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Foundation Unit 1 > Lectures 1.1-1.3 > Flashcards

Lectures 1.1-1.3 Flashcards

1
Q

What are the basic functions and components of biological membranes

A
  • is a permeable barrier that allows nutrients to pass through
  • serves as a barrier between the cell and external environment
  • allows selective transport in and out of cell
  • allows interactions with other cells (through cell signaling and cell-cell contacts)
  • allows interactions with the external environment
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2
Q

What is the structure of Phospholipids?

A

amphipathic molecules that have a hydophilic polar head and hydrophobic hydrocarbon tails (usually fatty acids)

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3
Q

How do Phospholipids form bilayers?

A

form spontaneously due to the hydrophobic effect. hydrophilic head groups are exposed to the aqueous environment while the hydrophobic tail groups face each other and form a weak bond that attaches the leaflets to each other.

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4
Q

Structure of cholesterol?

A

rigid ring structure, a single polar hydroxyl group, and a short hydrocarbon tail.

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5
Q

how does cholesterol contribute to membrane fluidity?

A

intercalates between phospholipids and helps maintain the structural integrity of the membrane. (ie maintains the correct fluidity of membrane).

Decreases permeability of bilayer to small water soluble molecules

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6
Q

glycolipid

A

sphingolipids that are attached to sugar moieties

  • can partition in specialized microdomains of the membrane
  • protects membrane
  • facilitates in cell-recognition processes
  • is entry point for bacterial toxins and other human pathogens
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7
Q

What are the different types of membrane proteins? and what are their roles?

A
  • integral and Peripheral (and Glycocalyx)
  • transport ions and polar molecules
  • bind peptide and polypeptide hormones
  • signal transduction across membrane
  • is apart of the structural stability of bilayer
  • gives cell its distinct functional properties
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8
Q

glycoproteins

A

most cell-surface membrane proteins are glycosylated (i.e. the carbohydrate is attached to a hydroxyl or other functional group of another molecule)

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9
Q

glycocalyx

A

the glycoproteins and glycolipids form a carbohydrate rich layer at the plasma membrane.

  • protects against mechanical and chemical damage
  • facilitates cell-cell recognition and interactions
  • binds antigens and enzymes to cell surface
  • aids in the attachment of cells to extracellular matrix components
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10
Q

membrane domain

A

two broad domains: apical and basolateral

  • the composition is not uniform around the cell
  • each different domain has a specific function/job
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11
Q

microdomain

A

small “patches” of membrane with distinct phospholipid composition found on the cell surface

  • can be called lipid rafts
  • enriched in sphingolipids and cholesterol
  • used to localize proteins that must work together
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12
Q

lipid bilayer asymmetry (how it is established and maintained)

A
  • each leaflet has distinct lipid composition
  • allows the two sides of the membrane to be functionally distinct
  • established by specific translocating enzymes within the endoplasmic reticulum and the plasma membrane
  • maintained by these enzymes (flippases, floppases, scramblases)
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13
Q

why is membrane fluidity important?

A

proteins and lipids of biological membranes diffuse laterally within the membrane

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14
Q

How do lipids affect membrane fluidity?

A

more saturated fatty acids = less fluid

more unsaturated fatty acids = more fluid

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15
Q

amphipathic

A

hydrophilic head and hydrophobic tail

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16
Q

fluid mosaic model

A

model of plasma membrane that is made up of many different macromolecules (mosaic) and allows components to move laterally throughout the memberane (fluid)

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17
Q

phosphoglyceride

A

Most abundant phospholipid with a glycerol backbone, a phosphate group, and one of several head groups

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18
Q

sphingolipid

A

lipid found in cell membrane with a sphingoid base

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19
Q

proteoglycan

A

heavily glycosylated protein

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20
Q

integral membrane proteins

A
  • completely span the lipid bilayer

- can span the membrane multiple times

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21
Q

peripheral membrane proteins

A
  • bound to the surface of the membrane
  • can be removed without dissolving the membrane
  • can attach to membrane by ionic interactions or with phosopholipid head group
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22
Q

single pass membrane protein

A

type of integral membrane protein

- passes one time through bilayer

23
Q

multi pass transmembrane proteins

A

type of integral membrane protein

- passes through bilayer multiple times

24
Q

tight junctions

A

separates domains on plasma membrane

- also involved in cell-cell connections

25
Q

flippase

A

enzyme that facilitates in taking molecules from inside the cell to outside the cell

