8 - Enzymes, ATP & Energy Flashcards
Chapters (2.3, 9.1 & 3.5)
0
Q
define energy
A
the capacity to do work 2 Kinds: - potential energy - kinetic energy
1
Q
Describe the difference b/t Potential energy and kinetic energy
A
Potential energy - result of location and structure; stored energy; the ability to do work; associated w/ chemical bonds and electrical-chemical charge imbalance concentration gradient
Kinetic energy - the energy of motion
2
Q
What is the ultimate source of energy?
A
the sun
3
Q
What is the 1st law of thermodynamics?
A
Energy cannot be created nor destroyed, only transferred and transformed
4
Q
What is the second law of thermodynamics
A
entropy increases in an isolated system more order to less order
5
Q
Why can’t we recycle energy over and over?
A
as energy changes some of it moves to different forms (heat, light sound, etc) and those are not reversible transactions
6
Q
When a reaction is exergonic, what is that saying about the rxn?
A
- spontaneous - lower energy in product than reactants - catabolic energy is released
7
Q
When a rxn is endergonic, what is that saying about the rxn?
A
- not spontaneous - have to add energy to make it work - energy is consumed - anabolic - makes product rich in PE
8
Q
catabolic means….
A
to break down
9
Q
define anabolic
A
to build up ie - use of steroids
10
Q
What chemical is considered the currency of the cell?
A
ATP Adenosine triphosphate
11
Q
When a phosphate group is removed from ATP what are the products?
A
ADP & Pi
12
Q
Why is there high potential energy in ATP?
A
The three phosphate groups have hight PE b/c 4 neg charges grouped together repelling each other
13
Q
What molecule is ATP similar to that we’ve seen before?
A
neucleotide
14
Q
the hydrolysis of ATP an exergonic or endergonic rxn?
A
exergonic
15
Q
Define energy coupling
A
when an endergonic and exergonic rxn couple to perform work
16
Q
ATP powers cellular work, list the three general types of work done
A
- chemical work
- mechanical work
- Transportation work - channels
17
Q
When the net change in potenital energy is positive (+G) is the reaction spontanious
A
no, it needs the input of energy or Pi
18
Q
Phosphorylation adds ___________ energy and causes the changed substance to ___________ shape
A
negative electron; change
This can power flagella, cilia, ion pump, etc
19
Q
When something is oxidized, what has happened here
A
loss of electrons
e_ transferred completely from one atom to another
20
Q
the change in electron ______ the energy state
A
increases or decreases
21
Q
list some of the molecules with a high amount of C-H bonds
A
carbohydrates
fats
22
Q
What does NADH do
A
it is an electon carrier, easily donates H+ -> NAD+
23
Q
Why don`t energy molecules like glucose spontaneously create energy
A
energy barrier and need either the input of energy to get over it, or a catalyst that will lower the barrier for the reaction
24
define catalyst
a substance that lowers the activation energy of a reactions and decreases the time it takes for the rxn to happen
it remains the same before and as after
25
What is the role of an enzyme
1. to bring together reactants in a special orientation
2. to stabilyze transition states
26
Why would adding heat to a rxn be impractical in a biological system
it would denature stuff
27
# Define activation energy
the amount of free energy required to get a substrate to its transition state
EA
28
When products have lower net energy, it is said to be
exothermic
29
Enzymes catalize rxn`s in 3 steps, what are they
1. Initiation
2. transition state faciliation
3. termination
30
In biological systems, ATP functions by
Select one:
A. acting as an enzyme and lowering the activation energy of certain reactions
B. interacting with enzymes as a cofactor to stimulate chemical reactions
C. providing the energy necessary for an endergonic reaction by coupling it with an exergonic reaction
D. adjusting the pH of solutions to maintain optimal conditions for enzyme activity
E. regulating the speed at which endergonic reactions proceed
C
31
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is knows as
Select one:
A. Noncooperative inhibition
B. Feedback inhibition
C. Metabolic inhibition
D. Competitive inhibition
feedback inhibition
32
Molecules that bind within the active site of an enzyme are\_\_\_\_\_\_\_\_\_\_, whereas molecules that bind at a site distant from the active site are\_\_\_\_\_\_\_\_\_\_\_\_\_.
Select one:
A. Competitive inhibitors, non-competitive
B. Cofactors, products
C. Competitive inhibitors, coenzymes
D. Products, allosteric inhibitors
Molecules that bind within the active site of an enzyme are competitive inhibitiors, whereas molecules that bind at a site distant from the active site are non-competitive.
