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Biology Exam Notes: Macromolecules, Cells, Tissues, Skin, Bone

Biological Macromolecules

  • Saturated Fats: Solid at room temp, straight chains, tightly packed.
  • Unsaturated Fats: Kink in tail, not tightly packed (e.g., olive oil).
  • Proteins:
    • Monomer: Amino acids (H_2N-C(R)-COOH structure).
    • Amino acids linked by peptide bonds (dehydration reaction) to form polypeptides, then proteins.
    • 20 amino acids: half polar, half non-polar.
  • Nucleotides: Subunits of DNA/RNA, energy carriers (ATP), building blocks for nucleic acids.
  • Adenosine Triphosphate (ATP): Energizes molecules via phosphate-group transfers.

Cell Theory & Components

  • Cell Theory: Simplest unit of life, organisms are cells, cells from preexisting cells.
  • All cells evolved from a common ancestral cell (3.5-3.8 \text{ BYA}).
  • Cell size/shape vary by gene expression and chemical needs.
  • Major Components: Cytoplasm, organelles, plasma membrane (proteins and lipids).

Membrane Transport Mechanisms

  • Plasma Membrane: Selectively permeable.
  • Passive Transport (no ATP):
    • Filtration: Pressure involved (e.g., blood capillaries).
    • Diffusion: High to low concentration (affected by temp, gradient, surface area).
    • Osmosis: Water movement towards higher non-permeable solute concentration, often via aquaporins.
  • Active Transport (requires ATP): Moves solutes against concentration gradient.
    • Primary Active Transport: Direct ATP use.
    • Secondary Active Transport: Indirect ATP use, relies on other pumps.
  • Carrier-Mediated Transport: Involves transmembrane proteins.
    • Uniport: Transports one solute.
    • Symport: Transports two+ solutes in same direction.
    • Antiport: Countertransports two+ solutes (e.g., Na^+/K^+ pump).
  • Facilitated Diffusion: Down concentration gradient, no ATP, uses channels/transporters.
  • Vesicular Transport (requires ATP, motor proteins, microtubules):
    • Endocytosis (into cell):
      • Phagocytosis: Engulfing large particles (e.g., pseudopodes).
      • Receptor-mediated: Selective uptake via specific receptors and clathrin.
      • Pinocytosis: Taking in ECF droplets.
    • Exocytosis (out of cell): Discharging material.
    • Transcytosis: Transport across cell (e.g., insulin).

Cell Organelles

  • Endoplasmic Reticulum (ER):
    • Rough ER: Ribosomes present, produces phospholipids, membrane proteins.
    • Smooth ER: No ribosomes, detoxification, Ca^{2+} storage (abundant in kidney/liver).
  • Ribosomes: Protein + RNA, read mRNA and assemble proteins (can form polyribosomes).
  • Golgi Complex: Packages products with vesicles, modifies proteins (sorts, cuts, splices, adds carbs).
  • Mitochondria: Contain own DNA, divide by binary fission, produce ATP, enabled complex multicellularity.
  • Lysosomes: Contain hydrolytic enzymes (active at acidic pH), break down proteins, nucleic acids, carbs, phospholipids; pH maintained by an ATP-driven H^+ pump.
  • Proteasome: Protein complex with protease, breaks down ubiquitin-tagged proteins.
  • Ubiquitin: Small protein that tags other proteins for destruction by proteasomes.

Genetics and Chromosomes

  • Genes: Unit of heredity; DNA segment coding for RNA to a functional product.
    • Alternative Splicing: Allows multiple proteins from one gene.
    • Gene Regulation: Cells express genes at different rates; mis-regulation leads to disease.
    • Methylation: Activates or silences genes (histones + DNA).
  • Polygenic Traits: Multiple genes contribute to one trait (e.g., eye color).
  • Pleiotropy: One gene has multiple phenotypic effects (e.g., sickle cell disease).
  • Karyotype: Organized set of 23 pairs of homologous chromosomes (autosomes, sex chromosomes).
  • Mutations: Uncorrected DNA Polymerase errors, spontaneous events, chemicals, radiation, viruses.
  • Sex-linked Disorders: Gene on X chromosome (e.g., color blindness, hemophilia).

