What is the term for the set of metabolic reactions that break large molecules into smaller ones and release energy?
Catabolism
✓
Anabolism
Homeostasis
Transamination
Correct Answer
Catabolism
Catabolism breaks down large organic molecules such as glucose and triglycerides, and the energy released from their bonds is captured partly as ATP and partly lost as heat. Anabolism is the opposite process, building larger molecules and consuming energy. Homeostasis is the maintenance of a stable internal environment, not a class of reactions. Transamination is a specific transfer of an amine group between molecules.
Category: Metabolic Reactions
Question 2
Which hormone stimulates anabolic processes such as cellular glucose uptake and glycogen synthesis?
Cortisol
Insulin
✓
Glucagon
Epinephrine
Correct Answer
Insulin
Insulin is an anabolic hormone that promotes uptake of glucose into cells and its storage as glycogen and fat. Cortisol is a catabolic hormone that promotes breakdown of stored fuels. Glucagon is catabolic and raises blood glucose by mobilizing stores. Epinephrine is also catabolic, releasing stored energy during stress.
Category: Metabolic Reactions
Question 3
In an oxidation-reduction reaction, what happens to the molecule that is oxidized?
Gains electrons
Gains a phosphate group
Loses electrons
✓
Loses a neutron
Correct Answer
Loses electrons
Oxidation is the loss of electrons, often carried as hydrogen atoms, and it is always paired with the reduction of another molecule. Gains electrons describes reduction, not oxidation. Gains a phosphate group describes phosphorylation, a different reaction. Loses a neutron is a nuclear change that does not occur in metabolism.
Category: Metabolic Reactions
Question 4
Where in the cell does glycolysis take place?
Mitochondrial matrix
Nucleus
Inner mitochondrial membrane
Cytoplasm
✓
Correct Answer
Cytoplasm
Glycolysis splits glucose into pyruvate in the cytoplasm and does not require mitochondria, which is why cells without mitochondria can still use it. The mitochondrial matrix is the site of the Krebs cycle. The nucleus holds DNA and plays no role in glycolysis. The inner mitochondrial membrane holds the electron transport chain.
Category: Carbohydrate Metabolism
Question 5
The protein complexes of the electron transport chain are embedded in which structure?
Inner mitochondrial membrane
✓
Outer mitochondrial membrane
Mitochondrial matrix
Cytoplasm
Correct Answer
Inner mitochondrial membrane
The electron transport chain complexes sit in the inner mitochondrial membrane, where they pump hydrogen ions to build the gradient that drives ATP synthase. The outer mitochondrial membrane is permeable and does not hold the chain. The mitochondrial matrix is the fluid space where the Krebs cycle runs. The cytoplasm is where glycolysis occurs.
Category: Carbohydrate Metabolism
Question 6
Which molecule is the final electron acceptor at the end of the electron transport chain?
Carbon dioxide
Oxygen
✓
NAD+
Pyruvate
Correct Answer
Oxygen
Oxygen accepts electrons at the end of the electron transport chain and combines with hydrogen ions to form water, which keeps the chain moving. Carbon dioxide is a waste product released by the Krebs cycle, not an electron acceptor. NAD+ picks up electrons earlier in metabolism, becoming NADH, which delivers them to the start of the chain. Pyruvate is the end product of glycolysis.
Category: Carbohydrate Metabolism
Question 7
Under anaerobic conditions, what is pyruvate converted into so that glycolysis can continue?
Acetyl CoA
Glycerol
Lactate
✓
Urea
Correct Answer
Lactate
When oxygen is limited, pyruvate is converted to lactate, a step that regenerates the NAD+ glycolysis needs to keep producing ATP. Acetyl CoA forms from pyruvate only under aerobic conditions in the mitochondria. Glycerol is a component of triglycerides. Urea is the nitrogenous waste made from protein breakdown.
Category: Carbohydrate Metabolism
Question 8
Which process builds new glucose from noncarbohydrate molecules such as glycerol and certain amino acids?
Glycogenesis
Glycogenolysis
Glycolysis
Gluconeogenesis
✓
Correct Answer
Gluconeogenesis
Gluconeogenesis, mainly in the liver, makes new glucose from noncarbohydrate sources during fasting so the brain keeps a supply of fuel. Glycogenesis links glucose into glycogen for storage. Glycogenolysis breaks stored glycogen back into glucose but does not make new glucose. Glycolysis breaks glucose down into pyruvate.
Category: Carbohydrate Metabolism
Question 9
Which pathway breaks fatty acids into two-carbon acetyl CoA units inside the mitochondria?
Beta-oxidation
✓
Lipogenesis
Ketogenesis
Glycolysis
Correct Answer
Beta-oxidation
Beta-oxidation removes two carbons at a time from a fatty acid chain, producing acetyl CoA that can enter the Krebs cycle. Lipogenesis is the synthesis of fatty acids, the opposite direction. Ketogenesis converts excess acetyl CoA into ketone bodies. Glycolysis breaks down glucose, not fatty acids.
Category: Lipid Metabolism
Question 10
Which molecule is produced in the liver when excess acetyl CoA is diverted away from the Krebs cycle during prolonged fasting?
Pyruvate
Acetoacetate
✓
Glycerol
Lactate
Correct Answer
Acetoacetate
Acetoacetate is a ketone body that liver mitochondria make from excess acetyl CoA when carbohydrate is scarce, as in starvation or uncontrolled diabetes. Pyruvate is the product of glycolysis. Glycerol comes from triglyceride breakdown. Lactate forms from pyruvate under anaerobic conditions.
