Exam 2 Preparation: General Biology Study Guide

Biomolecules (Chapters 3 and 4)

Biomolecules are the fundamental building blocks of life, including proteins, carbohydrates, lipids, and nucleic acids. Understanding their structure and function is essential for studying cellular processes.

• Amino Acids and Proteins: Amino acids are the monomers of proteins, each with a central carbon, amino group, carboxyl group, hydrogen atom, and a variable side chain (R group). The side chain determines the properties of each amino acid.

• Peptide Bond: A covalent bond formed between the amino group of one amino acid and the carboxyl group of another, releasing water (dehydration synthesis).

• Protein Structure:

  • Primary structure: Linear sequence of amino acids.

  • Secondary structure: Local folding into alpha helices and beta sheets, stabilized by hydrogen bonds.

  • Tertiary structure: Three-dimensional folding due to interactions among side chains.

  • Quaternary structure: Association of multiple polypeptide chains.

• Nucleic Acids: DNA and RNA are polymers of nucleotides, each consisting of a phosphate group, a five-carbon sugar, and a nitrogenous base.

• Phosphodiester Bond: The covalent bond linking nucleotides in nucleic acids.

• Carbohydrates: Include monosaccharides (simple sugars), disaccharides, and polysaccharides (complex carbohydrates).

• Lipids: Include fats, phospholipids, and steroids. Triglycerides are composed of glycerol and three fatty acids.

Example: Hemoglobin is a protein with quaternary structure, composed of four polypeptide subunits.

Cell Structure (Chapter 7)

Cells are the basic units of life. Eukaryotic cells contain membrane-bound organelles, each with specialized functions.

• Nucleus: Contains genetic material (DNA) and controls cellular activities.

• Endoplasmic Reticulum (ER): Rough ER synthesizes proteins; smooth ER synthesizes lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Mitochondria: Site of cellular respiration and ATP production.

• Lysosomes: Contain digestive enzymes to break down waste.

• Chloroplasts: Present in plant cells; site of photosynthesis.

• Double Membrane Organelles: Mitochondria and chloroplasts have double membranes, supporting the endosymbiotic theory.

Example: The mitochondrion has an inner membrane with folds called cristae, increasing surface area for ATP production.

Cellular Respiration (Chapter 9)

Cellular respiration is the process by which cells convert biochemical energy from nutrients into ATP, the energy currency of the cell.

• ATP (Adenosine Triphosphate): The main energy carrier in cells.

• Stages of Cellular Respiration:

  1. Glycolysis: Occurs in the cytoplasm; breaks down glucose into pyruvate, producing ATP and NADH.

  2. Pyruvate Oxidation: Converts pyruvate into acetyl-CoA in the mitochondrial matrix.

  3. Citric Acid Cycle (Krebs Cycle): Completes the breakdown of acetyl-CoA, generating NADH, FADH2, and ATP.

  4. Electron Transport Chain (ETC): Series of protein complexes in the inner mitochondrial membrane; transfers electrons from NADH and FADH2 to oxygen, pumping protons to create a gradient.

  5. Oxidative Phosphorylation and Chemiosmosis: ATP synthase uses the proton gradient to synthesize ATP from ADP and inorganic phosphate.

• Fermentation: Anaerobic process that regenerates NAD+ when oxygen is absent, producing lactic acid or ethanol.

Key Equations:

• Overall cellular respiration:

• ATP synthesis (chemiosmosis):

Example: Muscle cells perform lactic acid fermentation during intense exercise when oxygen is limited.

Gas Exchange (Chapters 42.4, 19.1, Figures 19.7, 22)

Gas exchange is the process by which organisms obtain oxygen and remove carbon dioxide, essential for cellular respiration.

• Diffusion: Gases move from areas of higher to lower concentration.

• Partial Pressure: The pressure exerted by a single type of gas in a mixture; drives diffusion across respiratory surfaces.

• Respiratory Surfaces: Adapted for efficient gas exchange (e.g., alveoli in mammals, gills in fish, stomata in plants).

• Factors Affecting Gas Exchange: Surface area, thickness of the membrane, and concentration gradients.

• Oxygen Transport: Hemoglobin in red blood cells binds oxygen; myoglobin stores oxygen in muscle cells.

• Stomata: Pores in plant leaves that regulate gas exchange and water loss.

Example: In humans, oxygen diffuses from alveoli into capillaries, while carbon dioxide diffuses in the opposite direction.

Diagrams and Structures

Be able to draw and label the following:

• An amino acid, indicating the side chain (R group), amino group, and carboxyl group.

• A nucleotide, labeling the pentose sugar, phosphate group, and nitrogenous base.

• Phospholipid bilayer structure, showing hydrophilic heads and hydrophobic tails.

• Cellular organelles: nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosome, chloroplast (for plant cells).

Vocabulary (Including Carbohydrates - Chapter 5)

Understanding key vocabulary is essential for mastering biological concepts. Below is a table summarizing important terms and their definitions.

Additional info: Some definitions and context have been expanded for clarity and completeness.