IB BIOLOGY C1.1 & C1.2 REVIEW SL/HL

Anabolic reaction

A chemical reaction that synthesizes larger, complex molecules from smaller units, requiring an overall input of energy.

Catabolic reaction

A chemical reaction that breaks down complex molecules into simpler units, releasing energy overall.

Condensation reaction

A chemical process that joins two molecules together through a covalent bond with the simultaneous release of a water molecule.

Hydrolysis reaction

A chemical process that cleaves a covalent bond by the addition of a water molecule.

Primary contrast between anabolic and catabolic processes

One builds complex molecules and consumes energy, while the other breaks down molecules and releases energy.

Examples of anabolic processes in biology

Protein synthesis from amino acids and glucose synthesis during photosynthesis.

Example of a catabolic process in biology

Cellular respiration breaking down glucose into simpler molecules to release energy.

Effect of increasing temperature toward an enzyme's optimum

The rate of reaction increases because molecules gain kinetic energy and collide more frequently and successfully.

Optimum temperature of an enzyme

The specific temperature at which an enzyme catalyzes a reaction at its maximum possible rate.

Consequence of heating an enzyme past its optimum temperature

The enzyme denatures as thermal energy disrupts bonds stabilizing the active site, causing activity to drop sharply.

Effect of low temperatures on enzyme activity

The reaction rate declines because molecules possess lower kinetic energy and collision rates drop, without causing denaturation.

Optimum pH of an enzyme

The specific hydrogen ion concentration at which the enzyme exhibits its highest catalytic activity.

Mechanism of enzyme denaturation at extreme pH levels

Alters charges on amino acid residues, disrupting hydrogen and ionic bonds that maintain the active site shape.

Lock-and-key model

Proposes that an enzyme's active site possesses a rigid, pre-formed shape precisely complementary to its substrate.

Induced-fit model

Proposes that an enzyme's active site undergoes subtle conformational adjustments upon substrate binding to maximize catalysis.

Mechanism by which enzymes lower activation energy

They provide an alternative reaction pathway that requires less initial energy for reactant molecules to react.

Influence of enzymes on net free energy change of a reaction

They have no effect on overall energy released or absorbed; they lower only the activation energy barrier.

Activation energy ($E_a$)

The minimum kinetic energy that colliding particles must possess for a chemical reaction to occur.

Aerobic respiration

The cellular breakdown of organic substrates using oxygen to produce ATP, yielding carbon dioxide and water as products.

Reactants and products of aerobic respiration

Reactants are glucose and oxygen; products are carbon dioxide, water, and ATP.

Word equation for aerobic cellular respiration

$$\text{Glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water}$$

Subcellular location of glycolysis

The cytoplasm of the cell.

Subcellular location of the link reaction and Krebs cycle in human cells

The mitochondrial matrix.

Subcellular location of the electron transport chain

The inner mitochondrial membrane.

Anaerobic respiration in human muscle tissue

The breakdown of glucose in the absence of oxygen to generate ATP alongside lactate.

Reactants and products of human muscle anaerobic respiration

Glucose is the primary reactant; lactate and a small yield of ATP are the products.

Cellular site where anaerobic respiration occurs

The cytoplasm.

Comparison between human aerobic and anaerobic respiration

Aerobic respiration uses oxygen to yield carbon dioxide, water, and high ATP; anaerobic respiration proceeds without oxygen, producing lactate and low ATP.

Alcoholic fermentation

An anaerobic pathway carried out by yeast that converts sugars into ethanol and carbon dioxide.

Word equation for alcoholic fermentation

$$\text{Glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}$$

Reason bread dough expands during yeast fermentation

Carbon dioxide gas released during anaerobic metabolism is trapped within the dough matrix, causing it to rise.

Fundamental building blocks of carbohydrates

Monosaccharides, which are single sugar units.

Monosaccharide

A simple single-unit sugar molecule, such as glucose or fructose.

Disaccharide

A carbohydrate formed from two monosaccharide units joined covalently by a glycosidic bond.

Products formed when two glucose molecules undergo condensation

Maltose and water.

Products formed when glucose and fructose undergo condensation

Sucrose and water.

Glycosidic bond

A covalent linkage formed between carbohydrate monomers through a condensation reaction.

Role of $\text{NAD}^+$ in cellular respiration

Acts as an electron and hydrogen carrier, becoming reduced to carry electrons to other stages of respiration.

Biological oxidation

The loss of electrons from a molecule, often characterized by the loss of hydrogen atoms or the gain of oxygen.

Decarboxylation

The biochemical removal of a carboxyl group from a substrate molecule, resulting in the release of carbon dioxide.