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WBiology > Cell Membrane > Flashcards

Cell Membrane Flashcards

1
Q

Why is the cell membrane model called what it is?

A

Fluid Mosaic Model

- Many parts move

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2
Q

What is the structure of the phospholipids?

A
  • Amphipathic

- Forms micelle when mixed with water

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3
Q

What is the structure of cholesterol?

A
  • Hydrophobic so interior of bilayer

- Inserts itself in spaces

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4
Q

What is the function of cholesterol?

A

Stabilizes the membrane by decreasing fluidity at room temperature

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5
Q

What is the general structure of proteins?

A
  • Unless attached to cytoskeleton, can flip as needed

- Amphipathic because of hydrophobic R groups

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6
Q

What is the specific functions of proteins?

A
  • Transport Proteins: facilitated diffusion, active transport
  • Enzymes: speed up chemical reactions
  • Receptor Sites: bind to substances (ligand) causing an effect
  • Cell Adhesion: hold cells together to form tissues
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7
Q

What is the structure of the integral/transmembrane proteins?

A

Embedded in hydrophillic part of bilayer

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8
Q

What is the structure of peripheral proteins?

A

Penetrate the ends of the membrane

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9
Q

What is the structure of ion channels?

A

Pores

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10
Q

What is the function of ion channels?

A

Transport ions through

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11
Q

What is the function of integral/transmembrane proteins?

A

Transport ions through

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12
Q

What is the structure of the cytoskeleton?

A

Rigid scaffolding that determines shape of cell

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13
Q

What is the function of the cytoskeleton?

A

Anchors proteins in place to maintain cell shape

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14
Q

What is the general function of carbohydrate chains?

A

Acts as cell identity markers

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15
Q

What are glycoproteins/glycolipids?

A

Glycoproteins: Proteins with carbs attached
Glycolipids: Phospholipids with carbs attached

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16
Q

What are the membrane functions?

A
  1. Acts as a boundary by separating the cell from the environment
  2. Controls the movement of substances
  3. Interact with environment
  4. Interact with other cells
  5. Determines shape of cell
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17
Q

What can pass freely? How does selective transport happen?

A
  • Phospholipids only allows small nonpolar molecules (CO2, O2) to pass freely
  • Proteins allow selective transport
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18
Q

What is the definition of selectively permeable membranes?

A

living allows some substances across and not others

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19
Q

What is the definition of semi-permeable membranes?

A

nonliving membranes that prevents substances from passing through

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20
Q

What is the difference between selectively and semi permeable membranes?

A

Living membranes based on cell’s need not size.

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21
Q

What is diffusion?

A

Random movement of particles from area of high concentration to low as particles move down concentration gradient

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22
Q

What is osmosis?

A

Special type of diffusion concerning only water

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23
Q

How does water get in?

A

It is small so can move through gaps in phospholipids as they move by osmosis

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24
Q

What is the description of a hypotonic solution?

A
  • Lower solute concentration than cell
  • Water will diffuse into cell
  • Animal cell will burst
  • Plant cell will become turgid: water in vacuole pushes against cell wall
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25
Q

What is the description of a hypertonic solution?

A
  • Higher solute concentration than cell
  • Water will diffuse out of cell
  • Animal cell will shrink
  • Plant cell will undergo plasmolysis: process when cell membrance pulls away from cell wall)
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26
Q

What is the description of an isotonic solution?

A
  • Same solute concentration as cell
  • Water will diffuse equally in or out
  • No net water movement (equillibrium) so no changes in size
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27
Q

What happens during facilitated diffusion?

A
  • Integral proteins form a channel that allows specific molecules to move from a side where they have a high concentration to low
28
Q

What is facilitated diffusion?

A
  • When molecules that are too big or polar are transported through its own carrier protein
  • Process is highly specific
  • Process is passive as substances move down concentration gradient
29
Q

What is active transport and how does it work?

A
  • Transport substances against concentration gradient
  • Cell must use energy in the form of ATP
  • A carrier protein is needed
  • Process is highly specific
30
Q

What is an example of active transport and why is this example important?

A

Sodium/potassium pump: ensures proper functioning of nerve cells by maintaining certain concentrations (Na out, K inside) to conduct currents

31
Q

How does the sodium/potassium pump work?

A
  • Channel is open to inside
  • 3 Na ions from inside bind to transport protein
  • ATP gives phosphate group energy to bind to transport protein which causes a change in shape
  • Channel is open to outside, Na go away
  • Binding sites for K are created
  • 2 K ions bind to transport, releasing phosphate group
  • Protein reverts to normal shape
32
Q

What is thermodynamics?

A

the study of changes in energy

33
Q

What is energy?

A

ability to do work

34
Q

What are the types of energy and their definitions?

A

Kinetic: energy of motion

Potential: energy due to location or structure

  • Chemical: in chemical bonds
  • Concentration Gradient: particles have potential to move
  • Excited Electron: electrons raised to higher energy levels
35
Q

What is metabolism and what determines it?

A
  • Total reactions in organism

- Thermodynamics determines metabolism as it determines whether reaction will proceed

36
Q

What are metabolic pathways?

A
  • Series of enzyme catalyzed reactions that route substrates (reactants) to endpoints (products)
  • Products of 1 reaction is used immediately as reactants for next one
37
Q

What are the kinds of metabolic pathways?

A
  1. Catabolic Pathway: degative pathway that breaks large molecules into smaller; release energy so G is negative (eg. cellular respiration)
  2. Anabolic Pathway: synthetic pathway that build large molecules from small ones; require energy so G is positive (eg. photosynthesis)
38
Q

What are allosteric enzymes?

A

Regulates direction and rate of substrate flow to where it’s needed

39
Q

What is the first law of thermodynamics?

