Metabolism (Ch. 25) Part 2 Flashcards
(189 cards)
1
Q
What is the electron transport chain?
A
A series of proteins in the inner mitochondrial membrane that pass electrons and produce ATP.
2
Q
Where is the electron transport chain located?
A
In the inner mitochondrial membrane (cristae) of mitochondria.
3
Q
What are cristae?
A
Folds in the inner mitochondrial membrane that increase surface area for more electron transport chains.
4
Q
What happens when a carrier picks up electrons?
A
It becomes reduced.
5
Q
What happens when a carrier gives up electrons?
A
It becomes oxidized.
6
Q
How is energy released in the electron transport chain?
A
Through small steps as electrons move down the chain (exergonic reactions).
7
Q
What is the final electron acceptor in cellular respiration?
A
Oxygen.
8
Q
What is chemiosmosis?
A
The process that uses electron movement to pump hydrogen ions and generate ATP.
9
Q
What is oxidative phosphorylation?
A
The combined process of the electron transport chain and chemiosmosis that produces most of the cell’s ATP.
10
Q
What is formed when oxygen accepts electrons at the end of the chain?
A
Water.
11
Q
What is chemiosmosis?
A
The process that uses a proton gradient to produce ATP in mitochondria.
12
Q
What powers the electron transport chain?
A
Energy from NADH + H⁺
13
Q
What does the electron transport chain pump across the inner mitochondrial membrane?
A
H⁺ ions (protons)
14
Q
Where do protons (H⁺) accumulate during chemiosmosis?
A
In the space between the inner and outer mitochondrial membranes.
15
Q
What is created when H⁺ builds up in the intermembrane space?
A
A proton gradient (or concentration gradient).
16
Q
What protein allows H⁺ ions to flow back into the mitochondrial matrix?
A
ATP synthase.
17
Q
How is ATP produced during chemiosmosis?
A
When H⁺ ions flow back into the matrix through ATP synthase, the energy is used to convert ADP to ATP.
18
Q
Why is the H⁺ pump also called a ‘proton pump’?
A
Because H⁺ ions consist of a single proton.
19
Q
What drives the pumping of H⁺ from the matrix to the intermembrane space?
A
Energy released as electrons move through the electron transport chain.
20
Q
What are the three main steps of chemiosmosis?
A
- Pumping H⁺ out of the matrix 2. Building up H⁺ concentration in the intermembrane space 3. H⁺ flowing back through ATP synthase to produce ATP.
21
Q
What is the electron transport chain (ETC)?
A
A series of protein carriers in the inner mitochondrial membrane that pass electrons and pump H⁺ ions to produce ATP.
22
Q
Where does the ETC take place?
A
In the inner mitochondrial membrane, which is folded into cristae to increase surface area.
23
Q
What molecules bring electrons to the ETC?
A
NADH and FADH₂ from the Krebs cycle and glycolysis.
24
Q
What happens to electrons in the ETC?
A
They move along electron carriers (like FMN, cytochromes, Fe-S centers, and coenzyme Q) in a step-by-step process, releasing energy.
25
What does the energy released by electrons in the ETC do?
It powers proton pumps, moving H⁺ ions (protons) from the matrix to the intermembrane space.
26
What happens as H⁺ ions are pumped into the intermembrane space?
A proton gradient is created, with more H⁺ outside the matrix, resulting in proton motive force (stored energy).
27
Why is oxygen important in the ETC?
Oxygen is the final electron acceptor, combining with electrons and H⁺ to form water.
28
What protein allows H⁺ ions to flow back into the mitochondrial matrix?
ATP synthase, a channel that also produces ATP.
29
How does ATP synthase make ATP?
H⁺ ions flowing through ATP synthase spins the enzyme, generating energy to combine ADP + P into ATP.
30
How many ATP molecules are made from NADH in the ETC?
Approximately 2.5 ATP per NADH molecule.
31
How many ATP molecules are made from FADH₂ in the ETC?
Approximately 1.5 ATP per FADH₂ molecule because it enters the chain later.
32
What is the combined process of the ETC and chemiosmosis called?
Oxidative phosphorylation.