33
A spontaneous reaction is one in which
Select one:
A. Entropy is decreased
B. Energy is required
C. The reactants have a higher free energy than the products
D. The products have a higher free energy than the reactants
A spontaneous reaction is one in which the reactants have a higher free energy than the products
34
Enzymes speed up reactions by
Select one:
A. providing chemical energy to fuel a reaction
B. none of the answers apply
C. causing an endergonic reaction to become an exergonic reaction
D. lowering the activation energy necessary to initiate the reaction
E. substituting for one of the reactants necessary for the reaction
Enzymes speed up reactions by lowering the activation energy necessary to initiate the reaction
35
Which of the following metabolic processes can occur without a net influx of energy from some other process?
Select one:
A. 6 CO2 + 6 H2O --\> C6H12O6 + 6 O2
B. C6H12O6 + 6 O2 --\> 6 CO2 + 6 H2O
C. Glucose + fructose --\> sucrose
D. ADP + Pi --\> ATP + H2O
E. Amino acids --\> protein
**B**
36
Where is the energy stored in a molecule of ATP
Select one:
A. in the oxygen double bond
B. in the carbon bonds found in the ribose
C. in the bonds connecting the two terminal phosphate groups
D. within the bonds between nitrogen and carbon
in the bonds connecting the two terminal phosphate groups
37
A covalent bond between two atoms represents what kind of energy?
Select one:
A. Potential energy
B. Mechanical energy
C. Kinetic energy
D. Solar energy
PE
38
Entropy could best be described as
Select one:
A. Sitting at the top of a slide, about to go down
B. Climbing up the ladder of a slide
C. Cleaning a messy room
D. A messy room
a messy room
39
What are the three charateristics of the induced fit model
1. E - unique & specific 3D shape =\> function
2. E specific to substrate
3. E + substrate = decreased EA =\> catalyzes rxn
40
Do enzymes work alone
what other things do some enzymes require in order to do work
use coenzymes
Zn2+ & Mg+
41
Do enzymes change the an endergonic reaction to an exergonic reaction
no
42
does an enzyme change the delta G
nope
43
An enzyme catalyzes in 3 steps, what are they
1. **initiation** - microenvironment orientation & pH
2. **transition state facilitation** - interaction bt E & substrate = lowers activation energy & time
3. **termination** - when products have a lower affinity for active site - enzyme remains unchanged after rxn
44
True or false
an enzyme is rigid and static
false
flexible and dynamic
45
Activation energies drop because enzymes may destablize bonds in reactant, stabalize the \_\_\_\_\_\_\_\_\_, make acid-base rxn more favorable and rxn time mechanism through covalent bonding interaction
active site
46
What happens when there are deficiencies in enzyme cofactors like Vitamin C
the coenzyme become a cofactor in the active site, without = deficiencies - Vit C & Scurvey
47
name and describe the types of regulation
1. **competitive inhibition** binds to active site causing block, yet if you add lots of substrate that you would like to bind = higher chance of getting in there
2. **allosteric regulation** - changes shape of protein by binding to a different site than the receptor site, and changing the shape inhibits the active site binding can either increase or decrease speed of rxn
48
What is feedback inhibition
when the product of the rxn regulates the reaction by binding at the allosteric site, ie ATP
49
How does ATP typically transfer energy from exergonic to endergonic rxn in the cell
one of the Pi groups chopped off = ADP + Pi there fore transfering energy to endergonic processing
50
You should be able to explain why precise orientation of rxn in an active site is important
so specific
in bonds, pH, phillic or phobic has to be exact
51
you should be able to explain why shape change during allosteric regulation can change an enzymes activity
52
Which of the following combinations has more free energy: glutamic acid + ammonia + ATP, or, glutamin + ADP + Pi
Explain
glutamic acid + ammonia + ATP
The first rxn makes the second. The first combination rxn = exergonic & has more free energy
53
Why is an enzyme`s shape and structure essential to its function
so precise to its orientation or stresses bonds in substrate = lowers EA required to make new bonds
54
What environmental factors affect the functioning of an enzyme
pH
temp
[salt]
regulatory molecules
55
What are some examples of enzymes that work in extreme temperatures
hot springs
56
What do the following do to the food to prevent waste
Canning
freezing
salting
Pickeling
They each interfere with enzymes and bacteria that would cause food degredation
Canning - boiling denatures enzyme structures
Freezing - stops rxn bc frozen
Salting - denatures enzyme structure
Pickeling - low pH denatures
57
Catabolic & anabolic pathways are often coupleing in a cell because:
1. the intermediates of a catabolic pathway are used in the anabolic pathway
