Cellular Metabolism Flashcards
1
Q
What is metabolism?
A
the sum of all chemical reactions occurring in a cell
2
Q
What are chemical reactions?
A
- reactants (or substrates) –> products
A + B –> C + D
3
Q
Describe the directions of reaction.
A
- forward (reactants transformed into products)
- reverse (products transformed into reactants)
- chemical reactions are bidirectional
A + B C + D
4
Q
What are metabolic reactions?
A
chemical reactions occurring in the body
5
Q
What is catabolism?
A
breakdown of larger molecules into smaller molecules
6
Q
What is anabolism?
A
synthesis of larger molecules from smaller reactants
7
Q
Describe the metabolic pathway.
A
A–> B–> C–> D (intermediates along the way)
- initial substrate
- intermediates
- end product
8
Q
Metabolic reactions have ____ ______ and _____ ______ reactions.
A
- energy releasing
- energy requiring
9
Q
What is energy?
A
capacity to do work
10
Q
Name the 2 forms of energy.
A
- kinetic energy
- potential energy
11
Q
Describe kinetic energy.
A
- associated with motion
- thermal, radiant, electromagnetic, electrical
12
Q
Describe potential energy.
A
- stored energy
- don’t have more than enough work for 2-3 seconds
- chemical, mechanical, nuclear, gravitational
13
Q
Energy releasing reactions are called ______ reactions.
A
exergonic reactions
14
Q
Describe energy releasing reactions.
A
- catabolic
- proceeds spontaneously
- released energy may power an energy requiring reaction (ex. breakdown of phosphocreatine, glycolysis, body cells transporting ions)
15
Q
All reactions involve ____________________.
A
an exchange of energy
16
Q
____ possess more energy than ______.
A
reactants, products
17
Q
What is the equation for change of energy in a reaction?
A
ΔE = Eproducts – Ereactants
18
Q
Energy requiring reactions are called ______ reactions.
A
endergonic reaction
19
Q
Describe energy requiring reactions.
A
- anabolic
- does not proceed spontaneously
- energy input required
Reactants + Energy → Products
20
Q
What is the unit of energy?
A
- ΔE expressed in calories (cal) or joules (J)
- 1 cal = 4.18 J
- 1 cal = energy required to raise the temperature of 1 mL of water by 1 degree C
21
Q
Describe chemical equilibrium.
A
reactant product
- rate of forward and reverse reactions are equal
- no net charge in concentration of product or reactants
- ΔE = zero
22
Q
Increased reactant concentration pushes a reaction _____.
A
forward
23
Q
Increased product concentration pushes a reaction in _____.
A
reverse
24
Q
What reduces the activation energy barrier?
A
enzymes
25
energy of barrier = ______ ______
activation energy
26
What limits how fast a reaction goes?
activation energy barrier
27
What are the 6 factors that affect reaction rate?
- reactant and product concentrations
- temperature (hypothermia and hyperthermia)
- height of activation energy barrier (decreased height = increased rate, increased height = decreased rate)
- reactant and product concentrations (law of mass action)
28
What do catalysts do in chemical reactions?
- proteins that are catalysts for reactions in biological systems
- catalysts increase the rates of chemical reactions
29
What are the roles of enzymes in chemical reactions?
- catalysts
- decrease the activation energy
- enzymes are specific for one set of substrates or a group of similar substrates
- constant (not changed or consumed in the reaction)
30
Enzymes have the suffix ...
...ase
31
What are the 2 models of substrate specificity?
- lock and key model
| - induced fit model
32
Describe the lock and key model.
- perfect fit
| - cannot explain the reversibility of most enzyme reactions
33
Describe the induced fit model.
- Active site approximately fits substrates
- As the substrate begins to bind, a conformational change in the enzyme allows it to fit
better
34
What are cofactors?
- ions or molecules required by an enzyme for the enzyme to be active
- trace metals: Mg, Cu, Zn, Fe
- allow the substrate to bind to the active site
35
What are coenzymes?
- vitamins
| - transfer small chemical groups
36
What is used to synthesize adenosine triphosphate (ATP)?
energy from exergonic reactions
37
Describe ATP synthesis.
ADP + Pi + Energy → ATP (+H20)
- A condensation reaction (water is produced)
- A phosphorylation reaction (phosphate is used)
- Substrate-level phosphorylation
38
What is the formula for substrate level phosphorylation?
X-P + ADP → X + ATP
39
Oxidative phosphorylation requires:
electron transport chain
| ADP + Pi → ATP
40
Describe ATP breakdown.