33
What is the role of the proton gradient (proton motive force)?
It stores energy to drive H⁺ ions back into the matrix, powering ATP production.
34
Why is the ETC so important for cells?
It produces most of the cell’s ATP, providing the energy needed for vital processes like movement, repair, and brain function.
35
How many total ATP molecules can be produced from one glucose molecule?
30 or 32 ATP molecules.
36
How many ATP molecules come from glycolysis?
2 ATP (via substrate-level phosphorylation).
37
How many ATP molecules come from the Krebs cycle?
2 ATP (via substrate-level phosphorylation).
38
How many ATP molecules come from oxidative phosphorylation (electron transport chain)?
26-28 ATP molecules.
39
How many ATP come from NADH from all sources?
23-25 ATP (from 10 NADH molecules).
40
How many ATP come from FADH₂?
3 ATP (from 2 FADH₂ molecules).
41
What is the overall chemical reaction for cellular respiration?
Glucose + Oxygen → Carbon dioxide + Water + 30 or 32 ATP.
42
Where does glycolysis take place?
In the cytosol of the cell.
43
What happens during glycolysis?
Glucose is broken into two pyruvate molecules, producing a small amount of ATP and NADH.
44
Where does acetyl CoA formation occur?
In the mitochondrial matrix.
45
What happens during acetyl CoA formation?
Pyruvate is converted to acetyl CoA, releasing CO₂ and generating NADH.
46
Where does the Krebs cycle take place?
In the mitochondrial matrix.
47
What happens during the Krebs cycle?
Acetyl CoA is broken down to produce NADH, FADH₂, a small amount of ATP, and CO₂ as a byproduct.
48
Where does the electron transport chain (ETC) occur?
In the inner mitochondrial membrane.
49
What happens during the electron transport chain?
NADH and FADH₂ transfer electrons to the ETC, generating a proton gradient that powers ATP synthase to produce ATP. Oxygen accepts electrons to form water.
50
Which stage produces the most ATP?
The electron transport chain (ETC) produces the majority of ATP.
51
What are the relative locations of glucose catabolism stages?
Glycolysis: Cytosol
Acetyl CoA formation + Krebs cycle: Mitochondrial matrix
ETC: Inner mitochondrial membrane.
52
What is glycogenolysis?
The breakdown of stored glycogen into glucose to provide energy for the body.
53
How is glycogenolysis different from glycolysis?
Glycogenolysis breaks down glycogen into glucose, while glycolysis breaks down glucose into pyruvic acid.
54
When does glycogenolysis occur?
When the body needs energy (ATP) for activities.
55
What hormones trigger glycogenolysis?
Glucagon (from the pancreas) and epinephrine (from adrenal glands).
56
Is glycogenolysis a simple reversal of glycogenesis?
No, it uses different steps and enzymes than glycogenesis.
57
What enzyme starts the breakdown of glycogen?
Phosphorylase.
58
What is the first product when glycogen is broken down?
Glucose 1-phosphate.
59
Can muscle cells release glucose into the bloodstream?
No, muscle cells lack the enzyme phosphatase needed to convert glucose 6-phosphate to glucose.
60
Why can liver cells (hepatocytes) release glucose but muscle cells cannot?
Liver cells have the enzyme phosphatase, which muscle cells lack.
61
How can muscle glycogen indirectly contribute to blood glucose?
Muscle glycolysis produces lactic acid, which can be converted to glucose in the liver.
62
What happens to glucose 1-phosphate in muscle cells?
It's used locally for ATP production through glycolysis and the Krebs cycle.
63
What's the difference between liver and muscle glycogen use?
Liver glycogen maintains blood glucose levels, while muscle glycogen provides energy directly to the muscles.
64
What is glycogenesis?
The process of converting excess glucose into glycogen for storage in the liver, stimulated by insulin.
65
What is glycogenolysis?
The process of breaking down stored glycogen into glucose to raise blood sugar levels, stimulated by glucagon and epinephrine.
66
What enzyme converts glucose to glucose 6-phosphate in the liver?
Hexokinase.
67
What does the enzyme phosphorylase do?
