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Questions and Answers
What is the primary function of metabolism in the body?
Which factor does NOT contribute to overall metabolism?
What is adenosine triphosphate (ATP) known as?
How is the energy from food primarily utilized in cells?
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What is coupled with chemical reactions to provide energy for physiological functions?
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What is the predominant monosaccharide circulating in the blood?
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What percentage of glucose plays a central role in carbohydrate metabolism?
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What does ΔG represent in the context of nutrient oxidation?
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What mechanism allows glucose to pass through the cell membrane?
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What is the role of sodium in glucose absorption in the gastrointestinal tract?
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Which physiological activity is NOT listed as requiring energy from ATP?
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What happens to glucose immediately upon entering cells?
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What is the primary product of glycolysis?
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How many total moles of ATP are produced for each mole of glucose metabolized?
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What is the process of forming glycogen from glucose called?
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What is the primary role of the pentose phosphate pathway?
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Which hormones are primarily involved in the breakdown of stored glycogen?
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What happens to excess glucose when glycogen storage capacity is met in the liver?
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During fasting, what is a critical function of gluconeogenesis?
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Which of the following stimuli would increase the rate of gluconeogenesis?
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Which statement regarding energy metabolism pathways is correct?
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How many ATP molecules are formed for each glucose molecule degraded to CO2 and H2O?
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What percentage of energy from glucose is released as heat during its complete oxidation?
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What is the function of phosphofructokinase in glycolysis?
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What occurs when oxygen becomes unavailable during glycolysis?
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What is the maximum efficiency of energy transfer during glucose oxidation?
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How much ATP is produced from glycolysis when inadequate oxygen is present?
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Which molecules activate energy processes again in the presence of low ATP levels?
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What is the total amount of calories available from the complete oxidation of one gram-molecule of glucose?
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How many ATP molecules are formed during glycolysis?
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What is the primary source of ATP formation during glucose metabolism?
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What happens to the hydrogen atoms during glucose degradation?
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What is the total number of hydrogen atoms released during glycolysis and the citric acid cycle for each molecule of glucose?
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How many ATP molecules are formed from each complete cycle of the citric acid cycle?
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Which statement about the conversion of pyruvic acid to Acetyl CoA is correct?
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What is the role of electrons during oxidative phosphorylation?
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Where does the citric acid cycle occur within the cell?
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Study Notes
Metabolism of Nutrients
- Metabolism is the sum of all energy-requiring and energy-consuming processes in the body.
- Many factors contribute to overall metabolism, including: lean muscle mass, the amount and quality of food consumed, and physical demands on the body.
- Nutrients (carbohydrates, lipids, and proteins) are broken down in the cells to release energy.
- This energy is used for various physiological functions within the cell.
Release of Energy From Foods
- Chemical reactions in cells release energy from food.
- This energy fuels muscle activity, secretion by glands, maintenance of nerve and muscle membrane potentials, and synthesis of substances within cells, along with many other processes.
Coupled Reactions
- Energy foods are oxidized within cells, releasing large amounts of energy (heat).
- The energy needed by cells is not heat but energy to cause mechanical movement, concentrate solutes, and other cellular processes.
- This energy transfer occurs through coupled reactions involving enzymes and energy transfer systems.
- The amount of energy released from complete oxidation of a food is often expressed in calories per mole (or grams) of the substance. For example, one mole (180 grams) of glucose releases 686,000 calories.
Adenosine Triphosphate (ATP)
- ATP is the energy currency of the body.
- ATP is present throughout the cytoplasm and nucleoplasm of cells.
- All energy-requiring physiological mechanisms use ATP.
- Food in the cells gets oxidized, and the released energy is used to create new ATP, maintaining ATP supply.
- Energy transfer reactions occur via coupled reactions.
Transport of Glucose Through the Cell Membrane
- Glucose (glc) has a high molecular weight, so it doesn't easily diffuse through cell membranes.
- Insulin facilitates glucose diffusion. (Facilitated diffusion)
- Carrier proteins facilitate the movement of glucose through the membrane.
