Chapter 2: Cell Chemistry & Cell Components – Key Study Notes

Cell Chemistry & Cell Components

Chemical Definitions

This section introduces fundamental chemical concepts essential for understanding cellular structure and function in anatomy and physiology.

• Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.

• Matter: Anything that occupies space and has mass.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Molecule: Two or more atoms chemically bonded together.

• Compound: A substance formed from two or more different elements bonded together.

Subatomic Particles

• Proton: Positive charge (+1)

• Neutron: Neutral charge (0)

• Electron: Negative charge (-1)

Bohr Model & Valence Shell

• The Bohr model illustrates electrons orbiting the nucleus in energy levels.

• The valence shell is the outermost electron shell, crucial for chemical bonding.

Isotopes

Isotopes are variants of elements with differing neutron numbers, affecting atomic mass but not chemical properties.

• Definition: Atoms with the same number of protons but different numbers of neutrons.

• Subatomic particle that differs: Neutron

• Benefits: Used in medical imaging, dating fossils, and as tracers in biochemical research.

Chemical Bonding

Chemical bonds are forces holding atoms together, forming molecules and compounds.

• Ionic Bonds: Formed by transfer of electrons; example: NaCl (table salt).

• Covalent Bonds: Formed by sharing electrons.

  • Nonpolar: Equal sharing (e.g., O2).

  • Polar: Unequal sharing (e.g., H2O).

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and DNA structure.

Chemical Reactions

Chemical reactions involve breaking and forming bonds, essential for cellular metabolism.

• Requirements: Reactants, energy, and enzymes.

• Metabolism: All chemical reactions in the body.

• Anabolism: Building complex molecules from simpler ones.

• Catabolism: Breaking down complex molecules into simpler ones.

• Energy: Capacity to do work; often released or absorbed in reactions.

Types of Chemical Reactions

1. Synthesis: $A + B \rightarrow AB$ (building molecules)

2. Decomposition: $AB \rightarrow A + B$ (breaking molecules)

3. Exchange: $AB + CD \rightarrow AD + CB$ (swapping components)

4. Reversible: $A + B \rightleftharpoons AB$ (can proceed in both directions)

Enzymes

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

• Definition: Proteins that catalyze biochemical reactions.

• Macromolecule type: Protein

• Energy of Activation Curve: Enzymes lower the energy barrier for reactions, making them proceed faster.

Inorganic vs Organic Compounds

Compounds in the body are classified as inorganic or organic based on their chemical structure.

• Nutrients: Substances required for growth and maintenance.

• Metabolites: Molecules involved in metabolism.

• Inorganic compounds: Usually lack carbon (e.g., water, salts).

• Organic compounds: Contain carbon and hydrogen (e.g., carbohydrates, proteins).

• Example: Inorganic: NaCl; Organic: Glucose

Properties of Water

Water is vital for life due to its unique chemical properties.

• Bond within molecule: Polar covalent bond

• Bond between molecules: Hydrogen bond

• Three properties:

  1. High heat capacity

  2. Solvent ability

  3. Cohesion and adhesion

pH

pH measures the concentration of hydrogen ions in a solution, indicating its acidity or basicity.

• Definition: pH is the negative logarithm of hydrogen ion concentration: $\text{pH} = -\log_{10}[H^+]$

• Acidic: pH < 7

• Neutral: pH = 7

• Basic: pH > 7

• Blood pH: Approximately 7.4

• Importance: pH affects enzyme activity and cellular function.

• Example: Wine (acidic) has more hydrogen ions than baking soda (basic).

Macromolecules

Macromolecules are large biological molecules essential for cell structure and function.

• Monomer: Single building block (e.g., amino acid)

• Polymer: Chain of monomers (e.g., protein)

• Conversion: Monomers join via dehydration synthesis; polymers break down via hydrolysis.

Macromolecule	Monomer	Polymer	Bonds	Function
Carbohydrate	Monosaccharide	Polysaccharide	Glycosidic	Energy storage
Protein	Amino acid	Polypeptide	Peptide	Structure, enzymes
Nucleic Acid	Nucleotide	DNA/RNA	Phosphodiester	Genetic information
Lipid	Fatty acid	Triglyceride	Ester	Energy storage, membranes

Protein Structure

• Four levels:

  1. Primary (sequence)

  2. Secondary (alpha helix, beta sheet)

  3. Tertiary (3D folding)

  4. Quaternary (multiple polypeptides)

• Hemoglobin structure: Quaternary

Nucleic Acids

• Three components of a nucleotide: Sugar, phosphate, nitrogenous base

• DNA vs RNA: DNA is double-stranded, RNA is single-stranded

• Genetic information: DNA

• Protein production: RNA

• High-energy bonds: ATP (a nucleotide)

Fats

• Triglycerides

• Phospholipids

• Steroids

• Fatty acids

Additional info: Academic context was added to expand brief points and clarify definitions, examples, and functions for exam preparation.