biology paper 1

• All life consists of cells which can be seen with a normal light microscope and the nucleus but the subcellular structures may not be visible using an electron microscope.
• Electron microscopes have a better resolving power and a higher resolution than light microscopes, allowing us to see finer details of the organelles.
• The size of a cell can be calculated by knowing the magnification of the microscope, which is equal to image size divided by object size.
• The actual cell size can be measured by dividing the image size by the magnification.
• Eukaryotic cells have a nucleus in which their DNA is found, while prokaryotic cells don't have a nucleus and their DNA is found in a ring called a plasmid.
• Both eukaryotic and prokaryotic cells contain similar organelles or subcellular structures such as the cell membrane, which keeps everything inside the cell but is also semi-permeable, allowing certain substances to pass through.
• Most bacteria have an extra cell wall made of cellulose providing a rigid structure for them.
• Cytoplasm is the liquid that makes up the cell in which most chemical reactions take place.
• Mitochondria is where respiration takes place, releasing energy for the cell to function.
• Ribosomes are where proteins are assembled or synthesized.
• Plant cells contain chloroplasts which contain chlorophyll and photosynthesis takes place.
• Plant cells also contain a permanent vacuole in which sap is stored.
• Bacteria multiply by binary fission, so the number doubles every 10 minutes, meaning that if we started with one bacterium after an hour, we'd have 2 to the power of 6 that's 64.
• Light intensity follows an inverse square relationship, meaning if you double the distance from the light source, the intensity quarters.
• Metabolism is defined as the sum of all reactions in a cell or organism, including respiration, conversion of glucose and starch, glycogen and cellulose, glucose build-up into cellulose, and the breakdown of excess proteins.
• The independent variable in photosynthesis can be the light intensity, which is changed by varying the distance from the light source, such as a lamp.
• This process is what you feel when your muscles ache during intense exercise.
• The oxygen debt built up during exercise means more oxygen is needed afterward to break it down in the liver.
• Anaerobic respiration occurs when there's a lack of oxygen, and glucose is instead converted straight into lactic acid, which releases less energy.
• Every cell, including red blood cells, has a mitochondria which is where respiration takes place to provide energy for other chemical reactions, movement, and warmth.
• During exercise, the breathing rate and heart rate increase to increase the rate of oxygen delivered to cells for respiration.
• The rate of photosynthesis can be measured by submerging pond weeds in an inverted measuring cylinder and measuring the volume of oxygen made over time.
• Plants and yeast cells respire anaerobically, but slightly different, where glucose is turned into ethanol and carbon dioxide.
• Aerobic respiration means with oxygen, represented by the word and balanced chemical equation.
• A virus is a parasite that reproduces in a cell, causing the cell to produce more copies of the virus, which can then infect more cells.
• Communicable diseases are caused by pathogens that enter the body and cause viral, bacterial, or fungal infections.
• The vascular bundle includes the xylem and phloem, and the lower epidermis has holes called stomata which gases enter and exit.
• Stents are small tubes inserted into blood vessels to keep them open, allowing blood to flow.
• Statins are drugs that reduce cholesterol, which in turn reduces the fatty deposits in the arteries.
• Measles is a virus that causes a rash and can be pretty deadly, spread by droplets from sneezes or coughs.
• Plants have organs called leaves which photosynthesis takes place in, and water leaves the plant through them, allowing transpiration to take place.
• Cardiovascular disease (CVD) is an example of a non-communicable disease, caused by factors from inside the body such as obesity, too much sugar, smoking, lack of exercise, alcohol, and a poor diet.
• The waterproof waxy cuticle on the top of a leaf prevents water from entering or evaporating, and the upper epidermis consists of transparent cells that allow light to pass through to the palisade mesophyll layer.
• Faulty heart valves result in backflow occurring, which can be replaced with artificial ones along with plasma and red blood cells.
• Bacteria release toxins that damage the body's cells, like salmonella in undercooked food or gonorrhea.
• Fungi and protists are parasites that damage the body's cells in a similar way to bacteria.
• Coronary heart disease (CHD) is a condition where the heart's arteries are blocked by fatty deposits, leading to a heart attack if untreated.
• The spongy mesophyll layer has lots of gaps around the cells to increase the surface area through which gas exchange can occur.
• Blood carries white blood cells which combat infections, and platelets which clump together to clot wounds and stop bleeding.
• HIV is an STD that compromises the immune system, spread by people sharing needles or having unprotected sex.