Core Concepts in Biology: Immunity, Cells, and Health

Posted on Apr 2, 2025 in Biology

Question 1: Immunity and Population Data

Part A

c

Part B: Antibody Production

When the body is exposed to a virus or disease (pathogen), it produces antibodies to protect itself and fight against the pathogen. These antibodies involve specialized white blood cells called lymphocytes, which can remain in the body after the infection has passed, providing immunity.

Part C: Data Analysis

  1. 21 * 11.8
  2. Calculating rates (e.g., per 100,000 people) makes it easier to compare health statistics between countries, as each country has a different total population size.
  3. Health outcomes vary because each country has different environmental conditions, healthcare systems, and lifestyle factors, meaning overall health rates can differ significantly.

Question 2: Plant Cells and Microscopy

Part A: Meristems and Slide Preparation

  1. The meristem is found in areas of active growth in plants, such as root tips and shoot tips. It contains undifferentiated cells that divide rapidly to produce new cells for growth.
  2. Preparing a Microscope Slide of Meristem Cells:
    1. Place a drop of iodine solution (stain) in the center of a clean microscope slide.
    2. Using tweezers, carefully place the thin section of meristem tissue into the iodine drop.
    3. Gently lower a coverslip onto the sample, starting at an angle, to minimize air bubbles.
    4. Place the finished slide onto the microscope stage and adjust the light source (mirror or lamp) and focus knobs to view the cells.

Part B: Cellular Processes and Types

  1. It provides/releases/generates energy (likely referring to mitochondria via cellular respiration).
  2. A prokaryotic cell (like bacteria) lacks a true nucleus and membrane-bound organelles (e.g., mitochondria). The cell in Figure 3 is likely eukaryotic, possessing these structures.

Question 3: Evolution and Classification

Part A: Genetic Variation

  1. (Answer seems missing, assuming it related to a diagram/figure)
  2. C
  3. Mutation

Part B: Natural Selection

Natural selection is the process where organisms possessing certain inherited traits (genetic variations) that make them better adapted to their environment are more likely to survive and reproduce. Over time, this leads to an increase in the frequency of advantageous traits in the population. For example, natural selection could increase the number of birds with longer beaks if that trait helps them access food more effectively, leading to better survival and reproduction rates, thus passing the long-beak gene to offspring.

Part C: Domains of Life

  1. A
  2. Early classification systems were revised because genetic analysis revealed that some species thought to be closely related were actually very distantly related. This led to the establishment of the three-domain system: Archaea, Bacteria, and Eukaryota.

Question 4: Enzymes and Digestion

Part A: Enzyme Experiments

  1. The starch has already been broken down (hydrolyzed) by the enzyme.
  2. Controlled Variables in Enzyme Experiments:
    1. Ensure all reactions are incubated for the same amount of time in the water bath.
    2. Keep other factors constant, such as enzyme concentration, substrate (starch) concentration, and total volume.

Part B: Amylase Activity and pH

Amylase is an enzyme that breaks down complex carbohydrates, such as starch, into simpler sugars. We can use iodine solution (typically yellow-brown) to test for the presence of starch; iodine turns blue-black in the presence of starch. By testing samples from reactions run at different pH levels over time, we can determine the rate of starch digestion. The pH at which the blue-black color disappears fastest (indicating the quickest starch breakdown) is the optimum pH for amylase activity.

Experimental Note: Set up test tubes containing starch solution and amylase buffered at different pH values. Incubate them and periodically test small samples with iodine. The reaction finishing first indicates the optimum pH.

Part C: Amylase in the Stomach

The stomach environment is highly acidic (very low pH) due to hydrochloric acid. When amylase (which functions optimally at a near-neutral pH) enters the stomach, the extreme acidity causes the enzyme to denature. Denaturation changes the enzyme’s three-dimensional shape, destroying its active site and rendering it non-functional.

Question 5: Data and Neurons

Part A: Data Calculation

  1. Calculate the differences between data points and divide by the number of differences (this might refer to calculating the mean difference or average deviation).

Part B: Nervous System

  1. Motor neuron
  2. D

Question 6: Health, BMI, and Disease

Part A: Body Fat and Cancer Risk

  1. Excess body fat can produce signals that affect the body’s growth and metabolism. These signals may promote increased or abnormal cell division, which can contribute to the development of cancer.
  2. C

Part B: Body Mass Index (BMI)

BMI (Body Mass Index) is a value derived from a person’s mass (weight) and height, used as an estimate of whether their weight is healthy. It is calculated as mass in kilograms divided by height in meters squared (kg/m²). A person categorized as ‘normal weight’ (typically BMI 18.5-24.9) could be taller than a person considered ‘obese’ (typically BMI 30+), resulting in different BMI values despite potential similarities or differences in weight alone.

Part C: Cardiovascular Disease Treatment

Cardiovascular disease refers to conditions affecting the heart and blood vessels, often involving high blood pressure. Treatments can include:

  • Lifestyle modifications: regular exercise, healthy diet, quitting smoking.
  • Medications: drugs to lower blood pressure or cholesterol.
  • Surgical interventions: procedures like angioplasty with stent insertion (inserting a small mesh tube) to widen narrowed or blocked blood vessels.

Hormonal Control of the Menstrual Cycle (6 Marker)

The human menstrual cycle is a complex process regulated by the interplay of four primary hormones:

  1. Follicle Stimulating Hormone (FSH): Produced by the pituitary gland, FSH stimulates the development and maturation of an egg within a follicle in the ovary. It also stimulates the ovaries to begin producing oestrogen.
  2. Oestrogen: Produced mainly by the developing follicle in the ovaries (stimulated by FSH), oestrogen causes the lining of the uterus (endometrium) to thicken and prepare for potential pregnancy. High levels of oestrogen stimulate the release of LH and inhibit further FSH production.
  3. Luteinising Hormone (LH): Also produced by the pituitary gland, a surge in LH (triggered by high oestrogen levels) causes ovulation – the release of the mature egg from the follicle – typically around day 14 of the cycle.
  4. Progesterone: Produced primarily by the corpus luteum (the structure remaining after the follicle releases the egg), progesterone maintains the thickened uterine lining, making it ready to support a fertilized egg. It also inhibits the release of both FSH and LH, preventing the development of new follicles during the latter half of the cycle or during pregnancy. If fertilization does not occur, the corpus luteum degenerates, progesterone levels fall, and menstruation begins.