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Bio 107 > Cell Processes > Flashcards

Cell Processes Flashcards

1
Q

Fluid Mosaic Model

A

50% lipid, 50% protein held together by H-bonds
Lipid is the barrier for entry/exit of polar substances
Proteins regulate traffic

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2
Q

What is membrane fluidity determined by

A

Lipid tail length - the longer the tail, the less fluid the membrane

Number of double bonds – more double bonds increases fluidity

Amount of cholesterol – more decreases fluidity

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3
Q

Integral membranes (INTRINSIC)

  • How is located in membrane?
  • What are the regions and what do they do?
A

Extend into or completely across membrane
Amphipathic
Hydrophobic core- coiled helices of non-polar amino acids
Hydrophilic end interacts with aq. solution

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4
Q

Peripheral proteins (EXTRINSIC)

  • how does it interact?
  • What removes it?
  • how is it attached?
A

Attached inner or outer surface of CM
Easily removed by detergents- break H-bonds

Indirectly bound- attach to integral proteins
OR
Interact w/ lipid polar head group

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5
Q

Example of Peripheral protein and its importance

A

Cytochrome C

Essential in ETC, links complex 3 and 4

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6
Q

How can peripheral proteins be disrupted?

A

Change in pH or salt concentration

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7
Q

What can membrane proteins act as?

A

Receptors, Cell ID markers, Linkers, Enzymes, Channels, Transporters

Every triathelete really loves cutting corners

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8
Q

Lipid bilayer permeable to

A

Uncharged non-polar- O2, N2, benzene
Small uncharged polar- water, urea, CO2, glycerol
Lipid soluble- Steroids, fatty acids, some vitamins

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9
Q

Lipid bilayer impermeable to

A

Large uncharged polar- Glucose, amino acids

Ions- Na, K, Cl, Ca, H

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10
Q

Diffusion

  • what factors give faster diffusion
  • when is diffusion fast
A

High-> low conc.

Greater diff. between two sides of membrane, High temp, high SA, small size, shorter diffusion distance

INCREASE RoD

Fast only across short distances

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11
Q

What is the size limit for diffusion?

A

20 um

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12
Q

What are the two gradients across a cell membrane?

A

Conc. gradient

Electrochemical gradient

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13
Q

Conc. gradient

- Definition

A

Non-charged molecules, DOWN conc. gradient

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14
Q

Electrochemical gradient

  • what ions are high in and outside cell?
  • what direction and how do they travel
A

“Salty banana”

High Na, Cl outside
High K inside

So ions travel to lower side. diffuse down con. grad

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15
Q

What do conc. and electrochemical gradients represent?

A

Stored energy

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16
Q

Osmosis

  • Defintion
  • what is colligative property?
A

Diffusion of water across semi-permeable, high to low

Depends on number not types of particles in solution

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17
Q

Osmotic pressure

A

Pressure applied to prevent osmosis

E.g. more water on one side of membrane as it has more solute

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18
Q

Isosmotic definition

A

Solution has same osmolarity compared to reference solution

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19
Q

Hyposmotic definition

A

Lower osmolarity than reference solution

low solute conc.
high water conc.

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20
Q

Hyperosmotic definition

A

Higher osmolarity than reference solution

high solute conc.
low water conc.

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21
Q

What is the osmolarity of body fluid?

- what occurs when osmosis occurs?

A

280 mOsmol

Change in cell volume occurs if osmosis occurs

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22
Q

Tonicity

- definition

A

Effect of cell volume due to solution

only influenced by cells that can’t cross semi-permeable membrane

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23
Q

Isotonic

A

No change in cell volume

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24
Q

Hypotonic

A

Swelling, lysis (haemolysis- rupture of RBC)

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25
Q

Hypertonic

A

Cell shrinkage (crenation)

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26
Q

What do membranes mimic?

- what can they store

A

Capacitors

Can separate and store charge

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27
Q

Width of bilayer membrane

A

8 nm (8x10^-9 m)

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28
Q

Glycolipid

  • location
  • function
A

Attached to membrane

Cell recognition, maintain stability

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29
Q

Glycoprotein

  • what type of membrane protein is it?
  • function
A

Intergral membrane protein- have carbohydrate branching off coiled a.a membrane

Cell to cell recognition

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30
Q

Water permeability in relation to membrane fluidity

A

More fluid= higher lipid-water permeability

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31
Q

What are the two ways water can cross lipid bilayer

A

Diffusion

Aquaporins

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32
Q

What is more permeable to water, aquaporin or diffusion through lipid bilayer

A

Aquaporin > lipid bilayer

Pf > Pd

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33
Q

What are the properties of water moving through lipid bilayer?

