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Biology > BIOSCI 107 Cell Processes Short Answers > Flashcards

BIOSCI 107 Cell Processes Short Answers Flashcards

1
Q

What is the Basic Membrane Structure?

A

A thin, 8nm flexible and sturdy barrier surrounding the cytoplasm of a cell.

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2
Q

What are the 4 Characteristics of the Fluid Mosaic Model?

A

Sea of lipids with proteins floating like icebergs, membrane 50% lipid, 50% protein, barrier to entry or exit of polar substances, proteins regulate traffic.

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3
Q

Where are Cholesterol and Glycolipids?

A

Scattered among a double row of phospholipid molecules.

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4
Q

What does Amphipathic Mean? Give an Example.

A

Has both a polar and non-polar region - phospholipid molecules.

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5
Q

Which 3 Factors Determine Fluidity?

A

Lipid tail length (longer = less fluid), number of double bonds (more = increased fluidity), amount of cholesterol (more = less fluid).

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6
Q

What are Integral Proteins?

A

Extend into or completely across cell membrane.

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7
Q

What are Peripheral Proteins?

A

Attached to inner or outer surface of cell membrane (easily removed).

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8
Q

What do the Hydrophilic Ends of Proteins do?

A

Interact with the aqueous solution.

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9
Q

What are the 3 Characteristics of Integral Membrane Proteins?

A

Amphipathic, have hydrophobic regions, have regions of non polar amino acids coiled into helices.

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10
Q

What are the 6 Functions of Membrane Proteins?

A

Receptors, cell identity markers, linkers, enzymes, ion channels, transporter proteins.

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11
Q

What is Selective Permeability?

A

The membrane allows some substances to cross but excludes others.

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12
Q

What is the Lipid Bilayer Permeable to?

A

Non-polar molecules, lipid soluble molecules, small uncharged polar molecules.

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13
Q

What are some Examples of a Non-Polar, Uncharged Molecule?

A

O2, N2 benzene.

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14
Q

What are some Examples of a Lipid Soluble Molecule?

A

Steroids, fatty acids, some vitamins.

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15
Q

What are some Examples of a Small Uncharged Polar Molecule?

A

Water, Urea, Glycerol, CO2.

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16
Q

What are some Examples of a Large Uncharged Polar Molecule?

A

Glucose, amino acids.

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17
Q

What is the Lipid Bilayer Impermeable to?

A

Large uncharged polar molecules, ions.

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18
Q

How does Temperature Affect Rate of Diffusion?

A

Higher temp = Faster diffusion.

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19
Q

How does the Molecule Size Affect Diffusion Rate?

A

Larger = slower.

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20
Q

How does Diffusion Distance Affect Diffusion Rate?

A

Increased distance = slower rate of diffusion.

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21
Q

How can a Cell Increase Diffusion?

A

Increase membrane area available for exchange.

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22
Q

How do Molecules Interact with Concentration Gradients?

A

Non charged molecules will diffuse down their concentration gradients.

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23
Q

How do Molecules Interact with Electrical Gradients?

A

Ions will be influenced by membrane potential in addition to their concentration gradient.

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24
Q

What is Movement of Ions influenced by?

A

Electrochemical gradient.

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25
Q

What does the Selectivity Membrane enable?

A

A difference in concentration or gradient across the membrane to be established.

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26
Q

How do Cells Establish an Electrical Gradient?

A

Difference in charged ions between the membrane.

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27
Q

What is Osmosis?

A

Net movement of water through a selectively permeable membrane from an area of lower water concentration.

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28
Q

What is Osmotic Pressure?

A

The pressure applied by a solution to prevent the inward flow of water across a semi-permeable membrane.

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29
Q

What are the 3 Properties of a Water Permeable Membrane - Lipid Bilayer?

A

Small, mercury insensitive, temp dependent.

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30
Q

What are the 3 Properties of a Water Permeable Membrane - Channel?

A

Large, mercury sensitive, temp independent.

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31
Q

What is Pf is Mediated by?

A

The aquaporins (9 isoforms).

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32
Q

What is Non-Mediated Transport?

A

Does not directly used a transport protein.

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33
Q

What is Mediated Transport?

A

Moves materials with the help of a transport protein.

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34
Q

What is Passive Transport?

A

Moves substances down their concentration gradient with only their kinetic energy.

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35
Q

What is Active Transport?

A

Uses energy to drive substances against their concentration or electrochemical gradients.

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36
Q

What is Vesicular Transport?

A

Move materials across membranes in small vesicles either by exocytosis or endocytosis.

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37
Q

What is Non-Mediated Transport Important for?

A

Absorption of nutrients, excretion of wastes.

