GCSE Biology AQA Trible Paper 1

Mitochondria are the site of respiration, where energy is released for the cell to function.

The two main groups of cells are Eukaryotic cells, which have a nucleus (e.g., plant and animal cells), and Prokaryotic cells, which do not have a nucleus.

Bacteria multiply by binary fission.

Stem cells are undifferentiated cells that have not yet specialized. They are found in human and animal embryos and in the meristem of plants (the top of the shoot). Additionally, stem cells are produced in bone marrow throughout life, specializing into blood cells.

Diffusion is the movement of molecules or particles from an area of high concentration to an area of low concentration, moving down the concentration gradient without requiring energy input, making it a passive process.

Osmosis is the specific movement of water across a selectively permeable membrane, while diffusion refers to the movement of any molecules. For example, if there is a higher concentration of glucose outside a cell, water moves out of the cell instead of glucose diffusing in, resulting in a decrease in mass.

The rate of diffusion and osmosis can be increased by:

1. Increasing the difference in concentrations
2. Increasing the temperature
3. Increasing the surface area of the membrane.

Active transport is the movement of substances through a membrane against the concentration gradient, using energy provided by carrier proteins in the membrane. An example is the movement of mineral ions into plant root hair cells.

Similar cells connected together form a tissue (e.g., heart tissue), which then forms organs (e.g., the heart). Organs work together in an organ system, such as the circulatory system, to perform complex functions.

Enzymes are biological catalysts that break down larger molecules into smaller ones, which can then be absorbed by the villi in the small intestine. For example, amylase breaks down starch into glucose.

The lock and key principle states that enzymes are specific and only break down certain molecules. The substrate must fit into the enzyme's active site to form a complex, which can only occur if the substrate is the right shape.

As temperature increases, the rate of enzyme activity increases due to molecules having more energy, until the active site changes shape, causing the substrate to no longer bind. This process is called denaturation.

The optimum temperature or pH is the point at which the enzyme works best, indicated by the shortest time taken for starch to be broken down. It is determined by plotting times against pH or temperature and identifying the lowest points, but interpolation between points is not allowed.

In food tests, the iodine solution turns from orange to black in the presence of starch.

Air moves down the trachea into the bronchi, then into the bronchioles, and finally reaches the alveoli, where it diffuses into the blood vessels.

Oxygen binds to hemoglobin in red blood cells, which then transport it to every cell in the body for use in respiration.

The heart is at the center of the circulatory system, functioning as a double circulatory system where blood enters the heart twice during each complete circuit around the body.

Arteries have thicker walls to withstand higher pressure and a thinner lumen, while veins have thinner walls due to lower pressure and contain valves to prevent backflow.

Capillaries have one cell thick walls that allow for the fast diffusion of molecules in and out of cells, facilitating nutrient and gas exchange.

Coronary heart disease (CHD) occurs when the coronary artery is blocked by fatty deposits, leading to a reduced supply of oxygen and blood to the heart muscle, which can result in a heart attack.

Statins are drugs that reduce cholesterol levels, which in turn helps to decrease the buildup of fatty deposits in the arteries, thereby reducing the risk of heart disease.

Benign tumors do not spread through the body and are relatively easy to treat, while malignant tumors involve cancerous cells that spread throughout the body, making them much more serious.

BMI is an indication of how healthy a person's weight is relative to their height, categorizing individuals into bands such as underweight, healthy weight, overweight, or obese.

Transpiration is the process where water evaporates from the leaves of a plant. Its rate can be increased by higher temperatures, lower humidity, and increased air movement around the plant.

Chlorosis is the yellowing of leaves, which can occur due to magnesium deficiency, as magnesium is essential for the production of chlorophyll.

Guard cells control the size of stomata, which are holes in the lower epidermis of leaves. They change size to regulate the rate at which gases enter and exit the leaf, closing at night to reduce water loss.

Communicable diseases are caused by pathogens such as viruses, bacteria, fungi, and protozoa (single-celled parasites), all of which can reproduce in the body and cause damage.

A virus is a protein casing that surrounds genetic code. It injects this genetic code into host cells, causing the cells to produce more copies of the virus. Eventually, the infected cell explodes, releasing new viruses to infect more cells.

Measles is spread by droplets from sneezes or coughs and can cause a rash. It can be pretty deadly.

HIV is a sexually transmitted disease (STD) that compromises the immune system, leading to AIDS. It can also be spread through sharing needles.

Bacteria release toxins that damage body cells, such as salmonella from undercooked food or gonorrhea causing yellow discharge. Fungi, like those causing athlete's foot, also damage body tissues.

Mosquitoes are the vector for malaria, which is caused by a protest that burrows into red blood cells to multiply, eventually destroying them.

The tobacco mosaic virus affects plants by discoloring leaves due to inhibiting chlorophyll production, leading to reduced photosynthesis and stunted growth.

The body's first defenses include skin as a barrier, mucus in the nose and trachea to trap pathogens, and acid and enzymes in the digestive system to destroy them.

Lymphocytes produce antitoxins to neutralize toxins from pathogens and create antibodies that bind to antigens on pathogens, preventing further infection and facilitating their destruction by phagocytes.

When exposed to a pathogen, lymphocytes create various antibodies until one fits the antigen. The immune system then stores a copy of this antibody alongside the antigen for future protection, resulting in immunity.

A vaccine is a dead or inert version of a pathogen that exposes the immune system to it, allowing the body to produce antibodies without causing infection. For example, the flu vaccine uses an irradiated virus.

The COVID-19 vaccine uses mRNA technology, injecting the DNA needed to trick cells into making part of the virus, including the antigen, rather than using a dead or inert virus.

Antibiotics are designed to kill bacteria, not viruses. They target specific bacteria to avoid damaging beneficial bacteria in the body. However, bacteria can mutate and become resistant to antibiotics over time.

Drug testing involves several stages: lab trials on cell tissue, trials on animals, and then human trials. In human trials, one group receives the drug while a control group receives a placebo, often in a blind or double-blind trial setup.

Monoclonal antibodies are made from clones of a cell that produces a specific antibody to combat a disease. They are produced by combining lymphocytes from mice with tumor cells to create a hybrid cell, which is then cloned to produce many antibodies for treatment.

Chlorophyll is found in chloroplasts in plant cells and is essential for photosynthesis, as it captures light energy needed for the reaction to occur, making it an endothermic process.

The rate of photosynthesis can be limited by light intensity, carbon dioxide concentration, and temperature. If one of these factors is insufficient, it can restrict the overall rate of photosynthesis, regardless of the levels of the other two.

The rate of photosynthesis can be measured by submerging pondweed in an inverted measuring cylinder and measuring the volume of oxygen produced over time. Counting bubbles is another method, though less accurate.

Aerobic respiration occurs with oxygen and produces more energy compared to anaerobic respiration, which occurs without oxygen and converts glucose into lactic acid, releasing less energy.

After intense exercise, lactic acid builds up in the body, creating an oxygen debt. More oxygen is needed afterward to break down lactic acid in the liver, where it is converted back into glucose.

Fermentation is the process by which yeast converts glucose into ethanol and carbon dioxide. This process is used in baking to make bread rise and in the production of alcoholic drinks.

Metabolism is defined as the sum of all reactions in a cell or organism, including respiration, conversion of glucose into starch, glycogen, and cellulose, as well as the breakdown of excess proteins.

The process of mitosis involves the following steps:

1. Duplication of genetic material.
2. The nucleus breaks down.
3. One set of each chromosome pair is pulled to opposite sides of the cell.
4. A new nucleus forms around each set of copied chromosomes, resulting in two identical cells.