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BI101 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

Basic Requirements of a Cell

A
  1. a system, to encode/transmit information
    2.a membrane to separate inside from
  2. ENERGY
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2
Q

Energy

A

the capacity to do work or to be transferred as heat

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3
Q

Kinetic energy examples

A
  • ocean waves, falling rocks, moving hockey puck
  • electricity (flow of electrons)
  • light (photons)
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4
Q

Potential Energy

A

stored energy

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5
Q

Potential energy example

A

object, because of its position
- boulder at the top of a hill

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6
Q

do electrons further away from the nucleau possess more or less potential energy

A

more

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7
Q

what happens when an electron gains energy

A

it moves to a higher energy level that is farther away from the nucleus

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8
Q

what forms does energy exist in

A

chemical, electrical, mechanical, electromagnetic radiation, visible light

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9
Q

Can energy be transformed between forms

A

yes, flashlight

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10
Q

Kinetic energy

A

nergy possessed by an object because it is in motion

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11
Q

What is thermodynamics

A

study of energy and its transformations

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12
Q

What are the three types of systems

A

open, closed, isolated

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13
Q

isolated system

A

does not exchange matter or energy with its surrounding (universe)

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14
Q

closed system

A

can exchange energy but not matter with its surroundings (earth)

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15
Q

Open system

A

both energy and matter can move freely between the system and surroundings (the ocean absorbs and releases energy/ part if the hydrological cycle)

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16
Q

What systems do thermodynamics apply to

A

biotic and abiotic

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17
Q

1st law of thermodynamics

A

Energy cannot be created or destroyed, it can only be transferred or transformed.

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18
Q

2nd law of thermodynamics

A

The transfer or transformation of energy increases the entropy of a system and its surroundings (entropy is always increasing)

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19
Q

What can make reactions spontaneous

A

entropy and enthalpy

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20
Q

Entropy (S)

A

The tendency of energy to become dispersed or spread out

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21
Q

Can you ever have 100% energy

A

no

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22
Q

What happens when energy is transferred or transformed

A

energy is lost

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23
Q

When do reactions tend to be spontaneous

A

if products have less potential energy than reactants

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24
Q

Total energy = ?

A

Total energy= usable energy+ usable energy
H = G + TS

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25
Q

Enthalpy

A

the heat content of a system ΔH
Reflects the number and kinds of chemical bonds that exist between atoms

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26
Q

Exothermic Reactions

A

Products have less total/thermal energy than reactants
Energy released
-‘ve ΔH
spontaneous

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27
Q

Endothermic Reactions

A

Products have more total/thermal energy than reactants
Requires input of energy
+‘ve ΔH
Tend to be non-spontaneous

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28
Q

Free energy

A

energy available to do work

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29
Q

free energy equation

A

ΔG = Gproducts - Greactants
ΔG = ΔH − TΔS

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30
Q

Two groups of metabolic reactions:

A

Exergonic, endergonic

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31
Q

what do exergonic and endergonic reactions require

A

activation energy

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32
Q

Diffusion

A

Molecules move spontaneously from higher concentration to lower concentration

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33
Q

What is diffusion driven by

A

increase in entropy and the energy associated with the molecules is spread out

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34
Q

equillibrium

A

maximum stability

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35
Q

when is the equilibrium point reached

A

reactants are converted to products and products are converted back to reactants at equal rates.

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36
Q

As a system approaches equilibrium what happens to its free energy

A

it lowers

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37
Q

What kind of system are living systems

A

open

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38
Q

metabolic pathway

A

series of sequential reactions in which products of one reaction are used immediately as reactants for the next reaction in the series

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39
Q

catabolic pathway

A

Energy is released by breakdown of complex molecules to simpler compounds

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40
Q

Anabolic pathway

A

Consumes energy to build complicated molecules from simpler ones

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41
Q

Catabolism vs Anabolism vs metabolism

A

Catabolism:Breakdown of molecules into smaller units, releasing energy
Anabolism: Building of molecules from smaller units, requiring an input of energy
Metabolism: Collection of all chemical reactions present within a cell or organism

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42
Q

ATP Hydrolysis:

A

ATP hydrolysis releases free energy that can be used as a source of energy for the cell

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43
Q

energy coupling

A

the coupling of an endergonic reaction to an exergonic reaction

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44
Q

Enzyme-Catalyzed Reactions

A

Enzymes bind to a reactant (substrate)
After binding to reactant, and ultimately releasing the product(s), the enzyme is unchanged
Highly specific, recognizing a unique substrate or a class of similar substrates

