Metabolism (Ch. 25) Part 1 Flashcards
1
Q
What happens to most of the food molecules your body absorbs?
A
Most are used to supply energy for various life processes like muscle movement, cell activities, and protein production.
2
Q
Give two examples of life processes that require energy from food.
A
Active transport (moving substances in/out of cells) and muscle contractions.
3
Q
What is the second main fate of absorbed food molecules?
A
They serve as building blocks for making complex structural or functional molecules in the body.
4
Q
Name two complex molecules that your body builds using nutrients from food.
A
Muscle proteins and hormones.
5
Q
What is the third main fate of absorbed food molecules?
A
Some are stored for future use when the body needs extra energy.
6
Q
Name two forms in which the body stores nutrients for later use.
A
Glycogen (stored mainly in liver and muscles) and triglycerides (stored as fat).
7
Q
Why does the body store some nutrients instead of using them immediately?
A
To have energy reserves available for times when you’re not eating or when you need extra energy.
8
Q
What does metabolism mean?
A
Metabolism refers to all of the chemical reactions happening in the body.
9
Q
What are the two types of metabolic reactions?
A
1) Catabolic (breakdown reactions)
2) Anabolic (building reactions)
10
Q
What is catabolism?
A
Catabolism breaks down complex molecules into simpler ones (decomposition).
11
Q
Does catabolism release or use energy?
A
Catabolism is exergonic, meaning it releases energy by releasing chemical energy stored in molecules.
12
Q
What is anabolism?
A
Anabolism combines simple molecules to build complex ones (synthesis).
13
Q
Does anabolism release or use energy?
A
Anabolism is endergonic, meaning it uses more energy than it produces.
14
Q
What are examples of anabolic reactions?
A
- Forming peptide bonds to make proteins
- Building fatty acids into phospholipids
- Storing glucose as glycogen
15
Q
What is metabolism the result of?
A
Metabolism results from the balance of anabolic and catabolic reactions.
16
Q
Can anabolic and catabolic reactions occur simultaneously?
A
Yes, both can be occurring at the same time in different parts of the cell.
For example, catabolism may happen in mitochondria while anabolism occurs in the endoplasmic reticulum.
17
Q
What is the primary energy molecule that connects anabolic and catabolic reactions?
A
ATP (adenosine triphosphate) is the energy molecule that couples and participates in the two types of reactions.
18
Q
What determines which metabolic reactions occur in a cell?
A
Metabolic reactions depend on enzymes active in the cell at a particular time. Different enzymes catalyze different reactions.
19
Q
What happens to biological molecules in living tissues?
A
Recycling of biological molecules occurs continuously in living tissue – some more rapidly than others. Most molecules have limited lifetimes before being broken down and their components recycled.
20
Q
How does ATP function in metabolism?
A
ATP captures energy released from catabolic reactions and delivers it to energy-requiring anabolic reactions, serving as the primary energy currency of cells.
21
Q
What is the difference between anabolic and catabolic reactions?
A
Anabolic reactions build complex molecules from simpler ones and require energy (endergonic), while catabolic reactions break down complex molecules into simpler ones and release energy (exergonic).
22
Q
What type of reactions are important in energy transfer in cells?
A
Oxidation-reduction reactions (redox reactions).
23
Q
What is oxidation?
A
Oxidation involves the removal of electrons from an atom or molecule.
24
Q
What happens to a molecule’s energy when it undergoes oxidation?
A
Its potential energy decreases.
25
What's a common example of an oxidation reaction in the body?
The conversion of lactic acid to pyruvic acid.
26
In the conversion of lactic acid to pyruvic acid, what is removed?
Two hydrogen atoms (H⁺ + H⁻) are removed.
27
Why are oxidation reactions important for cellular processes?
They release energy that can be captured and used to power other cellular activities.
28
What happens to electrons during oxidation?
Electrons are removed from the molecule that is being oxidized.
29
How does the structure of lactic acid change when it's oxidized to pyruvic acid?
The -OH group on lactic acid is converted to a C=O group in pyruvic acid through the removal of hydrogen.
30
What is reduction in biochemistry?
Reduction involves the addition of electrons (or hydrogen atoms) to a molecule.
31
What happens to a molecule's energy when it undergoes reduction?
Its potential energy increases.
32
What's an example of a reduction reaction in the body?
The conversion of pyruvic acid to lactic acid.
33
In the conversion of pyruvic acid to lactic acid, what is added?
Two hydrogen atoms (H⁺ + H⁻) are added.
