GCSE Biology Higher Tier Paper 1H June 2024 Study Guide

Cardiovascular Disease and Heart Health

  • Coronary Heart Disease (CHD): This condition specifically affects the arteries, providing the heart muscle with blood. A build-up of fatty material causes these vessels to narrow, reducing blood flow.

  • Emergency Cardiac Care:

    • Chest Compressions: When a heart stops beating, a first-aider pushes down on the chest to put pressure on the heart. This action manually pumps blood around the body, maintaining the delivery of oxygen and glucose to vital organs, particularly the brain.

    • Rescue Breaths: By blowing into a person’s mouth, a first-aider forces air into the lungs. This provides oxygen that can then be absorbed into the blood and removes carbon dioxide (CO2CO_2) from the body.

  • Medical Treatments for CHD:

    • Statins: A type of drug used to decrease the level of cholesterol in the blood, which slows down the rate of fatty material deposit in the coronary arteries.

    • Stents: These are small tubes/devices fitted into the coronary arteries. They work by keeping the narrowed arteries open, ensuring that blood can continue to flow to the heart muscle cells.

  • Impact of Smoking on Cardiovascular Health:     Data shows a clear correlation between smoking and the percentage increase in the risk of various cardiovascular diseases:

    • Disease E: 14%14\% increase.

    • Disease F: 20%20\% increase.

    • Disease G: 29%29\% increase.

    • Disease H: 70%70\% increase.

    • Conclusions: As smoking increases, the risk of all listed cardiovascular diseases increases. Some diseases (like H) are significantly more sensitive to the effects of smoking than others (like E).

  • Lifestyle Risk Factors: Beyond smoking, other lifestyle choices increase the risk of cardiovascular disease, including:

    • High-fat diets (leading to high cholesterol).

    • Lack of regular exercise.

    • Alcohol consumption.

    • Obesity.

Cystic Fibrosis: Genetics and Physiological Impact

  • Genetics: Cystic fibrosis (CF) is an inherited disorder caused by a faulty gene. This gene is located in the nucleus of the cell (specifically on chromosomes).

  • Organ Systems Affected: The primary organs impacted by CF include the lungs, the pancreas, and the small intestine.

  • Digestive Complications:

    • Mechanism: CF often causes thick, sticky mucus to block the pancreatic duct. This reduces the amount of digestive enzymes (carbohydrases, proteases, and lipases) reaching the small intestine.

    • Consequences:

      • Difficulty Digesting Food: Large food molecules are not broken down into smaller, soluble molecules effectively.

      • Difficulty Gaining Body Mass: Because food is not fully digested, fewer nutrients (like amino acids and glucose) are absorbed into the blood. Therefore, there is less raw material for growth, repair, or energy storage.

  • Respiratory Impact:

    • Reduced Oxygen Absorption: CF limits the amount of oxygen that enters the blood from the alveoli.

    • Body-wide Effects: A reduced oxygen supply leads to a lower rate of aerobic respiration. This results in less energy (ATP) being released, causing fatigue, shortness of breath, and reduced physical performance.

Respiratory System and Gas Exchange

  • Alveoli Adaptation: Gas exchange occurs in the alveoli of the lungs. They are adapted to maximize efficiency through:

    1. Large Surface Area: To allow a greater volume of gas to diffuse at once.

    2. Thin Walls: Providing a short diffusion path (only one cell thick).

    3. Good Blood Supply: Surrounded by networks of capillaries to maintain a steep concentration gradient.

    4. Moist Surfaces: To allow gases to dissolve before diffusing.

Digestive Processes and Chemical Testing

  • Chemical Tests for Carbohydrates in Food:

    • Starch Test: Distinguish starch using Iodine solution. A positive result changes the reagent color from orange/brown to blue-black.

    • Sugars Test (Reducing Sugars): Use Benedict's solution and heat the mixture in a water bath. A positive result changes from blue to green, yellow, or brick-red depending on the sugar concentration.

    • Risk Assessment: Using a hot water bath for Benedict's test presents a scalding hazard. Safety goggles should be worn when handling chemical reagents.

  • Starch Digestion Investigation:

    • In an experiment where different breads (Brown, White, Wholemeal) were held in the mouth without chewing, they eventually tasted sweet.

    • Explanation: Saliva contains the enzyme amylase, which breaks down the complex carbohydrate starch into simpler, sweet-tasting sugars (like maltose/glucose).

    • Variables:

      • Dependent Variable: The time taken for the bread to taste sweet (measured in seconds).

      • Control Variables: The mass or volume of the bread piece, the starting temperature of the bread, or the person performing the test.

    • Data Results:

      • White bread took 35 s35\,s.

      • Brown bread took 43 s43\,s.

      • Wholemeal bread took 57 s57\,s.

    • Validity Issues: The point at which a person "tastes sweetness" is subjective, leading to inconsistent timing.

Plant Tissues and Transport Systems

  • Leaf Tissue Specialization:

    • Palisade Mesophyll: Contains the most chloroplasts for photosynthesis.

    • Spongy Mesophyll: Contains many air spaces to facilitate gas diffusion.

    • Meristem Tissue: Found at growing tips; these cells can differentiate throughout the entire life of the plant.

  • Transport Tissues:

    • Xylem: Transports water and minerals. Its cell walls are strengthened by lignin (in addition to cellulose).

    • Phloem: Transports dissolved sugars via a process called translocation.

