General Biology: Cell Structure, Function, and Metabolism Study Guide

Cellular Respiration

Overview of Cellular Respiration

Cellular respiration is the process by which cells convert biochemical energy from nutrients into ATP, releasing waste products. It is essential for energy production in both plant and animal cells.

• Stages: Glycolysis, Pyruvate Oxidation, Citric Acid Cycle (Krebs Cycle), Electron Transport Chain

• Location: Glycolysis occurs in the cytoplasm; the other stages occur in the mitochondria.

• ATP Production: Cellular respiration is more efficient than fermentation, producing more ATP per glucose molecule.

• Fermentation: Occurs when oxygen is absent; less efficient, produces less ATP.

Equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}$

• Glucose is oxidized and O2 is reduced during cellular respiration.

Fermentation

Fermentation is an anaerobic process that allows cells to generate energy without oxygen.

• Types: Alcoholic fermentation (yeast), lactic acid fermentation (muscle cells)

• ATP Yield: Much lower than cellular respiration

• Electron Acceptor: No electron acceptor in fermentation

Electron Transport Chain (ETC)

The ETC is the final stage of cellular respiration, occurring in the inner mitochondrial membrane.

• NADH and FADH2: Donate electrons to the ETC

• Proton Gradient: ETC pumps protons (H+) across the membrane, creating a gradient used to produce ATP

• ATP Synthase: Uses the proton gradient to synthesize ATP

Substrate-Level vs. Oxidative Phosphorylation

• Substrate-level phosphorylation: Direct transfer of phosphate to ADP during glycolysis and the citric acid cycle

• Oxidative phosphorylation: ATP production via the ETC and chemiosmosis

Cell Structure and Function

Cell Membrane Structure

The cell membrane is a selectively permeable barrier composed of a phospholipid bilayer and proteins.

• Phospholipids: Have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails

• Proteins: Integral and peripheral proteins serve various functions, including transport and signaling

• Cholesterol: Maintains membrane fluidity

Membrane Transport

Transport across the cell membrane can be passive or active.

• Passive Transport: Movement of substances down their concentration gradient without energy (e.g., diffusion, osmosis)

• Active Transport: Requires energy (ATP) to move substances against their concentration gradient

• Osmosis: Movement of water from low solute concentration to high solute concentration

Enzymes

Enzymes are biological catalysts that speed up chemical reactions.

• Structure: Most enzymes are proteins made of amino acids

• Function: Lower activation energy, increase reaction rate

• Denaturation: Loss of enzyme shape leads to loss of function

Cell Division

Mitosis

Mitosis is the process by which eukaryotic cells divide to produce genetically identical daughter cells.

• Phases: Prophase, Metaphase, Anaphase, Telophase

• Chromosome Alignment: Chromosomes align at the cell's midplate during metaphase

• Spindle Fibers: Separate chromosomes during mitosis

• Cytokinesis: Division of the cytoplasm, often involves a cleavage furrow in animal cells or cell plate in plant cells

Meiosis

Meiosis is the process by which gametes are produced, involving two rounds of cell division and resulting in four non-identical daughter cells.

• Purpose: Sexual reproduction, genetic diversity

• Phases: Meiosis I and II

Cell Cycle

The cell cycle consists of interphase (G1, S, G2) and mitotic phase (M).

• S Phase: DNA replication occurs

• M Phase: Mitosis and cytokinesis

• Checkpoints: Ensure proper division and prevent errors

Photosynthesis

Overview of Photosynthesis

Photosynthesis is the process by which plants convert light energy into chemical energy.

• Equation: $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$

• Light-dependent reactions: Occur in the thylakoid membranes, produce ATP and NADPH

• Calvin Cycle: Uses ATP and NADPH to fix CO2 into glucose

• Oxygen Source: O2 released comes from H2O, not CO2

Experimental Design and Data Interpretation

Osmosis Experiment

Experiments with red blood cells in sucrose solutions demonstrate osmosis and the effects of hypertonic and hypotonic environments.

• Hypertonic Solution: Higher solute concentration outside the cell; cells lose water and shrink

• Hypotonic Solution: Lower solute concentration outside the cell; cells gain water and swell

• Data Interpretation: As sucrose concentration increases, red blood cell mass decreases due to water loss

Tables

Comparison of Cellular Respiration and Fermentation

Process	Oxygen Required	ATP Yield per Glucose	End Products
Cellular Respiration	Yes	~30-32	CO2, H2O
Fermentation	No	2	Lactic acid or ethanol

Cell Cycle Phases

Phase	Major Event
G1	Cell growth
S	DNA replication
G2	Preparation for mitosis
M	Mitosis and cytokinesis

Key Terms and Definitions

• ATP (Adenosine Triphosphate): Main energy currency of the cell

• Enzyme: Protein that catalyzes biochemical reactions

• Phospholipid: Major component of cell membranes, with hydrophilic heads and hydrophobic tails

• Osmosis: Diffusion of water across a selectively permeable membrane

• Chromosome: DNA molecule with associated proteins, carrying genetic information

• Cleavage Furrow: Indentation that begins the process of cytokinesis in animal cells

• Cell Plate: Structure that forms during cytokinesis in plant cells

• Centromere: Region where sister chromatids are joined

• Benign Tumor: Noninvasive and noncancerous growth

Additional info:

• Experimental questions and data interpretation are included to reinforce understanding of osmosis and cell division.

• Short answer questions require application of concepts such as metabolic mutations and drug effects on mitosis.