Biology First Secondary – Units 1 & 2 Key Vocabulary

Biological Macromolecules – General Concepts

• Living organisms build their bodies from large polymers (biological macromolecules) that are produced by polymerization of small repeating units called monomers.
• 4 major classes ⇨ Carbohydrates, Lipids, Proteins, Nucleic Acids.
• Polymerization involves removal of water (dehydration / condensation). Conversely, hydrolysis splits polymers back to monomers.

Carbohydrates

• Elements ⇨ C, H, O only.
• General empirical formula ⇨ $(CH<em>2O)</em>n$.
• Key functions
– Fastest, primary energy source.
– Energy storage (plants: starch; animals + humans: glycogen in liver & muscles).
– Structural: cellulose in plant cell walls, components of protoplasm & membranes.
• Classification by size/structure
A) Simple sugars (water-soluble, sweet, low M.W.)
• Monosaccharides (1 unit)
– Glucose (Grape sugar) $C<em>6H</em>{12}O_6$
– Fructose (Fruit sugar)
– Galactose (in milk-producing glands)
– Ribose (5-C sugar of RNA)
• Disaccharides (2 units)
– Maltose = Glucose + Glucose
– Sucrose = Glucose + Fructose
– Lactose = Glucose + Galactose
B) Complex sugars (Polysaccharides)
• Cellulose • Starch • Glycogen (all are glucose polymers)
– Properties: insoluble, tasteless, very large M.W.
• Qualitative laboratory tests
– Benedict’s reagent: blue → orange/red if reducing sugar present (diagnosis of glucose in urine/blood; diabetic management).
– Iodine solution: orange → blue-black with starch.
• Health links: diabetics & obese patients should limit simple & starchy carbohydrates.

Lipids

• Elements ⇨ C, H, O (sometimes P, S).
• Water-insoluble; dissolve in non-polar solvents (benzene, $CCl_4$).
• Basic unit: 3 fatty acids + glycerol → triglyceride; presence/absence of other groups creates variants.
• Energy yield per gram > carbohydrates; constitute ≈ 5 % of cell organic matter.
• Biological roles
– Long-term energy reserve.
– Thermal insulation (polar bear blubber).
– Water-loss barrier (cuticular wax on desert plants, bird feather oil).
– Hormonal precursors (steroid hormones, cholesterol).
• Classification
A) Simple lipids
– Fats (solid, 3 saturated FA + glycerol; stored under skin for insulation).
– Oils (liquid, 3 unsaturated FA + glycerol; waterproof bird plumage).
– Waxes (long-chain FA + monohydric alcohol; coat cactus leaves, apple skins).
B) Complex lipids (phospho- & sulpholipids) ⇨ glycerol + 2 FA + phosphate + choline; major in plasma membranes.
C) Derivative lipids (from hydrolysis): steroids, cholesterol (component of membranes & precursor of sex hormones).
• Laboratory test: Sudan IV stains lipids brilliant red (detection in milk, peanut butter, cooking oils).

Proteins

• Basic structural & functional macromolecules: membranes, chromosomes, muscles, tendons, ligaments, organs, glands, skin, hair, nails; present in fluids (blood, lymph); essential to growth.
• Monomer = Amino acid (20 natural types).
– General structure: central C attached to $NH<em>2$ (basic), $COOH$ (acid), H, and variable R group. • Polymerization via peptide bond (between $COOH$ of one AA and $NH</em>2$ of next, releasing $H_2O$) → di-, tri-, polypeptide → protein.
• Determinants of protein diversity: types, order, and number of amino acids.
• Protein classes
A) Simple – only amino acids (e.g., albumin in blood, roots, leaves).
B) Conjugated – amino acids + additional group:
• Nucleoproteins (protein + DNA in chromatin)
• Phosphoproteins (casein of milk)
• Metalloproteins (hemoglobin + Fe)
• Iodoproteins (thyroxine of thyroid)
• Biuret test: violet/purple colour indicates peptide bonds (clinical assay for proteinuria).

Nucleic Acids

• Polymers of nucleotides; store & express genetic information.
• Nucleotide components

1. Pentose sugar
   – Ribose ($C<em>5H</em>{10}O<em>5$) → RNA – Deoxyribose ($C</em>5H<em>{10}O</em>4$) → DNA (lacks one O).

