General Biology: Structure and Function of Biomolecules Study Notes

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Chapter 1: Introduction to Biology

Properties of Life

Biologists study the characteristics that define living organisms. Understanding these properties is essential for distinguishing living things from non-living matter.

Definition: Properties of life include organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation.
Example: All living organisms maintain homeostasis, such as regulating internal temperature.

Scientific Investigations

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

Key Steps: Observation, hypothesis formation, experimentation, data analysis, and conclusion.
Example: Testing the effect of light on plant growth by forming a hypothesis and conducting controlled experiments.

Chapter 2: Atomic Structure and Chemical Bonds

Structure of an Atom

Atoms are the basic units of matter, composed of subatomic particles.

Definition: An atom consists of a nucleus (protons and neutrons) and electrons orbiting the nucleus.
Example: The carbon atom has 6 protons, 6 neutrons, and 6 electrons.

Chemical Elements and Compounds

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

Definition: Elements are listed in the periodic table; compounds have fixed ratios of elements.
Example: Water (H2O) is a compound of hydrogen and oxygen.

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds.

Covalent Bonds: Atoms share electrons.
Ionic Bonds: Atoms transfer electrons, forming charged ions.
Hydrogen Bonds: Weak attractions between partially charged regions of molecules, important in water and biological macromolecules.
Example: Hydrogen bonds stabilize the structure of DNA.

Macromolecules

Biological macromolecules are large, complex molecules essential for life.

Types: Proteins, nucleic acids, carbohydrates, and lipids.
Monomers: Building blocks of macromolecules (e.g., amino acids for proteins).
Polymerization: Monomers join to form polymers through dehydration synthesis.
Example: Starch is a polymer of glucose monomers.

Chapter 3: Proteins and Their Properties

Water Solubility and Amino Acids

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

Hydrophilic Amino Acids: Interact well with water; found on protein surfaces.
Hydrophobic Amino Acids: Avoid water; found in protein interiors.
Example: Serine is hydrophilic, while leucine is hydrophobic.

Protein Structure

Proteins have four levels of structure that determine their function.

Primary Structure: Sequence of amino acids.
Secondary Structure: Local folding (α-helix, β-sheet) stabilized by hydrogen bonds.
Tertiary Structure: Overall 3D shape of a single polypeptide.
Quaternary Structure: Association of multiple polypeptide chains.
Example: Hemoglobin has quaternary structure with four polypeptide subunits.

Protein Folding and Denaturation

Protein folding is essential for biological activity; denaturation disrupts structure and function.

Folding: Driven by interactions among amino acids and the environment.
Denaturation: Loss of structure due to heat, pH changes, or chemicals, leading to loss of function.
Example: Cooking an egg denatures its proteins.

Functions of Proteins

Proteins perform diverse roles in living organisms.

Enzymes: Catalyze biochemical reactions.
Structural Proteins: Provide support (e.g., collagen).
Transport Proteins: Move substances across membranes (e.g., hemoglobin).
Example: Actin and myosin are involved in muscle contraction.

Chapter 5: Carbohydrates

Monosaccharide Variations

Monosaccharides are simple sugars with structural variations.

Definition: Monosaccharides differ in carbon number, arrangement, and functional groups.
Example: Glucose and fructose are both six-carbon sugars but differ in structure.

Polysaccharides

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

Storage Polysaccharides: Starch (plants), glycogen (animals).
Structural Polysaccharides: Cellulose (plants), chitin (fungi and arthropods).
Example: Cellulose provides rigidity to plant cell walls.

Carbohydrate Structure and Function

The structure of carbohydrates determines their biological roles.

Key Features: Branching, linkage type (α or β), and monomer composition.
Example: Glycogen is highly branched, allowing rapid energy release.

Chapter 6: Lipids and Membranes

Types of Lipids

Lipids are hydrophobic molecules with diverse functions in cells.

Major Types: Fats (triglycerides), steroids, phospholipids.
Example: Cholesterol is a steroid important for membrane structure.

Phospholipids and Membrane Formation

Phospholipids spontaneously form bilayers in aqueous environments, creating cell membranes.

Structure: Hydrophilic head and hydrophobic tails.
Example: The plasma membrane is a phospholipid bilayer.

Properties of Substances in Water

Substances can be hydrophilic or hydrophobic, affecting their behavior in biological systems.

Hydrophilic: Water-loving; dissolve easily (e.g., glucose, Na+).
Hydrophobic: Water-fearing; do not dissolve (e.g., fats, cholesterol).
Example: Oil does not mix with water due to hydrophobic properties.

Fatty Acids and Lipid Classification

Fatty acids vary in saturation, affecting lipid properties.

Saturated Fatty Acids: No double bonds; solid at room temperature.
Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.
Example: Olive oil contains unsaturated fatty acids.

Membrane Transport

Cells transport substances across membranes using various mechanisms.

Passive Transport: Movement down a concentration gradient; includes diffusion and facilitated diffusion.
Active Transport: Movement against a gradient, requiring energy (ATP).
Example: Sodium-potassium pump uses ATP to maintain ion gradients.

Channel and Carrier Proteins

Proteins embedded in membranes facilitate transport of molecules.

Channel Proteins: Form pores for specific ions or molecules.
Carrier Proteins: Bind and transport substances across the membrane.
Example: Aquaporins facilitate water movement.

Sodium-Potassium Pump

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

Function: Uses ATP to move Na+ out and K+ into the cell, establishing an electrochemical gradient.
Equation:
Example: Maintains nerve cell resting potential.

Comparison of Membrane Transport Mechanisms

Transport Type	Energy Required	Direction	Example
Simple Diffusion	No	Down gradient	O2 across membrane
Facilitated Diffusion	No	Down gradient	Glucose via carrier protein
Active Transport	Yes (ATP)	Against gradient	Sodium-potassium pump