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38
Q

Which Molecules undergo Non-Mediated Transport?

A

Nonpolar, hydrophobic molecules - oxygen, co2, nitrogen, fatty acids, steroids, small alcohols.

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39
Q

What do Ion Channels Form?

A

A water filled pore that shields the ions from the hydrophobic core of the lipid bilayer.

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40
Q

Why is Ion Transport Rapid?

A

Ions do not bind to channel pore.

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41
Q

What is the Advantage of Ionic Selectivity?

A

Be being selective to a particular ion the channel can harness the energy stored in the different ion gradients.

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42
Q

What is Gating?

A

Channels contain gates that control opening and closing of the pore.

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43
Q

What are some Gate Stimuli?

A

Voltage, ligand binding, cell volume, pH, phosphorylation.

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44
Q

How is an Electrical Current Generated in Ion Channels?

A

The diffusion of over 1 million ions per second through a channel.

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45
Q

What do Fluctuations of Current in Ion Channels mean?

A

The opening and closing of single ion channels.

46
Q

What is Carrier Mediated Transport?

A

The substrate to be transported directly interacts with the transport protein.

47
Q

Which 4 Properties do Transport Proteins Exhibit?

A

Specificity, inhibition, competition, saturation.

48
Q

What is the Function of Transport Proteins?

A

Mediate transport across the cell membrane at a faster than normal rate.

49
Q

What do Transporter Proteins Display?

A

Enzyme kinetics.

50
Q

When does Glucose Transport Occur?

A

Until all binding sites are saturated.

51
Q

What is Active Transport?

A

An energy requiring process that moves molecules and ions against their concentration or electrochemical gradients.

52
Q

What are the Two Forms of Active Transport?

A

Primary and secondary.

53
Q

What is Primary Active Transport?

A

Energy is directly derived from the hydrolysis of ATP.

54
Q

What is Secondary Active Transport?

A

Energy stored in an ionic concentration gradient is used to drive the active transport of a molecule against its gradient.

55
Q

What happens during Na/KTPase?

A

3 Na ions removed from cell as 2K brought into cell.

56
Q

What is the Function of the Na Pump?

A

Maintains a low concentration of Na and a high concentration of K in the cytosol.

57
Q

What are the 6 Reasons Difference in Ion Concentration are Important?

A

MECMUM: Maintain membrane potential, Electrical excitability, Contraction of muscle, Maintenance of cell volume, Uptake of nutrients, Maintenance of pH.

58
Q

What is the Pump-Leak Hypothesis?

A

Na and K are continually leaking back into the cell down their respective gradients, so the pump works continuously.

59
Q

What Energy does Secondary Active Transport use?

A

Uses energy stored in ion gradients created by primary active transporters to move other substances against the gradient.

60
Q

What is an Example of Na Antiporter or Exchangers?

A

Na ions rush inward, Ca or H pushed out.

61
Q

What is an Example of Na Symporters or Cotransporters?

A

Glucose or amino acids rush inward together with Na ions.

62
Q

What are the 4 Basic Characteristics of Epithelial Tissue?

A

Cells arranged in continuous sheets in single/multiple layers, cells sit on basement membrane, boundary between organs and external environment, subject to physical breakdown and injury.

63
Q

What is the Function of Tight Junctions?

A

Hold epithelial cells together at their luminal edges.

64
Q

What are Tight Junctions Composed of?

A

Thin bands that encircle the cell, making contact with thin bands from adjacent cells.

65
Q

How do Tight Junctions appear in EM and Freeze Fractures?

A

EM: Membranes are fused

Freeze fracture: Interlocking network of ridges in plasma membrane.

66
Q

What are the 2 Major Functions of Tight Junctions?

A

A barrier and a fence - separating epithelial cells into two distinct membrane domains.

67
Q

What is Apical Membrane?

A

Faces the lumen of the organ or body cavity.

68
Q

What is the Basolateral Membrane?

A

Adheres to the adjacent basement membrane and interfaces with the blood.

69
Q

How is Epithelial Tissue Functionally Classified?

A

Leaky epithelium - Paracellular transport dominates

Tight epithelium - Transcellular transport dominates

70
Q

What are the 4 Characteristics of Proximal Tight Junctions?

A

Leaky epithelium, low electrical resistance, low number of strands, bulk transport.

71
Q

What are the 4 Characteristics of Distal Tight Junctions?

A

Tight epithelium, high electrical resistance, high number of strands, hormonally controlled.

72
Q

What is Absorption?

A

Transport from lumen to blood.

73
Q

What is Secretion?

A

Transport from blood to lumen.

74
Q

What are the 4 Rules of Trans-epithelial Transport about?

