1. Cell metabolism and Membrane transport

Question 1

List the 7 factors affecting solute diffusion across cell membranes

Answer 1

Conc gradient
Membrane permeability 
Membrane voltage gradients 
Molecular weight of diffusing substance
Diffusion distance
Membrane surface area
Temperature

Question 2

What conditions are necessary for osmosis?

Answer 2

Solute conc gradient
Membrane permeable to water
Simple diffusion and aquaporins

Question 3

What is facilitated diffusion?

Answer 3

Passive process where substrate conc gradient drives facilitated diffusion movement across the membrane depends on the availability of carrier proteins

Question 4

What is meant by isotonic?

Answer 4

Plasma and intersitial fluid are isotonic in healthy people

Question 5

What is meant by hypertonic?

Answer 5

More osmotically active particles than intracellular fluid

leads to osmotic water cell - cell shrinking - crenation

Question 6

What is meant by hypotonic?

Answer 6

less osmotically active particles than intracellular fluid

osmotic cell swelling - lysis

Question 7

What is meant by hypotonic?

Answer 7

less osmotically active particles than intracellular fluid

osmotic cell swelling - lysis

Question 8

Describe how facilitated diffusion works

Answer 8

Carrier proteins in cell membrane bind to specific substrate
undergo confromational change
substrate transported across membrane and is released on the other side

Question 9

What is primary active transport used for?

Answer 9

Control of cell volume

Question 10

Describe primary active transport

Answer 10

energy released by hydrolysis of ATP

requires carrier proteins

Question 11

Describe secondary active transport?

Answer 11

Energy released during passive movement of one substance down electrochemical gradient is used to transport another substance against a conc gradient

Question 12

What is endocytosis?

Answer 12

Ingestion by the cell

Question 13

What is vesicular transport?

Answer 13

transport ofsubstances within membrane bound vesicles

Question 14

What are the three different types of endocytosis?

Answer 14

Receptor-mediated endocytosis
Phagocytosis
Pinocytosis

Question 15

Describe receptor-mediated endocytosis

Answer 15

Cellular uptake of molecules that bind to specific receptors
1. Molecules attach to receptors on cell surface in coated pits. Pits are latticework of clathrin protein.

2. Membrane changes, pit invaginates inward, proteins close over.
3. Vesicles formed
4. Process requires ATP and Ca2+

Question 16

Describe the process of phagocytosis

Answer 16

Ingestion of large particles

1. Cell membrane receptors attach to surface of particle
2. Membrane edges around attachment points, evginate outward to surround entire particle (rapid process)
3. Actin and contractile fibrils in cytoplasm surround vesicle and push it to cell interior
4. Process requires ATP and Ca 2+

Question 17

Describe pinocytosis

Answer 17

Ingestion of fluid and macromolecules or minute particles

Question 18

Describe the process of exocytosis?

Answer 18

Stimulated by Ca 2+ entry to the cell
vesicle fuses with cell membrane
membrane’s outer surface opens
contents are extruded

Question 19

What does the body require energy for?

Answer 19

Body requires energy for numerous vital processes

• muscle contraction
• ion transport against conc gradients
• synthesis of complex

Question 20

Outline the main steps in cellular energy change

Answer 20

Glycolysis - glucose breakdown to pyruvic acid and ATP
Aerobic stage- Krebs cycle and ETC
intramitichondrial enzymes catalyse glycolysis products to ATP CO2 and H20

Question 21

Describe the role of ATP in energy exchange

Answer 21

Made from ADP and using energy from food

Energy released to provide energy for cellular work and chemical synthesis

Question 22

What is ATP used for?

Answer 22

Membrane transport
Protein synthesis
Muscle contraction