2. Phosphate group $(PO_4^{3-})$ linked to C-5′ of sugar.

3. Nitrogenous base attached to C-1′ of sugar:
   Purines: Adenine (A), Guanine (G) | Pyrimidines: Cytosine (C), Thymine (T, DNA only), Uracil (U, RNA only).
   • DNA: double helix, A pairs T, G pairs C; carrier of hereditary traits.
   • RNA: single-stranded, A pairs U, G pairs C; copies & expresses genetic information (transcription/translation).

Metabolism

• Sum of all biochemical reactions inside cells.
– Anabolism (building): simple → complex (requires energy). Examples • photosynthesis, protein synthesis.
– Catabolism (breakdown): complex → simple (releases energy). Example • cellular respiration of glucose.

Enzymes

• Biological protein catalysts; lower activation energy, ↑ reaction rate, ↓ cellular energy cost.
• Substrate = reactant enzyme acts upon.
• Factors affecting activity

1. Temperature
   – Optimal ≈ $37\,^{\circ}C$ (human), up to $40\,^{\circ}C$; denaturation above optimum; inactivity at $0\,^{\circ}C$ (reversible).

2. pH
   – Optimum differs: pepsin (pH < 7, stomach), trypsin (pH > 7, intestine), most enzymes (pH ≈ 7.4).
   – Dependent on $COOH$ / $NH_2$ ionization.
   • Specificity: each enzyme fits specific substrate(s).
   • Industrial/household note: detergent packages list ideal temp. to protect embedded enzymes.

Cell Theory & Microscopy

• Historical milestones
– 1665 Robert Hooke coined “cell” (cork, simple microscope).
– Antonie van Leeuwenhoek improved magnification (200 ×), first to see living cells (bacteria, protozoa).
– Schleiden (plants) + Schwann (animals) ⇒ all organisms made of cells.
– Virchow: cells arise from pre-existing cells; cell = structural & functional unit.
• Cell Theory

1. All living organisms are composed of one or more cells.

2. Cell is the basic unit of life.

3. Cells arise only from pre-existing cells.
   • Microscopes
   – Light (optical): glass lenses, light illumination, up to $\approx 1500\times$, direct ocular viewing. Contrast improved via stains or light intensity.
   – Electron • Scanning (SEM) for surfaces; Transmission (TEM) for internal ultrastructure; electromagnetic lenses, electrons, up to $10^6\times$ magnification, viewed on fluorescent screen; high resolution (shorter wavelength).
   • Magnification formula: $M<em>{total}=M</em>{objective}\times M_{eyepiece}$.

Cell Structure Overview

• Protoplasm = nucleus + cytoplasm enclosed by plasma membrane; in plants additional rigid cell wall (cellulose).

Comparative Table (Plant vs Animal Cell)

• Cell wall ✓ plant | × animal.
• Plastids ✓ plant | × animal.
• Centrioles × plant (except lower algae) | ✓ animal.
• Lysosomes rare in plants | abundant in animals.
• Vacuoles large central in plant | small & numerous in animals.

Plasma Membrane (Fluid-Mosaic Model)

• Bilayer of phospholipids: hydrophilic phosphate heads facing aqueous exterior & cytosol; hydrophobic fatty-acid tails inward.
• Embedded proteins (channels, carriers, receptors) + cholesterol (stability) + external carbohydrates (glycocalyx for recognition).
• Selective permeability, protection, maintains cytoplasmic integrity.

Cell Wall (plants, fungi, algae, bacteria)

• Primary component cellulose (fungi ⇨ chitin; bacteria ⇨ peptidoglycan).
• Fully permeable; provides rigidity, prevents bursting, allows diffusion of water & solutes.

Cytoplasm & Cytoskeleton

• Cytosol + organelles; microtubules & microfilaments form cytoskeleton (shape, movement, intracellular transport).