A

Entry and exit steps, electrochemical gradient, electroneutrality, osmosis.

75
Q

What are Entry and Exit Steps for Trans-epithelial Transport?

A

The entry step for absorption is the apical but for secretion is the basolateral membrane.

76
Q

What is the Electrochemical Gradient?

A

The entry or exit step; passive or active.

77
Q

What is Electroneutrality?

A

Movement of a positive or negative ion will attract a counter ion.

78
Q

How do Epithelial Cells Mediate Secretion and Absorption?

A

Using different collections of transporters and channels.

79
Q

What is Exploited in Oral Rehydration Therapy?

A

The ability of glucose to enhance the absorption of Na and hence Cl and water.

80
Q

What happens as a result of Glucose-Galactose Malabsorption Syndrome?

A

A mutation to the glucose symporter in the small intestine leads to sugar retention in the intestine lumen, increase in lumen osmolarity induces water efflux, increased water flow causes diarrhea.

81
Q

What is the Treatment for Glucose-Galactose Malabsorption?

A

Remove glucose and galactose from diet, use fructose as a carb source (GLUT5).

82
Q

Why is Glucose in the Kidney Filtered?

A

It must be filtered and reabsorbed or it will appear in urine.

83
Q

What is Glucosuria?

A

Glucose in the urine.

84
Q

What is the Renal Threshold?

A

Once the renal threshold is reached, glucose appears in urine.

85
Q

What is the Rate Limiting Step?

A

Cl can’t leave unless channel is open (gated) - this channel opening is the rate limiting step.

86
Q

What causes Secretory Diarrhoea?

A

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

87
Q

What effect do Enterotoxins have on the Colon?

A

Enterotoxins irreversibly activate adenylate cyclase causing a maximal stimulation of CFTR - leading to a secretion that overwhelms the absorptive capacity of the colon.

88
Q

What cause Excessive Stimulation of the Colon?

A

Abnormally high concentrations of endogenous secretagogues produced by tumours or inflammation. Also Enterotoxins.

89
Q

How can Secretory Diarrhoea be Treated?

A

Oral rehydration therapy.

90
Q

How is Cystic Fibrosis Inherited?

A

In an autosomal recessive fashion - heterozygotes are carriers but show no symptoms.

91
Q

How can Cystic Fibrosis affect Airways?

A

Clogging and impaired breathing.

92
Q

How can Cystic Fibrosis affect the Liver?

A

Plugging of bile ducts impedes digestion.

93
Q

How can Cystic Fibrosis affect the Pancreas?

A

Occlusion of ducts preventing delivery of critical enzymes to the bowel.

94
Q

How can Cystic Fibrosis affect the Small Intestine?

A

Obstruction of the gut.

95
Q

How can Cystic Fibrosis affect the Reproductive Tract?

A

Absence of fine ducts leads to infertility in males.

96
Q

How can Cystic Fibrosis affect Skin?

A

Sweat gland malfunction (more salt in sweat).

97
Q

What are the 4 Treatments for Cystic Fibrosis?

A

Chest percussion, antibiotics, pancreatic enzyme replacement, attention to nutritional status.

98
Q

What is CFTR?

A

A Cl channel regulated by protein kinase A dependent phosphorylation of the R domain and binding of ATP to the NBD.

99
Q

How do Normal Lung Epithelial Cells Behave?

A

Balance between secretion and absorption keeps lung surface most but prevents fluid build up.

100
Q

How do Cystic Fibrosis Epithelial Cells Behave?

A

Defective Cl- channel prevents isotonic fluid secretion and enhances Na+ absorption to give
a dry lung surface.

101
Q

What causes the Salty Sweat of CF Patients?

A

The failure of epithelial cells in the ducts of sweat glands to reabsorb NaCl.

102
Q

What is the Two Stage Process of Sweat Formation?

A

A primary isotonic secretion of fluid by acinar cells, then a secondary reabsorption of NaCl to produce a hypotonic solution.

103
Q

What is an Isosmotic Solution?

A

If the solution has the same osmolarity.

104
Q

What is a Hyposmotic Solution?

A

If the solution has a lower osmolarity.

105
Q

What is a Hyperosmotic Solution?

A

If the solution has a higher osmolarity.

106
Q

Why does the Osmolarity of Extracellular and Intracellular Fluids have to be Equal?

A

So that no net water flow (osmosis) occurs, leading to a change in cell volume.

107
Q

What is Tonicity?

A

The effect a solution has on cell volume.

108
Q

Which Factor determines Tonicity?

A

The membrane permeability of the solute.

109
Q

What is Lysis?

A

Cell swelling/explosion.

110
Q

What is Crenation?

A

Cell shrinkage.

Biology (15 decks)

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