Biology Remedial Course Notes

Biology Module Remedial Courses Overview

• Biology is the branch of science studying living things, their nature, functions, and interactions.
• It uses scientific methods to understand the organized matter unique to living organisms.
• Biology addresses critical issues like population growth and diseases.
• Opportunities in biology include research in developmental biology, immunology, and other fields.
• Biology is important for managing natural resources, preventing diseases, and improving life quality.

The Scientific Method

• Science is a systematically organized body of knowledge about nature, society, and thought.
• Studies in science involve interrelated concepts: method, field, and results of investigation.
• The scientific method is a logical series of steps to study natural processes and solve problems.
• Scientific knowledge is subject to testing, evaluation, and reconstruction over time.
• The scientific method is applicable in various contexts, such as crime investigation and disease diagnosis.

Steps of the Scientific Method

1. Observation:

   • Involves accurate data recording and organization, made directly through sensory systems or indirectly with equipment like microscopes.
   • Preliminary observations lead to identifying a specific problem or question.
   • Biological investigations often start with observing a structure, process, or behavioral pattern.

2. Defining the Problem/Question:

   • Experiments are based on a specific problem identified through observations and gathered facts.
   • Questions like "What will happen?", "Why is it so?", and "How does it take place?" are asked.

3. Gathering Information and Forming a Hypothesis:

   • Information gathered can be qualitative (color, taste) or quantitative (measurements).
   • Hypothesis: a suggested explanation of observed phenomena/problems, needing testing.
   • A hypothesis is a tentative theory, characterized by:
     • An intelligent guess
     • Gradual accumulation of indirect evidence
     • Potential for number of predictions
     • Interconnected statements giving a possible solution
   • Supporting observations strengthen a hypothesis; contradictory observations may lead to modification or rejection.

4. Testing Hypothesis/Experimentation:

   • Hypothesis testing often involves experimentation to control variables.

   • A hypothesis surviving many tests and allowing predictions becomes a theory.

   • A theory with strong predictive ability may be known as a law.

   • Variables in Experiments:

     • Independent variables: conditions or events under experimentation (e.g., temperature).
     • Dependent variables: variables that change due to independent variables (e.g., growth rate).
     • Controlled variables: conditions kept constant to avoid affecting the outcome (e.g., light in temperature experiment).

   • Components of a Carefully Planned Experiment:

     • Experimental group (treated group)
     • Control group (untreated group)

   • Controlled experiments test one factor at a time, keeping others constant.

   • Example: Testing if germinating seeds produce CO_2 during respiration involves:

     • Setup i: Germinating seeds in a test tube connected to limewater.
     • Setup ii: Non-germinating seeds (control) in a test tube connected to limewater.
     • Observation: Limewater turns milky in (i) due to CO_2 release.
     • Conclusion: CO_2 evolves during respiration.

5. Recording, Analysis, and Interpretation of Data:

   • Results should be carefully and systematically recorded and organized into data tables, charts, or graphs, with verbal explanations.
   • Analysis involves studying the organized material to discover essential facts.
   • Methods for data analysis include:
     • Using clear tables or figures
     • Examining the problem statement
     • Discussing with others
     • Statistical calculations for similarities/differences
   • Interpretation involves a careful, logical, and critical examination of results.

6. Drawing Conclusions:

   • Conclusions and generalizations require careful and objective data analysis.

7. Theory, Principles, Fact, and Law:

   • A hypothesis repeatedly tested and found acceptable becomes a theory.
   • A theory is open to tests, revisions, and tentative acceptance or rejection.
   • Example: Theory of evolution has changed over time.
   • Discoveries may take the form of a theory after subsequent findings (e.g., Robert Hooke's cell discovery).
   • When a theory proves invariable, it may be accepted as a fact, principle, or law.
   • A model is a mental map formed by analogy to simplify ideas (e.g., the key and lock model of enzyme action or the Crick and Watson model of DNA structure).

8. Evaluation:

   • Experiments need to be repeated to obtain consistent results.
   • This phase of scientific experimentation is known as evaluation.

9. Reporting and Publishing Results:

   • Communication through scientific journals, conferences, and publications is vital to avoid repetition and disseminate knowledge.

Basic Tools of a Biologist

• Biological information is gathered through observations and experiments in the lab and field.
• Practical interactions with biological objects and processes make theoretical knowledge concrete.
• Tools are divided into those used in the laboratory and those used in the open fields.