It breaks down glycogen into glucose 1-phosphate during glycogenolysis.
68
What does the enzyme phosphatase do?
It converts glucose 6-phosphate into glucose so it can be released into the bloodstream.
69
What hormone stimulates glycogenesis?
Insulin.
70
What hormones stimulate glycogenolysis?
Glucagon and epinephrine.
71
What is the difference between glycogenolysis and glycolysis?
Glycogenolysis breaks down glycogen into glucose, while glycolysis breaks down glucose into pyruvic acid for energy production.
72
What is the final step in glycogenesis?
Converting uridine diphosphate glucose (UDP-glucose) into glycogen for storage.
73
Why is the enzyme phosphatase important in liver cells?
It allows glucose 6-phosphate to be converted to glucose, which can then be released into the bloodstream to maintain blood glucose levels.
74
What is required to convert glucose to glucose 6-phosphate during glycogenesis?
ATP (adenosine triphosphate).
75
What intermediate compound appears in both glycogenesis and glycogenolysis?
Glucose 6-phosphate.
76
What is gluconeogenesis?
The process of creating new glucose from non-carbohydrate sources such as proteins, fats, and lactic acid.
77
When does gluconeogenesis typically occur?
When liver glycogen is depleted, during starvation, on very low-carb diets, or with certain endocrine disorders.
78
How is gluconeogenesis different from glycogenolysis?
Glycogenolysis releases glucose from glycogen stores, while gluconeogenesis creates brand new glucose from non-carbohydrate sources.
79
What percentage of amino acids can be used for gluconeogenesis?
About 60% of amino acids in the body.
80
Which part of triglycerides (fats) can be converted to glucose?
The glycerol portion of triglycerides.
81
What are three non-carbohydrate sources used for gluconeogenesis?
Amino acids from proteins, glycerol from fats, and lactic acid.
82
What hormone from the adrenal cortex stimulates gluconeogenesis?
Cortisol (a glucocorticoid).
83
How does cortisol help with gluconeogenesis?
It stimulates the breakdown of proteins into amino acids, which can be used to produce glucose.
84
What other hormones besides cortisol stimulate gluconeogenesis?
Glucagon and thyroid hormones (T3 and T4).
85
What do thyroid hormones (T3 and T4) mobilize for gluconeogenesis?
They mobilize proteins and triglycerides from adipose tissue.
86
What happens to amino acids like alanine and glycine during gluconeogenesis?
They are converted to pyruvic acid, which can then be synthesized into glucose.
87
What happens to glycerol during gluconeogenesis?
Glycerol is converted to glyceraldehyde 3-phosphate, which can form glucose or pyruvic acid.
88
Why can’t lipids like triglycerides dissolve in blood?
Lipids are hydrophobic (water-fearing) and do not dissolve in blood, which is mostly water.
89
How are lipids transported in the blood?
They combine with proteins to form lipoproteins, which make them water-soluble.
90
What are lipoproteins?
Lipoproteins are spherical particles with:
- An outer shell of proteins, phospholipids, and cholesterol.
- An inner core containing triglycerides and other lipids.
91
What role do apoproteins play in lipoproteins?
Apoproteins in the outer shell:
- Make lipoproteins soluble in blood.
- Direct lipoproteins to specific destinations in the body.
92
How are apoproteins labeled?
They are designated with letters like A, B, C, D, and E, each with specific functions.
93
Where are lipoproteins produced?
Lipoproteins are made in the liver and intestines.
94
What function do lipoproteins serve in the body?
Lipoproteins act as transport vehicles for carrying lipids to tissues for energy, storage, or cell membrane building.
95
Why is the outer shell of a lipoprotein important?
The outer shell provides water solubility, allowing it to travel easily in blood.
96
What type of molecules are carried in the inner core of lipoproteins?
Hydrophobic lipids like triglycerides and cholesterol esters.
97
Why are lipoproteins essential?
They ensure that hydrophobic lipids like triglycerides can be transported through the bloodstream efficiently.
98
What are lipoproteins?
Complexes of lipids and proteins that transport fats through the bloodstream.
