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Enzymes, intro to cellular respiration Flashcards

0
Q

There are different forms of some enzymes that…

A

assist different reactions.

  • cytosolic version of enzyme
  • mitochondrial version of enzyme (ex slide 5 lecture 12)
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1
Q

Can enzymes work in forward and reverse directions?

A

Some enzymes can

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2
Q

activity

A

total amount of reactant converted to product (over time)

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3
Q

number of enzyme molecules

A

genes

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4
Q

activity of each enzyme molecule

A

pH, temperature etc.
concentrations of substrates
inhibitors and activators

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5
Q

inhibitors

A

molecules that interact in some way with the enzyme to prevent it from working in the normal manner

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6
Q

enzyme activator

A

molecules that bind to enzymes and increase their activity

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7
Q

factors that affect enzyme activity

A

cofactors

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8
Q

cofactors

A 
nonprotein enzyme helpers
coenzyme
inorganic  (such as a metal ionic form)
-ex magnesium needed for hexokinase 
-forms complex with ATP
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9
Q

Coenzyme

A

organic cofactor

EX. vitamins

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10
Q

The regeneration of ATP

A

an organism at work us ATP continuously, but ATP is a renewable resource that can be regenerated by the addition of phosphate to ADP

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11
Q

what happens if the inhibitor attaches to the enzyme by covalent bonds?

A

inhibition is usually irreversible

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12
Q

Many enzyme inhibitors bind to the enzyme by weak interactions…

A

in which case inhibitions is reversible.

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13
Q

some reversible inhibitors resemble the normal substrate molecule…

A

and compete for admission into the active site

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14
Q

Competitive inhibitors

A

reduce the productivity of enzymes by blocking substrates from entering active sites

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15
Q

How can competitive inhibitors be overcome?

A

by increasing the concentration of substrate so that as active sites become available, more substrate molecules than inhibitor molecules are around to gain entry to the sites

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16
Q

noncompetitive inhibitors

A

do not directly compete with the substrate to bind to the enzyme at the active site. Instead they impede enzymatic reactions by binding to another part of the enzyme.

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17
Q

What does the noncompetitive inhibitors interaction cause?

A

This interaction cause the enzyme moleules to change its shape in such a way that the active site becomes less effective at catalyzing the conversion of substrate to product.

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18
Q

What does regulation of enzyme activity help?

A

helps control metabolism

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19
Q

Allosteric regulation

A

protein’s function at one site is affected by the binding of a regulatory molecule to a separate site.

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20
Q

allosteric activator

A

binds to the allosteric regulatory site

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21
Q

how can a substrate activate the enzyme?

A

by stabilizing it

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22
Q

feedback inhibition

A

When ATP allosterically inhibits an enzyme in an ATP generating pathway, the result is feed back inhibition

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23
Q

What happens in feedback inhibition?

A

a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway.