A

Its small,

Isn’t blocked by mercury (mercury- binds to proteins causing changes)

Temp. dependent (lipid fluidity)

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34
Q

What are the properties of water moving aquaporins?

A

Large

Mercury sensitive- mercury can bind to proteins in channels and block them- aquaporin can be inhibited

Temp independent

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35
Q

How many isoforms of aquaporins are there in human genome?

A

9

Expressed differently in different cells

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36
Q

Why can cells express different Pw?

A

Express different aquaporin isoforms

What is the osmotic gradient?
What is the permeability of membrane to water?

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37
Q

Difference between osmolarity and tonicity

A

osmolarity is difference in solute conc. and tonicity is the movement of solute which also brings movement of water

E.g. urea moves into RBC, and

38
Q

What causes change of shape in carrier protein

A

Hydrolyses of ATP, Phosphate group binds to carrier protein causing ‘flipping’ mechanism

39
Q

Secondary Active Transport

A

Uses energy from one solute moving down its conc. grad, and in return the energy given off from this is used to transport another diff. solute AGAINST its conc. gradient

40
Q

Antiporter (secondary)

A

Is a co-transporter

Transporting 2 different molecules across CM in opposite directions

41
Q

Symporter (secondary)

A

Co-transporter

Transport 2 different molecules across CM in SAME direction

42
Q

Pump-leak hypothesis

A

Na+ continuously leaking out & K+ in

Pump works continuously

43
Q

Tight Junctions

- act as…

A

Separate epithelial cells by lateral intercellular space

Barrier- restrict movement of substances through intercellular space between cells

Fence- prevent membrane proteins from diffusing in plane of lipid bilayer

Held together by luminal edges of tight junctions

44
Q

Apical membrane

A

Luminal/Mucosal

Faces lumen of organ or body cavity

45
Q

Basolateral membrane

A

Adheres to adjacent membrane and interfaces with blood

46
Q

Paracellular Transport

A

Transport across epithelium by passing through intercellular space

47
Q

Transcellular Transport

A

Substances travels through cell passing apical and basolateral membrame

create ion/conc. gradients that can drive paracellular

48
Q

2 types of transcellular transport

A

Absorption: lumen to blood

Secretion: blood to lumen

49
Q

Changes in tight junction resistance

A

Proximal –> Distal direction in GI and kidney

50
Q

Patch clamp technique

A

Seal off one ion channel, can monitor particular channel, see how it changes shape

51
Q

What do current fluctuations represent

A

Opening and closing of single ion channels

Conformational change in channel structure associated with channel gating

52
Q

Carrier mediated transport exhibit..

A

Specificity
Inhibition
Competition
Saturation (max. transport)

53
Q

Facilitated diffusion of glucose

A

Glucose binds to GLUT

Transporter protein changes shape. Glucose moves down conc. grad

Kinase enzymes reduce glucose conc. inside cell by converting glucose into glucose-6-phosphate

54
Q

What does the conversion of glucose do for cell

A

Maintains conc. gradient for glucose entry

55
Q

Paracellular tight junctions

A

Higher electrical resistance to ion flow = greater no. of tight junction strands holding cell together

56
Q

Leaky epithelium

A

Paracellular transport dominates

57
Q

Tight epithelium

A

Transcellular transport dominates

58
Q

SGLT

A

Na-gluose Symporter transporter
Secondary AT
Carrier-mediated

59
Q

GLUT

A

facilitative glucose transporter mediates glucose exit acorss basolateral membrae

Passive diffusion

60
Q

Pump-leak hypothesis for glucose absorption

A

Na+ enters cell by SGLT down grad. as more Na+ inside cell

as hypothesis states, Na+ needs to leave and it leaves by Na/K pump in basolateral

61
Q

Pump-leak hypothesis for glucose absorption

A

Na+ enters cell by SGLT down grad. as more Na+ inside cell

as hypothesis states, Na+ needs to leave and it leaves by Na/K pump in basolateral

62
Q

What is the last step in glucose absorption in SI

A

Cl and H2O via paracellular pathway from lumen into blood as Na+ ve draws -ve ion,

63
Q

How does glucose leave cell into blood

A

Travels down conc. grad. (cell) to low conc. (blood) facilitated diffusion through GLUT

64
Q

Oral rehydration therapy

A

Sugar solution containing glucose, increases absorption of Na+, thus Cl- and water

65
Q

Glucose-galactose malabsoprtion syndrome

A

genetic defect in SGLUT mutated, cant take up glucose

Sugar retained in intestine lumen

66
Q

Consequences of GGM syndrome

A

Glucose comes in broken down into, more particles mean higher osmolarity

Osmosis into lumen 
Water chyme (diarrhea)
67
Q

How to treat GGM syndrome?