99
What are the four main types of lipoproteins?
1. Chylomicrons 2. Very Low-Density Lipoproteins (VLDLs) 3. Low-Density Lipoproteins (LDLs) 4. High-Density Lipoproteins (HDLs)
100
What is the function of chylomicrons?
Transport dietary (eaten) fats from the intestine to adipose tissue for storage.
101
Where are chylomicrons formed?
In the small intestine after eating.
102
What is the function of Very Low-Density Lipoproteins (VLDLs)?
Transport triglycerides made in the liver to adipose tissue for storage.
103
Where are VLDLs formed?
In the liver.
104
Why is LDL called 'bad cholesterol'?
When present in excess, it can deposit cholesterol in artery walls, forming plaques that increase heart disease risk.
105
What is the function of Low-Density Lipoproteins (LDLs)?
Deliver cholesterol to cells for membrane repair and hormone production.
106
What percentage of blood cholesterol is carried by LDLs?
About 75% of total blood cholesterol.
107
Why is HDL called 'good cholesterol'?
It removes excess cholesterol from cells and blood, transporting it to the liver for elimination.
108
What is the function of High-Density Lipoproteins (HDLs)?
Remove excess cholesterol from the body and transport it to the liver for elimination.
109
What special protein in chylomicrons helps activate fat breakdown?
Apoprotein C-2 (Apo C-2) activates lipoprotein lipase.
110
How does having high HDL levels affect heart disease risk?
High HDL levels are associated with decreased risk of heart disease.
111
What happens when a cell has enough cholesterol?
It reduces production of LDL receptors through negative feedback.
112
What happens to VLDLs after they deposit triglycerides?
They are converted to LDLs.
113
Where does cholesterol come from?
Most cholesterol is made by liver cells (hepatocytes), while some comes from foods like eggs, dairy, and organ meats.
114
What does a lipid profile test measure?
It measures:
- Total cholesterol
- HDL cholesterol ('good')
- Triglycerides (VLDL)
- LDL cholesterol (often calculated from the other values)
115
Why is high total cholesterol a concern?
Increases in total cholesterol levels are associated with a greater risk of coronary artery disease.
116
What types of exercise can help reduce high cholesterol?
Aerobic exercise (like running, swimming) and nearly aerobic levels of activity help improve cholesterol levels.
117
How can diet affect cholesterol levels?
Reducing total fat intake, especially saturated fats, can help lower cholesterol levels.
118
Besides lifestyle changes, what other treatment options exist for high cholesterol?
Certain medications (like statins) can be prescribed to help lower cholesterol levels.
119
How do genetics affect cholesterol levels?
Genetics influence cholesterol levels through the presence or absence of LDL receptors, making some people naturally predisposed to higher cholesterol.
120
What is the difference between HDL and LDL cholesterol?
HDL ('good') removes excess cholesterol from the bloodstream, while LDL ('bad') can deposit cholesterol in artery walls.
121
Why might someone have high cholesterol despite a healthy diet?
Genetic factors can cause high cholesterol regardless of lifestyle, particularly if they have fewer LDL receptors due to inherited conditions.
122
What organs are most affected by high cholesterol?
The heart and blood vessels (cardiovascular system) are most affected, with high cholesterol increasing the risk of coronary artery disease.
123
What are triglycerides and how do they relate to cholesterol?
Triglycerides are a type of fat in the blood that's measured alongside cholesterol. High levels of both increase heart disease risk.
124
How frequently should cholesterol levels be checked?
Generally, healthy adults should have their cholesterol checked every 4-6 years, while those with risk factors may need more frequent testing.
125
What happens to lipids when the body needs energy?
Lipids can be oxidized to produce ATP (energy).
126
Where are excess lipids stored in the body?
In adipose tissue (fat deposits) throughout the body and in the liver.
127
What structural role do phospholipids play?
They are key components of cell membranes.
128
What is the function of lipoproteins?
They transport cholesterol and other lipids throughout the body.
129
What role does thromboplastin play?
It is needed for blood clotting.
130
What is the function of myelin sheaths?
They cover nerve cells and speed up nerve impulse conduction.