  • Mechanism of Sugar Movement in Phloem:

    • Movement of sugars from a low concentration (Cell X) into a high concentration (Phloem cell) requires Active Transport.

    • Sub-cellular structures: Phloem companion cells contain many mitochondria, which release energy through respiration to power the active transport of sugars against the concentration gradient.

    • Structural Changes: When unspecialised cells differentiate into phloem cells, they develop sieve plates (perforated end walls) or lose certain organelles to allow for the easy flow of sap.

Osmosis in Plant Tissues

  • Investigation Method: Measuring the mass change of uncooked potato pieces in varying concentrations of salt solution.

    1. Prepare different concentrations of salt solution (0.00.0 to 1.0 mol/dm31.0\,mol/dm^3).

    2. Cut potato pieces to the same size/length.

    3. Measure and record the initial mass of each piece.

    4. Place pieces in the solutions for a set period (e.g., 2424 hours).

    5. Remove pieces, blot dry (to remove excess surface liquid), and re-weigh to find the final mass/percentage change.

  • Results Analysis:

    • At 0.6 mol/dm³ salt concentration: The potato loses mass because the concentration of water is higher inside the potato cells than in the salt solution. Water moves out of the potato cells by osmosis through a partially permeable membrane.

    • At 1.0 mol/dm³ vs 0.6 mol/dm³: The higher salt concentration (1.0 mol/dm31.0\,mol/dm^3) results in a greater loss of mass because the concentration gradient is steeper, causing water to leave the cells more rapidly or in greater quantities.

Pathogens, Antibiotics, and Viruses

  • Antibiotics: Chemicals like Penicillin used to kill bacteria.

  • Antibiotic Resistance Investigation:

    • Bacteria are grown on agar plates with antibiotic-soaked paper discs.

    • A "clear zone" (zone of inhibition) around a disc indicates the bacteria were killed. If there is no clear zone (as with Antibiotic C in Figure 5), it proves the bacterium is resistant to that antibiotic.

    • Medical Concern: Doctors are concerned because resistant bacteria can cause infections that cannot be treated with standard drugs, potentially leading to untreatable epidemics.

  • Viruses:

    • Cannot be grown on agar because they require a live host cell (live tissue) to replicate.

    • Developing drugs to destroy viruses is difficult because viruses live and reproduce inside human cells. Drugs that target them may also damage the host's healthy tissues.

    • AIDS: A disease caused by a virus (HIV) that specifically damages white blood cells, weakening the immune system.

Photosynthesis and Limiting Factors

  • Testing for Photosynthesis:

    • The presence of starch is an indicator of photosynthesis, as plants store excess glucose as starch.

    • Leaf 1 (Covered in black paper): No starch; light was excluded, so no photosynthesis occurred.

    • Leaf 2 (Transparent plastic sealed): No starch; although light was present, the seal prevented CO2CO_2 from entering, which is required for the reaction.

    • Leaf 3 (Uncovered): Starch present; all requirements (light, CO2CO_2) were met.

  • Chlorophyll and Ions:

    • Variegated leaves: Green parts contain chlorophyll and produce starch; white parts lack chlorophyll and do not produce starch.

    • Deficiency: A deficiency in Magnesium ions (needed to make chlorophyll) or Iron leads to leaves turning yellow. The scientific term for this yellowing is chlorosis.

  • Rate Measurement: The rate of photosynthesis can be measured by collecting the volume of oxygen produced over a specific time period.

  • Limiting Factors:

    • Definition: A factor that specifically restricts the rate of a process (like photosynthesis) because it is in short supply.

    • Interactive Effects: Increasing temperature and CO2CO_2 concentration increases the rate of photosynthesis because there is more kinetic energy for enzymes and more reactants available, until another factor (like light) becomes limiting.

  • Inverse Square Law: The relationship between light intensity and distance is expressed as:     light intensity∝1distance2\text{light intensity} \propto \frac{1}{\text{distance}^2}

Cell Division, Cancer, and Magnification

  • The Cell Cycle:

    • Before division, a cell must replicate its DNA to form two copies of each chromosome.

    • The cell also increases the number of sub-cellular structures like mitochondria and ribosomes.

  • Cancer: Caused by changes in cells that result in uncontrolled cell division.

    • Treatment: Drugs (like Drug X) that stop cell division help treat cancer by preventing the tumor from growing or spreading.

    • Drug X Mechanism: If a drug prevents fibers (spindle fibers) from attaching to chromosomes, the chromosomes cannot be pulled apart to opposite poles of the cell, and the cell cannot divide into two identical daughter cells.

  • Magnification Calculation Example:

    • Given: Volume of structure Y = 24,500,000 nm324,500,000\,nm^3; Real radius = 125 nm125\,nm.

    • Formula for length: length=volumeπ×radius2\text{length} = \frac{\text{volume}}{\pi \times \text{radius}^2}

    • Calculation: Real length=24,500,0003.14×1252\text{Real length} = \frac{24,500,000}{3.14 \times 125^2}

    • Image length: 4 mm=4,000,000 nm4\,mm = 4,000,000\,nm.

    • Magnification Formula: Magnification=size of imagereal size of object\text{Magnification} = \frac{\text{size of image}}{\text{real size of object}}

  • Drug Testing Phases:

    • Preclinical Testing: Involves testing the drugs on live tissues or cells in a laboratory, as well as testing with chemicals and sometimes on animals, before human trials begin.