34
How does the structure change when pyruvic acid is reduced to lactic acid?
The C=O (carbonyl) group in pyruvic acid is converted to a C-OH (hydroxyl) group in lactic acid.
35
When might your body convert pyruvic acid to lactic acid?
During strenuous activity when there isn't enough oxygen, helping cells continue to produce energy temporarily.
36
Is reduction a way to store or release energy?
Reduction is a way to store energy in molecules.
37
What is the relationship between reduction and oxidation?
They are opposite processes - reduction adds electrons while oxidation removes them.
38
Why is reduction important for cellular energy processes?
It allows cells to store energy in molecules that can be used later for other cellular processes.
39
What happens to hydrogen atoms when a substance is oxidized?
The liberated hydrogen atoms are transferred by coenzymes to another compound.
40
What are the two main coenzymes that transfer hydrogen atoms during cellular energy processes?
Nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD).
41
What happens to NAD⁺ when it accepts hydrogen atoms?
NAD⁺ becomes NADH + H⁺ (the reduced form).
42
What happens to FAD when it accepts hydrogen atoms?
FAD becomes FADH₂ (the reduced form).
43
Which form of NAD carries more energy: NAD⁺ or NADH?
NADH carries more energy (the reduced form).
44
Which form of FAD carries more energy: FAD or FADH₂?
FADH₂ carries more energy (the reduced form).
45
What do we call the process when NAD⁺ accepts hydrogen and becomes NADH?
Reduction.
46
What do we call the process when NADH releases hydrogen and becomes NAD⁺?
Oxidation.
47
Why are coenzymes like NAD and FAD important for energy transfer in cells?
They pick up hydrogen atoms from oxidized substances and transport them to where energy is needed, serving as temporary energy carriers.
48
What do we call reactions where oxidation and reduction occur together?
Oxidation-reduction reactions or redox reactions.
49
Why are oxidation and reduction always coupled?
Because when one molecule loses electrons or hydrogen atoms (oxidation), another molecule must gain those electrons or hydrogen atoms (reduction).
50
In the example from the slide, what happens to lactic acid?
Lactic acid is oxidized, losing hydrogen atoms to become pyruvic acid.
51
What happens to NAD⁺ in the redox reaction with lactic acid?
NAD⁺ is reduced, gaining hydrogen atoms to become NADH + H⁺.
52
Is oxidation typically energy-releasing or energy-requiring?
Oxidation is usually exergonic (energy-releasing).
53
How do cells efficiently capture energy during metabolic processes?
Cells use multistep biochemical reactions to capture energy in small, manageable amounts.
54
What is the relationship between lactic acid and NAD⁺ in the example redox reaction?
Lactic acid donates hydrogen atoms (becomes oxidized) while NAD⁺ accepts those hydrogen atoms (becomes reduced).
55
What is the end result of the coupled oxidation-reduction reaction between lactic acid and NAD⁺?
Lactic acid is converted to pyruvic acid, and NAD⁺ is converted to NADH + H⁺.
56
Why are redox reactions important for cellular energy transfer?
They allow cells to transfer and store energy by moving electrons from one molecule to another.
57
What happens to glucose's energy during cellular metabolism?
Energy is captured at each step and transferred to ATP.
58
Why does glucose contain more potential energy than oxidized compounds?
Because it has many hydrogen atoms.
59
What happens to some of the energy released during oxidation reactions?
It's captured when ATP is formed.
60
What is the process of adding a phosphate group to ADP called?
Phosphorylation.
61
How is ATP formed from ADP?
A phosphate group is added to ADP along with energy.
62
What is the primary energy carrier molecule in cells?
ATP (adenosine triphosphate).
63
What are the components of ATP?
Adenosine attached to three phosphate groups.
64
Why does the body break down glucose in multiple steps?
To capture energy efficiently at each step and transfer it to ATP.
65
What is the normal blood glucose level?
90mg/100mL
66
What is the body's preferred source for making ATP?
Glucose
67
What are the four main uses of glucose in the body?
1. ATP production 2. Amino acid synthesis 3. Glycogen synthesis 4. Triglyceride synthesis
68
What happens to glucose when cells need immediate energy?
It's oxidized to produce ATP.
69
How can glucose contribute to protein production?
Glucose can be used to form several amino acids, which are then incorporated into proteins.
70
What is glycogenesis?
The process of combining hundreds of glucose molecules to form glycogen for storage.
71
How much glycogen can the liver store?
