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Biology 107 > Cell Processes > Flashcards

Cell Processes Flashcards

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1
Q

Fluid Mosaic Model

A

50% Proteins and 50% Lipids - lipids form a bilayer where lipids can move freely

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2
Q

Lipid bilayer is permeable to…

A
  • Non-polar uncharged molecules
  • Lipid soluble molecules (steroids)
  • Small uncharged, polar molecules (H2O, urea, CO2, Glycerol)
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3
Q

Lipid bilayer is impermeable to…

A
  • Large, uncharged polar molecules (Glucose, amino acids)

- Ions

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4
Q

What increases the rate of diffusion?

A
  • Greater concentration gradient
  • Higher temperature
  • Increased surface area of the membrane
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5
Q

What decreases the rate of diffusion?

A
  • Larger size of diffusion molecule

- Increased diffusion distance

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6
Q

Pd

A
  • Permeability through the bilayer for water
  • small
  • temperature dependant (lipid fluidity)
  • Mercury insensitive
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7
Q

Pf

A
  • Permeability through aquaporins
  • large
  • temperature independent
  • Mercury sensitive
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8
Q

Isosmotic

A

If 2 solutions have the same osmolarity

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9
Q

Hyposmotic

A

The solution with the lower osmolarity

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10
Q

Hyperosmotic

A

The solution with the higher osmolarity

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11
Q

Isotonic

A

No effect on cell volume

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12
Q

Hypotonic

A

Causes cell swelling and lysis

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13
Q

Hypertonic

A

Causes cell shrinkage (crenation)

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14
Q

Ion Channels Selectivity

A
  • Specific amino acids line the channel and determine selectivity
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15
Q

Carrier proteins exhibit

A
  • Specificity
  • Inhibition
  • Competition
  • Saturation
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16
Q

Primary Active Transport

A
  • Energy is derived from the hydrolysis of ATP
  • E.g. electrogenic Na+/K+ ATPase generates a net current - pump works consistently as there is leakage of Na+ into the cell
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17
Q

Secondary Active Transport

A
  • Uses energy released by a substance diffusing down its concentration gradient (potential energy) to actively transport another substance against its concentration gradient
  • Na+/Ca2+ Antiporter
  • Na+/Glucose Symporter
  • Na+/Amino Acid Symporter
18
Q

Phagocytosis

A

Cell eating

  • Pseudopods forming vesicle around foreign substance and membrane receptor
  • Phagolysosome
19
Q

Pinocytosis

A

Cell Drinking

- Directly ingested through vesicle

20
Q

Receptor Mediated Endocytosis

A
  • Specific substances/ligands
  • Substance binds to receptor protein in cathrin coated pit
  • Substance injected and receptor moves back to surface
21
Q

Tight Junctions

A
  • Claudins and Occludins
22
Q

Paracellular Transport

A
  • Transport via tight junctions
  • In a leaky epithelium paracellular dominates
  • Proximal
23
Q

Transcellular Transport

A
  • Tight epithelium transcellular dominates
  • Distal
  • Secretion or absorption
24
Q

Proximal

A
  • Leaky epithelium
  • Low electrical resistance
  • Low number of tight junction strands
  • Paracellular transport
  • E.g. duodenes, proximal tube
25
Q

Distal

A
  • Tight epithelium
  • High electrical resistance
  • High number of tight junction strands
  • Transcellular transport
  • E.g. coelum
26
Q

Types of epithelium

A
  1. Covering and lining epithelium

2. Glandular Epithelium

27
Q

Glandular Secretion

A
  • Acinar cells create the primary secretions

- Duct cells modify composition of primary secretion by absorbing or secreting molecules

28
Q

Steps to Glucose absorption

A
  1. Tight Junctions divide the cell into apical and basolateral membranes
  2. Na+/K+ Pump sets up ion gradients
  3. Na+/Glucose Symporter uses energy of Na+ gradient to transport glucose into the cell against concentration gradient
  4. Facilitative Glucose Transport mediates glucose exit across the basolateral membrane via passive diffusion
  5. Na+ taken up by symporter exits though the basolateral membrane
  6. This induces paracellular transport of Cl- and H2O
29
Q