A
  • Energy can’t be created or destroyed

- It can be transferred or transformed into another type of energy

40
Q

What is the second law of thermodynamics?

A

For every energy transformation, some of the useful energy becomes unusable (heat) and increases the entropy (s) of the universe

41
Q

What does free energy determine?

A

determines if reaction is spontaneous

42
Q

What is free energy?

A

Portion of system’s energy that can perform work (at uniform temperature)

43
Q

Is high free energy stable? What does the system want?

A

High free energy is unstable (system wants to be low which results in change)

44
Q

What is the equation for change in free energy?

A

ΔG = ΔH - TΔS
H: total energy/enthalpy
T: temperature
S: entrophy (always +)

45
Q

How does change in free energy tell us whether the reaction is spontaneous? What needs to happen for that?

A
  • Change in free energy (final-initial) tells whether reaction will be spontaneous (if it’s negative)
  • ΔH is negative
  • Large increase in entropy
46
Q

What happens if change in free energy is 0? Is this common, why?

A

If ΔG = 0, reaction is equillibrium and no work can be done

Rarely happens in cells because reactions are constantly removing products or supplying substrate

47
Q

What are the 2 types of reactions?

A

A + B ⟶ C (catalyzed by allosteric enzyme - one way)

A + B ↔ C (catalyzed by equillibrium enzyme - both directions)

48
Q

What is the reaction rate?

A

Amount of substrate converted to product per unit time

49
Q

How can the reaction rate be determined?

A

Can be measured by determining

  • How fast a substrate disappears
  • How fast a product appears
50
Q

What does activation energy determine?

A

determines rate of reaction

51
Q

What is activation energy?

A
  • Amount of energy needed to raise the reactants to transition state (the start of a reaction)
  • Energy required to break existing chemical bonds before new bonds can be formed
52
Q

What happens to the reaction if you increase the activation energy?

A

The greater the EA for a reaction, the slower the reaction will be

53
Q

What are some characteristics of an exogonic reaction?

A
  • Negative ΔG (free energy of reactants is higher than products)
  • Spontaneous becuse products are more stable
  • Energy is released
54
Q

What does heat do to a reaction?

A
  • Heat increases rate of reaction by providing more reactants with sufficient energy to react
  • However in the body, heat denatures proteins
55
Q

What are some characteristics of an endergonic reaction?

A
  • Positive ΔG (free energy of reactants is lower than products)
  • Not spontaneous because products are less stable
  • Energy is required
56
Q

How does coupling reactions work?

A

Endergonic + Exergonic (supplying energy necessary) = exergonic (eg. ATP)

57
Q

What are the protein organizations, and what forces are involved?

A
  1. Primary
    - Sequence of amino acids
    - Peptide Linkage (covalent)
  2. Secondary
    - Alpha helix, beta sheet
    - Hydrogen bond
  3. Tertiary
    - Globular
    - Hydrogen bond
    - London forces (nonpolar)
    - Dipole dipole forces
    - Ionic bond
    - Disulphide bridge (covalent)
  4. Quaternary
    - Multi-subunits
    - Hydrogen bond
    - London forces (nonpolar)
    - Dipole dipole forces
    - Ionic bond
58
Q

What are enzymes?

A

Globular proteins that increase reaction rate; also known as biological catalysts

59
Q

What are the properties of enzymes?

A
  • Forms temporary association with substrates (enzyme-substrate complex)
  • Lowers activation energy of reaction (increases rate)
  • Is not changed during reaction (reusable)
  • Groove will only bind to certain substrates (active site)
60
Q

What is the process for enzymes working?

A
  • Substrate binds to active site by the formation of weak bonds
  • Causes conformational change in enzyme called induced fit
  • Lowers activation energy by providing alternative pathway for reaction to occur
61
Q

How do enzymes lower the activation energy?

A
  • Placing substrates in proper orientation so they are closer
  • Providing microenvironment that will facilitate reaction
  • Briefly forming covalent bonds with substrate
  • Stressing bonds to make them unstable
62
Q

What influences the enzyme activity? How?

A

pH:
-Affects R group interactions

Temperature:

  • Collisions between enzyme and substrate
  • Effect of temperature on R group interactions

Substrate Concentration:
- Interaction between substrate and active site (too little or too much)

Enzyme Concentration:
- Enzyme substrate interactions/unit time

Cofactors & Coenzymes:

  • Cofactor: nonorganic helper
  • Coenzyme: organic cofactors
  • If not present, the enzyme will not work

Allosteric Regulation:

  • Regulatory binding sites bind activatos or inhibitors which change shape
  • Matches rate of pathway with cell’s need
  • If negative modifier, it will inhibit the reaction
  • Like a manager that wants something or doesn’t (calls the shots)

Competitive Inhibitors:

  • Molecules that have similar shape to substrate can bind temporarily to active site
  • Only slows significantly if there is a lot of inhibitors
  • Inactivates enzyme molecule

Noncompetitive Inhibitors:

  • Binds to enzyme at remote site
  • Changes shape of active site so it can’t bind to substrate
  • Inactivates enzyme molecule
63
Q

Why do plant and animal cells have different features?

A

Different needs for energy

64
Q

What is fluidity dependent on?

A
  • Temperature
  • Composition of lipid molecules (unsaturated fatty acids have double bonds which are more fluid)
  • Cholesterol reduce fluidity at high temperatures, at lower they prevent nonfluid gel
  • London forces
65
Q

What is the equation for activation energy?

A

Activation Energy = Change in potential energy of reactants

66
Q

What ensures that G is negative?

A

If H is large is negative or there is a large increase in entropy (s)

67
Q

What is negative feedback inhibition? What happens and how?

A
  • happens in metabolic pathways

- products near end of rxn inhibits rxn at start by binding to active site

WBiology (8 decks)

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