131
What are two essential fatty acids the body cannot make?
Linoleic acid and linolenic acid.
132
Where can we find essential fatty acids in our diet?
In vegetable oils and leafy vegetables.
133
What are the two main uses of lipids in the body?
Energy production (ATP) and structural/functional components.
134
How are lipids similar to carbohydrates in terms of energy?
Both can be oxidized to produce ATP for the body's energy needs.
135
Why are essential fatty acids called 'essential'?
Because the body cannot synthesize them and must obtain them from food.
136
Name four important functions of lipids in the body.
Energy production, cell membrane structure, nerve insulation, and blood clotting.
137
What is the main function of adipose tissue?
To remove triglycerides from chylomicrons and VLDLs and store them until needed for ATP production in other parts of the body.
138
What percentage of the body's energy reserves are stored as triglycerides?
98% of all body energy reserves are stored as triglycerides in adipose tissue.
139
Why are triglycerides stored more easily than glycogen?
Because triglycerides are hydrophobic and do not exert osmotic pressure on cell membranes.
140
Where is approximately 50% of stored triglycerides found?
In adipocytes (fat cells) in the subcutaneous tissue (under the skin).
141
List four locations where adipose tissue is found besides subcutaneous tissue.
Around the kidneys (12%), in the omenta (10-15%), in genital areas (15%), between muscles (5-8%), and behind the eyes, in heart sulci, and attached to the large intestine (5%).
142
What happens to stored triglycerides over time?
They are continually broken down and resynthesized, released from storage, transported in the blood, and redeposited in other adipose tissue cells.
143
What is lipid catabolism (lipolysis)?
The process of splitting triglycerides into fatty acids and glycerol.
144
What happens to fatty acids after lipolysis?
They undergo beta oxidation and can form ketone bodies.
145
What is lipid anabolism (lipogenesis)?
The process of synthesizing lipids from glucose or amino acids.
146
When does lipogenesis occur?
When individuals consume more calories than needed.
147
What are two additional functions of adipose tissue besides energy storage?
It provides insulation and protects various parts of the body.
148
What carries dietary triglycerides to adipose tissue for storage?
Chylomicrons.
149
What carries endogenous (body-made) triglycerides to adipose tissue?
Very-Low-Density Lipoproteins (VLDLs).
150
What happens to proteins during digestion?
Proteins are broken down into amino acids.
151
Are amino acids stored for future use?
No, amino acids are not stored. They are either oxidized for ATP production or used to synthesize new proteins.
152
What happens to excess dietary amino acids?
They are converted to glucose (gluconeogenesis) or triglycerides (lipogenesis) for storage, rather than being excreted.
153
Which hormones stimulate the transport of amino acids into cells?
Insulinlike growth factors (IGFs) and insulin.
154
What happens to amino acids immediately after digestion?
They are actively transported into cells and reassembled into proteins.
155
What are some functions of proteins in the body?
Enzymes: Catalyze chemical reactions.
Transportation: Proteins (e.g., hemoglobin) transport substances like oxygen.
Immunity: Proteins serve as antibodies to fight infections.
Clotting: Proteins like fibrinogen are involved in blood clotting.
Hormones: Proteins like insulin help regulate body processes.
Muscle Contraction: Proteins like actin and myosin enable muscle movement.
Structure: Proteins such as collagen, elastin, and keratin provide structural support to skin, bones, and hair.
156
What are enzymes, and how are they related to proteins?
Enzymes are proteins that speed up chemical reactions in the body.
157
How do proteins support muscle function?
Proteins like actin and myosin are involved in muscle contraction.
158
What structural roles do proteins play?
They serve as key components of collagen (bones, tendons), elastin (connective tissues), and keratin (hair, nails, skin).
159
Why are proteins important for transportation in the body?
They carry molecules like oxygen (hemoglobin) throughout the body.
160
How are proteins involved in blood clotting?
Proteins like fibrinogen help the blood clot to prevent excessive bleeding.
161
What happens if more amino acids are consumed than needed?
Excess amino acids are converted into glucose or fat for storage.
162
How are amino acids transported into cells after digestion?