Category: Lipid Metabolism
Question 11
Intestinal cells package absorbed triglycerides and cholesterol into which particles before they enter the lymph?
Micelles
Ketone bodies
Chylomicrons
✓
Glycogen granules
Correct Answer
Chylomicrons
Chylomicrons are lipoprotein particles formed in intestinal cells that leave by exocytosis and enter lacteals, then reach the blood through the lymph. Micelles are bile salt clusters that carry fats to the intestinal surface before absorption. Ketone bodies are liver-made fuels, not transport particles. Glycogen granules are stored carbohydrate inside liver and muscle cells.
Category: Lipid Metabolism
Question 12
What role does carnitine play in lipid metabolism?
Emulsifies fats in the small intestine
Converts ammonia into a less toxic waste
Stores glucose for later use
Moves fatty acids into the mitochondrial matrix
✓
Correct Answer
Moves fatty acids into the mitochondrial matrix
Carnitine shuttles fatty acyl groups across the mitochondrial membranes so beta-oxidation can occur in the matrix. Emulsifies fats in the small intestine describes bile salts. Converts ammonia into a less toxic waste describes the urea cycle. Stores glucose for later use describes glycogen synthesis.
Category: Lipid Metabolism
Question 13
Which enzyme in the wall of the small intestine converts inactive trypsinogen into trypsin?
Enterokinase
✓
Pepsin
Chymotrypsin
Amylase
Correct Answer
Enterokinase
Enterokinase, also called enteropeptidase, is made by the intestinal lining and activates trypsinogen, and trypsin then activates other pancreatic proteases. Pepsin is a stomach enzyme activated by acid. Chymotrypsin is itself activated by trypsin. Amylase digests starch, not protein.
Category: Protein Metabolism
Question 14
To prevent toxic buildup, the liver converts ammonium from amino acid breakdown into which compound that is excreted in urine?
Uric acid
Urea
✓
Creatinine
Bilirubin
Correct Answer
Urea
The urea cycle in the liver combines ammonium with carbon dioxide to form urea, which the kidneys excrete. Uric acid is a waste product of nucleic acid base breakdown. Creatinine comes from creatine phosphate in muscle. Bilirubin is a pigment from hemoglobin breakdown.
Category: Protein Metabolism
Question 15
What is the term for transferring an amine group from an amino acid to a keto acid?
Deamination
Phosphorylation
Transamination
✓
Hydrolysis
Correct Answer
Transamination
Transamination moves an amine group from one molecule to a keto acid, which allows the body to make some amino acids and to feed carbon skeletons into the Krebs cycle. Deamination removes an amine group without transferring it to another keto acid. Phosphorylation adds a phosphate group. Hydrolysis splits a bond by adding water.
Category: Protein Metabolism
Question 16
Which pancreatic hormone rises between meals and stimulates the liver to break down glycogen?
Insulin
Aldosterone
Oxytocin
Glucagon
✓
Correct Answer
Glucagon
Glucagon is released by pancreatic alpha cells when blood glucose falls in the postabsorptive state, and it drives liver glycogenolysis and gluconeogenesis. Insulin rises after meals and promotes glycogen storage. Aldosterone is an adrenal hormone that regulates sodium. Oxytocin is a posterior pituitary hormone involved in labor and milk ejection.
Category: Metabolic States
Question 17
During prolonged starvation, which fuel does the brain increasingly use in place of glucose?
Ketone bodies
✓
Fatty acids
Amino acids
Glycerol
Correct Answer
Ketone bodies
As starvation continues, the liver produces ketone bodies from fat, and the brain shifts to using them, which reduces the amount of body protein broken down to make glucose. Fatty acids fuel muscle and many other tissues but are not a major brain fuel. Amino acids are not a direct brain fuel; in starvation they are drawn from body protein and used by the liver for gluconeogenesis. Glycerol is used by the liver for gluconeogenesis rather than burned directly by the brain.
Category: Metabolic States
Question 18
Which brain region acts as the body's thermostat, setting and maintaining core temperature?
Cerebellum
Hypothalamus
✓
Medulla oblongata
Thalamus
Correct Answer
Hypothalamus
The hypothalamus monitors body temperature and triggers sweating and skin vasodilation when the body is too warm, or shivering and vasoconstriction when it is too cold. The cerebellum coordinates movement. The medulla oblongata controls heart rate and breathing. The thalamus relays sensory information to the cerebral cortex.
Category: Energy and Heat Balance
Question 19
Sitting on a cold metal bench draws heat away from the body through direct contact. Which mechanism of heat transfer is this?
Convection
Radiation
Conduction
✓
Evaporation
Correct Answer
Conduction
Conduction transfers heat between objects that touch, moving from the warmer body to the cooler bench. Convection carries heat away in moving air or water. Radiation transfers heat as infrared energy without contact. Evaporation removes heat as water such as sweat turns to vapor.
Category: Energy and Heat Balance
Question 20
Which vitamin is fat soluble and absorbed along with dietary lipids?
Vitamin C
Vitamin B12
Thiamine
Vitamin K
✓
Correct Answer
Vitamin K
Vitamin K is one of the fat-soluble vitamins, along with A, D and E, and it is absorbed with lipids and can be stored in the body. Vitamin C is water soluble and excess is excreted in urine. Vitamin B12 is a water-soluble B vitamin. Thiamine, vitamin B1, is also water soluble.
Category: Nutrition