2. both pathways use the same enzymes
3. the free energy released from one pathway is used to drive the other
4. the activation energy of the catabolic pathway can be used in the anabolic pathway
5. their enzymes are controlled by the same activators and inhibitors
Catabolic & anabolic pathways are often coupling in a cell because the free energy released from one pathway is used to drive the other
58
What is meant by induced fit:
1. the binding of the substrate is an energy-requiring process
2. a competitive inhibitor can outcompete the substrate for the active site
3. the binding of the substrate changes the shape of the active site, which can stress or bend substrate bonds
4. the active site creates a micro-environment ideal for the reaction
5. substrates are held in the active site by hydrogen & ionic bonds
What is meant by induced fit the binding of the substrate changes the shape of the active site, which can stress or bend substrate bonds
59
Which of the following parameters does an enzymen raise
1. delta G
2. Delta H
3. equilibrium of a reaction
4. speed of a reaction
5. free energy of activation
speed of a reaction
60
When a cell breaks down glucose, only about 35% of the energy is captured in ATP molecules. The remaining 65% of the energy is
1. lost as heat because of the second law of thermodynamics
2. used to increase the entrophy of the system by converting kinetic energy into potential energy
3. release when the ATP molecules are hydrolyzed
4. used to increase the rate of the reaction
lost as heat because of the second law of thermodynamics
61
Zinc, an essential trace element, may be found bound to the active site of some enzymes. What would be the most likely function of such zinc ions
1. a coenzyme necessary for catalysis
2. a cofactor necessary for catalysis
3. a substrate for the enzyme
4. a cometitiave inhibitor of the enzyme
a cofactor necessary for catalysis
62
In the metabolic pathway, A-B-C-D-E, what effect would molecule E likely have on the enzyme that catalyzes A-B
1. allosteric inhibitor
2. allosteric activator
3. competitive inhibitor
4. feedback activator
5. coenzyme
allosteric inhibitor
63
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ more reactive molecules created by the transfer of a phosphate group from ATP
Pi d intermediate
64
In the reaction C6H12O6 + 6 O2 ----- 6 CO2 + H2O,
1. oxygen becomes reduced
2. oxygen is a reducing agent
3. glucose becomes reduced
4. water is a reducing agent
5. oxygen becomes oxidized
oxygen becomes reduced
65
A substrate that is phosphorylated,
1. has lost a phosphate group
2. has been formed by the reaction ADP + Pi to--- ATP
3. has an increased reactivity; it is primed to do work
4. has been oxidized
5. will pass its electrons to the electron transport chain
has an increased reactivity; it is primed to do work
66
Substrate-level phosphorylation:
1. involves the shifting of a phosphate group from ATP to substrate
2. can use NADH or FADH2
3. takes place only in the cytosol
4. accounts for 10% of the ATP formed by fermentation
5. is the energy source for some bacteria under anaerobic conditioins
is the energy source for some bacteria under anaerobic conditioins
67
How many molecules of CO2 are generated for each molecule of acetyl CoA that enters the citric acid cycle
2
68
Which of the following reactions is incorrectly paired with its location
1. ATP synthesis - inner membrane of the mitochondrion (produced in the matrix) and cytosol
2. fermentation - cell cytosol
3. glycolysis - cell cytosol
4. substrate-level phosphorylation - cytosol and matrix
5. citric acid cycle - inner mitochondrial membrane
citric acid cycle - inner mitochondrial membrane
69
Which of the following produces the most ATP per gram:
1. glucose, because it is the starting place for glycolysis
2. glycogen or starch, because they are polymers of glucose
3. fats, because they are hightly reduced compounds
4. proteins, because of the energy stored in the tertiary structure
5. amino acids, because they can be fed directly into the citric acid cycle
fats, because they are hightly reduced compounds
70
Fats and proteins can be used as fuel in the cell because they
1. can be converted to glucose by enzymes
2. can be converted to intermediatees of glycolysis or the citric acid cycle
3. can pass through the mitochondrial mb to enter the citric acid cycle
4. contain unstable phosphate groups
can be converted to intermediatees of glycolysis or the citric acid cycle
71
The metabolic function of fermentation is to
1. oxidize NADH to NAD+ so that glycolysis can continue in the absence of oxygen
2. reduce NADH so that more ATP can be produced by the electron transport chain
3. produce lactate during aerobie exercise
4. oxidize pyruvate in order to release more energy
5. make beer
oxidize NADH to NAD+ so that glycolysis can continue in the absence of oxygen
72
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