Through active transport, a process stimulated by IGFs and insulin.
163
What is protein catabolism?
The process of breaking down proteins into amino acids. It occurs daily in the body and is stimulated mainly by cortisol from the adrenal cortex.
164
What are the possible fates of amino acids from protein catabolism?
1. Converted to other amino acids and recycled into new proteins 2. Converted to fatty acids, ketone bodies, or glucose by hepatocytes 3. Oxidized to generate ATP via the Krebs cycle and electron transport chain.
165
What is deamination?
The process of removing the amino group (NH₂) from amino acids, occurring in hepatocytes (liver cells). This is necessary before amino acids can enter the Krebs cycle.
166
What happens to ammonia produced during deamination?
The liver converts the toxic ammonia (NH₃) to relatively harmless urea, which is then excreted in the urine.
167
What is protein anabolism?
The formation of peptide bonds between amino acids to produce new proteins, carried out on ribosomes and directed by DNA and RNA.
168
Which hormones stimulate protein synthesis?
Insulinlike growth factors, thyroid hormones (T₃ and T₄), insulin, estrogens, and testosterone.
169
When is adequate dietary protein especially important?
During growth years, pregnancy, and when tissue has been damaged by disease or injury.
170
What are essential amino acids?
Amino acids that must be present in the diet because the body cannot synthesize them in adequate amounts. Humans have 10 essential amino acids.
171
Name the eight amino acids that humans cannot synthesize at all.
Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
172
Which two amino acids are considered essential but can be synthesized in inadequate amounts?
Arginine and histidine, especially during childhood.
173
What is a complete protein?
A protein that contains sufficient amounts of all essential amino acids. Examples include beef, fish, poultry, eggs, and milk.
174
What is an incomplete protein?
A protein that does not contain all essential amino acids. Examples include leafy green vegetables, legumes (beans and peas), and grains.
175
What is transamination?
The transfer of an amino group from an amino acid to pyruvic acid or to an acid in the Krebs cycle. This process allows the body to synthesize nonessential amino acids.
176
Will eating more protein (beyond adequate intake) increase bone or muscle mass?
No. Once dietary protein intake is adequate, only a regular program of forceful, weight-bearing muscular activity will increase muscle mass.
177
How do cells generate ATP from amino acids?
They convert amino acids to molecules that can enter the Krebs cycle (like acetyl CoA) after deamination, then oxidize them via the Krebs cycle and electron transport chain.
178
What happens to amino acids during protein metabolism?
Amino acids can be converted to various components of the Krebs cycle to produce energy (ATP).
179
Which amino acids are converted to pyruvic acid?
Alanine, glycine, serine, cysteine, and threonine.
180
What happens to pyruvic acid in the metabolic pathway?
Pyruvic acid is converted to acetyl CoA, which enters the Krebs cycle.
181
Which amino acids are directly converted to acetyl CoA?
Phenylalanine, tyrosine, leucine, lysine, and tryptophan.
182
How do aspartic acid and asparagine contribute to the Krebs cycle?
They are converted to oxaloacetic acid, a direct component of the Krebs cycle.
183
Which amino acids are converted to alpha-ketoglutaric acid?
Glutamic acid, arginine, histidine, glutamine, and proline.
184
How do phenylalanine and tyrosine enter the Krebs cycle?
They can be converted to fumaric acid, which is an intermediate in the Krebs cycle.
185
Which amino acids are converted to succinyl CoA?
Isoleucine, methionine, and valine.
186
Why does the body convert amino acids to Krebs cycle components?
To produce energy (ATP) when carbohydrates or fats are unavailable or insufficient.
187
What is the Krebs cycle?
A circular metabolic pathway in the mitochondria that generates energy (ATP) and is a central part of cellular respiration.
188
How many entry points for amino acids into the Krebs cycle are shown in the diagram?
Five entry points: acetyl CoA, oxaloacetic acid, alpha-ketoglutaric acid, succinyl CoA, and fumaric acid.
189
What happens to isoleucine, leucine, and tryptophan in protein metabolism?
They can be converted to acetyl CoA, which directly enters the Krebs cycle.