26
Q

net diffusion

A
  • occurs down chemical and electrical gradients

- described by Fick’s Law

27
Q

what is the role of chemical and electrical gradients during diffusion across a biological membrane

A

affect net diffusion as molecules what to move down the gradient in a energetically favorable manner

28
Q

osmosis

A

diffusion of water from a lower solute concentration to a higher solute concentration

29
Q

osmotic pressure

A

hydrostatic pressure produced by a difference in concentration between solutions on the two sides of a surface

30
Q

difference between channels and transporters

A
  • channels form aqueous pores that allow solutes to pass through them passively
  • transporters bind to specific solutes and undergo transformational changes to transfer the solutes. may be passive or active
31
Q

distinction between active and passive transport

A
  • Passive is driven by concentration gradient with electrochemical gradient
  • coupled to a source of metabolic energy to move up the electrochemical gradient
32
Q

uniporter

A

transporter that carries only one type of molecule

33
Q

primary active transport

A

use energy direct metabolic energy

34
Q

secondary active transport

A

metabolic energy is indirect. ATP creates an ion gradient and as one solute is moved down the gradient, this provides energy for another molecule to move up the gradient

  • transport is coupled
35
Q

types of pump proteins

A

use energy derived from the hydrolysis of ATP to transport molecules across the membrane

36
Q

mechanism of Na-K ATPase

A

pump that transports sodium and potassium against their electrochemical gradients

3 Na+ out of cell
2 K+ in to cell

37
Q

cotransport

A

couple the uphill transport of one solute across the membrane to the downhill transport of another

38
Q

distinction between symporters and antiporters

A

symport = solute moves in the same direction across the membrane

antiport = solute moves in the opposite direction across the membrane

39
Q

how are ion gradients established across cell membranes

A

by active transporters (Na+ -K+ -ATPase)

40
Q

why is Na+ gradient a good source of potential energy

A

Na+ is highly concentrated outside of the cell thus, it is energetically favorable to move down the electrochemical gradient in to the cell

41
Q

ABC transporter

A
  • transmembrane proteins that function in the transport of a wide variety of subtrates across the membrane
  • ATP-binding “cassettes” help pump small molecules
  • exports substance from the cytosol to extracellular space or to a membrane bound intracellular compartment (i.e. endoplasmic reticulum)
  • critical for many diseases and drug resistance
42
Q

ion channel selectivity and gating

A

selective of the molecules it transports and uses different gating mechanisms to open/close

43
Q

how does a semipermeable plasma membrane lead to a membrane potential?

A

as one ion moves across the semipermeable membrane, a gradient will start to form thus leading to a membrane potential

44
Q

osmolarity

A

number of osmoles / liter of solution

45
Q

isotonic

A

when two solutions have the same osmotic pressure across the semipermeable membrane

46
Q

hypotonic

A

concentration of solutes is greater inside the cell than outside of it

47
Q

hypertonic

A

concentration of solutes is greater outside the cell than inside of it

48
Q

voltage-gated

A

ion channels that are activated by changes in the electrical membrane potential near the channel. Membrane potential alters the conformation of the channel protein

49
Q

ligand-gated

A

ion channels that open when a chemical messanger (ie ligand) binds to them

50
Q

mechanically gated

A

ion channel that opens when physical force acts on the membrane

51
Q

sodium-potassium ATPase

A

enzyme found in the plasma membrane of cells that pumps sodium out of the cell while pumping potassium into the cell

52
Q

MDR protein

A

(Multi drug resistance) over expression of MDR can make cells resistant to a variety of chemically unrelated cytotoxic drugs and make cells resistant to anticancer drugs

53
Q

diffusion potential

A

potential difference generated across a membrane bc of a concentration difference of an ion (can only be generated if the membrane is permeable to the ion)

54
Q

equilibrium potential

A

the membrane potential where he net flow through any open channels is 0

Foundation Unit 1 (6 decks)

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