Physiology: Cell

Question 1

What are the factors effecting solute diffusion across the cell ?
7

Answer 1

1) concentration gradient
2) membrane permeability
3) electrochemical gradient due to charges ions
4) molecular weight ( light ions -faster)
5) diffusion distance
6) membrane SA and SA:V
7) temperature

Question 2

What conditions are necessary for osmosis ?

3

Answer 2

• solute concentration gradient
• membrane permeable to water and not the solute
• aquaporins

Question 3

What’s osmolarity ?

1

Answer 3

Total number of dissolved particles per litre of solvent

Question 4

what’s 1 osmole ? (2)

Answer 4

Mr/number of freely moving ions and particles the molecule can dissociate to in a solution.

“The standard unit of osmotic pressure. The osmole is equal to the molecular weight of the dissolved substance expressed in grams divided by the number of particles or IONS into which each molecule of the substance dissociates in solution,”

ie =low osmolality- too much fluid = oedema

Question 5

what is tonicity ? (1)

Answer 5

actual affect of a solution on living cells

Question 6

what’s osmotic pressure ? (1)

Answer 6

the pressure needed to oppose / prevent water molecules moving .

Question 7

what’s facilitated diffusion ? (2)

Answer 7

• passive diffusion of molecules through membrane down their concentration gradients
• using carrier proteins

Question 8

what’s primary active transport ? (1)

Answer 8

• molecules are actively moved against their concentration gradients using ATP

Question 9

what’s secondary active transport ? (2)

example ?(2)

Answer 9

• an examples would be a symport pump which pumps Na+ down its electrochemical gradient , releasing energy
• this energy is then used to pump glucose INTO the cell against its concentration gradient .
• passive movement of one substance down its electrochemical gradient used to transport another substance AGAINST its concentration gradient .

Question 10

what is an :
isotonic solution ?
hypertonic?
Hypotonic?
terms for the States ?
(6)

Answer 10

a) isotonic solution =both cell/ plasma have the same osmolarity / equal water potential
b) Hypertonic =higher water potential on the inside to water diffuses out = crenation
c) Hypotonic= low water potential on the inside so water diffuses in =lysis

Question 11

what are the three types endocytosis ?

Answer 11

1) receptor mediated endocytosis
2) phagocytosis
3) pinocytosis

Question 12

How does receptor-mediated endocytosis work?

6

Answer 12

1-ligand binds to the receptor
2-the receptors are on Clathrin Coated pit
3-the receptor/ligand molecules sink into a cell in a vesicle surrounded by Clathrin molecules
4-clathrin molecules leave and go back to the membrane
5-vesicle fuses with endosome ( another vesicle) and the ligands are separated from the receptor
6-then the ligand vesicle fuses with lysosome which then breaks down ligand to smaller molecules and is used in various regions around the cell

Question 13

what’s phagocytosis ? (1)

Answer 13

-Phagocytosis is the process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome.

Question 14

what’s pinocytosis ? (1)

Answer 14

-the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

Question 15

what’s exocytosis ? (1)

Answer 15

Exocytosis is the process of moving materials from within a cell to the exterior of the cell.
requires ATP

Question 16

outline the process of exocytosis ? (5)
(VTDPF)
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DIAMOND
PIERCINGS 
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Answer 16

V-vesicle trafficking to membrane
T-Tethering so vesicle and membrane have contact
D-Docking, the phospholipid bilayer merges with vesicle
P-Priming , there are changes in cell membrane to allow exocytosis
F-Fusing - either complete or temporary . Temporary allows veils to fuse for a period of Time until fusion pores made and then released .

Question 17

What is the function of the cytoskeleton ?

3

Answer 17

1-structural support ( contraction, division )
2-movement and shape change
3-strength

Question 18

What are the intermediate filaments ?

3

Answer 18

• provides structural support and help resist mechanical stress
• maintain the shape of cell ( desmosomes)
• keratin,Lamin and vimentin

Question 19

What’s a intermediate filament structurally ?
(3)
What’s it’s function ? (1)

Answer 19

-many tetramers ( non polar )
-2 tetramers coiled = filament
-like a rope
( very strong tensile strength / allows u to stretch )

Question 20

What is a lamin ?
(3)
What’s it like ?
How is it controlled ?

Answer 20

• a intermediate filament under nuclear membrane
• steel wool mesh work ( breaks and reforms each time the cell divides )
• assembly is controlled via protein phosphorylation
• assemble and de-assemble the nuclear envelope when mitosis occurs

Question 21

What is a microTUBULe ? 
- what is it made of ?
- is it hollow ?
-where are they in the cell?
-when are they used ?
- what’s their super power ? BTS DYNAMIte
(5)

Answer 21

• TUBULIN -alpha and beta molecules
• HOLLOW /POLAR
• anchored at centrosome
• used in cell division
• DYNAMIC INSTABILITY : they can grow and shrink independently ( grow and if they hook onto something they stay , if not they shrink back )
• they always grow from negative end

Question 22

How is dynamic instability in microtubules controlled ?

3

Answer 22

• controlled by GTP / G proteins
  -when they grow : GTP IS MADE
  when they shrink : GTP—> GDP

Question 23

What’s an actin filament ?

3

Answer 23

• alpha helix of actin
• polarised
• regulated by ATP/ADP

Question 24

What is the function of actin filament ?

4

Answer 24

• cell crawling
• phagocytosis
• cell division
• shape ( micro villi and projections )
• contraction of muscle cell

Question 25

What’s the process of cell crawling ? | 4

Answer 25

1) polymerisation of actin ( grows out ) 2) adhesion —> anchors down 3) translocation —>contraction of actin and myosin allow movement 4) de-adhesion of the back of the cell