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45
Q

Catalyst

A

Chemical agent that speeds up the rate of reaction without itself being chemically altered

46
Q

Enzyme Cofactors

A

Nonprotein groups necessary for catalysis to occur
Cofactors: Metallic ions (Mg2+, Fe2+, Cu2+, Zn2+)

47
Q

Coenzymes

A

: Organic cofactors such as vitamins

48
Q

Transition state

A

During catalysis, the substrate and active site of the enzyme form an intermediate transition state

49
Q

Enzymes facilitate the formation of the transition state via 3 major mechanisms:

A
  1. Bringing the reacting molecules into close proximity
  2. Exposing the reactant molecules to altered environments that promote their interactions
  3. Changing the shape of a substrate molecule
50
Q

When substrate concentration is low:

A

Reaction rate slows
Enzymes and substrates collide infrequently

51
Q

When substrate concentration is high:

A

Enzymes become saturated with reactants
Rate of reaction levels off

52
Q

Enzyme inhibitors

A

nonsubstrate molecules that can bind to an enzyme and decrease its activity

53
Q

Competitive inhibition

A

Inhibitor competes with the normal substrate for active site

54
Q

Noncompetitive inhibition

A

Inhibitor does not compete with normal substrate for active site, but combines with sites elsewhere on enzyme

55
Q

Enzyme regulation

A

Allosteric regulation- occurs with the reversible binding of a regulatory molecule to an allosteric site, a location on the enzyme that is different from the active site

56
Q

Noncompetitive activator

A

Allosteric activators convert an enzyme from the low to the high affinity state

57
Q

The importance of selectively permeable membranes

A

Cells and organelles need barrier to separate internal and external contents

58
Q

selectively permeable membrane Barrier must have following qualities:

A

Impermeable to most molecules and ions
Ability to exchange specific molecules/ions between compartments
Insoluble in water
Permeable to water

59
Q

What is a cellular Membrane

A

A permeability barrier that consists of:
Phospholipids, glycolipids
Sterols (except in bacteria):
Cholesterol (animals)
Ergosterols (fungi)
Phytosterols (plants)
Membrane proteins
Membrane proteins include:
Integral proteins (transmembrane)
Peripheral membrane proteins

60
Q

Fluid Mosaic Model of Membranes

A

Membranes are not rigid
They consist of a fluid lipid bilayer in which proteins are embedded and float freely

61
Q

The fluid mosaic model of membrane structure is supported by two major pieces of experimental evidence.

A
  • membranes are fluid
  • membrane asemmetry
62
Q

Hydrophobic molecules

A

No polar regions
Do not interact electrostatically with water
Disrupt hydrogen-bonded structure of water
Tend to coalesce with each other in water
Water molecules tend to exclude molecules that disrupt hydrogen bonding
Hydrophobic interactions are a major driving force in folding of molecules (like proteins), assembly of cellular structures, and membrane organization.

63
Q

Phospholipids are

A

Amphipathic

64
Q

Amphipathic

A

Polar head group → Hydrophilic (polar)
2 Non-polar hydrocarbon tails → Hydrophobic (non polar)

65
Q

what is fluidity dependent on

A

how densely individual lipid molecules can pack together

66
Q

What is maintaining proeper fluidity influenced by

A

Composition of lipid molecules; Degree of unsaturation of fatty acid tails, Presence of sterols
Temperature

67
Q

phospholipids composed of saturated fatty acids

A

Each carbon is bound to max number of hydrogens (all single bonds between C’s)
Straight shape
Tighter packing

68
Q

Phospholipids composed of unsaturated fatty acids

A

Double-bonds between carbons
introduce kinks
Less dense packing

69
Q

what happens at low temperatures

A

At low temperatures → enzymes and proteins cannot function if fluidity is not maintained

70
Q

what happens at high temperatures

A

At high temperatures → Too fluid, get leakage

71
Q

what do organisms do to optimize fluidity

A

Organisms can modify the lipid composition of their membranes to optimize fluidity in response to different temperatures by changing:

72
Q

key functions of membrane proteins

A
  1. transport
  2. enzymatic activity
    3.signal transduction
  3. attachment/recognition
73
Q

Integral Membrane Proteins

A

Proteins embedded in phospholipid bilayer

74
Q

what are integral memebrane proteins composed of

A

predominantly nonpolar amino acids usually coiled into alpha helices

75
Q

Peripheral Membrane Proteins

A

On surface of membrane
Do not interact with hydrophobic core
Held together by noncovalent bonds
Many on cytoplasmic side of membrane
Made up of mixture of polar and non- polar amino acids

