Chemical Level of Organization & Cell Biology: Study Notes

Chemical Level of Organization

Chemical Elements

Chemical elements are the simplest forms of matter and are fundamental to all biological processes. They cannot be broken down into simpler substances by ordinary chemical means.

• Definition: Elements are substances that cannot be broken down into simpler substances.

• Common biological elements: C, H, O, N, P, S (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur)

Structure of Atoms

Atoms are composed of subatomic particles that determine their chemical properties and behavior.

• Protons: Positive charge, located in the nucleus

• Neutrons: No charge, located in the nucleus

• Electrons: Negative charge, orbit the nucleus in shells

Electron Shells

• Electrons occupy shells around the nucleus

• Valence shell: Outermost shell, determines reactivity

Chemical Bonds

Chemical bonds form when atoms interact to achieve stable electron configurations.

• Octet Rule: Atoms are most stable with 8 electrons in their valence shell

• Covalent bonds: Atoms share electrons

• Ionic bonds: Transfer of electrons

• Hydrogen bonds: Weak attraction between slightly charged atoms (important in water and DNA)

Chemical Reactions

• Reactants: Starting substances

• Products: Substances formed

Forms of Energy

• Kinetic energy: Energy of motion

• Potential energy: Stored energy

Energy Transfer

• Exergonic: Releases energy

• Endergonic: Requires energy

Activation Energy

• Energy needed to start a reaction

• Depends on temperature, concentration, and catalysts

Catalysts

• Speed up reactions without being used up

• Enzymes: Biological catalysts

Types of Reactions

• Anabolic: Builds molecules (requires energy)

• Catabolic: Breaks down molecules (releases energy)

• Redox: Oxidation (loss of electrons), reduction (gain of electrons)

Inorganic Compounds & Solutions

Water

• Polar molecule

• Universal solvent

• High heat capacity

Hydrophilic vs. Hydrophobic

• Hydrophilic: Water-loving (polar/charged)

• Hydrophobic: Water-fearing (nonpolar)

Hydrolysis

• Breaks bonds using water

Dehydration Synthesis

• Forms bonds by removing water

Mixtures

• Solutions: Evenly mixed (solute + solvent)

• Colloid: Cloudy mixture, doesn’t settle

• Suspension: Particles settle out

Acids & Bases

• Acid: Releases H+ ions

• Base: Accepts H+ or releases OH-

Buffers

• Resist changes in pH

pH Scale

• Measures acidity/alkalinity

• Scale: 0–14

• Acidic: < 7

• Neutral: 7

• Basic: > 7

Organic Compounds

Carbohydrates

• Main energy source

• Monosaccharides: Glucose

• Disaccharides: Sucrose

• Polysaccharides: Glycogen, starch

Lipids

• Long-term energy storage

Fatty Acids

• Saturated: No double bonds (solid)

• Monounsaturated: One double bond

• Polyunsaturated: Multiple double bonds

Types

• Triglycerides: Fats & oils

• Phospholipids: Cell membranes

• Cholesterol: Membrane stability, hormones

Proteins

• Made of amino acids

• Linked by peptide bonds

• Form polypeptides

Levels of Protein Structure

• Primary: Amino acid sequence

• Secondary: Alpha helices & beta sheets

• Tertiary: 3D shape

• Quaternary: Multiple polypeptides

Enzymes

• Protein catalysts

• Properties:

  • Specific

  • Reusable

  • Sensitive to temperature & pH

• How they work:

  • Bind substrates at active site

  • Lower activation energy

Nucleic Acids

• DNA: Genetic information

• RNA:

  • mRNA: Carries instructions

  • tRNA: Delivers amino acids

  • rRNA: Ribosome structure

Nitrogenous Bases

• Adenine (A)

• Thymine (T) (DNA only)

• Cytosine (C)

• Guanine (G)

• Uracil (U) (RNA only)

Watson & Crick

• Discovered the double helix structure of DNA

ATP (Adenosine Triphosphate)

• Cell’s main energy currency

• Energy released when phosphate bond breaks

Cell

Three Main Parts of a Cell

1. Plasma membrane

2. Cytoplasm

3. Nucleus

Cell Processes

• Metabolism

• Growth

• Reproduction

• Transport

Plasma Membrane

• Selectively permeable barrier

Molecules in Plasma Membrane

• Phospholipid bilayer

• Proteins

• Cholesterol

• Carbohydrates

Membrane Proteins

• Integral proteins: Embedded

• Peripheral proteins: Surface

• Receptors: Signal binding

• Enzymes: Chemical reactions

• Carriers/Channels: Transport

Membrane Transport

Diffusion

• Movement from high to low concentration

Simple Diffusion

• Small, nonpolar molecules

Facilitated Diffusion

• Uses carrier proteins

Osmosis

• Diffusion of water across membrane

Active Transport

• Requires ATP

Primary Active Transport

• Uses ATP directly

Secondary Active Transport

• Uses energy from ion gradients

Vesicular Transport

• Endocytosis: Into cell

  • Phagocytosis: Solids

  • Pinocytosis: Liquids

• Exocytosis: Out of cell