BIO 120 Quiz 2

Chapter 6: How Cells Harvest Energy

Overview

• Cellular respiration is the process by which cells break down glucose to produce ATP, the main energy currency of the cell.

• Occurs in three main stages:

1. Glycolysis (in cytoplasm)

2. Pyruvate oxidation & Citric Acid Cycle (in mitochondria)

3. Oxidative phosphorylation (in mitochondria)

Key Concepts

1. Glycolysis (Anaerobic Process)

• Location: Cytoplasm

• What happens?

• Glucose (6C) is split into two molecules of pyruvate (3C each).

• Produces a net gain of 2 ATP and 2 NADH.

• Reactants: Glucose, ATP, NAD⁺

• Products: 2 Pyruvate, 2 ATP (net), 2 NADH

2. Pyruvate Oxidation & Citric Acid Cycle (Krebs Cycle)

• Location: Mitochondrial matrix

• Pyruvate Oxidation:

• Pyruvate (3C) is converted into Acetyl-CoA (2C).

• 1 NADH & 1 CO₂ are produced per pyruvate.

• Citric Acid Cycle:

• Acetyl-CoA enters the cycle and goes through a series of redox reactions.

• Produces:

• 3 NADH, 1 FADH₂, 1 ATP, 2 CO₂ per Acetyl-CoA.

• Total per glucose molecule (since 2 Acetyl-CoA enter per glucose):

• 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂

3. Oxidative Phosphorylation (Electron Transport Chain & Chemiosmosis)

• Location: Inner mitochondrial membrane

• Process:

• NADH and FADH₂ donate electrons to the Electron Transport Chain (ETC).

• Oxygen is the final electron acceptor, forming water.

• The energy from the electrons pumps H⁺ into the intermembrane space, creating a proton gradient.

• ATP synthase uses the gradient to drive ATP production (chemiosmosis).

• ATP Yield: About 34 ATP per glucose.

Fermentation (Anaerobic Respiration)

• Occurs when no oxygen is available.

• Two types:

1. Lactic Acid Fermentation (muscle cells, some bacteria) – Pyruvate is converted into lactate.

2. Alcohol Fermentation (yeast) – Pyruvate is converted into ethanol + CO₂.

• Only produces 2 ATP per glucose (compared to ~38 in aerobic respiration).

Chapter 7: Photosynthesis

Overview

• Photosynthesis: Process by which plants, algae, and some bacteria convert solar energy into chemical energy (glucose).

• Occurs in two stages:

1. Light Reactions (Thylakoid membrane)

2. Calvin Cycle (Stroma)

Key Concepts

1. Light Reactions (Light-Dependent Reactions)

• Location: Thylakoid membrane

• Reactants: Light, H₂O, NADP⁺, ADP

• Products: O₂, ATP, NADPH

• Process:

• Light excites electrons in chlorophyll, which travel through the electron transport chain.

• Water is split (photolysis), producing oxygen.

• ATP and NADPH are produced to power the Calvin Cycle.

2. The Calvin Cycle (Light-Independent Reactions)

• Location: Stroma of the chloroplast

• Reactants: CO₂, ATP, NADPH

• Products: Glucose (C₆H₁₂O₆)

• Three Phases:

1. Carbon Fixation – CO₂ is captured by RuBisCO and attached to RuBP.

2. Reduction – ATP and NADPH convert molecules into G3P (sugar precursor).

3. Regeneration of RuBP – Some G3P is used to regenerate RuBP for the next cycle.

Comparing Photosynthesis & Cellular Respiration

• Opposite reactions:

• Photosynthesis stores energy in glucose, respiration releases it.

• Photosynthesis removes CO₂, respiration produces CO₂.

Chapter 8: Cell Reproduction & Inheritance

Key Concepts

1. Cell Cycle

• Interphase (90% of cell’s life)

• G1 Phase – Growth

• S Phase – DNA replication

• G2 Phase – Preparation for division

• M Phase (Mitosis or Meiosis)

2. Mitosis (Somatic Cell Division)

• Produces two genetically identical diploid cells (2N → 2N).

• Stages:

1. Prophase – Chromosomes condense, spindle forms.

2. Metaphase – Chromosomes align at the center.

3. Anaphase – Sister chromatids separate.

4. Telophase – Nucleus reforms, cells split (cytokinesis).

3. Meiosis (Gamete Formation)

• Produces four genetically unique haploid cells (2N → N).

• Two divisions:

• Meiosis I: Homologous chromosomes separate.

• Meiosis II: Sister chromatids separate.

• Genetic Variation Mechanisms:

• Independent assortment

• Crossing over