Membranous Organelles

• Endoplasmic Reticulum (ER)
– Rough (RER): ribosome-studded; synthesizes & modifies proteins; abundant in stomach lining & endocrine cells.
– Smooth (SER): lipid synthesis, glycogen metabolism, detoxification; abundant in liver; forms new membranes.
• Golgi Apparatus: stacks of sacs; receives ER products, modifies, packs into vesicles; forms lysosomes.
• Lysosomes: vesicles of hydrolytic enzymes; digest worn organelles, pathogens; “suicide bags”.
• Mitochondria: double membrane; inner folds (cristae) increase surface for enzymes of cellular respiration; produce ATP.
• Vacuoles: storage (water, ions, pigments); large central vacuole maintains plant turgor.
• Plastids (plants)
– Chloroplast (green, chlorophyll) – photosynthesis; structure: double membrane, grana (thylakoids), stroma.
– Chromoplast (carotenoids red-orange-yellow) – colour petals/fruits.
– Leucoplast (colourless) – starch storage in tubers, inner cabbage leaves.

Non-Membranous Organelles

• Ribosomes: protein synthesis; free (cytosolic) or bound to RER.
• Centrosome: pair of centrioles (9×3 microtubule arrangement); organizes spindle in mitosis, forms cilia/flagella; present in animals & some fungi; absent in higher plants.

Nucleus

• Largest organelle; controls metabolism & division.
– Nuclear envelope (double membrane with pores for RNA/protein traffic).
– Nucleoplasm (karyolymph).
– Nucleolus: rRNA synthesis, ribosome assembly; number correlates with protein secretory activity.
– Chromatin: DNA + histone proteins; condenses to chromosomes in mitosis (each chromosome = 2 chromatids joined at centromere).

Plant Tissues

• Simple (one cell type)

1. Parenchyma: living, thin-walled, air spaces; functions – photosynthesis, storage (starch), aeration.

2. Collenchyma: living, cellulose-thickened corners; support & flexibility.

3. Sclerenchyma: dead, lignified; strength, hardness (fibres, sclereids; linen fibres tensile).
   • Complex (multiple cell types)

4. Xylem: vessels & tracheids (dead, lignified, no protoplasm), parenchyma; transports water & minerals upward; mechanical support.

5. Phloem: sieve tubes (dead, enucleate, perforated plates) + companion cells (living, nucleated, energy supply); transports organic food bidirectionally.

Animal Tissues

• Epithelial
– Simple: squamous (lung alveoli, capillary lining), cuboidal (kidney tubules), columnar (stomach, intestine).
– Stratified squamous (many layers; skin protection).
Functions: absorption (intestine), secretion (goblet cells mucus), protection (skin).
• Connective

1. Proper (loose & dense): elastic, collagen fibres; dermis, mesenteries.

2. Skeletal: bone (calcified, solid) & cartilage (semi-solid); support.

3. Vascular: blood & lymph; transport gases, nutrients, wastes.
   • Muscle
   – Smooth: unstriated, involuntary; walls of digestive tract, vessels, bladder.
   – Skeletal: striated, voluntary, multinucleated; attached to skeleton, move limbs; rich in glycogen & mitochondria.
   – Cardiac: striated, involuntary; intercalated discs synchronize heartbeat; confined to heart walls.
   • Nervous: neurons conduct impulses from receptors to CNS & from CNS to effectors.

Science, Technology & Society Connections

• Stem Cells: undifferentiated cells able to specialize; therapeutic use – Dopamine production for Parkinson’s, regenerating cardiac tissue, producing insulin-secreting pancreatic cells.
• Cell Fractionation: ultracentrifugation separates organelles by density for biochemical studies of enzymes, macromolecules.

Common Laboratory Colour Tests (Summary)

• Reducing sugar ⇨ Benedict → orange/red.
• Starch ⇨ Iodine → blue-black.
• Lipids ⇨ Sudan IV → red stain.
• Proteins ⇨ Biuret → violet/purple.

Numerical / Chemical Highlights

• Glucose $C<em>6H</em>{12}O<em>6$; Ribose $C</em>5H<em>{10}O</em>5$; Deoxyribose $C<em>5H</em>{10}O<em>4$. • Glycosidic linkage formation between 2 glucose → maltose (loss of one $H</em>2O$).
• Complete aerobic oxidation of 1 glucose yields $38\,ATP$; fatty acid oxidation yields >$38\,ATP$ (higher energy density).

Ethical & Practical Notes

• Managing diabetes/obesity requires monitoring dietary carbohydrates and lipids.
• Detergent manufacturers list optimal wash temperatures to preserve enzymatic additives, saving household energy.
• Electron microscopy, although high-resolution, kills specimens; staining for light microscopy can also damage living cells—balance needed between visibility & viability.