chapter 8/9 (metabolism, cellular respiration)

What is metabolism?

The sum of all biochemical reactions in a cell, including metabolic pathways and enzymes

What are catabolic reactions?

Reactions that break down molecules and release energy, such as aerobic cellular respiration, making them exergonic and “downhill”

What are anabolic reactions?

Reactions that build larger molecules like photosynthesis, requiring energy and being “uphill”

What is energy in biology?

The ability to perform work in a cell, including mechanical, chemical, and transport work

What are exergonic and endergonic reactions?

Exergonic reactions release free energy while endergonic reactions require energy

What does the First Law of Thermodynamics state?

Energy cannot be created or destroyed, only transformed or transferred

What does the Second Law of Thermodynamics state?

Every energy transformation increases entropy, or disorder, in the universe

What is ATP?

Adenosine triphosphate, the main energy currency of the cell

How is ATP used in cells?

ATP is hydrolyzed to ADP and Pi to release energy, phosphorylates target molecules to perform work, and is regenerated in an endergonic process

What are enzymes?

Biological catalysts made mostly of proteins that speed up reactions without being consumed

How do enzymes work?

They lower activation energy by stressing covalent bonds and using an induced fit mechanism

What factors affect enzyme activity?

Temperature and pH are key environmental factors

What are enzyme cofactors?

Inorganic minerals like Cu, Zn, Fe or organic coenzymes like vitamins that assist enzymes

What is fermentation?

An anaerobic process that regenerates ATP without oxygen

What are the two types of fermentation?

Alcohol fermentation, which produces ethanol and CO₂, and lactic acid fermentation, which produces lactate

What are obligate anaerobes?

Organisms that live only without oxygen

What are facultative anaerobes?

Organisms that can live with or without oxygen

What is aerobic respiration?

A more efficient ATP-generating process requiring oxygen, occurring in mitochondria

What is the equation for cellular respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP and heat)

What type of reaction is cellular respiration?

A catabolic exergonic redox reaction where glucose is oxidized and oxygen is reduced

What is NAD⁺?

A coenzyme electron acceptor that becomes NADH when reduced by electrons from glucose

What is the electron transport chain (ETC)?

A sequence of proteins in the mitochondrial membrane that transfer electrons and generate ATP through oxidative phosphorylation

What is chemiosmosis?

The diffusion of hydrogen ions across the inner mitochondrial membrane to power ATP synthesis

What is ATP synthase?

A molecular motor enzyme that produces ATP using the proton motive force

What are the three stages of cellular respiration?

Glycolysis, the Citric Acid (Krebs) Cycle, and the Electron Transport Chain

What is glycolysis?

The breakdown of glucose into two pyruvate molecules, producing 2 ATP and 2 NADH in the cytoplasm

What happens during pyruvate oxidation?

Pyruvate is converted into Acetyl CoA, releasing CO₂ and generating NADH

What occurs in the Citric Acid Cycle?

Acetyl CoA is oxidized to CO₂, producing ATP, NADH, and FADH₂

What are the total energy yields of cellular respiration?

About 30–32 ATP molecules per glucose

What is photosynthesis?

The process where light energy converts CO₂ and H₂O into glucose and oxygen

What type of reaction is photosynthesis?

An anabolic endergonic redox reaction where CO₂ is reduced and water is oxidized

What is the main photosynthetic organelle?

The chloroplast

What part of the plant carries out photosynthesis?

The leaf, particularly in chloroplasts of mesophyll cells

How do cellular respiration and photosynthesis relate?

They are complementary, with the products of one serving as reactants for the other

What are the two main reactions of photosynthesis?

The light reactions that produce ATP and NADPH, and the dark (Calvin) reactions that use them to fix CO₂ into sugars

What are the products of the light reactions?

Oxygen, ATP, and NADPH

What happens in the Calvin Cycle?

CO₂ is fixed into G3P sugar using ATP and NADPH

What are the three phases of the Calvin Cycle?

Carbon fixation, reduction, and regeneration of RuBP

What is Rubisco?

The enzyme that fixes CO₂ in the Calvin Cycle and is the most abundant enzyme on Earth

What are C3 plants?

Plants that fix CO₂ directly through Rubisco and are common in moderate climates

What are C4 plants?

Plants that use PEP carboxylase to fix CO₂ and reduce photorespiration, adapted to hot and dry climates

What are CAM plants?

Plants that open stomata at night to store CO₂ as organic acids and close them during the day to conserve water

What are examples of CAM plants?

Pineapple, cacti, and succulents

What is photorespiration?

A wasteful process where Rubisco fixes oxygen instead of CO₂, reducing photosynthetic efficiency

What is chlorophyll?

The green pigment that captures light energy for photosynthesis, containing magnesium at its center

What are the main types of chlorophyll?

Chlorophyll a (primary) and other accessory pigments that absorb additional wavelengths

What wavelengths of light are most effective for photosynthesis?

Red, blue, and violet light

What are the three aspects of light important to green plants?

Quality, quantity, and duration

What is the electromagnetic spectrum range of visible light?

380–740 nanometers

What is cellulose?

A carbohydrate produced by plants for structure, the most abundant organic compound on Earth