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Biosci107 > Cellular Processes > Flashcards

Cellular Processes Flashcards

1
Q

What is the thickness of the outer cell membrane?

A

8nm

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2
Q

What is the cellular membrane composed of?

A

50% lipid and 50% proteins

  • The lipids are a barrier for polar substance,
  • The proteins are “gatekeepers”
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3
Q

What are the 3 types of molecules that the cell membrane is permeable to?

A
  1. Lipid Soluable
  • Fatty Acids
  • Vitamins
  • Steriods
  1. Non-polar uncharged e.g O2, CO2
  2. Small, polar uncharged molecules e.g. H2O, Urea.
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4
Q

What are the 2 types of molecules that the cell membrane is impermeable to?

A
  1. Charged e.g ions; Ca2+, K+, Cl-, Na+.
  2. Large Polar
  • Glucose
  • Amino Acids

They require transporters

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5
Q

What is the role of Cholesterol in the cell membrane?

A

Act as a buffer for the fluidity of the phospholipis bilayer. As the temp. increases so does the fluidity so cholesterol decreases fluidity to stabilise the membrane and the opposite when the temp gets colder.

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6
Q

What causes changes in fluidity

A
  1. Longer Tails decrease fluidity
  2. Increase in double bonds increase fluidity
  3. Cholesterol decreases fluidity
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7
Q

What are 6 cell membrane proteins?

A
  1. Receptor Proteins
  2. Cell Identity Markers
  3. Linkers
  4. Enzymes
  5. Ion channels
  6. Transporter Proteins
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8
Q

Defintion of diffusion?

A

Net movement of a substance from an area of high conc. to an area of low conc.

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9
Q

What 5 factors affect diffusion?

A
  1. Change in concentration
  2. Change in temperature
  3. Surface area
  4. Distance
  5. Size
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10
Q

What percentage of resting membrane potential energy is used to maintain concentration and electrical gradients

A

30%

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11
Q

What is the definition of osmosis?

A

Net movement of water through a selectively permeable membrane from an area of high water conc. to an area of low water conc.

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12
Q

How many isoforms are there of aquaporins?

A

9

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13
Q

What is the definition of non-mediated transport?

A

There is no direct use of a transport protein

example; Ion channels, these are selectively permeable and can be gated.

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14
Q

What is the definition of mediated transport? What do they exhibit?

A

Moves a material with the help of a transport protein. There are two types passive and active. They behave like enzymes.

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15
Q

What is the definition of passive transport?

A

Moves substances down their conc. or EC gradients with only their kinetic energy.

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16
Q

What is the definition of active transport?

A

Uses energy to drive substances against their conc. or EC gradients.

17
Q

What is the definition of vesicular transport?

A

Moves materials across membranes un small vesicles by exocytosis or endocytosis

18
Q

What are the 3 steps in facilitated diffusion of glucose?

A
  1. Glucose binds to GLUT
  2. Protein changes shape and glucose moves across cell membrane.
  3. Kinase enzyme reduces glucose conc. by converting it into glucose-6-phosphate
19
Q

What is primary active transport?

A

Transport that requires energy to pump ions against their conc. gradient. Primary mean the energy is directly from the hydrolysis of ATP

20
Q

What is secondary active transport?

A

Transport that requires energy to pump ions against their conc. gradient. Secondary means the energy is stored in an ionic conc. gradient e.g. Na+ antiporter uses the Na+ Conc gradient to pull glucose into the cell

21
Q

What is Na/K ATPase?

A

A primary active transporter. 3 Na+ ions are removed from the cell as 2K+ ions are brought in. The pump generates a net current

22
Q

What are the 6 effects the Na pump important for?

A
  1. Maintain resting membrane potential
  2. Electrical excitability
  3. Contraction of muscle
  4. Maintenance of steady state cell volume
  5. Uptake of nutrients my secondary active transporters
  6. Maintenance of intracellular pH by secondary active transporters
23
Q

What are the functions of tight junctions?

A

They form a barrier to separate the apical surface of an epithelial cells from the basolateral surface of an epithelial cell. This prevents movement of substances between cells

24
Q

What is the difference between transcellular and Paracellular transport?

A

Transport can occur both ways; the transcellular transport pathway is through the cell and paracellular transport is between the cells.

25
Q

What is the difference between leaky epithelium and tight epithelium?

A

Leaky epithelium has predominantly paracellular transport where is tight epithelium has predominantly transcellular transport

26
Q

what are the two types of transcellular transport?

A
  1. Absorption: transport from the lumen to the blood
  2. Secretion: transport from blood to lumen
27
Q

What are the four areas of transepithelial transport?

A
  1. Entry and exit steps
  2. Electrochemical gradient
  3. Electroneutrality
  4. Osmosis
28
Q

What are the 5 steps of glucose absorption?

A
  1. Na+ pump Sets up and ion gradient with Na+ exiting out into the blood
  2. The sodium glucose symporter creates a glucose conc. gradient using Na+ to bring glucose into the cell (from lumen)
  3. GLUT transporters take glucose out and into the blood
  4. Na+ then exits into the blood
  5. The Cl- and H2O pass paracellularly into the blood.
29
Q

What is Glucose- galactose malabsorption syndrome?

A

A disease that causes diarrhoea. This is because of a mutation to the glucose symporter in the small intestine. This means that sugar is retained in the intestine lumen. m

Treatment: ORT

30
Q
A

Biosci107 (6 decks)

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