76
Q

Integral Membrane Proteins Interact with …

A

the Membrane Hydrophobic Core

77
Q

Peripheral Membrane Proteins Interact with…

A

the Membrane Hydrophilic Surface

78
Q

Passive Membrane Transport

A

Movement of molecules across a membrane without need to expend chemical energy such as ATP

79
Q

what is passive transport driven by

A

diffusion

80
Q

Diffusion

A

Net movement of substance from region of higher to lower concentration

81
Q

driving force of diffusion

A

increase in entropy

82
Q

There Are Two Types of Passive Transport

A

simple, facilotated

83
Q

Simple diffusion

A

Passive transport of molecules across a membrane without the involvement of a transporter

84
Q

Facilitated Diffusion

A

Passive transport of molecules across a membrane with the aid of a transporter

85
Q

Carrier Proteins

A

Bind a specific single solute and transport it across the lipid bilayer (uniport transport)
Undergo conformational changes that move the solute-binding site from one side of the membrane to the other
Can become saturated when there are too few transport proteins to handle all the solute molecules

86
Q

Most proteins that carry out facilitated diffusion of ions are controlled by

A

“gates” that open or close their transport channels

87
Q

Gates can be opened or closed in response to various stimuli, such as

A

voltage across the membrane or the presence of signal molecules

88
Q

Osmosis

A

Diffusion of water molecules

89
Q

Water can move (slowly) across membranes by

A

simple diffusion

90
Q

water moves from

A

From hypotonic solution (lower concentrations of solute molecules) To hypertonic solution (higher concentrations of solute molecules)

91
Q

Active transport requires

A

a direct or indirect input of energy derived from ATP hydrolysis or concentration gradients

92
Q

Active Membrane Transport Moves substances against

A

against their concentration gradients; requires cells to expend energy

93
Q

Active Membrane Transport depends on

A

membrane transport proteins

94
Q

Two Kinds of Active Transport:

A

primary and secondary

95
Q

Primary active transport

A

Same protein that transports the molecules also hydrolyzes ATP to power transport directly

96
Q

Secondary active transport

A

Transport indirectly driven by ATP hydrolysis

97
Q

Primary Active Transport

A

Moves positively charged ions across membranes
- H+ pumps (proton pumps)
Cells lining stomach
- Ca2+ pump
Maintain low intracellular Ca2+ concentration
Na+/K+ pump
– 3 Na+ out, 2 K+ in for every pump cycle
Creates negative membrane potential
Electrochemical gradient across membrane

98
Q

Secondary Active Transport involves

A

symport and antiport

99
Q

symport

A

Cotransported solute moves through
membrane channel in same direction
as driving ion

100
Q

antiport

A

Driving ion moves through membrane
channel in one direction, providing
energy for active transport of another
molecule in opposite direction

101
Q

Exocytosis and endocytosis move

A

large molecules and particles in and out of cells

102
Q

Exocytosis

A

Secretory vesicle carries secreted materials
Moves through cytoplasm and contacts the plasma membrane
Vesicle membrane fuses with plasma membrane, releasing contents to cell exterior

103
Q

Endocytosis

A

Encloses materials outside cell in plasma membrane
Pockets inward and forms endocytic vesicle onmcytoplasmic side

104
Q

Two forms of endocytosis

A

Bulk-phase (pinocytosis)
Receptor-mediated endocytosis

105
Q

Receptor-Mediated Endocytosis

A

Molecules bind to receptor proteins on outer cell surface
After binding, receptors collect into a depression in PM called a coated pit
- Network of proteins, called clathrin, on cytoplasmic side
Pit pinches off PM to form endocytic vesicle

106
Q

Why is membrane signaling important?

A

Ability to sense and respond to external stimuli, or changes in the environment, is a key characteristic of life

107
Q

steps in cell signalling

A

receptor activation, signal transduction, response, termination

108
Q

Reception by a Cell-Surface Receptor

A

Signal molecules: Hormones, Neurotransmitters
Receptors:Integral membrane glycoproteins
Responses usually rapid,short-lived events (regulate enzyme activity)

109
Q

Reception by a Receptor Within Cell

A

Signal molecules: Steroid hormones -testosterone, estrogen
Intracellular receptors: Steroid hormone receptor- Hormone-binding domain & DNA-binding domain
Responses typically occur over a longer time due to changes in gene expression

110
Q

Cell communication systems based on surface receptors have three components:

A

Extracellular signal molecules
Surface receptors that receive the signals
Internal response pathways triggered when receptors bind a signal

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