Oral Rehydration Therapy

A

The use of Glucose and Na+ (NaCl) to stimulate fluid uptake

  • Given to dehydrated babies suffering from diarrhoea
  • Via steps of glucose absorption
30
Q

Glucose/Galactose Malabsorption Syndrome

A
  • Mutation in Na+/Glucose Symporter SGLT
  • Accumulation of Glucose and Galactose in the lumen of Small Intestine
  • Osmotic imbalance attacking water resulting in severe diarrhoea
  • Facilitative glucose transporter is capable of taking up glucose from the blood
31
Q

Treatment of Glucose/Galactose Malabsorption Syndrome

A
  • Remove Glucose/Galactose from the diet and replace with Fructose
32
Q

Glucose Reabsorption in Kidney (Glycosuria)

A
  • In the kidney glucose in the plasma is filtered and needs to be reabsorbed or it will appear in urine
  • If SGLT has exceeded capacity glucose will appear in urine - renal threshold
  • Cause is diabetes as insulin activity is deficient and cannot stimulate SGLT
33
Q

Steps to Chloride Secretion

A
  1. Tight junctions separate cell into apical and basolateral membranes
  2. Na+/K+ Pump sets up ion gradients
  3. NaKCl2 Symporter uses the energy of the Na+ gradient to actively accumulate Chlorine above its concentration gradient
  4. Cl- leaves the cell at apical membrane through highly regulated ion change (passive)
  5. Na+ exits at the basolateral membrane through the Na+/K+ Pump, K+ exits via channel
  6. Induces paracellular transport of Na+ and H2O
34
Q

Cystic Fibrosis (CF)

A
  • Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)
  • Over stimulation results in secretory diarrhoea, disfunction results in CF
  • Autosomal recessive
35
Q

Sweat formation of CF

A
  • Primary isotonic secretions of fluid by acing cells
  • In normal people there would be a secondary absorption of NaCl to produce a hypotonic solution
  • In case of CF there is not reabsorption producing the salty sweat
  • Apical membrane of duct cells have a low permeability to H2O
36
Q

Clinical Management of CF

A
  • Antibiotics
  • Pancreatic enzyme replacement
  • Attention to nutrition
  • Chest percussions to improve clearance of infected secretions
37
Q

Defect in Cl- Secretion

A
  • In a normal lung there is balance between secretion and absorption to kept the lung surface moist
  • In CF the defection Cl- channels prevent isotonic fluid secretion and enhances Na+ absorption giving a dry lung surface
  • Mucus becomes thick and hard to remove
  • Bacteria proliferate and attract immune cells damaging healthy tissue
  • DNA released from bacteria and lung cells adds to stickiness
  • Airways become plugged
38
Q

CFTR Protein

A
  • CFTR is a Cl channel regulated by protein Kinase A dependant phosphorylation of the R domain and binding of ATP then binding to the Nucleotide Binding Domain
39
Q

Secretory Diarrhoea

A
  • Enterotoxins secreted by bacteria irreversibly activate adenylate cyclase (over production of cAMP) causing a maximum stimulation of CFTR leading to secretion of Cl- and this H2O that overwhelms absorptive capacity of colon
  • Happens with Cholera
  • Keep hydrated and crypt cells in the gut will move past the secretion area in 5 days
40
Q

Transcellular Transport - Secretion

A
  1. Entry and exit steps
    - Entry in the basolateral membrane
    - Exit in the apical membrane
  2. Electrochemical gradient
    - Is the entry/exit step passive or active
    - Typically a Primary Active Transporter setting up ion gradients for the Secondary Active Transporters to use
  3. Electroneutrality
    - The movement of a positive ion will attract a negative ion
    - How can we preserve electroneutrality?
  4. Osmosis
    - Net movement of ions will establish a difference in osmolarity and cause water to move
41
Q

Transcellular Transport - Absorption

A
  1. Entry and exit steps
    - Entry in the apical membrane
    - Exit in the basolateral membrane
  2. Electrochemical gradient
    - Is the entry/exit step passive or active
    - Typically a Primary Active Transporter setting up ion gradients for the Secondary Active Transporters to use
  3. Electroneutrality
    - The movement of a positive ion will attract a negative ion
    - How can we preserve electroneutrality?
  4. Osmosis
    - Net movement of ions will establish a difference in osmolarity and cause water to move

Biology 107 (5 decks)

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