Ch. 7 - Membrane Structure and Function

Overview of Biological Membranes

Biological membranes are essential structures that define cell boundaries and compartmentalize cellular functions. They are primarily composed of a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol.

• Phospholipid Bilayer: Provides fluidity and selective permeability.

• Membrane Proteins: Include integral and peripheral proteins, responsible for transport, signaling, and structural support.

• Carbohydrates: Attached to lipids (glycolipids) or proteins (glycoproteins), important for cell recognition.

• Cholesterol: Modulates membrane fluidity and stability.

Example: The plasma membrane regulates the entry and exit of substances, maintaining homeostasis.

Transport Across Membranes

Cells utilize various mechanisms to move substances across membranes.

• Passive Transport: Includes diffusion and facilitated diffusion; does not require energy.

• Active Transport: Requires ATP to move substances against their concentration gradient.

• Osmosis: Diffusion of water across a selectively permeable membrane.

Equation:

Ch. 8 - An Introduction to Metabolism

Metabolic Pathways and Energy

Metabolism encompasses all chemical reactions within a cell, divided into catabolic (breaking down molecules) and anabolic (building molecules) pathways.

• Catabolic Pathways: Release energy by breaking down complex molecules (e.g., cellular respiration).

• Anabolic Pathways: Consume energy to build complex molecules (e.g., protein synthesis).

• ATP: The primary energy currency of the cell.

Equation:

Enzymes and Regulation

Enzymes are biological catalysts that speed up metabolic reactions by lowering activation energy.

• Active Site: Region where substrate binds.

• Enzyme Regulation: Includes feedback inhibition and allosteric control.

Example: Hexokinase catalyzes the first step of glycolysis.

Ch. 9 - Cellular Respiration and Fermentation

Cellular Respiration

Cellular respiration is the process by which cells extract energy from glucose, primarily through aerobic pathways.

• Stages: Glycolysis, Krebs cycle (Citric Acid Cycle), and Electron Transport Chain.

• Overall Equation:

Example: Muscle cells use cellular respiration to generate ATP during exercise.

Fermentation

Fermentation occurs in the absence of oxygen, allowing cells to produce ATP through glycolysis.

• Lactic Acid Fermentation: Produces lactic acid in animals.

• Alcoholic Fermentation: Produces ethanol and CO2 in yeast.

Example: Yeast cells ferment sugars to produce alcohol in brewing.

Ch. 10 - Photosynthesis

Photosynthetic Process

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy.

• Light Reactions: Occur in the thylakoid membranes; produce ATP and NADPH.

• Calvin Cycle: Occurs in the stroma; uses ATP and NADPH to fix CO2 into glucose.

• Overall Equation:

Example: Green plants use photosynthesis to produce food and oxygen.

Ch. 12 - The Cell Cycle

Phases of the Cell Cycle

The cell cycle is the series of events that cells go through as they grow and divide.

• Interphase: Includes G1, S, and G2 phases; cell grows and DNA replicates.

• M Phase: Includes mitosis (division of nucleus) and cytokinesis (division of cytoplasm).

Example: Skin cells undergo the cell cycle to replace damaged tissue.

Regulation of the Cell Cycle

The cell cycle is tightly regulated by checkpoints and proteins such as cyclins and CDKs.

• Checkpoints: Ensure proper DNA replication and division.

• Cyclins/CDKs: Control progression through the cell cycle.

Example: Cancer results from uncontrolled cell cycle progression.

Ch. 13 - Meiosis and Sexual Life Cycles

Meiosis

Meiosis is a type of cell division that reduces the chromosome number by half, producing four genetically unique gametes.

• Phases: Meiosis I (separation of homologous chromosomes) and Meiosis II (separation of sister chromatids).

• Genetic Variation: Achieved through crossing over and independent assortment.

Example: Meiosis produces sperm and egg cells in animals.

Sexual Life Cycles

Sexual life cycles involve alternation between haploid and diploid stages.

• Haploid: One set of chromosomes (n).

• Diploid: Two sets of chromosomes (2n).

• Fertilization: Fusion of gametes restores diploid number.

Example: Flowering plants alternate between sporophyte (diploid) and gametophyte (haploid) generations. ----------------------------------------