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LS 2 Midterm 1 > Midterm 1: Lec 4 Slides > Flashcards

Midterm 1: Lec 4 Slides Flashcards

1
Q

Importance of membranes (3)

A
  • Permeability barrier that can transport certain molecules
  • Important in cell response to external stimuli
  • Involved in energy transduction
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2
Q

Biological membrane components (and their functions)

A
  • Lipids: provide physical integrity
  • Proteins: carry out specific functions
  • Carbohydrates: recognition sites on cell surface
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3
Q

What influences fluidity of lipid bilayer?

A

Composition and temperature

  • Lower temperature means more rigidity (goes through phase transition from fluid to gel)
  • Phase transition temp. is lower if hydrocarbon chains are short or have double bonds
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4
Q

How does cholesterol orient itself in the bilayers of animal cells?

A

Polar head group close to polar head group of phospholipid; it intercollates

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5
Q

How do water-soluble molecules pass through the bilayer?

A

Presence of specific protein molecules

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6
Q

What does the fluid mosaic model explain?

A

How proteins are incorporated into lipid bilayer; carbs are attached to proteins or phospholipids on outer surface of plasma membrane

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7
Q

Integral proteins - what do they do?

A

Penetrate into lipid bilayer; most are transmembrane proteins

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8
Q

What are transmembrane proteins (type of integral protein)?

A

Contain alpha-helix of nonpolar amino acids extending across membrane’s hydrophobic interior

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9
Q

Where are peripheral proteins found?

A

Outside lipid bilayer on cytoplasmic surface, attached by noncovalent bonds to polar head groups of lipid bilayer or integral membrane proteins

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10
Q

Where are lipid-anchored proteins found?

A

Covalently attached to phospholipid or fatty acid embedded in the bilayer

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11
Q

3 classes of membrane proteins

A

Integral, peripheral, lipid-anchored

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12
Q

Describe cytoskeletal protein network in red blood cells

A

SPECTRIN forms mesh beneath cytoplasmic surface of cell; spectrin attached to membrane junctional complexes by ACTIN and to peripheral protein ANKYRIN, which is attached to anion channel (integral protein)

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13
Q

Roles of membrane proteins (3)

A
  • Transport
  • Receptors for molecular messengers from other cells
  • Form junctions between cells
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14
Q

Where are membrane carbohydrates found?

A

Projecting from the exterior surface of the plasma membrane when attached to proteins or phospholipids within membrane

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15
Q

Most carbohydrates in membranes are bound to ____ forming ______

A

proteins, glycoproteins

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16
Q

What do glycolipids do?

A

Form cell identity markers (e.g., blood group markers)

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17
Q

Types of specific cell junctions in animal cells

A

Tight junctions, desmosomes, gap junctions

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18
Q

Homotypic vs. heterotypic binding

A

Same membrane proteins vs. different membrane types

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19
Q

What do tight junctions prevent?

A

Permeability (fluid cannot get through)

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20
Q

What do desmosomes do?

A

They are structural features joining cells together and don’t prevent molecules slipping between cells

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21
Q

What is the structure of gap junctions and what do they facilitate? Give an example of where they’re important.

A

Form an aqueous pore between two adjacent cells, allowing small molecules like ions to move between them (important in heart, so action potentials can move between cells and cause heart contraction)

22
Q

What do integrins do?

A

Mediate the noncovalent attachment of animal cells to extracellular matrix - integrin attaches to fibronectin

23
Q

What feature do plants have that is similar to gap junctions in animal cells?

A

Plasmodesmata (aqueous pores)

24
Q

What are the four basic mechanisms of movement across membranes?

A
  • Simple diffusion
  • Simple diffusion through an aqueous channel (pore)
  • Facilitated diffusion involving a membrane protein carrier
  • Active transport involving a membrane protein carrier and requiring energy
25
Q

In which forms of transmembrane transport is the movement down the concentration gradient?

A

Everything except active transport (diffusion, diffusion w/ aqueous pore, and facilitated diffusion)

26
Q

What molecules can diffuse across the lipid bilayer?

A

Small nonpolar molecules and gases (O2 and CO2)

27
Q

Which molecules diffuse more rapidly across the lipid bilayer?

A

Those with higher lipid solubility

28
Q

What is osmosis and why is it important?

A

Diffusion of water molecules across a selectively permeable membrane - important for maintaining water balance between cells and surroundings

29
Q

Osmolarity - what is it, and what does it meant to be hypo- or hyperosmotic? And what’s blood plasmas’a osmolarity?

A

Sum of ions and solutes in solution

  • Hypoosmotic: 300 mosmol/L
  • Blood plasma has ~300 mosmol/L
30
Q

What does it mean if a cell is in hypertonic solution?

A

Water will diffuse out and it will shrink (outside solution has higher concentration of solute than cell and therefore less water, so water moves out of cell)

31
Q

What does it mean if a cell is in hypotonic solution?

A

Water will diffuse into cell and it will inflate and either burst (animal cell) or be turgid (plant cell) (outside solution has lower solute concentration than cell and therefore more water, so water moves into cell)

32
Q

How do ions like Na+ move across membranes?

A

They pass through water-filled pores created by intrinsic membrane proteins (channels)

33
Q

What are gated channel proteins?

A

They don’t stay open for extended periods of time; stimulus molecule binds to them to open them

34
Q

What does aquaporin do to cells?

A

Increases membrane permeability to water

35
Q

How does facilitated diffusion work? Is energy needed?

A

Molecules (e.g., glucose) bind to carrier proteins in membrane to be transported across - this is passive, as net movement is direction of lowest concentration

36
Q

What is specific facilitated diffusion?

A

A particular carrier protein transports only certain molecules

37
Q

What does it mean if the facilitated diffusion carriers are saturated?

A

All protein carriers are in use, as there are only a fixed amount of carriers in the present cells

38
Q

What is active transport?

A

Transport across a membrane by a carrier-mediated process against the concentration gradient (going uphill); requires chemical energy

39
Q

What is primary active transport?

A

Requires direct participation of ATP

40
Q

What is secondary active transport?

A

Doesn’t directly use At is TP; instead uses energy in ion gradient established by primary active transport

41
Q

What is a uniporter protein?

A

Moves a single substance in one direction

42
Q

What is a symporter protein?

A

Moves two substances in the same direction

43
Q

What is an antiporter protein?

A

Moves two substances in opposite directions (one into cell/organlle, and one out)

44
Q

What is a coupled transporter?

A

Moves two substances at once (symporter and antiporter)

45
Q

What does endocytosis do and how does it work?

A

Transports macromolecules, large particles and small cells into eukaryotic cells - plasma membrane envelops materials and forms vesicle inside cell

46
Q

What are the 3 types of endocytosis?

A

Phagocytosis, pinocytosis, and receptor-mediated

47
Q

What is phagocytosis?

A

Large particles/cells are engulfed

48
Q

What is pinocytosis?

A

Small dissolved solutes or fluids enter cell

49
Q

What is receptor-mediated endocytosis?

A

Specific membrane receptor binds to particular macromolecules at sites called coated pits (which contain clathrin)

50
Q

What is exocytosis?

A

Materials vesicles are secreted from the cell when vesicles fuse with the plasma membrane

LS 2 Midterm 1 (7 decks)

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