b2.1 - membranes and membrane transport

Question 1

types of active transport

Answer 1

direct & indirect

Question 2

direct active transport

Answer 2

energy released by exergonic rxn like breakdown of ATP used to transport molecules across cell membrane

• transport proteins: ATPases/ ATPase pumps

Question 3

indirect active transport

Answer 3

movement of one solute down gradient drives movement of another molecule

Question 4

what does active transport help with

Answer 4

• take up essential nutrients
• remove secretory/ waste materials
• maintain concentrations of ions in cells

Question 5

what type of transport proteins are involved in active transport

Answer 5

carrier proteins

Question 6

facilitated diffusion

Answer 6

movement of a molecule down its concentration gradient w/ the help of specialized transport proteins (carrier and channel) across cell membrane

Question 7

facilitated diffusion by channel protein

Answer 7

form channels for ions (Na+, K+)

Question 8

facilitated diffusion by carrier proteins

Answer 8

• binds to solute molecules & undergoes conformational change to transfer molecules to the other side
• sites specific for solute

Question 9

osmosis

Answer 9

movement of water molecules across a semi-permeable membrane from high to low concentration

Question 10

what does permeability of membrane depend on?

Answer 10

• size
• polar nature of molecules

Question 11

osmosis continues until no net movement of water (same on both sides)

Question 12

aquaporins (AQP)

Answer 12

• channel proteins
• facilitate transport of water across cell membranes
• integral proteins
• tetrameric protein (4 water channels)
• bidirectional

Question 13

what is attached to the phospholipid backbone

Answer 13

• a negatively charged phosphate molecule linked to molecules like choline or serine forming a polar, hydrophilic, ‘head’ group. polar head forms hydrogen bonds with water
• 2 non-polar fatty acid chains forming the hydrophobic ‘tails’ (saturated & unsaturated)

Question 14

glycoprotein

Answer 14

covalent bonding of short carbohydrate chains

Question 15

glycolipid

Answer 15

covalent bonding of carbs to lipids

Question 16

functions of glycolipids and glycoproteins (3)

Answer 16

• cell-cell recognition
• cell adhesion
• cell signaling

Question 17

cell adhesion of glycolipids and glycoproteins

Answer 17

• CAMS (cell adhesion moelcules)
• helps cells attach and bind to other cells to form tissues

Question 18

cell signaling of glycoproteins and glycolipids

Answer 18

• act as receptors for enzymes & other molecules
  —> receiving and transmitting chemical signals

Question 19

glycocalyx

Answer 19

sticky layer formed by the carbohydrate groups of glycolipids and glycoproteins
- helps protect cell surface

Question 20

functions of membrane proteins (integral + peripheral)

Answer 20

• transport proteins
• recognition
• receptors (binding sites/ chemical signals for hormones & neurotransmitters)
• enzymes
• cell-adhesion

Question 21

plasmolysis

Answer 21

shrinking of the cell due to hypertonic solution (too little solute)

Question 22

cytolysis

Answer 22

popping of the cell due to hypotonic solution (cell bursts!) (too much solute)

Question 23

isotonic

Answer 23

concentration inside = concentration outside of solute and solvents

Question 24

facilitated diffusion vs active transport

Answer 24

facilitated diffusion is passive transport

active transport uses energy

Question 24

what is ATP made of

Answer 24

adenosine: adenine and ribose + triphosphate

Question 25

ATP + water

Answer 25

ADP (hydrolysis to form diphosphate, energy is released)

Question 26

active transport

Answer 26

- net movement of particles through cell membrane from low to high concentration, using energy from respiration (ATP) - exergonic rxn (breakdown of atp)

Question 27

example of active transport

Answer 27

- uptake of glucose from the lumen of the intestine to the epithelial cells lining the small intestine

Question 28

The Electrochemical Gradient.

Answer 28

- determines the direction that ions will flow through an open ion channel and is a combination of two types of gradients: a concentration gradient and an electrical field gradient.

Question 29

Na+/K+ pumps

Answer 29

The Na+/K+ makes use of ATP to help the interior of the cell maintain a net negative charge by pumping out three sodium ions and importing two potassium ions.

Question 30

Indirect active transport role example

Answer 30

Indirect active transport plays an important role in reabsorbing nutrients like glucose in the small intestine and the nephron

Question 31

Identify the way(s) in which nicotinic acetylcholine receptors are similar to voltage-gated ion channels.

Answer 31

(I) Both result in the movement of ions. (II) Both result in depolarisation and changes in membrane potential.

Question 32

simple diffusion

Answer 32

- net movement of particles from a region of higher concentration to lower concentration - spontaneous process - passive process (no energy)

Question 33

phospholipid

Answer 33

- 2 non polar fatty acid tails - neg phosphate linked to choline or serine (head)

Question 34

what CAN pass through lipid bilayers

Answer 34

- non polar, lipid molecules - small, uncharged molecules

Question 35

what CANNOT pass through lipid bilayers

Answer 35

- ions - uncharged polar molecules (ex. glucose)

Question 36

integral proteins

Answer 36

embedded in plasma membrane, cannot be easily extracted - amphipathic

Question 37

peripheral proteins

Answer 37

attached to plasma membrane, can be easily extracted - hydrophilic

Question 38

channel proteins (in facilitated diffusion) open and close in response to:

Answer 38

- change in voltage - binding to small molecules - mechanical forces like pressure

Question 39

hypotonic vs hypertonic solution

Answer 39

Hypotonic: Water moves into cells → swelling or bursting (lysis). Hypertonic: Water moves out of cells → shrinking or shriveling (crenation or plasmolysis).