Laboratory Tools/Instruments

1. Dissecting kit (forceps, scalpel, mounting needle, scissors, dropper, brush)
2. Mortar and pestle
3. Pipette
4. Microscope (slides, cover slips)
5. Hand lens
6. Petri-dish
7. Rulers
8. Centrifuge, water-bath oven
9. Glassware, aquarium
10. Balance, test tubes
11. Calculators
12. Computer

Field Tools/Instruments

1. Plant press, plastic bags, envelopes
2. Insect net
3. Secateurs
4. Auger
5. Meter
6. Altimeter
7. GIS/GPS*
8. Traps, Cages
9. Digger

• GIS (Geographical Information System): software for displaying spatial data.
• GPS (Geographical Positioning System): equipment to find a location.

The Microscope

• Microscopes are precision devices used to see objects too small for the naked eye.
• Most cells are microscopic.
• Advancements in biology are due to the invention, improvement, and modernization of the microscope.
• Light Microscope: uses light as an energy source to enlarge the image of an object and improve its vision.
  • Magnifies up to 1500 times (x1500) the original size.
  • Resolving power: The ability of the microscope to scatter the image and show more details

Categories of Microscopes

A. Simple Microscope

• The hand lens is an example, consisting of a biconvex lens in a supporting frame.
• Used to observe external form, not internal structures.
• Magnification power is usually between x10 and x20.
• The first microscopes were simple microscopes.

B. Compound Microscope

• Uses two convex lenses: the eye piece (ocular lens) and the objective lens.
• Uses light rays from a source (open light or an electric bulb).
• Used to investigate internal structure of objects.
• Allows observation of living cells and single-celled organisms.
• Limit of resolution: about 0.2 micrometers for standard light microscopes.

C. Electron Microscope

• Uses a beam of electrons instead of light with a greater resolving power.

  1. Transmission Electron Microscope (TEM):

     • Shines a beam of electrons at a specimen and then magnifies the specimen onto a fluorescent screen.
     • Reveals the innermost details of the cell interior.

  2. Scanning Electron Microscope (SEM):

     • Beam of electrons scans back & forth across the surface of the specimen.
     • Detectors pick up the information to form an image on a TV screen.
     • Allows study of the surface of objects in their dimensional detail.

• Limitation: living cells must be killed before they can be observed.

D. Other Types of Microscopes

1.  Dissecting Microscope

    *   Enables small objects to be dissected or manipulated while viewed under a moderate degree of magnification.
    *   Consists of a stage above which is mounted a single lens magnifying about x10.
    *   Binocular, which has two oculars.
    *   This type of microscope is intended for use in manipulative biological work, and for the examination of relatively large objects such as insects.
2.  Phase Contrast Microscope

    *   Popular with research workers.
    *   Important in studying fine structures in living cells.
3.  Interference Microscope

    *   Same principle as a phase contrast microscope.
    *   Detects smaller differences in contrast as a result of interference between light waves.
    *   Gives color effects.

Parts of the Compound Microscope and Their Functions

Resolution and Magnification Principle of a Microscope

• Resolution: The ability to distinguish between two separate objects.
• Magnification: simple enlargement of the specimen for a better observation.
• The resolution of an electron microscope is about 0.5nm and that of the light microscope is 200nm.
• The total magnification using any combination of these lenses is simply obtained by multiplying the magnification power of the eyepiece lens by that of the objective lens.
  • Total Magnification = (Magnifying power of objective) x (Magnifying power of eyepiece)

Biochemical Molecules

• Biomolecules: compounds required for living organisms.
• Elements: smallest units that make up a cell.
• Six key elements: carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), & sulfur (S).
• These elements form organic compounds: carbohydrates, lipids, proteins & nucleic acids.
• Biomolecules are formed by joining many small units together to form a long chain. This process is called synthesis.
• Dehydration synthesis: a water molecule is removed in the process.

Carbohydrates

• Carbohydrates contain C, H, & O with the general formula Cx(H2O)_y
• Carbohydrates are good energy sources for living organisms.
• Divided into: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

• Single sugar units; monomer for carbohydrates.




• General formula: (CH2O)n




• Classified by carbon atoms: trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C) & heptoses (7C).




• Hexoses are the most common monosaccharides.




• Glucose: a six-carbon sugar important for brain cells, plant food, blood maintenance, and cellular energy.




