Biology FA4 Examination Topics - 2024 PDF

1. Aerobic Respiration ---------------------- **Stages of aerobic respiration (Glycolysis, Krebs Cycle, Electron Transport Chain)** - Glycolysis occurs in the cytoplasm (cytosol), breaks down glucose in the cytoplasm into ATP and NADH - The Krebs cycle (citric acid cycle) occurs in the mi...

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Aerobic Respiration ---------------------- **Stages of aerobic respiration (Glycolysis, Krebs Cycle, Electron Transport Chain)** - Glycolysis occurs in the cytoplasm (cytosol), breaks down glucose in the cytoplasm into ATP and NADH - The Krebs cycle (citric acid cycle) occurs in the mitochondria, converts pyruvate into CO2 and generates ATP, NADH, FADH2. - The electron transfer chain (electron transport chain) occurs in the mitochondria and uses electrons from NADH and FADH2 to produce ATP. **ATP production**  - Glycolysis: Makes 2 ATP from one glucose. - Krebs Cycle: Produces 2 ATP and creates NADH and FADH2. - Electron Transport Chain (ETC): Generates 28-34 ATP by using electrons from NADH and FADH2. **Role of mitochondria** Mitochondria are essential for aerobic respiration, where they perform the Krebs Cycle and Electron Transport Chain to produce ATP and utilize oxygen to form water. **Glycolysis with fermentation** Glycolysis is the first step in breaking down glucose in the cytoplasm, turning it into two pyruvate molecules and making 2 ATP and 2 NADH. If there\'s no oxygen, fermentation happens to keep making ATP. There are two types: 1. Lactic Acid Fermentation: Changes pyruvate into lactic acid, like in muscles. 2. Alcoholic Fermentation: Turns pyruvate into ethanol and carbon dioxide, like in yeast. **Biochemical processes like cellular respiration and photosynthesis** - Cellular Respiration: This happens in plants and animals, breaking down glucose with oxygen to make ATP, carbon dioxide, and water. It includes glycolysis, the Krebs cycle, and the electron transport chain. - Photosynthesis: This occurs in plants, algae, and some bacteria and changes light energy into chemical energy, using carbon dioxide and water to produce glucose and oxygen through two stages: light-dependent and light-independent reactions. These processes are connected; photosynthesis makes the glucose that cellular respiration uses, and respiration produces the carbon dioxide that photosynthesis needs. 3. Cell Biology --------------- **Cell structure and function** A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm.\ \ The cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell, protecting the internal environment.\ \ The nucleus is the control center of the cell, housing the cell\'s genetic material (DNA) and telling the cell what to do (reproduction, growth).\ \ The cytoplasm is the jelly-like substance that fills the cell, all the organelles float here, and many processes happen.  **Cell organelles and their roles** Cell organelles are like tiny organs within a cell, each with a specific job. For example, mitochondria help produce energy, while ribosomes make proteins.  4. Cell Membrane Structure -------------------------- **~~Phospholipid bilayer~~** ~~The phospholipid bilayer is a key component of the cell membrane, consisting of two layers of phospholipids. Each phospholipid has a hydrophilic (water-attracting) \"head\" and two hydrophobic (water-repelling) \"tails.\" This arrangement creates a barrier that protects the cell while allowing certain substances to pass through.~~ **Membrane proteins** Membrane proteins are proteins embedded in or attached to the phospholipid bilayer of the cell membrane. They play various roles, such as acting as channels to help transport substances across the membrane, serving as receptors for signaling molecules, and providing structural support. These proteins are essential for communication and transport in and out of the cell. **Transport mechanisms (diffusion, osmosis, active transport)** The transport mechanism that requires energy is active transport. Unlike diffusion and osmosis, which are passive processes, active transport moves substances against their concentration gradient, necessitating energy input. 5. Cell Size and Diffusion -------------------------- **Surface area to volume ratio** As a cell grows, its volume increases faster than its surface area, which can limit the cell\'s ability to efficiently exchange materials with its environment. A higher ratio allows for better diffusion of substances. Larger cells can increase their surface area through flattening. **Limitations on cell size** As a cell increases in size, its volume grows faster than its surface area, making it harder for the cell to transport nutrients and waste effectively. This is why most cells remain relatively small, allowing for efficient diffusion and cellular processes 7. Gaseous Exchange in Alveoli ------------------------------ **Structure of alveoli** Alveoli are tiny air sacs in the lungs where gas exchange occurs. - Very thin wall made of epithelial cells (allowing for efficient diffusion of oxygen and carbon dioxide). - Surrounded by a network of capillaries (facilitate the transfer of gases between the air in the alveoli and blood). - The large surface area provided by numerous alveoli enhances the efficiency of gas exchange in the lungs. **Gas exchange process** 1\. Inhalation: Air enters the lungs and reaches the alveoli.\ 2. Diffusion: Oxygen moves from the alveoli into the capillaries.\ 3. Binding: Oxygen binds to hemoglobin in red blood cells.\ 4. Carbon Dioxide Release: Carbon dioxide diffuses from the blood into the alveoli.\ 5. Exhalation: Carbon dioxide is expelled from the lungs. **Relationship between structure and function** For example, alveoli have thin walls and a large surface area, which helps them exchange oxygen and carbon dioxide efficiently. Hemoglobin has a special shape that allows it to carry oxygen in the blood effectively. 