ATP (+H20) → ADP + Pi + energy
- temporary energy storage
- hydrolysis reaction (water is used)
41
What are the stages of glucose oxidation?
- glycolysis
- Krebs cycle
- oxidative phosphorylation
- electron transport chain
42
In glycolysis, what does glucose/glycogen turn into?
2 pyruvate molecules
43
Glucose comes from...
carbohydrates in blood, can move it into cell
44
What is glycogen?
- glucose molecules stuck together
| - stored in muscle and liver
45
How many ATP are produced from glycogen and how many from glucose?
- glycogen: 3 ATP
| - glucose: 2 ATP
46
When is glycolysis needed?
when we need ATP quickly
47
How many steps are in glycolysis? Where does it take place?
- 10 steps
| - cytosol
48
What is the net gain of glycolysis?
- 2 or 3 ATP
- 2 NADH molecules
- no O2 consumed/no CO2 produced
49
Show the formula for glycolysis.
Glucose + 2NAD++2ADP+2Pi → 2 pyruvate + 2 NADH + 2H++ 2ATP
50
How does glycolysis link to the Krebs cycle?
- pyruvate turns into acetyl CoA
- unidirectional
- 1 NADH molecule produced (per pyruvate molecule)
- 1 CO2 per pyruvate
- acetyl group comes from CHO, fat, or protein breakdown
51
Where is CoA synthesized?
in the body
52
What is the initial substrate for the Kreb's cycle?
acetyl CoA
53
What is produced per each acetyl CoA?
- 1 GTP produced = 1 ATP
| - 3 NADH + 3H+ and 1 FADH2
54
What waste is produced per each acetyl CoA?
2CO2
55
Glucose generates ____ acetyl CoA molecules, thus the cycle turns ______.
- 2 acetyl CoA
| - twice
56
What are the reducing equivalents in oxidative phosphorylation?
electron carriers (NADH and FADH2)
57
Glycolysis and Krebs cycle = net gain of ____.
4 ATP
58
Bulk of ATP is formed in _______.
ETC
59
Movement of electrons down the ETC is used to...
synthesize ATP.
60
Oxidative phosphorylation requires ______.
oxygen
61
What is the electron transport system? Where is it located?
- chain of molecules
| - inner mitochondrial membrane
62
What kind of reactions do molecules undergo in the ETC?
- oxidation-reduction reactions
| - from high to low energy
63
Energy released from the ETC is used to...
synthesize ATP by oxidative phosphorylation
64
What is the last electron accepter in the ETC?
O2
65
Why does glucose catabolism occur in the absence of oxygen? What happens?
- low oxygen availability
- electron transport in chain backs up
- Krebs cycle stops
- Glycolysis can progress only if NADH is oxidized
- lactate is synthesized
66
Describe the conversion of pyruvate to lactate.
- muscles can operate with low O2
- ATP production inefficient
- lactate accumulation
67
What happens when O2 levels return?
- lactate --> pyruvate
| - oxidative phosphorylation continues
68
What else converts lactate back into pyruvate?
Cori cycle in liver
69
What is glycogen metabolism?
liver glycogen provides glucose for other cells/organs
70
Glucose can leave the cell, with the exception of ____________.
glucose-6-phosphate
71
What is glycogenolysis?
breakdown of glycogen to glucose-6-phosphate and glycogen
72
The liver has glucose-6-phosphatase (enzyme), which does what.
- converts G-6-P to glucose
| - muscle does not contain this enzyme
73
What is gluconeogenesis?
- synthesis of new glucose
- mainly in the liver
- other enzymes are involved (not a reverse of glycolysis)
74
What are the substrates involved with gluconeogenesis?
- glycerol
- lactate
- amino acids
75
Most energy is stored as...
triglycerides
76
triglycerides = _______ + _______
3 fatty acids + glycerol
77
lipids = _ kcal/g
| carbohydrates or proteins = ~_ kcal/g
- 9 kcal/g
| - ~4 kcal/g
78
Where are triglycerides stored?
adipocytes
79
What happens in lipolysis?
Triglycerides + lipases → glycerol + 3 fatty acids
Glycerol → glycolysis (20 ATP)
Fatty acids → beta-oxidation
80
Why does deamination of amino acids occur?
for energy
81
What is proteolysis?
Proteins → amino acids
82
What happens in deamination?
Amino group (-- NH2) removed
→ keto acid + ammonia (NH3)
Keto acid = pyruvate or acetyl CoA → Krebs cycle
