General Biology: Structure and Function of Biomolecules and Cell Transport

Chapter 1: Introduction to Biology

Properties of Life

Biologists study living organisms by identifying key properties that distinguish life from non-life. These properties are essential for understanding biological systems.

• Define: Properties of life include organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation through evolution.

• Example: All living things are composed of cells and can reproduce.

Scientific Investigations

Scientific investigations in biology use systematic methods to explore natural phenomena.

• Describe: The scientific method involves observation, hypothesis formation, experimentation, and analysis of results.

• Example: Testing the effect of sunlight on plant growth by setting up controlled experiments.

Chapter 2: Atomic Structure and Chemical Bonds

Structure of an Atom

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons.

• Describe: An atom contains a nucleus (protons and neutrons) and electrons orbiting the nucleus.

• Example: A carbon atom has 6 protons, 6 neutrons, and 6 electrons.

Chemical Elements and Compounds

Elements are pure substances made of one type of atom, while compounds are substances formed from two or more elements chemically bonded.

• Relate: Elements combine to form compounds with new properties.

• Example: Water (H2O) is a compound formed from hydrogen and oxygen.

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds.

• Distinguish: Covalent bonds involve sharing electrons; ionic bonds involve transfer of electrons; hydrogen bonds are weak attractions between polar molecules.

• Example: Sodium chloride (NaCl) forms via ionic bonding; water molecules are held together by hydrogen bonds.

Macromolecules

Macromolecules are large, complex molecules essential for life, including proteins, nucleic acids, carbohydrates, and lipids.

• Relate: Monomers (small units) join to form polymers (large molecules).

• Example: Amino acids are monomers that form protein polymers.

Chapter 3: Proteins and Their Structure

Water Solubility and Amino Acids

The solubility and interaction of amino acids in water affect protein structure and function.

• Predict: Amino acids with polar side chains are more soluble in water than those with nonpolar side chains.

• Example: Glutamine (polar) vs. leucine (nonpolar).

Protein Structure

Proteins have four levels of structure that determine their shape and function.

• Describe:

  1. Primary structure: Sequence of amino acids.

  2. Secondary structure: Local folding (alpha helices, beta sheets).

  3. Tertiary structure: Overall 3D shape.

  4. Quaternary structure: Association of multiple polypeptide chains.

• Example: Hemoglobin has quaternary structure with four polypeptide subunits.

Protein Folding and Denaturation

Protein folding is crucial for function; denaturation disrupts structure and leads to loss of function.

• Explain: Denaturation can be caused by heat, pH changes, or chemicals, resulting in loss of biological activity.

• Example: Cooking an egg denatures its proteins.

Proteins in Living Systems

Proteins perform diverse functions in cells, including catalysis, transport, and structural support.

• Define: Enzymes, transport proteins, and structural proteins are examples of protein functions.

• Example: Actin and myosin are structural proteins in muscle cells.

Chapter 5: Carbohydrates

Monosaccharide Variations

Monosaccharides are simple sugars with structural variations that affect their properties.

• Describe: Glucose, fructose, and galactose are common monosaccharides with different arrangements of atoms.

• Example: Glucose and fructose both have the formula C6H12O6 but differ in structure.

Polysaccharides

Polysaccharides are long chains of monosaccharides with storage or structural roles.

• Differentiate: Storage polysaccharides (e.g., starch, glycogen) vs. structural polysaccharides (e.g., cellulose, chitin).

• Example: Starch stores energy in plants; cellulose provides structural support.

Carbohydrate Structure and Function

The structure of carbohydrates determines their function in cells and organisms.

• Explain: Branching and linkage types affect digestibility and function.

• Example: Glycogen is highly branched for rapid energy release.

Chapter 6: Lipids and Membranes

Types of Lipids

Lipids are hydrophobic molecules including fats, steroids, and phospholipids.

• Identify:

  • Fats: Energy storage.

  • Steroids: Hormones and membrane components.

  • Phospholipids: Major component of cell membranes.

• Example: Cholesterol is a steroid; triglycerides are fats.

Phospholipids and Membrane Formation

Phospholipids spontaneously form bilayers in water due to their amphipathic nature.

• Explain: Hydrophilic heads face water; hydrophobic tails face inward, forming a bilayer.

• Example: Cell membranes are composed of phospholipid bilayers.

Categories of Substances in Solution

Substances can be classified by their solubility and polarity.

• Compare:

  • Polar molecules: Dissolve in water (e.g., glucose).

  • Nonpolar molecules: Do not dissolve in water (e.g., lipids).

  • Ions: Dissolve in water (e.g., Na+, Cl-).

• Example: Salt (NaCl) dissolves in water due to ionic interactions.

Fatty Acids and Cholesterol

Fatty acids vary in saturation, affecting membrane fluidity and function.

• Predict: Saturated fatty acids are solid at room temperature; unsaturated fatty acids are liquid.

• Example: Butter (saturated fat) vs. olive oil (unsaturated fat).

Solution Properties

Solutions can be isotonic, hypotonic, or hypertonic, affecting cell water balance.

• Describe:

  • Isotonic: Equal solute concentration inside and outside the cell.

  • Hypotonic: Lower solute concentration outside; cell swells.

  • Hypertonic: Higher solute concentration outside; cell shrinks.

• Example: Red blood cells in pure water swell and burst (hypotonic).

Membrane Transport

Cells transport substances across membranes via passive and active mechanisms.

• Compare and Contrast:

  • Passive transport: No energy required; includes diffusion and facilitated diffusion.

  • Active transport: Requires energy (ATP); moves substances against concentration gradient.

• Describe: Channel and carrier proteins facilitate transport.

• Example: Glucose enters cells via facilitated diffusion; sodium-potassium pump uses ATP for active transport.

Sodium-Potassium Pump

The sodium-potassium pump is an essential active transport protein in animal cells.

• Explain: The pump uses ATP to move 3 Na+ ions out and 2 K+ ions into the cell, maintaining electrochemical gradients.

• Equation: $\text{ATP} + 3\text{Na}^+_{\text{in}} + 2\text{K}^+_{\text{out}} \rightarrow 3\text{Na}^+_{\text{out}} + 2\text{K}^+_{\text{in}} + \text{ADP} + \text{P}_i$

• Example: Nerve impulse transmission relies on sodium-potassium pump activity.

Table: Comparison of Membrane Transport Mechanisms

Transport Type	Energy Required	Direction	Example
Simple Diffusion	No	Down concentration gradient	Oxygen entering cells
Facilitated Diffusion	No	Down concentration gradient	Glucose transport via carrier protein
Active Transport	Yes (ATP)	Against concentration gradient	Sodium-potassium pump