8. Gas Exchange in Plants ------------------------- **Stomata and guard cells** Stomata are small openings on the leaf surface that allow for gas exchange, while guard cells are specialized cells that surround each stoma and regulate its opening and closing. When guard cells swell with water, they open the stomata, allowing carbon dioxide to enter for photosynthesis and oxygen to exit. Conversely, when they lose water, the stomata close to prevent water loss.  **Gas exchange in leaves** Gas exchange in leaves primarily occurs through the stomata, which are openings regulated by guard cells. When stomata open, carbon dioxide enters the leaf for photosynthesis, and oxygen produced during this process exits. Additionally, water vapour can also escape during transpiration. This exchange is crucial for maintaining plant health and supporting photosynthesis.  9. Homeostasis -------------- **Definition and importance** Homeostasis is the ability of an organism to maintain a relatively stable internal environment, even when external conditions fluctuate. This involves regulating factors such as temperature, pH, and blood pressure to ensure optimal functioning of biological processes. The importance of homeostasis lies in its role in keeping the body\'s systems balanced, which is crucial for survival. For example, maintaining a stable body temperature allows enzymatic reactions to occur efficiently. **Negative feedback mechanisms** Negative feedback mechanisms are processes that help maintain homeostasis by reversing a change in a controlled variable. When a stimulus causes a deviation from a set point (like an increase in body temperature), the body responds by initiating processes that counteract that change (such as sweating to cool down). For example, if blood sugar levels rise after eating, the pancreas releases insulin, which facilitates the uptake of glucose by cells, lowering blood sugar levels back to normal. This self-regulating system is crucial for maintaining stability within the body.  **Examples (thermoregulation, osmoregulation)** Thermoregulation: This process helps maintain a stable body temperature. When your body temperature rises, sensors in the brain trigger mechanisms like sweating and increased blood flow to the skin to release heat. If your body temperature drops, it initiates shivering and constricts blood vessels to conserve heat. Osmoregulation: This process regulates water balance in the body. When you\'re dehydrated, the brain detects higher salt levels in the blood and releases a hormone called ADH, which helps your kidneys reabsorb more water, reducing urine output. If you\'re well-hydrated, ADH levels decrease, allowing your body to excrete excess water. 10. Immune System ----------------- **Innate and adaptive immunity** Adaptive Immunity: This is a slower but specific response. It learns to recognize particular germs after the first encounter, so it can respond faster and more effectively if the same germ attacks again. **Cells involved in immune response (T cells, B cells, macrophages)** T Cells: These are a type of lymphocyte that helps coordinate the immune response. There are different types of T cells, such as helper T cells, which activate other immune cells, and cytotoxic T cells, which kill infected cells directly. B Cells: Another type of lymphocyte, B cells are responsible for producing antibodies. These antibodies bind to specific antigens on pathogens, marking them for destruction and preventing them from infecting cells. Macrophages: These are large immune cells that engulf and digest pathogens and debris. They also help stimulate the adaptive immune response by presenting pieces of pathogens (antigens) to T cells. 11. Inflammatory Response ------------------------- **Processes involved (vasodilation, increased permeability, phagocytosis)** The processes involved, such as vasodilation, increase blood flow to the affected area, while increased permeability allows immune cells to reach the site of injury more effectively. Phagocytosis is the process where immune cells engulf and digest pathogens. **Role of the complement system** The complement system is made up of a large number of distinct plasma proteins that react with one another to fight pathogens and induce a series of inflammatory responses that help to fight infection.  12. Nephron Function -------------------- **Structure of the nephron (glomerulus, Bowman's capsule, proximal convoluted tubule, Loop of Henle)** The nephron is the functional unit of the kidney, consisting of several key structures.\ \ The glomerulus is a network of capillaries where blood filtration begins. Bowman\'s capsule surrounds the glomerulus and collects the filtrate that is produced.\ The proximal convoluted tubule reabsorbs nutrients and water from the filtrate.\ \ The Loop of Henle helps concentrate urine by allowing water and salts to be reabsorbed. **Functions in urine production** 1. Filtration occurs in the glomerulus, where blood is filtered, and water, ions, and small molecules are separated from larger molecules and blood cells.\ \ 2. Reabsorption happens primarily in the proximal convoluted tubule and Loop of Henle, where essential substances like glucose, amino acids, and water are reclaimed back into the bloodstream.\ \ 3. Secretion involves the transport of additional waste products from the blood into the nephron, particularly in the distal tubule, to be excreted as urine. **Function and direction of impulse** The function of an impulse in the nervous system is to transmit signals between neurons, facilitating communication throughout the body. Impulses travel along the axon of a neuron in a specific direction, typically from the cell body, down the axon, and towards the axon terminal, where they can influence other neurons or target cells.  