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My bio: Core principles > Cell membranes > Flashcards

Cell membranes Flashcards

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1
Q

Roles of plasma membranes

A

Separates cell contents from outside environment
Regulates transport on nutrients in and out: selectively permeable
Recognition by antigens
Receptor sites

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2
Q

Function of internal membranes

A

Separate cell components from cytoplasm
Hold components of metabolic pathways in place e.g ribosomes on RER
Location of chemical reactions e.g respiration on cristae of mitochondria

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3
Q

Who proposed fluid mosaic model of plasma membranes

A

Singer and Nicholson, 1972

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4
Q

Why ‘fluid’ in fluid mosaic?

A

Phospholipid molecules move around each other

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5
Q

why ‘mosaic’ in fluid mosaic?

A

Proteins embedded between phospholipids vary in shape, size and pattern

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6
Q

What type of molecules does the phospholipid bolster allow to enter?

A

lipid- soluble molecules

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7
Q

What is phospholipid bilayer a barrier to?

A

Large polar molecules
Water soluble molecules
Ions

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8
Q

What is phospholipid bilayer freely permeable to?

A

Lipid soluble substances
Non polar molecules
Very small polar molecules e.g H2O, CO2, O2

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9
Q

What can vary permeability of membranes

A

Increase in temp, increase in Ek, vibrate faster. Membrane becomes more fluid so more permeable

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10
Q

Components of plasma membrane

A

Phospholipid bilayer
Proteins
Cholesterol
Glyco proteins/lipids

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11
Q

Distance across phospholipid bilayer

A

7nm

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12
Q

Proteins found in membrane?

A

Intrinsic and extrinsic

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13
Q

Intrinsic proteins?

A

Proteins that extend across bilayer

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14
Q

Function and types of intrinsic proteins

A

Provide structural support
Some are carrier proteins, some are channel proteins

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15
Q

Carrier proteins?

A

Move large polar molecules or water soluble substances e.g sugars and amino acids across bilayer by changing shape when the particular molecule attaches to the binding site

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16
Q

Channel proteins structure?

A

3d globular protein with hydrophilic R groups facing inwards to line the pore

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17
Q

Channel protein function?

A

Water filled, allowing water soluble molecules to pass through. Specific, bc of specific protein shape so each protein only allows specific molecules or ions through. Channel can be gated to ppen/close in specific circumstances

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18
Q

Extrinsic proteins

A

Either side of bilayer

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19
Q

cholesterol location?

A

Fits between fatty acids

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20
Q

Cholesterol function

A

Provide stability and rigidity bc they are between fatty acids

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21
Q

What is the glycocalyx?

A

Carbohydrate layer around membrane: glycoproteins and lipoproteins

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22
Q

Function of glycocalyx

A

Cell to cell communication, recognition and hormone reception

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23
Q

Concentration gradient?

A

Difference in concentration of a substance between two regions

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24
Q

Diffusion?

A

Passive movement of molecules from a region oc hight concentration to low concentration down a concentration gradient

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25
Q

For molecules to move freely they must have?

A

Ek

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26
Q

7 factors affecting diffusion across bilayer?

A

Temp, SA, conc gradient, thickness of membrane, diffusion distance, size of molecule, lipid solubility

27
Q

Equation for rate of diffusion

A

(surface area x difference in conc)÷ length of diffusion path

28
Q

Facilitated diffusion

A

Diffusion through the bilayer requiring carrier or channel proteins. Req no ATP, req conc gradient

29
Q

Relationship between rate of diffusion and conc gradient?

A

Directly proportional

30
Q

Active transport?

A

Movement of ions and other molecules across bilayer, can be from low to high conc against conc gradient req ATP. Occurs via carrier proteins

31
Q

Example of active transport

A

sodium-potassium pump

32
Q

what movement of particles do both diffusion and facilitated diffusion involve

A

Random movement

33
Q

Process of active transport?

