Cell Membranes And Their Transport Systems

Question 1

What are membranes

Answer 1

-selectively permeable barriers
-maintain constant internal environment and enclose cell contents
-very thin

Question 2

What are phospholipids

Answer 2

-has a dynamic structure so components are free to move around
*amphipillic: both hydrophilic and hydrophobic parts
*polar head: negatively charged phosphate group
*non polar tail: no charge
*phospholipid: “self-assembles” to create the bilayer. They migrate but rarely flip

Question 3

Two types of tails

Answer 3

Saturated and Unsaturated
Saturated: single bonds only
Unsaturated: at least one double bond
Double bond creates a kink in the fatty acid chain of the tail

Question 4

What do higher concentrations of saturated fatty acids cause?

Answer 4

Reduces cell membrane fluidity

Question 5

What do higher concentrations of unsaturated fatty acids cause?

Answer 5

Promote membrane fluidity

Question 6

What do concentrations of unsaturated phospholipids affect?

Answer 6

It affects membrane fluidity

Question 7

2 types of carbohydrates

Answer 7

Glycolipids and glycoproteins

Question 8

3 roles of carbohydrates

Answer 8

Maintain membrane stability, cell protection and aids in cell adhesion

Question 9

What is a lipid

Answer 9

Has polar and non polar regions, wedges itself between phosplipid tails and can migrate and flip between membrane layers

Question 10

Proteins function

Answer 10

Serve as enzymes, carrier proteins, channel proteins, receptors, cell adhesion and recognition

Question 11

Two types of proteins

Answer 11

Integral proteins- firmly inserted into the brain
Peripheral-loosely attached to the membrane

Question 12

Membrane fluidity is affected by

Answer 12

Extreme temps- hot (More kinetic energy, phospholipids move further away and membranes have more fluid )
Cold (Less kinetic energy, phospholipids pack together and membranes have less fluid )

Concentration of unsaturated fatty acids

Cholesterol levels - it maintains fluidity by preventing lipids from getting too close together or too far apart from each other

Question 13

Red blood cells quantity

Answer 13

Equal amounts of lipid and protein
Small amounts of carbohydrates

Question 14

Nerve cells quantity

Answer 14

Higher amounts of lipid in the cell membrane

Question 15

Passive transport

Answer 15

moves down a concentration gradient
Three types: simple diffusion, facilitated diffusion and osmosis
-uses inherent kinetic energy

Question 16

Active transport

Answer 16

-moves against a concentration gradient
-has directionality
-requires a specific carrier protein
Two types: primary and secondary
-needs external energy source

Question 17

Simple diffusion

Answer 17

small, uncharged non polar molecules
Properties:
-no metabolic energy is required
-uses kinetic energy
-the rate of diffusion is proportional to the concentration gradient

Question 18

Facilitated diffusion

Answer 18

uses specific proteins
-the rate of diffusion is proportional to the concentration gradient

Question 19

Simple diffusion and facilitated diffusion kinetics:

Answer 19

Simple diffusion= linear relationship between concentration and rate of diffusion
Facilitated diffusion= the rate of diffusion reaches a plateau since the proteins become fully occupied

Question 20

Osmosis

Answer 20

net movement of water down a concentration gradient

Question 21

Primary active transport:

Answer 21

movement of Na+ and K+ uses the Na+/K+/ATPase pump
-maintains ion concentration differences inside the cell
-hydrolysis of ATP results in= phosphorylation of the pump —> results in conformational change of pump
-causes transport of 3Na+ out and 2K+ into the cell

Question 22

Secondary active transport (co-transport):

Answer 22

*A substance against its concentration gradient—> active transport
*Ion movement down its concentration gradient—> usually facilitated diffusion
-energy used for secondary active transport comes from the electrochemical gradient across the membrane.

Question 23

What are the two types of secondary active transports?

Answer 23

Symport;
*transported substances move in the same direction

-Antiport;
*Transported substances move in the opposite direction

Question 24

What is endocytosis?

Answer 24

Moves large molecules into the cell
Three types: phagocytosis, pinocytosis and receptor- mediated

Question 25

What is exocytosis?

Answer 25

Moves large molecules out of the cell
*Used for: hormone secretion, neurotransmitter release and mucous secretion

Question 26

What are vesicles?

Answer 26

vesicular transportation of large molecules
*bubble-like membranous sacs
*made up of phospholipid bilayer containing fluid

Question 27

Endocytosis- phagocytosis

Answer 27

ingestion of large particles by specialised cells (phagocytes -> immune system)
-macrophages
-certain white blood cells
*used for removing bacteria and debris
*when bacteria binds to a phagocyte the cell membrane wraps itself around the particle= results in a phagosome containing the particle

Question 28

Endocytosis pinocytosis

Answer 28

occurs in most cells
*process used to take in extracellular fluid with dissolved substances

Question 29

Endocytosis- receptor mediated

Answer 29

main mechanism for specific uptake of macromolecules
*very selective method
*uptakes substances (hormones, cholesterol) found in small amounts
*receptors for this are specific membrane proteins