Chapter 7 Membranes

Question 1

Vesicle merges with cell membrane to chuck out stuff.

Answer 1

Exocytosis

Question 2

Cell membrane pinches in to make a vesicle

Answer 2

Endocytosis

Question 3

Factors impacting membrane fluidity

Answer 3

Temperature (solidifies when cold)
Saturation of phospholipids (if there are kinks in the fatty acid tails, they will be more spread apart)
Cholesterol (reduces movement of phospholipids)

Question 4

Adapting membrane fluidity

Answer 4

Varying amounts of unsaturated phospholipids in their membrane depending on the climate they live in. Some have different types of lipids that solidify at different temperatures.
Some plants/cells can change the amount of unsaturated phospholipids at different seasons or external temperatures.

Question 5

Integral proteins

Answer 5

Rooted into the hydrophobic centre of phospholipid bilayer.
May pierce through the membrane entirely (transmembrane protein), or only partly.

Question 6

Hydrophobic regions of integral proteins

Answer 6

Made of sections of non-polar amino acids (usually 20-30 amino acids long)

Question 7

Peripheral proteins

Answer 7

Proteins that are not embedded into the hydrophobic centre of lipid bilayer.
Only loosely bound or attached to integral proteins.

Question 8

Membrane sided-ness

Answer 8

The 2 lipid layers can consist of different phospholipids.Interior of lumen membrane is the same as the exterior of plasma membrane.

Question 9

Steps of synthesis of a membrane glycoprotein

Answer 9

Protein synthesised in the Rough ER, where it is embedded into RER membrane. In the lumen, carbohydrates added to the protein.Transported to Golgi apparatus, where carbohydrate is modified.Vesicle from Golgi fuses with plasma membrane.

Question 10

6 functions of membrane proteins

Answer 10

Cell-cell recognitionCell-cell attachmentAttachment to ECMTransport EnzymesSignalling molecules

Question 11

Cross-membrane movement of non-polar molecules

Answer 11

Non-polar molecules are hydrophobic and dissolve easily through the lipid bilayer.CO2, O2, hydrocarbons

Question 12

Cross-membrane movement of polar molecules

Answer 12

Polar molecules are hydrophilic. Even small molecules such as water move through the membrane much slower than non-polar molecules.H2O, sugars, ions.

Question 13

Aquaporin

Answer 13

Membrane protein.
Provides channel for water to pass through much faster than through the lipid bilayer.

Question 14

Methods of facilitated diffusion

Answer 14

Protein channels (eg. aquaporin) just provide a hydrophillic hole for molecules to move through.Carrier proteins (eg. glucose transporter) change shape upon binding to a molecule which moves them to the other side.

Question 15

Passive transport types

Answer 15

Diffusion (small molecules usually)Facilitated diffusion (some larger molecules)Osmosis

Question 16

Sodium-potassium pump

Answer 16

Carrier protein; Transports 3 Na+ outside the cell when a phosphate group (from ATP) is added to change its shape.2 K+ ions from outside the cell can bind to the protein after this.K+ are released into the cell when the phosphate group is released.

Question 17

Membrane potential

Answer 17

Cytoplasmic side is about -50 to -200 mV more negative than outside the cell.

Question 18

Electrochemical gradient

Answer 18

Combines concentration gradient with the electric forces of a membrane potential.
Ions and other charged particles are impacted.

Question 19

Electrogenic pump

Answer 19

An active transport protein that also creates a membrane potential.
Eg. sodium-potassium pump that removes 3 Na+ but only introduces 2 K+ so contributes to a negative membrane potential.

Question 20

Major electrogenic pump in animals

Answer 20

Sodium-potassium pump.

Question 21

Major electrogenic pump of plants/fungi/bacteria

Answer 21

Proton pump

Question 22

Cotransport

Answer 22

The diffusion of one substance down the concentration gradient is used to power the active transport of another thing against its concentration gradient.
Eg. Plant cells transport glucose and amino acids in the cell when protons enter (because of the negative membrane potential). Protons trigger active transport protein in the membrane!

Question 23

Amphipatic

Answer 23

Possessing both hydrophobic and hydrophilic parts