmembrane proteins

Question 28

Describe endocytosis

Answer 28

Uptake of macromolecules by formation of vesicles with plasma membranes to bring it inside cell

Question 29

What are the three types of endocytosis

Answer 29

1) Phagocytosis = surrounds “stuff” outside cell with cell membrane to create food vacuole
2) Pinocytosis = unspecific uptake of extracellular fluid and dissolved solutes
3) Receptor-mediated endocytosis = specific molecules bind to receptor