About 125g
72
How much glycogen can skeletal muscles store?
About 375g
73
What happens to glucose when glycogen storage is full?
It's transformed into glycerol and fatty acids to make triglycerides (fat).
74
Where are triglycerides stored, and what is special about this storage?
Triglycerides are stored in adipose tissue (fat), which has virtually unlimited storage capacity.
75
Why must glucose pass through the plasma membrane?
To be used by the cell, glucose must enter the cytosol (inside of the cell).
76
How does glucose enter cells in the digestive tract and kidneys?
Through secondary active transport using sodium-glucose symporters.
77
What transport method moves glucose into most body cells?
Facilitated diffusion using GluT transporters.
78
How does insulin affect glucose transport?
Insulin increases the insertion of GluT4 transporters into the plasma membrane, increasing the rate of glucose entry.
79
Which cells don't require insulin for glucose entry?
Neurons (brain cells) and hepatocytes (liver cells).
80
What type of GluT is always present in the membranes of neurons and liver cells?
A different type of GluT (not GluT4) that allows glucose entry to be 'always turned on.'
81
What happens to glucose after it enters a cell?
It becomes phosphorylated, which traps it inside the cell.
82
Why can't phosphorylated glucose leave the cell?
Because GluT transporters cannot transport phosphorylated glucose.
83
What are GluT molecules?
A family of transporters that bring glucose into cells via facilitated diffusion.
84
What is cellular respiration?
The oxidation of glucose to produce ATP (energy).
85
What are the four main steps of cellular respiration?
1. Glycolysis 2. Formation of acetyl coenzyme A 3. Krebs cycle 4. Electron transport chain
86
What happens during glycolysis?
One glucose molecule is broken down into two pyruvic acid molecules, producing 2 ATP and 2 NADH + H⁺.
87
Does glycolysis require oxygen?
No, glycolysis can occur under both aerobic (with oxygen) and anaerobic (without oxygen) conditions.
88
What is the purpose of forming acetyl coenzyme A?
It's a transition step that prepares pyruvic acid for entrance into the Krebs cycle, producing NADH + H⁺ and CO₂.
89
What happens in the Krebs cycle?
Acetyl coenzyme A is oxidized, producing CO₂, ATP, NADH + H⁺, and FADH₂.
90
What happens in the electron transport chain?
NADH + H⁺ and FADH₂ are oxidized, transferring their electrons through a series of carriers to produce 26-28 ATP.
91
Which steps of cellular respiration require oxygen?
The Krebs cycle and electron transport chain require oxygen (collectively called aerobic respiration).
92
What happens when oxygen is not available?
Only glycolysis occurs, and pyruvic acid is converted to lactic acid (anaerobic glycolysis).
93
How many total ATP molecules can be produced from one glucose molecule in aerobic respiration?
About 30-32 ATP molecules.
94
How many ATP molecules are produced during anaerobic glycolysis alone?
Only 2 ATP molecules.
95
What is the starting molecule for cellular respiration?
1 glucose molecule
96
What are the four main stages of cellular respiration?
1. Glycolysis 2. Formation of acetyl coenzyme A 3. Krebs cycle 4. Electron transport chain
97
What does glycolysis produce?
2 pyruvic acid molecules, 2 ATP, and 2 NADH + 2H⁺
98
What happens during the formation of acetyl coenzyme A?
Pyruvic acid is converted to acetyl CoA, producing 2 NADH + 2H⁺ and 2 CO₂
99
What does the Krebs cycle produce?
2 ATP, 6 NADH + 6H⁺, 2 FADH₂, and 4 CO₂
100
What is the role of the electron transport chain?
It transfers electrons from NADH and FADH₂ through a series of carriers to produce 26-28 ATP.
101
What does the electron transport chain use oxygen for?
Oxygen (6 O₂) accepts electrons at the end of the chain, combining with hydrogen to form 6 water molecules (H₂O).
102
How many total ATP molecules are produced from one glucose molecule?
Approximately 30-32 ATP molecules.
103
Where do the electrons for the electron transport chain come from?
From NADH and FADH₂ produced during earlier stages of cellular respiration.
104
What is the total CO₂ produced during complete cellular respiration of one glucose molecule?
6 CO₂ molecules (2 from acetyl CoA formation and 4 from the Krebs cycle).
105
What are the four main steps of cellular respiration?
1. Glycolysis 2. Formation of acetyl coenzyme A 3. Krebs cycle 4. Electron transport chain
106
Where does glycolysis take place in the cell?
