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BIOLOGY

BIOLOGY NOTES

MODULE 2

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INDEXTOPIC 1: CELL STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . . 5

1. Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Light & Electron Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Cell Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Magnification Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Magnification vs. Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Eukaryotic Cells & Cellular Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. Organelles Involved in the Production & Secretion of Proteins . . . . . . . . . . . . . . . 15 8. Cytoskeleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9. Structure & Ultrastructure of Prokaryotic & Eukaryotic Cells . . . . . . . . . . . . . . . . 16

TOPIC 2: BIOLOGICAL MOLECULES . . . . . . . . . . . . . . . . . 18 1. Hydrogen Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2. Monomers & Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. Biological Molecules and Their Chemical Elements . . . . . . . . . . . . . . . . . . . . . . 21 4. Glucose and Ribose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5. Formation and Breakage of Glycosidic Bonds . . . . . . . . . . . . . . . . . . . . . . . . . 23 6. Starch, Glycogen & Cellulose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7. Triglycerides and Phospholipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 8. The General Structure of an Amino Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 9. Dipeptides, Polypeptides and Peptide Bonds . . . . . . . . . . . . . . . . . . . . . . . . . 28 10. The Levels of Protein Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 11. Globular and Fibrous Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 12. Inorganic Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 13. Chemical Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 14. Concentration of a Chemical Substance in a Solution . . . . . . . . . . . . . . . . . . . . 33 15. Thin Layer Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

TOPIC 3: NUCLEOTIDES & NUCLEIC ACIDS . . . . . . . . . . . . . 35 1. Nucleotides & Polynucleotides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2. ADP & ATP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3. Deoxyribonucleic Acid (DNA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4. Semi-Conservative DNA Replication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 5. The Genetic Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 6. Transcription and Translation of Genes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

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TOPIC 4: ENZYMES . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 1. Enzymes & Catalysing Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2. Enzyme Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3. Factors Affecting Enzyme Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4. Coenzymes, Cofactors & Prosthetic Groups . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5. Inhibitors & Enzyme-Controlled Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

TOPIC 5: BIOLOGICAL MEMBRANES . . . . . . . . . . . . . . . . . 50 1. Role of Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2. The Fluid Mosaic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3. Membrane Structure and Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4. The Movement Molecules Across Membranes . . . . . . . . . . . . . . . . . . . . . . . . 52

TOPIC 6: CELL DIVISION, CELL DIVERSITY AND CELL ORGANISATION . . . . . . . . . . . . . . . . . . . . . . . 55

1. The Cell Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 2. How the Cell Cycle is Regulated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3. The Main Stages of Mitosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4. The Significance of Mitosis in Life Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 5. The Significance of Meiosis in Life Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 6. Stages of Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 7. Cells of Multicellular Organisms and their specialised Functions . . . . . . . . . . . . . . 63 8. Tissues, Organs and Organ systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 9. Stem Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 10. Erythrocytes & Neutrophils Derived from Stem Cells in Bone Marrow . . . . . . . . . . 65 11. Xylem Vessels & Phloem Sieve Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 12. The Potential of Stem Cells in Research & Medicine . . . . . . . . . . . . . . . . . . . . . 66

TOPIC 1

Cell Structure

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Cell Structure

1 Microscopy

Scientists use a range of different types of microscopes to observe Eukaryotic cells and their structures, which are too small to see with the naked eye:

1. Light microscope:

2. Transmission electron microscope:

3. Scanning electron microscope:

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4. Laser scanning microscope:

EXAM TIPGet familiar with the units mm, ųm and nm. You’re expected to be confident converting

between them.

1mm = 1000ųm

1 ųm = 1000nm

2 Light & Electron Microscopy

Using a light microscope:

Light microscopes are the most commonly used microscopes used to examine cells. This is because the equipment used is relatively inexpensive, requires minimal user training, and yields good results in terms of identifying cell structures and activity.

• A number of lenses are used to produce an image • Image viewed directly through eyepiece • Light passes from bulb under the stage, through condenser lense, then through specimen • Beam of light then focused through objective lens, then through eyepiece lens • Four different objective lenses (x4, x10, x40, x100) allow for specimen to be viewed at different magnifications

• Eyepiece lens magnifies image again, usually x10 • Total magnification is given by multiplying the magnification of the 2 lenses • Magnification possible with light microscope: up to 1500x

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