14. Osmoregulation ------------------ **Differences between osmoregulators and osmoconformers** Osmoregulators: maintain internal osmotic concentration of their body fluids regardless of external concentration changes\ Osmoconformers: change the internal osmotic concentration of their body fluids to maintain the same osmotic concentration of the external environment **Mechanisms of maintaining water balance** Maintaining water balance involves various mechanisms in both plants and animals. For example, plants use structures like stomata to regulate water loss through transpiration, while osmoregulators in animals help maintain internal osmotic concentration despite external changes. Additionally, hormones like ADH in the kidneys regulate water reabsorption, ensuring that the body retains enough water.  **Examples in different organisms** 1. Plants: Cacti have a thick waxy layer (cuticle) to keep water in and fewer openings (stomata) to lose less water.\ 2. Salt-loving plants (halophytes): They can get rid of extra salt to survive in salty places.\ 3. Animals: Insects have a protective outer layer to prevent water loss, while mammals use kidneys to keep water in their bodies. 16. Phagocytosis ---------------- **Definition and process** Phagocytosis is a type of endocytosis where a cell engulfs large particles or microorganisms. The process begins when the cell membrane extends around the particle, forming a pocket that eventually pinches off to create a vesicle containing the ingested material. This vesicle then merges with lysosomes, which digest the contents. **Role in immune response** Phagocytosis helps the immune system by allowing certain cells to \"eat\" and destroy germs like bacteria and viruses. When these immune cells find harmful invaders, they engulf them to keep the body safe from infections. **Types of cells involved (macrophages, neutrophils)** Macrophages are larger cells that can engulf many pathogens and also help alert other immune cells. Neutrophils are smaller and quicker, responding rapidly to infections and also engulfing bacteria.  18. Plant Biology ----------------- **Structure and function of plant cells** Plant cells have certain distinguishing features, including chloroplasts, cell walls, and intracellular vacuoles.\ Photosynthesis takes place in chloroplasts.\ Cell walls allow plants to have strong, upright structures.\ Vacuoles help regulate how cells handle water and the storage of other molecules. 19. Stem Cells -------------- **Characteristics of stem cells (specialized vs. unspecialized)** Unspecialized cells have the unique ability to self-renew, meaning they can continuously divide and produce more stem cells. They also possess potency, which refers to their ability to differentiate into specialized cell types.\ \ In contrast, specialized cells have specific functions and cannot transform into other cell types.  **Types of stem cells (embryonic, adult)** Embryonic stem cells are pluripotent, meaning they can develop into any cell type in the body. Adult stem cells, such as hematopoietic stem cells, are typically multipotent, meaning they can only differentiate into a limited range of cell types. **Potential uses in medicine** They can be used to treat conditions such as leukemia through stem cell transplants, where new blood cells are generated. Additionally, stem cells may help in repairing damaged tissues or organs, such as in heart disease or spinal cord injuries. 20. Thermoregulation -------------------- **Mechanisms of maintaining body temperature** Vasodilation occurs when blood vessels widen to increase heat loss, while the anterior heat loss centre is stimulated by increased body temperature to help cool the body down. Another mechanism is thermogenesis, where the body generates heat through an increased metabolic rate. **Differences between endotherms and ectotherms** Endotherms and ectotherms differ primarily in how they regulate their body temperature.\ \ Endotherms, like mammals and birds, generate internal heat to maintain a stable body temperature, regardless of the environment. In contrast, ectotherms, such as reptiles and amphibians, rely on external heat sources to regulate their body temperature, often changing their behaviour to warm up or cool down. **Examples of thermoregulatory behaviours** Thermoregulatory behaviours include various actions taken by organisms to maintain their body temperature. For example, animals may bask in the sun to absorb heat (common in ectotherms) or seek shade to cool down. Additionally, some mammals may huddle together to conserve heat during cold weather or engage in panting to enhance evaporative cooling when they are overheated.  21. Transpiration in Plants --------------------------- **Process of transpiration** Transpiration is the process of losing water vapor from plant surfaces, primarily through small openings called stomata. This process helps in the uptake of nutrients and water from the soil through the xylem.  **Factors affecting transpiration rates (temperature, humidity, wind)** High temperatures can increase the rate of transpiration, while high humidity can decrease it. Wind can enhance transpiration by removing the moisture from around the leaf surface.  **Adaptations to reduce water loss** Waterproof cuticle to prevent water loss and gas exchange, except through the stomata.\ \ All cells and gas exchange surfaces remain moist in the leaf due to air in the leaf remaining humid as the spongy mesophyll cells maintain a transpiration stream, and stomata close to retain moisture. **Mechanisms of water and nutrient transport** The mechanisms of water and nutrient transport in plants involve several processes. Water is primarily transported through the xylem via capillary action, cohesion, and adhesion, while nutrients are often transported through the phloem via translocation. **Transpiration-cohesion-tension theory** The transpiration-cohesion-tension theory explains how water moves from the roots to the leaves in plants. It states that as water evaporates from the stomata during transpiration, it creates a negative pressure that pulls water upward through the xylem. Cohesion among water molecules helps maintain the column of water, while adhesion helps water molecules stick to the xylem walls.to