Tissues and Glands

  • Tissues: Groups of similar cells and matrix with specific roles (Histology is tissue study).
  • Four Basic Tissue Types: Nervous, Muscle, Epithelial, Connective.
  • Epithelial Tissue: Closely packed cells, avascular, rapid repair.
    • Basal Membrane: Faces basement membrane.
    • Apical Surface: Faces away from basement membrane.
    • Basement Membrane: Regulates material passage, supports epithelia.
  • Simple Epithelia (one layer): Squamous, Cuboidal, Columnar, Pseudostratified Columnar.
    • Simple Squamous: Thin, flattened cells; secretes serous fluid (alveoli, glomeruli).
    • Simple Cuboidal: Round/square cells; absorption, secretion (liver, kidney tubules).
    • Simple Columnar: Tall cells, microvilli, goblet cells; absorption, mucus (GI tract, uterus).
    • Pseudostratified Columnar: Looks multilayered, all cells touch basement; secretes/propels mucus (respiratory tract).
  • Stratified Epithelia (multiple layers):
    • Keratinized Squamous: Dead, keratin-packed cells; packed with keratin (epidermis, palms/soles).
    • Nonkeratinized Squamous: Resists abrasion, pathogens (tongue, esophagus, vagina).
    • Stratified Cuboidal: 2+ layers; secretes sweat, produces sperm/ovarian hormones (sweat glands).
    • Transitional (Urothelium): Multilayered, cells change shape (round to flat); allows urinary tract filling (ureter, bladder).
  • Glands: Secretory epithelial cells.
    • Endocrine Glands: Secrete hormones directly into blood, lack ducts (e.g., beta cells secrete insulin).
    • Exocrine Glands: Secrete products onto body surfaces via ducts (e.g., acinar cells secrete digestive enzymes).

Connective Tissue

  • Most abundant, widely distributed, histologically variable.
  • Four Types: Fibrous, Adipose, Supportive (Cartilage, Bone), Fluid (Blood).
  • Fibrous Connective Tissue:
    • Cells: Fibroblasts, leukocytes, macrophages, adipocytes.
    • Fibers: Collagen (strong), Reticular (support), Elastic (stretch).
    • Loose CT: Areolar, Reticular.
    • Dense CT: Regular (parallel fibers), Irregular (random fibers).
  • Adipose Tissue: Adipocytes store fat (white fat: cushions; brown fat: generates heat).
  • Cartilage (3 types):
    • Hyaline: Eases joint movement, growth of long bones.
    • Elastic: Flexible, elastic support.
    • Fibrocartilage: Collagen bundles, absorbs shock.
  • Bone: Calcified connective tissue.
    • Spongy Bone: Heads of long bones, middle of flat bones.
    • Compact Bone: Dense, no visible spaces, external surfaces.
  • Blood (Fluid CT): Transports cells and matter; composed of plasma and formed elements (RBCs, WBCs, platelets).

Nervous and Muscle Tissue

  • Nervous Tissue: Communication via electrical and chemical signaling.
    • Neurons: Detect stimuli, transmit information.
    • Neuroglial Cells: Support neurons (e.g., astrocytes, microglia, Schwann cells).
  • Muscle Tissue: Cells (muscle fibers) contract when stimulated.
    • Skeletal Muscle: Attaches to bone, multinucleated, striated, voluntary.
    • Cardiac Muscle: Heart wall, cardiomyocytes (short, branched, 1 nucleus), intercalated discs, striated, involuntary.
    • Smooth Muscle: Short, fusiform cells, 1 central nucleus, non-striated, involuntary, forms walls of hollow organs.

Membranes

  • Cutaneous Membrane: Skin.
  • Internal Membranes: Mucous and serous membranes.

Integumentary System (Skin)

  • Most vulnerable organ; contains skin, hair, nails, associated glands.
  • Epidermis: Stratified squamous keratinized, avascular, dead cells at surface.
    • Contains stem cells, keratinocytes, melanocytes, tactile cells, dendritic cells.
  • Dermis: Connective tissue, vascular; papillary and reticular zones.
    • Contains sebaceous glands (holocrine, oily/waxy secretion) and sweat glands (eccrine, apocrine).
  • Hypodermis (Subcutaneous Tissue): More areolar and adipose tissue, binds skin to underlying tissues.

Bone Tissue

  • Connective tissue providing support, protection, and movement.
  • Classifications: Flat, Long, Short/Irregular Bones.
  • Structure:
    • Flat Bone: Two layers of compact bone with periosteum, middle spongy bone layer ("Diploe") lined with endosteum.
    • Consists of outer compact bone and inner spongy bone.
  • Connective Tissue Layers: Periosteum (outer covering), Endosteum (inner lining).