A

Molecule or ion combines with a specific carrier protein on outside of membrane
ATP transfers a phosphate group to carrier protein on inside of membrane
Carrier protein changes shape and transports the substance
The molecule or ion is released into the cytoplasm
The phosphate ion is released from the carrier protein back to the cytoplasm and combines with the ADP to reform ATP
The carrier protein returns to it’s original shape

34
Q

The effect of respiratory inhibitors on active transport?

A

e.g Cyanide, active transport is reduced or stopped

35
Q

Examples of processes involving active transport

A

Protein synthesis, muscle contraction, absorption of mineral salts by plant roots, absorption of glucose in kidneys

36
Q

Co-transport?

A

Type of facilitated diffusion where 2 substances are transported in the same direction at the same time

37
Q

Example of co-transport?

A

sodium-glucose co-transport into the blood in the plenum and kidney nephron

38
Q

Endocytosis?

A

Bulk movement of substances into the cell using ATP to provide energy to move membranes to form vesicles to contain entering substances

39
Q

Phagocytosis?

A

Process by which cell obtains solid materials too large to enter by diffusion or active transport.

40
Q

Pinocytosis

A

Entry of liquids into the cell by the same mechanism as phagocytosis but the vesicles produced are smaller

41
Q

Exocytosis?

A

Bulk removal of substances from the cell after being transported through the cytoplasm in a vesicle

42
Q

Description of the process of phagocytosis

A

Membrane engulfs material
Membrane fuses back together
Vesicles is formed

43
Q

Invaginate meaning?

A

Like caving inwards: cell membrane of phagocyte invaginates to take in pathogens

44
Q

Describe process of phagocytosis of pathogens

A

Antigens on pathogen bind to receptors on phagocyte
Cell membrane off phagocyte invaginates producing a phagosome vesicle
Lysosome merges membranes with phagosome to become a phagolysosome
Pathogen is digested and contents of phagolysosome are excreted from the cell by exocytosis

45
Q

Osmosis?

A

movement of H2O from area of high water potential to area of low water potential down a water potential gradient across a partially permeable membrane

46
Q

water potential?

A

Tendency for water molecules to enter or leave a solution by osmosis.

47
Q

What is the measure for water potential

A

Kilopascals KPa

48
Q

What represents water potential

A

Greek letter psi (looks like a pitch fork)

49
Q

What is the water potential of pure water

A

0KPa, adding solutes reduces it, making it negative

50
Q

Highest possible water potential?

A

0KPa

51
Q

Hypertonic solution?

A

Lower water potential than the cell cytoplasm so contains more solutes and water moves out of the cell

52
Q

Isotonic solution

A

Same water potential as in the cell cytoplasm so zero net movement or water

53
Q

Hypotonic solutions

A

Higher water potential than cell cytoplasm so contains fewer solutes. Net movement of water is into the cell

54
Q

Process of cells bursting

A

cytolysis

55
Q

Process of animal cells shrivelling

A

crenation

56
Q

Equation describing relationship between forces in plant cell

A

water potential= solute potential+ pressure potential

57
Q

solute potential?

A

concentration of dissolved solute in cell vacuole

58
Q

Pressure potential?

A

Opposing force developed as outwards pressure on the cell wall builds due to entrance of water into the cell cytoplasm and vacuole

59
Q

which is the negative and which is the positive component of water potential equation

A

solute potential is negative, pressure potential is positive

60
Q

Incipient plasmolysis?

A

Cell membrane must begins to move away from the cell wall. Occured sin isotonic solutions

61
Q

Plasmolysis

A

Cell membrane shrinks away from the cell wall. When complete the cell is said to be flaccid

62
Q

functions of extrinsic proteins

A

provide structural support
Cell to cell recognition
Receptor sites for hormone attachment

63
Q

In which conditions do water molecules move more freely

A

Water moves more freely in dilute compared to more concentrated

64
Q

why dies increasing conc of ions increase the rate of uptake by active transport

A

Increases the chance that ion will collide with carrier protein

My bio: Core principles (12 decks)

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