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24
certain cells use this five step pathway to synthesize the amino acid isoleucine from threonine...
as isoleucine accumulates, it slows down its own synthesis by allosterically inhibiting the enzyme for the first step of the pathway. feedback inhibition thereby prevents the cell from wasting chemical resources by making more isoleucine than is necessary
25
If the cell is not using products(isoleucine)....
...product of the pathway builds up
26
if the cell is using product (isoleucine)...
product of the pathways does not build up | -initial substrate can bind to active site
27
sites of enzyme activity
- cytoplasm/cytosol - membranes - plasma membrane - endomembranes - mitochondrial membrane, - thylakoid membrane
28
how is sunlight a part of metabolism?
by converting the energy of sunlight to a usable form of chemical energy, photosynthesis is the source of virtually all metabolic energy in biological lsystems
29
major catabolic pathways- exergonic breakdown of organic molecules
- fermentation - anaerobic respiration - aerobic respiration-oxygen - glycolysis - Krebs cycle - oxidative phosphorylation
30
Aerobic respiration
a form of cellular respiration that requires oxygen in order to generate energy
31
oxidized
glucose and other substrates are | "burned"
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oxidation
loss of electrons
33
reduction
gain of electrons
34
fermentation
catabolic process, is a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
35
aerobic respiration
most efficient catabolic pathway, oxygen is consumed as a reactant along with the organic fuel. cells of most eukaryotic and many prokaryotic organisms can carry out aerobic respiration.
36
anaerobic respiration
some prokaryotes use substances other than oxygen as reactants in a similar process that harvests chemical energy without oxygen
37
Cellular respiration
includes both aerobic and anaerobic processes, but is often used to refer to the aerobic process. is the set of metabolic reactions and processes that take place in the cells that take place in the cells of organisms to convert biochemical energy from nutrients into ATP. considered an exothermic redox reaction, releases heat.
38
what reactions are involved in respiration?
catabolic reactions
39
redox reaction
transfer of one or more electrons from one reactant to another
40
what makes them good fuels?
organic molecules that have an abundance of hydrogen are excellent fuels because their bonds are a source of hilltop electrons, whose energy may be released as these electrons fall down an energy gradient when they are transferred to oxygen.
41
How is the redox reaction involved in cellular respiration?
occurs when glucose C5H12O6 (Fuel) is oxidized to carbon dioxide, Hydrogen (H) and electrons removed from glucose oxygen (O2) is reduced to water-hydrogen added to oxygen
42
biological oxidation
series of steps
43
Abiotic oxidation of free hydrogen gas
heat light explosion uncontrolled
44
Biological electron carrier NAD+ (nicotinaminde adenine dinucleotide)
The H atoms are not transferred directly to O, but instead are usually passed first to an electron carrier, a coenzyme called NAD+
45
Why is NAD+ well suited as an electron carrier?
because it can cycle easily between oxidized (NAD+) and reduced (NADH) states
46
How does NAD+ trap electrons from glucose and the other organic molecules in food?
enzymes called dehydrogenases remove a pair of hydrogen atoms from the substrate, thereby oxidizing it, the enzyme delivers the 2 electrons along with 1 proton to its coenzyme, NAD+, The other proton is released as a H ion (H+) into the surrounding solution
47
Why is oxygen the terminal electron acceptor need in CR?
The low energy electrons that emerge from the electron transport system are taken up by O2. The negatively changed O molecules take up protons from the medium and form water.
48
cellular respiration
glucose is oxidized to carbon dioxide and oxygen is reduced to water
49
electrons lose energy as....
they are transferred to oxygen
50
Electrons are passed from glucose to NAD+...
(forming NADH) in a stepwise fashion through ETC to oxygen
51
Energy released is used to make....
ATP
52
how is oxidative phosphorylation powered?
powered by redox reaction ETC most ATP O is last electron acceptor
53
substrate level
phosphorylation: enzyme transfers Pi directly from substrate to ADP
54
What happens if energy is released from a fuel all at once?
it cannot be harnessed efficiently for constructive work.
55
Glycolysis
a series of reactions that ultimately splits glucose into pyruvate. occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.
56
Citric acid cycle
a chemical cycle involving 8 steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol or prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration.
57
glycolysis
- Splitting of sugar - breaks down glucose into two molecules of pyruvate (a 3 carbon sugar) - harvests chemical energy by oxidizing glucose to pyrucate
58
What phases does glycolysis go through?
2 phases, 10 steps energy investment phase energy payoff phase
59
glycolysis, which occurs in the cytosol, begins the degradation process by...
breaking glucose into two molecules of a compound called pyruvate
60
What happens in glycolysis?
6 carbon sugars is split into two 3 carbon sugars. these smaller sugars are then oxidized and their remaining atoms rearranged to form two molecules of pyruvate
61
Energy investment phase
the cell actually spends ATP
62
Steps in investment phase
1. glucose is phosphorylated-chemically reactive,becomes charged, trapped in cell 2. glucose is converted to its isomer 3. another phosphate added to fructose-6-phosphate 4. fructose bisphosphate split into 2 trioses (isomers of each other)
63
payoff phase
5. each G3P is oxidized to 1,3 bisphosphoglycerate, NAD+ reduced to NADH 6.enzyme(kinase) transfers phosphate groups from substrate to ADP->ATP: substrate level phosphorylation-exergonic reaction -product has high potential energy 7. relocation of phosphate group 8.dehydration reaction to form PEP 9.Phosphate groups added to ADPs->2ATP (substrate level phosphorylation), conversion of PEP to pyruvate 10. pyruvate
64
Used by glycolysis
Glucose (what your breaking down) O2 (it accepts protons and electrons at the end to produce water) ADP+Pi (is used to make ATP)
65
Produced by glycolysis
CO2 ( its how all the carbons from glucose escape) | ATP (the entire point of these processes)
66
what is both used and produced in glycolysis?
NADH (first made then used in the ETC) | NAD+
67
Glycolysis is...
- in cytosol | - oxidation of glucose to 2 pyruvate, 2 ATP net, pyruvate to TCA, HADH to ETC
68
O2 is present:
pyruvate to the citric acid cycle in mitochondrion
69
O2 absent
pyruvate oxidized via fermentation
70
Where does the citric acid cycle / Krebs cycle occur?
In mitochondrial matrix in eukaryotes | in cytosol of prokaryotes
71
pyruvate first converted to...
acetyl CoA upon entry into mitochondrion.
72
Acetyl CoA is...
oxidized by Krebs cycle
73
Conversion of pyruvate to Acetyl CoA
1. pyruvate enters mitochondria by active transport 2. carboxyl group removed carbon dioxide produced (will diffuse out) 3. Two carbon fragment oxidized, NAD reduced to NADH 4. Coenzyme Q added to acetyl group, AcetylCoA has very high potential NRG
74
The citric acid cycle
has 8 steps, each catalyzed by a specific enzyme | for each turn of the citric acid cycle, two carbons enter in the the relatively reduced form of an acetyl group
75
The citric acid cycle steps
1. Acetyl group of acetyl CoA combines with oxaloacetate, forming citrate-the rest of cycle converts the citrate 6Cs back to oxaloacetate 4Cs-carbon leaves as CO2 2. Citrate converted to its isomer 3. Oxidation of isocitrate, reduction of NAD+ to NADH and CO2 is produced 4. CO2 is removed from alpha ketoglutarate-attachement of CoA-reduction of NAD+ to NADH intermediate oxidized 5. CoA displaced, GDP phosphorylated(ATP can be generated from by GTP) 6. Succinate oxidized; hydrogens transferred to FAD 7. Malate oxidized, NAD+reduced to NADH 8. Oxaloacetate regenerated
76
NADH produced at...
3 steps
77
The citric acid cycle is..
- in mitochondrion | - acetyl CoA combined with oxaloacetate to form citrate,citrate cycle back to oxaloacetate
78
Where is oxidative phosphorylation found?
in the cristae of the mitochondrion of eukaryotes, plasma membrane of prokaryotes
79
what is oxidative phosphorylation?
folding of the membrane increase the surface area for the enzymes
80
electron transport chain
- collection of molecules embedded in the inner membrane of the mitochondrion in eukaryotic cells, in prokaryotes they reside in the plasma membrane. - the folding of the inner membrane to form cristae increases its surface area, providing space for thousands of copies of the chain in each mitochondrion

Biology (16 decks)

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