• Functions:

  • Brain cell importance
  
  
  • Green synthesis as food production
  
  
  • Constant functioning level in blood
  
  
  • Fuel usage and energy release
  
  
  • Storage in liver and muscles
  
  
  • Starch storage in liver
  
  
  • Cellulose production for building block of cell
    

• Formed when two monosaccharides combine (usually hexoses) by a chemical reaction called condensation (removal of water).
• Glycosidic bond: bond formed between two monosaccharides as a result of condensation.
• Common disaccharides: maltose (glucose + glucose), lactose (glucose + galactose) & sucrose (glucose + fructose).
• Maltose & lactose are reducing sugars while sucrose is the only common non-reducing sugar.

Polysaccharides

• Polymers of monosaccharides; function as food/energy stores (starch, glycogen) and structural material (cellulose).
• Large size makes them insoluble.
• Chitin (fungi cell walls) & murein (bacterial cell walls) are related compounds.
• Pectin is a polysaccharide in cell walls.
• Hemicelluloses: made up of pentose sugar & sugar acid residues.
• Inulin: a polymer of fructose, a reserve carbohydrate.

Lipids

• Organic molecules with C, H, & O (less O, more H than carbohydrates).
• Sometimes contain Sulfur (S) & sometimes Phosphorous (P).
• Insoluble in water (hydrophobic) but soluble in organic solvents.
• Two types: fats (solid at room temperature) & oils (liquid).
• Made up of fatty acids & glycerol (an alcohol).
• Fatty acids contain the acid group -COOH (the carboxyl group).
• Unsaturated fatty acids contain one or more double bonds (C=C).
• Lipids that lack a double bond are saturated.
• Unsaturated fatty acids melt at much lower temperatures than saturated fatty acids.
• Most lipids are triglycerides.
• Glycerol has three hydroxyl groups (-OH).
• Triglyceride: three fatty acid molecules attached to a glycerol molecule.
• Function:
  • Provide heat and energy with more energy on oxidation than cards because lipids contain a greater proportion of hydrogen than carbohydrates
  • Cell membrane constructiion
  • Hormone structure (steroids)
  • Bile acids that involve in digestion & vitamin D (involve in calcium ion absorption)

Proteins

• Made up of amino acids.


• 20 amino acids are commonly found in proteins.


• Amino acid structure: central carbon ( a -carbon) + acidic carboxylic group (-COOH) + basic amino group (-NH) + hydrogen atom.


• The R group distinguishes one amino acid from other


• Essential amino acids must be included in the diet.


• Amino acids react via condensation to form peptide bonds.


• Dipeptide: has two amino acids.


• Tripeptide has three amino acids.


• Polypeptide: many amino acids joined.


• The specific sequence of amino acids is determined by DNA.


• The protein possesses a characteristic three-dimensional shape, its conformation.


• Four levels of structure are primary, secondary, tertiary & quaternary.
  

• Polymers of nucleotides.
• Parts:
  • Phosphoric acid (phosphate, H3PO4)
  • Pentose sugar: ribose (C5H{10}O5) and deoxyribose (C5H{10}O4)
  • Organic base: Pyrimidines and Purines
    • Pyrimidines: Cytosine (C), Thymine(T) and Uracil(U)
    • Purines: Adenine (A) and Guanine(G).
• Nucleotides joined via phosphodiester bonds.
• Dinucleotide: formed from similar condensation reaction.

Deoxyribonucleic Acid (DNA)

• Double-stranded nucleotide polymer with deoxyribose sugar.


• Organic bases: adenine, guanine, cytosine, and thymine (no uracil).


• James Watson and Francis Crick (1953) suggested double helix structure of DNA.


• Two strands linked to pair organic bases by hydrogen bonds. The pairing is always cytosine (C) with guanine (G) and adenine (A) with thymine (T)
  

• Single-stranded nucleotide polymer with ribose sugar.
• Organic bases: adenine, guanine, cytosine, and uracil (no thymine).
• Three types of RNA: ribosomal RNA (rRNA), transfer RNA (tRNA), messenger RNA (mRNA).
  *Rrna Is complex molecules made up of both double and single helix chain.
  T-RNA Is a small molecule comprising a single strand which contains nuclear DNA
  M-mRNA is a long single stranded molecule which is formed into Helix chain,
  Ribosomal RNA