Can be seen with a normal light microscope, but subcellular structures are not visible. Electron microscopes have better resolving power and resolution to see finer details.
Cell size
Can be calculated by knowing the magnification of the microscope: Magnification = Image size / Object size
Cell types
Eukaryotic cells (have a nucleus)
Prokaryotic cells (no nucleus, DNA in a ring called a plasmid)
Eukaryotic and prokaryotic cells
Contain similar organelles or subcellular structures
Cell membrane
Keeps everything inside the cell, semi-permeable to allow certain substances to pass through
Plant cells and most bacteria
Have an extra cell wall made of cellulose, providing a rigid structure
Cytoplasm
The liquid that makes up the cell, where most chemical reactions take place
Mitochondria
Where respiration takes place, releasing energy for the cell to function
Ribosomes
Where proteins are assembled or synthesized
Plant cells
Contain chloroplasts with chlorophyll, where photosynthesis takes place
Contain a permanent vacuole to store sap
Bacterial multiplication
1. Binary fission, number doubles every 10 minutes
2. Can be demonstrated through a practical using agar in a Petri dish and aseptic technique
Diploid cells
Cells with 23 pairs of chromosomes (e.g. human cells)
Haploid cells
Cells with 23 single chromosomes (e.g. gametes)
Cell division
Mitosis: Genetic material is duplicated, nucleus breaks down, chromosomes are pulled to opposite sides, new nuclei form, resulting in two identical cells
Cell specialization
Cells specialize depending on their function (e.g. nerve, muscle, root hair, xylem, phloem, stem cells)
Stem cells
Unspecialized cells that can differentiate into various cell types, found in embryos and bone marrow
Diffusion
The movement of molecules or particles from an area of high concentration to an area of low concentration, down the concentration gradient, without requiring energy input
Osmosis
The diffusion of water across a semi-permeable membrane
Factors affecting diffusion and osmosis
Increased concentration difference, temperature, or surface area can increase the rate
Practical on osmosis
Cut equal-sized vegetable cylinders, weigh, place in varying sugar solutions, reweigh after a day, calculate percentage change in mass, plot against concentration to find the point of no change (same concentration inside and out)
Active transport
The movement of substances through a membrane against a concentration gradient, using energy
Tissues
Groups of similar cells connected and working together
Organs
Groups of tissues working together to perform a specific function
Organ systems
Groups of organs working together (e.g. circulatory, digestive)
Enzymes
Biological catalysts that break down larger molecules into smaller ones, specific to certain substrates due to the lock-and-key principle
Factors affecting enzyme activity
Increased temperature and optimal pH increase the rate, but extreme conditions can denature the enzyme
Practical on enzyme activity
Mix amylase with starch at different temperatures or pH, time how long it takes to break down all the starch, plot a curve to find the optimum conditions
Food tests
Iodine for starch, Benedict's solution for sugars, Biuret's reagent for proteins, ethanol for lipids
Breathing vs respiration
Breathing provides the oxygen for respiration to occur in cells
Respiratory system
Air moves down the trachea, bronchi, bronchioles to the alveoli where gas exchange occurs
Oxygen binds to hemoglobin in red blood cells and is transported to cells
Carbon dioxide and water are expelled during exhalation
Circulatory system
A double circulatory system, with deoxygenated blood entering the right side of the heart, going to the lungs, then oxygenated blood returning to the left side of the heart and pumped to the body
Heart
Has thicker walls in the left ventricle to pump blood to the whole body
Electrical pulses from the right atrium cause the heart to contract and beat
Coronary arteries supply the heart muscle with oxygen and nutrients
Blood vessels
Arteries carry oxygenated blood away from the heart, veins carry deoxygenated blood towards the heart, capillaries allow fast diffusion
Non-communicable diseases
Diseases caused by factors within the body, e.g. cardiovascular disease, autoimmune conditions, cancer
Communicable diseases
Diseases caused by pathogens that can be transmitted between organisms
Coronary artery
Delivers blood to the heart muscle to supply oxygen
Coronary heart disease (CHD)
Occurs when coronary arteries are blocked by fatty deposits, causing a heart attack
Stent
A small tube inserted into blood vessels to keep them open and allow blood flow
Statins
Drugs that reduce cholesterol and fatty deposits
Faulty heart valves
Result in backflow, can be replaced with artificial ones