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• Cells can be seen with a normal light microscope, but electron microscopes allow us to see finer details of subcellular structures
• Eukaryotic cells have a nucleus where DNA is found, while prokaryotic cells don't have a nucleus and their DNA is in a ring called a plasmid
• Both eukaryotic and prokaryotic cells contain similar organelles like mitochondria, ribosomes, and a cell membrane
• Plant cells and most bacteria have an extra cell wall made of cellulose, providing a rigid structure
• Mitochondria is where respiration takes place in cells, releasing energy for cell functions
• Ribosomes are where proteins are assembled or synthesized in cells
• Chloroplasts in plant cells contain chlorophyll and are where photosynthesis takes place
• Plant cells also contain a permanent vacuole in which sap is stored
• Bacteria multiply by binary fission, doubling in number every 10 minutes
• A practical on bacteria growth involves producing a culture on agar in a Petri dish using aseptic technique to prevent contamination
• Eukaryotic cell nuclei contain DNA stored in chromosomes, with humans having 23 pairs in every nucleus
• New cells are constantly made for growth and repair through duplication by mitosis
• Stem cells are unspecialized cells found in human and animal embryos and the meristems of plants
• Diffusion is the movement of molecules from high to low concentration, while osmosis is the diffusion of water across a semi-permeable membrane
• Active transport uses energy to move substances against a concentration gradient through carrier proteins
• Enzymes are biological catalysts that break down larger molecules into smaller ones for absorption
• Enzymes are specific and work on a lock and key principle, where the substrate must fit the enzyme's active site
• Enzyme activity increases with temperature due to molecules having more energy until the active site changes shape and the substrate no longer binds, leading to denaturation
• Enzyme denaturation can occur at extreme pH levels, affecting the enzyme's ability to function
• Practicals on enzyme activity involve mixing amylase with starch at different temperatures or pH levels, timing the breakdown of starch with iodine, and plotting these times to find the optimum temperature or pH
• The respiratory system involves breathing and gas exchange, where oxygen diffuses into the blood in the alveoli, binds to hemoglobin, and is transported to cells for respiration; carbon dioxide is exhaled
• The heart, part of the circulatory system, operates as a double circulatory system with deoxygenated blood entering the right side, getting oxygenated in the lungs, and then pumped out to the body through the left side
• Blood vessels include arteries carrying oxygenated blood (except the pulmonary artery) and veins carrying deoxygenated blood; arteries have thicker walls and veins have valves to prevent backflow
• The heart's own blood supply is delivered by the coronary artery; blockages can lead to heart attacks, and treatments include stents to keep vessels open and statins to reduce cholesterol
• Blood also carries white blood cells to combat infections and platelets for clotting wounds; cardiovascular disease (CVD) is a non-communicable disease
• Non-communicable diseases like heart disease, diabetes, and cancer can be caused by factors such as obesity, smoking, and alcohol consumption
• Plants have organs like leaves for photosynthesis, roots for water and mineral absorption, and stems for cell growth; xylem transports water, while phloem transports sugars
• Transpiration in plants can be influenced by factors like temperature, humidity, and air movement, affecting the rate of water evaporation from leaves
• Infection and response involve communicable diseases caused by pathogens like viruses, bacteria, fungi, or protists, which reproduce in the body and cause damage
• A virus is a protein casing surrounding genetic code that injects into a cell, causing it to produce more virus copies before the cell explodes, allowing the virus to infect more cells
• Measles is a virus that causes a rash and can be deadly, spread by droplets from sneezes or coughs
• HIV is an STD that compromises the immune system, also known as AIDS, spread through sexual contact or sharing needles
• Bacteria release toxins damaging body cells, like salmonella in undercooked food or gonorrhea, an STD causing a yellow discharge from the genitalia
• Fungi, like athlete's foot, and protists, like the protist causing malaria, affect organisms differently
• Mosquitoes are vectors for diseases like malaria, where the protist burrows into red blood cells, multiplies, and bursts out, destroying the cell
• Plants are susceptible to fungal infections like rose black spot, treated with fungicides; tobacco mosaic virus affects plants by discoloring leaves due to inhibiting chlorophyll production
• Our immune system protects us from pathogens; skin acts as the first barrier, mucus, acid, and enzymes in the digestive system destroy pathogens, and white blood cells combat them
• Lymphocytes produce antitoxins to neutralize poisons pathogens produce and antibodies that stick to antigens on pathogens, preventing infection and causing them to clump together for phagocytes to destroy
• A vaccine exposes the immune system to a dead or inert pathogen, like the flu vaccine, to produce antibodies without causing infection
• Antibiotics kill bacteria, not viruses; penicillin was the first antibiotic, designed to be specific to bacteria to avoid damaging good bacteria in the body