Biology Unit 3

Metabolism

Metabolism

The set of chemical reactions that occur in living organisms to maintain life and carry out essential functions.

Bond forming reactions

Reactions in which two or more atoms or molecules come together to form a chemical bond. Example:The formation of a peptide bond between amino acids in protein synthesis.

Bond breaking reactions

Reactions in which a chemical bond is broken, resulting in the separation of atoms or molecules. Example:The hydrolysis of ATP to ADP and inorganic phosphate.

Exergonic reactions

Reactions that release energy. They have a negative change in free energy (∆G). Example:Cellular respiration.

Endergonic reactions

Reactions that require energy input. They have a positive change in free energy (∆G). Example:Photosynthesis.

Catalyst

A substance that speeds up the rate of a chemical reaction by lowering the activation energy required for the reaction to occur.

Activation energy

The minimum amount of energy required to start a chemical reaction.

Enzyme

A biological catalyst, usually a protein, that speeds up chemical reactions in living organisms.

Substrate

The molecule or molecules on which an enzyme acts.

Active site

The region on an enzyme where the substrate binds and the catalytic reaction takes place.

Catabolic reaction

A reaction that involves the breakdown of complex molecules into simpler ones, releasing energy. Example:Glycolysis.

Anabolic reaction

A reaction that involves the synthesis of complex molecules from simpler ones, requiring energy. Example:Protein synthesis.

Induced fit

The concept that the active site of an enzyme changes shape upon substrate binding to facilitate the catalytic reaction.

Initial concentration of substrate

The amount of substrate present at the beginning of a reaction. It affects the rate of enzyme activity.

Enzyme concentration

The amount of enzyme present in a reaction. It affects the rate of enzyme activity.

pH

The measure of acidity or alkalinity of a solution. It can affect the activity and stability of enzymes.

Temperature

The measure of the average kinetic energy of molecules. It can affect the rate of enzyme activity.

Cofactors

Inorganic molecules or ions that are required for the proper functioning of some enzymes. Example:Zinc, magnesium.

Coenzymes

Organic molecules that assist enzymes in carrying out catalytic reactions. Example:NAD+, FAD.

Competitive inhibitors

Molecules that compete with the substrate for binding to the active site of an enzyme, reducing the enzyme's activity. They resemble the substrate.

Noncompetitive inhibitors

Molecules that bind to an allosteric site on an enzyme, causing a conformational change that reduces the enzyme's activity. They do not resemble the substrate.

Heterotrophs

Organisms that obtain energy by consuming organic compounds produced by other organisms.

Autotrophs

Organisms that can produce their own organic compounds using energy from sunlight or inorganic chemicals.

ATP

Adenosine triphosphate, a molecule that stores and releases energy for cellular processes. It consists of adenine, ribose, and three phosphate groups.

Glycolysis

The catabolic degradation of glucose by cellular respiration, resulting in the production of ATP, NADH, and pyruvate.

Three main metabolic stages of cellular respiration

Glycolysis, the Krebs cycle (citric acid cycle), and oxidative phosphorylation (electron transport chain).

Anaerobic respiration

Respiration that occurs in the absence of oxygen. It involves the use of alternative electron acceptors, such as sulfate or nitrate.

Aerobic respiration

Respiration that occurs in the presence of oxygen, resulting in the complete oxidation of glucose to carbon dioxide and water.

Fermentation

A metabolic process that occurs in the absence of oxygen, converting pyruvate into either lactate or ethanol and carbon dioxide, regenerating NAD+.

Two types of fermentation

Lactic acid fermentation (occurs in muscle cells and some bacteria) and alcoholic fermentation (occurs in yeast and some bacteria).

Overall map of cellular respiration

Glycolysis → Pyruvate oxidation → Krebs cycle → Electron transport chain → ATP synthesis.

Glycolysis

The first step of cellular respiration, occurring in the cytoplasm of the cell. It does not require oxygen and breaks down glucose into pyruvate.

Krebs cycle

Also known as the citric acid cycle, it takes place in the mitochondrial matrix and completes the oxidation of glucose, producing ATP, NADH, and FADH2.

Electron transport system

A series of proteins located in the inner mitochondrial membrane that transfers electrons from electron carriers (NADH, FADH2) to generate ATP.

ATP synthase

A protein complex located in the inner mitochondrial membrane that uses the flow of hydrogen ions (protons) to produce ATP from ADP and inorganic phosphate.

Autotroph

An organism that can produce its own organic compounds using energy from sunlight or inorganic chemicals.

Heterotroph

An organism that obtains energy by consuming organic compounds produced by other organisms.

Chloroplast

The organelle in plant cells where photosynthesis takes place.

Stroma

The fluid-filled space inside the chloroplast, where the Calvin cycle occurs.

Thylakoid

A flattened, disc-shaped membrane structure in the chloroplast where the light-dependent reactions of photosynthesis occur.

Thylakoid space

The space inside the thylakoid where protons accumulate during the light-dependent reactions.

Grana

Stacks of thylakoids in the chloroplast.

Inner membrane

The innermost membrane of the chloroplast that separates the stroma from the thylakoid space.

Outer membrane

The outermost membrane of the chloroplast.

Photosynthesis formula

6CO2 + 6H2O + light energy → C6H12O6 + 6O2.

Two main metabolic stages of photosynthesis

Light-dependent reactions (light reactions) and the Calvin cycle (dark reactions).

Light-dependent reactions

The first stage of photosynthesis that occurs in the thylakoid membrane, where light energy is converted into chemical energy (ATP and NADPH).

Calvin cycle

The second stage of photosynthesis that occurs in the stroma, where carbon dioxide is fixed and used to synthesize organic molecules (such as glucose).

Calvin cycle purpose

To convert carbon dioxide into glucose and other organic compounds using ATP and NADPH produced during the light-dependent reactions.

Calvin cycle

Anabolic, as it involves the synthesis of complex organic molecules from simpler ones using energy.

Rubisco

The enzyme responsible for carbon fixation in the Calvin cycle, and it is the most abundant protein on Earth.