In the cytoplasm.
107
What happens to glucose during glycolysis?
One glucose molecule (6 carbons) is split into two pyruvic acid molecules (3 carbons each).
108
What energy molecules are produced during glycolysis?
2 ATP and 2 NADH.
109
Does glycolysis require oxygen?
No, glycolysis does not require oxygen.
110
What are the intermediate molecules shown in glycolysis?
Dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
111
What happens during the formation of acetyl coenzyme A?
Pyruvic acid is converted to acetyl CoA, producing CO₂ and NADH.
112
Where do the Krebs cycle and electron transport chain take place?
In the mitochondria.
113
What does the Krebs cycle produce?
CO₂, ATP, NADH, and FADH₂.
114
What is the role of the electron transport chain?
It accepts electrons from NADH and FADH₂ and passes them through a series of carriers to produce large amounts of ATP (26-28).
115
What is the final electron acceptor in the electron transport chain?
Oxygen (O₂), which combines with hydrogen to form water (H₂O).
116
How much total ATP is produced from one glucose molecule through all steps of cellular respiration?
About 30-32 ATP (2 from glycolysis, 2 from Krebs cycle, and 26-28 from the electron transport chain).
117
Which step of cellular respiration produces the most ATP?
The electron transport chain (26-28 ATP).
118
What is glycolysis?
The process that splits a 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules.
119
How many ATP molecules are produced in glycolysis?
Net production of 2 ATP (uses 2 ATP, produces 4 ATP).
120
How many reactions make up glycolysis?
10 reactions.
121
Which steps in glycolysis produce ATP?
Steps 6 and 10 each produce 2 ATP molecules.
122
What happens in the first half of glycolysis (steps 1-5)?
ATP is invested and glucose is split into two glyceraldehyde 3-phosphate (G3P) molecules.
123
What happens in the second half of glycolysis (steps 6-10)?
The two G3P molecules are converted to pyruvic acid and ATP is generated.
124
What enzyme regulates the rate of glycolysis?
Phosphofructokinase (PFK).
125
When is phosphofructokinase activity high?
When ADP concentration is high (indicating the cell needs energy).
126
What happens to glucose when phosphofructokinase activity is low?
Glucose is converted to glycogen for storage instead of entering glycolysis.
127
What are the end products of glycolysis?
Two pyruvic acid molecules, 2 NADH, and a net gain of 2 ATP.
128
What is the starting molecule for glycolysis?
One glucose molecule (a 6-carbon sugar).
129
What happens in Step 1 of glycolysis?
ATP donates a phosphate to glucose, forming glucose 6-phosphate.
130
What happens in Step 2 of glycolysis?
Glucose 6-phosphate is rearranged into fructose 6-phosphate.
131
What happens in Step 3 of glycolysis?
Another ATP is used to add a second phosphate, creating fructose 1,6-bisphosphate.
132
What enzyme controls Step 3 of glycolysis?
Phosphofructokinase.
133
What happens in Step 4 of glycolysis?
Fructose 1,6-bisphosphate splits into two 3-carbon molecules: dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
134
What happens in Step 5 of glycolysis?
Dihydroxyacetone phosphate is converted to glyceraldehyde 3-phosphate.
135
What happens in Step 6 of glycolysis?
Each glyceraldehyde 3-phosphate is modified, producing NADH and adding another phosphate to form 1,3-bisphosphoglyceric acid.
136
What happens in Step 7 of glycolysis?
ADP receives a phosphate from 1,3-bisphosphoglyceric acid, producing ATP and 3-phosphoglyceric acid.
137
What happens in Step 8 of glycolysis?
3-phosphoglyceric acid is converted to 2-phosphoglyceric acid.
138
What happens in Step 9 of glycolysis?
2-phosphoglyceric acid is converted to phosphoenolpyruvic acid.
139
What happens in Step 10 of glycolysis?
ADP receives a phosphate from phosphoenolpyruvic acid, producing ATP and pyruvic acid.
140
What are the end products of glycolysis?
2 pyruvic acid molecules, 2 NADH, and a net gain of 2 ATP.
141
How many ATP molecules are consumed in glycolysis?
2 ATP molecules (in Steps 1 and 3).
142
How many ATP molecules are produced in glycolysis?
4 ATP molecules (2 in Step 7 and 2 in Step 10).
143
What is the net ATP gain in glycolysis?
2 ATP molecules (4 produced minus 2 consumed).
144
What happens to pyruvic acid under anaerobic conditions (low oxygen)?