A

Replace glucose in diet with FRUCTOSE, GLUT5 facilitative transporter

68
Q

Glucose Reabsorption in kidney

A

Glucose reabsorbed by SGLUT in lumen, then facilitative diffusion into blood

69
Q

What happens if SGLUT not functioning fast enough

A

Glucosuria- glucose in urine as it can’t be absorbed fast enough

DIABETES MELLITUS
- insulin activity deficient and blood sugar too high (>200mg/ml)

70
Q

When does glucose appear in urine?

A

When renal threshold reached @ 200 mg/100 ml plasma

Transport maximum of SGLT reached 375mg/min of glucose

71
Q

What form of transport is glucose in kidney

A

Carrier mediated transport- all transporters used up

secondary AT

72
Q

Chloride secretion

A

1) Tight junction divides apical and basolateral membrane
2) Na/K pump sets up ion gradient (primary AT, electrogenic)
3) NaK2CL symporter uses energy of Na gradient to accumulate chloride above electrochemical gradient, so Cl- wants to leave cell now
4) Cl leaves cell by passive diffusion through Chloride ion channel
5) Na exits via basolateral Na-pump and via K+ via channel
6) Lumen now -ve, so Na+ and H2O moves paracellular down conc. grad into lumen

73
Q

Rate limiting step

A

Cl- can’t leave cell unless channel open

Opening of Cl- channel gated

Channel called CFTR

74
Q

CFTR

A

Cystic Fibrosis Transmembrane conductance Regulator

75
Q

Consequence of over stimulation of CFTR and

A

Secretory diarrhea and its dysfunction causes cystic fibrosis

76
Q

How is secretory diarrhea caused and what causes this excessive stimulation

A

Excessive stimulation of secretory cells in crypts of small intestine and colon

Excessive stimulation due to abnormally high conc. of endogenous secretagogues produced by tumours or inflammation

77
Q

Secretagogue

- where do they bind to

A

substance that promotes secretion, NA and ACh

bind to GPCR, which releases a G-protein

G-protein binds to adenylate cyclase, releasing cAMP

cAMP activates Protein Kinase A which sticks a phosphate onto CFTP on apical membrane, staying open

78
Q

Enterotoxin

- what does it do in secretory diarrhea

A

toxin affecting intestines

vibrio cholerae

79
Q

Difference between normal mechanism and mechanism of cholera

A

Instead of G-protein binding to Adenylate cyclase cholera toxin binds irreversibly to Adenylate cyclase

80
Q

How to treat secretory diarrhea

A

Give them glucose/electrolytes

81
Q

What happens to cells of crypts after 5 days

A

The crypts cells move up villus changing from secretion cells to glucose absorption cells @ top of villus

82
Q

Cystic fibrosis

A

Inherited disorder affecting children and young adults

Autosomal Recessive= chromosome 7

1/4 chance

83
Q

Which ethnic group is CF most common

A

Northern Europe

1: 2500 CF
1: 25 carriers

84
Q

Organs affected by cystic fibrosis

A

airways- infection bronchial passages, lung cancer

liver- plug small bile ducts

pancreas- prevent digestive enzymes delivered to bowel

small intestine- thick stool blocks gut

reproductive tract

skin- salty sweat

85
Q

Events in CFTR

A

Secretagogue had to bind, activate cAMP, activate protein kinase A, phosphorylate Regulatory domain

ATP binds to Nucleotide binding domain (NBD)

86
Q

How to shut the CFTR channel

A

Hydrolyse ATP to ADP and P

87
Q

How to permanently close channel

A

Dephosphorylation

88
Q

Lung epithelial cells in CF

A

Defective Cl- channel prevents isotonic fluid secretion

Enhances Na+ absorption to give dry lung surface

89
Q

Clinical treatment of CF

A

Chest percussions improve clearance of infected secretions

Antibiotics

Pancreatic enzyme replacement- pill before eating for digestion 6

90
Q

two stages of sweat

A

Primary isotonic secretion fluid by acinar cells

secondary reabsorption of NaCL but NOT water produces hypotonic solution

91
Q

What is the difference in CF patients producing sweat

A

Epithelial cells in ducts of sweat glands don’t absorb NaCl and thus producing salty sweat

Bio 107 (4 decks)

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