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Science For Medicine > Forces Acting Across Membranes > Flashcards

Forces Acting Across Membranes Flashcards

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Biology 101 flashcards
1
Q

What does the cell membrane do?

A

Separates ECF and ICf and is responsible for maintaining the differnce in composition

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2
Q

What makes up the extracellular fluid?

A

Interstitial fluid and plasma

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3
Q

What does not penetrate the cell membrane but passes freely across the capillary wall (so exchanges readily between plasma and ISF)?

A

Ions

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4
Q

Where is [K+] high?

A

ICF

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5
Q

Where is [K+] low?

A

ECF

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6
Q

Where is [Na+] low?

A

ICF

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7
Q

Where is [Na+] high?

A

ECF

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8
Q

Where is there a high concentration of large anions and proteins?

A

ICF

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9
Q

What is important about the permeability of the cell membrane?

A

Permeability can vary at different times which is important for different cell functions

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10
Q

What is embedded in the cell membrane?

A

Receptors for chemical signals e.g. Hormones and neurotransmitters which regulate cellular activity

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11
Q

What does it mean by saying a membrane is dynamic?

A

They are continually being formed and maintained or dismantled and metabolism depending on the needs of the cell

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12
Q

What is the structure of the cell membrane?

A

Phospholipids with hydrophilic (lipophobic) phosphate head and a hydrophobic (lipophilic) fatty acid tail, embedded with proteins

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13
Q

What are membranes insulators against?

A

Insulators against movement of electrical charge - prevents the passage of electrons

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14
Q

What are the four general classe of membrane proteins?

A
  1. Receptors
  2. Transporters
  3. Enzymes
  4. Peripheral proteins
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15
Q

What are the three membrane protein classes that make up the Integral Membrane Proteins (IMP)?

A

Receptors, transporters and enzymes

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16
Q

What membrane protein class is not incorporated into the membrane itself?

A

Peripheral proteins

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17
Q

What do membrane receptors do?

A

Allows communication of an extracellular signal to the intracellular space to create a cellular response

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18
Q

What do membrane transporters do?

A

Proteins which allow movement of ions or molecules across the membrane

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19
Q

What are the two types of transporter membranes?

A

Carrier and channels

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20
Q

What do carrier proteins do?

A

Open to ECF, then ICF, but never at same time; move larger molecules than channels

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21
Q

What do channel proteins do?

A

Create a pore through the membrane through which molecules flow - can be open or gated

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22
Q

What do membrane enzymes do?

A

Membrane enzymes catalyse chemical reactions on the cell membrane

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23
Q

What are the three main roles of peripheral membrane proteins?

A
  1. Maintain structure of cells by anchoring membrane to intracellular cytoskeleton
  2. Attach cells to the extracellular matrix
  3. Perform signalling functions within cells
24
Q

What is the typical protein content of plasma membranes?

A

50%

25
Q

What is the typical protein content of membranes involved in energy transduction?

A

75%

26
Q

What are examples of membrane carbohydrates?

A

Glycoproteins and glycolipids

27
Q

What do membrane carbohydrates have an important role in?

A

Self vs non-self recognisition by the immune system

28
Q

What causes the concentration gradient across the cell membrane?

A

Ions which are charged particles

29
Q

What drives the direction of passive movement?

A

Electrochemical gradient

30
Q

What are some mechanisms of movement across the cell membrane?

A

Endocytosis and exocytosis, diffusion, mediated transport, osmosis and filtration

31
Q

What happens during endocytosis?

A

Invagination of the membrane to form a vesicle which eventually separates on the cytoplasmic surface of the membrane and migrates within the cell to its destination

32
Q

What is diffusion?

A

Process by which gas/substance in solution expands to fill all available volume; from high conc to low conc

33
Q

What is the permeability coefficient?

A

The ease with which a molecule can pass through a given membrane

34
Q

What are cell membranes inpermeable to?

A

Intracellular proteins and organic anions

35
Q

What three qualities do molecules need to have to pass through the lipid bilayer?

A
  1. Small
  2. Lipophilic (hydrophobic)
  3. UNCHARGED
36
Q

What is THE most important quality for a molecule to have to pass easily through the lipid bilayer?

A

Uncharged

37
Q

How do mineral ions diffuse through channels?

A

Transmembrane IMPs that act as an aqueous route through the membrane for diffusion of ions

38
Q

What kind of channel does H2O pass through?

A

Aquaporins

39
Q

What do ions use to cross membranes at a faster rate than predicted by their lipid permeability?

A

Channels or mediated transport proteins

40
Q

What are channels made up of?

A

Individual protein subunits

41
Q

How does a gated channel work?

A

Remains closed until a stimulus (chemical or change in electrical charge) causes them to open

42
Q

How do voltage gated channels work?

A

Open/close in response to alterations in membrane electrical potential (muscle/nerve cells)

43
Q

How do ligand gated channels work?

A

Open/close when they bind a chemical (neurotransmitter/hormone) to a receptor binding site on the channel protein

44
Q

What is facilitated diffusion?

A

Movement of molecules through transport proteins down their electrochemical gradients

45
Q

What is active transport?

A

Movement of molecules through transport protiens AGAINST their electrochemical gradients requiring ATP

46
Q

What is an example of an active transporter?

A

Na+/K+ pump

47
Q

What doe s Na+/K+ATPase do?

A

Helps maintain this difference by continually pumping out 3 Na+ ions and pumping in 2 K+ ions for each molecule of ATP hydrolysed

48
Q

What is the electrogenic pump?

A

A net movement of positive charge out of the cell to create a charge difference across the membrane - as in the Na+/K+ pump

49
Q

How much of the body’s resting energy is used by Na+/K+ATPase?

A

40%

50
Q

What is osmosis?

A

Net movement of H2O from high H2O region to low H2O region

51
Q

How is the H2O concentration related to the solute concentration?

A

Inversely proportional (the more solute particles, the more they will displace H2O molecules, lowing H2O conc)

52
Q

What happens if a solution of different conc is separated by a membrane permeable to H2O only?

A

After time will end up with: equal concentration either side of membrane but different volumes

53
Q

What is the osmotic pressure?

A

The pressure required to oppose an increase in volume/to prevent water movement

54
Q

What does a mole consist of?

A

6.02x10^23 molecules

55
Q

What determines the osmotic effect on [H2O]?

A

Number of solute particles

56
Q

What is the normal osmolarity of human plasma?

A

285 mOsmol/l

Science For Medicine (7 decks)

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