The sum of all the chemical reactions that take place in a cell, both those that use energy and those that release it, is called its metabolism.
Missing Word
metabolism
Metabolism includes every reaction in a cell, organized into pathways that build molecules and pathways that break them down. The two kinds are linked, because energy released by breakdown powers building.
Category: Energy and Thermodynamics
Question 2
The energy that an object has because it is moving is called kinetic energy.
Missing Word
kinetic
Kinetic energy is the energy of motion, such as a rolling ball or moving molecules. Stored energy, such as the energy held in chemical bonds, is potential energy.
Category: Energy and Thermodynamics
Question 3
The process that uses light energy to build sugar from carbon dioxide and water, releasing oxygen, is photosynthesis.
Missing Word
photosynthesis
Photosynthesis is an anabolic process that stores energy in sugar molecules. Cellular respiration roughly reverses it, using oxygen to break sugar down and releasing carbon dioxide and water.
Category: Energy and Thermodynamics
Question 4
Adding water to break the bond between the last two phosphate groups of ATP, a reaction called hydrolysis, releases energy the cell can use.
Missing Word
hydrolysis
Hydrolysis is the splitting of a bond by adding a water molecule. When ATP is hydrolyzed to ADP and phosphate, energy is released that can drive other reactions in the cell.
Category: Energy and Thermodynamics
Question 5
An enzyme is a biological catalyst, a substance that speeds up a chemical reaction without being used up by it.
Missing Word
catalyst
A catalyst speeds a reaction and is unchanged at the end, so it can be used again. Most enzymes are proteins, and each is specific to one or a few reactions.
Category: Enzymes
Question 6
The specific reactant molecule that binds to an enzyme's active site and is changed by the reaction is called the substrate.
Missing Word
substrate
A substrate is the molecule an enzyme acts on. The chemical environment of the active site, formed by amino acid side chains, matches a particular substrate.
Category: Enzymes
Question 7
Inorganic ions such as iron and magnesium that help some enzymes function are called cofactors.
Missing Word
cofactors
Cofactors are inorganic helpers, often metal ions, that some enzymes need in order to work. Organic helper molecules, many derived from vitamins, are called coenzymes.
Category: Enzymes
Question 8
One glucose molecule provides enough acetyl groups for 2 turns of the citric acid cycle.
Missing Word
2
Glycolysis splits glucose into two pyruvates, and each pyruvate becomes one acetyl CoA. Each acetyl CoA drives one turn of the cycle, so one glucose yields two turns.
Category: Citric Acid Cycle
Question 9
The production of ATP powered by hydrogen ions flowing down their gradient through ATP synthase is called chemiosmosis.
Missing Word
chemiosmosis
Chemiosmosis couples the hydrogen ion gradient built by the electron transport chain to ATP synthesis. It makes the great majority of the ATP produced during aerobic respiration.
Category: Electron Transport and ATP Synthesis
Question 10
In alcohol fermentation, removing carbon dioxide from pyruvate forms acetaldehyde, which then accepts electrons from NADH to become ethanol.
Missing Word
acetaldehyde
Acetaldehyde is the two-carbon intermediate of alcohol fermentation. When it accepts electrons from NADH, it becomes ethanol and NAD+ is regenerated for glycolysis.
Category: Fermentation
Question 11
Wine and bread rely on yeast, single-celled fungi that carry out alcohol fermentation when oxygen is scarce.
Missing Word
yeast
Yeast are single-celled fungi that can ferment sugar into ethanol and carbon dioxide. The carbon dioxide makes bread rise and puts the bubbles in sparkling wine and beer.
Category: Fermentation
Question 12
Animals store excess glucose for short-term use as glycogen, a branched polymer kept mainly in the liver and muscles.
Missing Word
glycogen
Glycogen is the storage polysaccharide of animals. When blood sugar drops, it is broken back down to glucose, which then enters glycolysis.
Category: Connected Pathways
Question 13
Removing the amino group from an amino acid produces ammonia, which the mammalian liver converts to urea.
Missing Word
ammonia
Ammonia is the toxic nitrogen compound formed when amino groups are removed so that amino acids can be used for energy. The liver detoxifies it by making urea, which leaves the body in urine.
Category: Connected Pathways
Question 14
The disaccharide sucrose, ordinary table sugar, is split into glucose and fructose in the small intestine.
Missing Word
sucrose
Sucrose is a disaccharide made of one glucose and one fructose. Once it is split, both sugars are absorbed into the blood and can be broken down for energy.
Category: Connected Pathways
Question 15
Galactose is the simple sugar released along with glucose when the milk sugar lactose is digested, and it is absorbed directly into the blood.
Missing Word
Galactose
Galactose is a monosaccharide released when lactose is digested into glucose and galactose. Like fructose, it is converted into an intermediate of glycolysis and yields the same amount of ATP as glucose.
Category: Connected Pathways