Transport of Glucose in the GI Tract
- Active sodium-glucose co-transport is used to absorb glucose against its concentration gradient in the GI tract.
- Sodium actively transported against a concentration gradient provides energy for absorbing glucose.
- A sodium-glucose transporter (symport) and a sodium-potassium ATPase are involved.
What Happens Immediately Upon GLC Entry into Cells?
- Glucose is immediately phosphorylated to glucose-6-phosphate.
- This process is catalyzed by glucokinase or hexokinase and is nearly irreversible (except in organs with glucose phosphatase).
What Happens Immediately Upon GLC Entry into Cells (continued)?
- The phosphorylated glucose can be used for energy production or be stored as glycogen in different cells.
- Glycogen storage capacity varies among different tissues (5-8% for liver; 1-3% for muscle).
Glycogenesis and Glycogenolysis
- Glycogenesis is the formation of glycogen (storage form of glucose).
- Glycogenolysis is the breakdown of glycogen to glucose.
- These processes are important in regulating blood glucose levels.
- Enzyme-mediated processes catalyze these reactions.
Release of Energy From Glucose - the Glycolytic Pathway
- The glycolytic pathway, also known as glucose breakdown, breaks down glucose to produce energy.
- It involves 10 successive chemical reactions, each catalyzed by specific enzymes.
- The end products of glycolysis are oxidized to produce energy.
What Happens Next to Pyruvate?
- Pyruvate is converted to Acetyl CoA, a crucial molecule for further energy production via the citric acid cycle.
Citric Acid Cycle (Krebs Cycle)
- The citric acid cycle is a crucial energy-producing pathway.
- Acetyl-CoA is degraded, releasing carbon dioxide and hydrogen atoms.
Net Reaction Per Molecule of Glucose
- Overall, glucose breakdown produces 38 ATP molecules.
What Happens to H Atoms?
- Hydrogen atoms are released during glycolysis and the citric acid cycle.
- These hydrogen atoms are critically important for energy production via oxidative phosphorylation.
What Happens to CO2?
- Carbon Dioxide (CO2) is released as a gaseous waste product during different stages of cellular respiration.
- Expired air contains CO2 that was produced during cellular reactions.
Can U See the Problem? Where Is the ATP?
- Despite complex biological pathways, there are limited molecules of ATP formed during initial breakdown stages.
Oxidative Phosphorylation
- Almost 90% of ATP is created through subsequent oxidation of hydrogen atoms, a process that happens in the mitochondria.
Summary of ATP Formation During the Breakdown of Glucose
- 38 ATP molecules are produced per glucose molecule in a complete breakdown. Different stages have varying ATP outputs.
Additional Information about Glucose
- Excess glucose is converted to glycogen for storage.
- Glycogen stores can sustain energy needs for 12 to 24 hours.
- Eventually, excess glucose is converted to fat for long-term storage.
Additional Notes on Gluconeogenesis
- Gluconeogenesis is the formation of new glucose from non-carbohydrate sources like proteins and fats.
- It's vital for maintaining blood glucose levels during fasting.
- Important for sustaining energy needs, especially when glycogen stores are depleted. The Brain relies strongly on glucose.
How Is Gluconeogenesis Regulated?
- Hormone levels and cellular glucose levels influence gluconeogenesis.
Anaerobic Glycolysis
- Anaerobic glycolysis produces insufficient energy versus aerobic processes, but is crucial for short-term energy needs.
Anaerobic Glycolysis (continued/notes)
- Anaerobic glycolysis involves converting pyruvate to lactic acid, especially in conditions with insufficient oxygen.
Is This the Only Way for Energy Production?
- The pentose phosphate pathway is another way to produce energy.
- It's an alternative pathway that helps with energy production in specific situations.
Glucose Conversion to Glycogen or Fat
- Excess glucose is converted into glycogen or fats (triglycerides) for future use.
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Description
This quiz explores the metabolism of nutrients, including carbohydrates, lipids, and proteins, and how they are broken down to release energy necessary for physiological functions. Learn about the factors affecting metabolism, the role of chemical reactions in energy release, and the significance of coupled reactions in cellular processes.