Pyruvic acid is reduced to lactic acid to regenerate NAD+ and continue glycolysis.
145
Why is lactic acid formation important in anaerobic conditions?
It allows glycolysis to continue by regenerating NAD+.
146
What happens to lactic acid in the body?
It diffuses into the bloodstream and is converted back to pyruvic acid by liver cells when oxygen is available.
147
What are potential effects of excess lactic acid?
Muscle fatigue and a burning sensation.
148
What happens to pyruvic acid under aerobic conditions (high oxygen)?
Pyruvic acid is converted to acetyl CoA inside the mitochondria.
149
Why is acetyl CoA important?
It links glycolysis to the Krebs cycle, the next step in energy production.
150
Why can red blood cells only process pyruvic acid anaerobically?
They lack mitochondria, so they rely solely on glycolysis for ATP production.
151
Summarize the fate of pyruvic acid in low vs. high oxygen conditions.
Low oxygen: Pyruvic acid ➝ Lactic acid (temporary energy system).
High oxygen: Pyruvic acid ➝ Acetyl CoA ➝ Krebs cycle for energy production.
152
What enzyme converts pyruvic acid to acetyl CoA?
Pyruvate dehydrogenase in the mitochondrial matrix.
153
What happens during the decarboxylation of pyruvic acid?
One CO₂ molecule is removed, producing acetyl groups.
154
What coenzyme is reduced during pyruvic acid oxidation?
NAD+ is reduced to NADH + H⁺, storing energy.
155
How many acetyl CoA molecules are produced per glucose molecule?
Two acetyl CoA molecules (one per pyruvic acid).
156
What are the final products of the transition step for one glucose molecule?
2 acetyl CoA, 2 CO₂, and 2 NADH + H⁺.
157
What is the role of acetyl CoA in cellular respiration?
It enters the Krebs cycle to continue energy production.
158
What are the three main stages of cellular respiration?
1. Glycolysis 2. Krebs cycle (citric acid cycle) 3. Electron transport chain (ETC)
159
Where does glycolysis occur?
In the cytoplasm of the cell.
160
What does glycolysis produce from one glucose molecule?
2 pyruvic acid molecules, 2 ATP, and 2 NADH.
161
What happens to pyruvic acid before the Krebs cycle?
It's converted to acetyl CoA, releasing CO₂ and producing NADH.
162
Where does the Krebs cycle occur?
In the mitochondrial matrix.
163
What does the Krebs cycle produce for each acetyl CoA?
1 ATP, 3 NADH, 1 FADH₂, and 2 CO₂.
164
How many times does the Krebs cycle run for one glucose molecule?
Twice (once for each acetyl CoA from one glucose).
165
What happens in the electron transport chain?
Electrons from NADH and FADH₂ move through protein complexes, creating ATP and forming water.
166
What is the final electron acceptor in the electron transport chain?
Oxygen (O₂), which combines with hydrogen to form water.
167
Which stage of cellular respiration produces the most ATP?
The electron transport chain.
168
What is the first molecule formed in the Krebs cycle?
Citric acid (when acetyl CoA combines with oxaloacetic acid).
169
What are the final products of complete cellular respiration?
ATP, CO₂, and H₂O (water).
170
What other name is used for the Krebs cycle?
The citric acid cycle.
171
Where does the Krebs cycle occur in the cell?
In the matrix of mitochondria.
172
How many chemical reactions make up the Krebs cycle?
8 reactions.
173
What are the two main coenzymes that carry energy from the Krebs cycle?
NADH and FADH₂.
174
How many ATP molecules are produced directly by the Krebs cycle per glucose?
2 ATP molecules.
175
How many times does the Krebs cycle run for each glucose molecule?
Twice (once for each pyruvic acid).
176
What is the first compound formed in the Krebs cycle?
Citric acid.
177
What is the end product of the Krebs cycle?
Oxaloacetic acid.
178
What happens to oxaloacetic acid at the end of the cycle?
It combines with a new acetyl CoA to start the cycle again.
179
How many NADH molecules are produced by the Krebs cycle per glucose?
6 NADH molecules.
180
How many FADH₂ molecules are produced by the Krebs cycle per glucose?
2 FADH₂ molecules.
181
What waste product is released during the Krebs cycle?
Carbon dioxide (CO₂).
182
Why are NADH and FADH₂ the most important products of the Krebs cycle?
They carry energy to the electron transport chain where most ATP is produced.
