2All living things are made up of cells All living things are made up of cells. The structures of different types of cells are related to their functions.
3Parts of cells which animal and plant cells have in common: FunctionNucleusContains genetic material, which controls the activities of the cellCytoplasmMost chemical processes take place here, controlled by enzymesCell membraneControls the movement of substances into and out of the cellMitochondriaMost energy is released by respiration hereRibosomesProtein synthesis happens here
4Parts of cells which only plant and algal cells contain: Part Function Cell wallStrengthens the cellChloroplastsContain chlorophyll, which absorbs light energy for photosynthesisPermanent vacuoleFilled with cell sap to help keep the cell turgid
5Bacteria are single celled organisms which contain: cytoplasm cell membrane cell wall no distinct nucleus
6Yeast is a single-celled organism, similar to bacteria, containing: CytoplasmCell membraneCell wallBut, they also have a nucleus.
7Cells may be specialised for a particular function Cells may be specialised for a particular function. Their structure will allow them to carry this function out.CellJobAdaptationsLeaf cell:absorbs light for photosynthesislots of chloroplastsRoot hair cell:absorbs water and mineral ionsfinger like shape for large surface areaSperm cell:fertilises an egghead contains an enzyme to help penetrate eggRed blood cell:carries oxygen to the cellsthin outer membrane so oxygen diffuses easily
8Substances have to pass through the cell membrane to get into or out of a cell. Diffusion is a process that allows this to happen. Particles diffuse from an area of high concentration to an area of low concentration.
9Diffusion happens in our: Gut: digested food particles diffuse from the gut cavity to blood in the villusLungs: oxygen moves from the alveoli into capillaries around the lungs
10A tissue is a group of specialised cells that have a similar structure and function. cells tissues organs organ systemsTissueFunctionMuscular tissueContracts, bringing about movementGlandular tissueProduces substances such as enzymes and hormonesEpithelial tissueCovers some parts of the body
11Organ systems are groups of organs that carry out a particular function. For example, the digestive system:
12Plants also usually contain differentiated cells, tissues and organs.
13Leaves are adapted to absorb sunlight for photosynthesis
14Three factors can limit the speed of photosynthesis: light intensitycarbon dioxide concentrationtemperature
15Think about economics: Farmers can use their knowledge of limiting factors on photosynthesis to increase crop yields.Artificial light – extends time for photosynthesisHeating – increases the rate of photosynthesisAdding carbon dioxide (CO2) – increases the rateThink about economics:The cost of providing extra lighting, heatand carbon dioxide has to be weighedagainst the increased crop yield and theextra income it will provide.Tip: paraffin lamps provide light,heat and CO2!
16Cellulose - which strengthens the cell wall Glucose is produced during photosynthesis and is used by the plant to make:Cellulose - which strengthens the cell wallProteins - such as enzymes and chlorophyllGlucose is stored by plants as starch, fats and oils.Plants also need nitrates to do this
17The distribution of living organisms in a particular habitat may be affected by physical factors, such as:TemperatureAmount of lightAvailability of waterAvailability of nutrientsAvailability of oxygen and carbon dioxide
18Sampling: Quadrat Square frame Used to sample a small area Samples chosen at random
19Sampling: Along a Transect Not randomTape stretched between two pointsSamples taken along the line using a quadratShows how the distribution of organisms changes along the line
20Boardworks GCSE Additional Science: Biology Enzymes Biological catalysts: speed up reactions.Enzymes are protein molecules, and so are made up of amino acids.
21What happens at the active site? Boardworks GCSE Additional Science: BiologyEnzymesWhat happens at the active site?The enzyme is the lock, and the reactant is the key.++↔↔enzymereactant+enzyme-reactant complex↔products
22Key phrases:Catalyst: A substance which changes the rate of a chemical reaction without being changed itself. Enzyme: A biological catalyst. Active site: Where substrates bind to an enzyme and undergo a chemical reaction. Activation energy: The minimum amount of energy particles must have to be able to react.+
23Temperature and enzymes Most enzymes in the human body work best at about 37oC. Over 40oC most enzymes will stop working. The amino acids they are made form start to unravel and the shape of the active site changes. We say that the enzyme is denatured.
24pH and enzymes Changes in pH alter an enzyme’s shape. The best pH for an enzyme depends on where it normally works.For example, intestinal enzymes have an optimum pH of about 7.5 (alkaline).Enzymes in the stomach have an optimum pH of about 2 (acidic).
25AmylaseMade in the salivary glands, pancreas and small intestine. It breaks down starch into sugars. It works in the mouth and small intestine.
26ProteaseMade in the stomach, pancreas and small intestine. It breaks down protein into amino acids. It works in the stomach and small intestine.
27LipaseMade in the pancreas and small intestine. It breaks down lipids (fats and oils) into fatty acids and glycerol. It works in the small intestine.
28The enzymes made in the pancreas and small intestine work best in alkaline conditions. The liver produces bile which is released into the small intestine. Bile neutralises the acid that was added to the food in the stomach.
29What do enzymes do for us? IndustryFunction of enzymesconfectionery (sweets)change glucose into fructose, which is sweeter so less is needed and is used in 'slimming' foods (isomerase).baby foodstart off digestion of food (proteases and lipases)biological detergentbreak down stains (proteases and lipases).
30tiny organelles found in most plant and animal cells. Mitochondria:tiny organelles found in most plant and animal cells.Where the respiration reactions happen.More active cells have more mitochondria.Liver cells are very active so have many mitochondria. Other cells can develop them trhough training, such as muscle cells.
31Aerobic respiration (with oxygen) glucose + oxygen → carbon dioxide + water (+ energy)When too little oxygen reaches the muscles during exercise, they use anaerobic respiration to obtain energy.Anaerobic respiration (without oxygen)glucose → lactic acid (+ energy)
32This is achieved by increasing: During exercise, the muscle cells respire more than they do at rest. This means that:Oxygen and glucose must be delivered to them more quicklyWaste carbon dioxide must be removed more quicklyThis is achieved by increasing:depth of breathingrate of breathingheart rate
33Where is the genetic information in a cell? Inside each cell is a nucleus.Inside the human nucleus are 46 chromosomes (two sets of 23, one set from Mum, one set from Dad).Chromosomes are made from DNA.A section of DNA is called a gene.
34Mitosis Mitosis is used for growth or to replace cells. The genetic material is copiedThe cell divides once to form two genetically identical body cellsMitosis is used for growth or to replace cells.
35Meiosis Forms gametes (sex cells). The cell divides twice to form four gametes.Each daughter cellcontains half of the chromosomes ofthe original cell.
36Stem CellsUnspecialised - they can become any type of cell in the human body. As the cells of an embryo divide (by mitosis) and the embryo develops, the cells become differentiated.
37Stem cells can be used in new treatments for Parkinson's disease and paralysis. Can be harvested from inside embryos, umbilical cords and bone marrow. There are social and ethical issues concerning the use of human embryonic stem cells.
38Plant cellsMost plant cells stay unspecialised. They can differentiate all through their lives. Unspecialised cells are made at the stems and roots, where mitosis takes place almost constantly. This makes it very easy to clone plants.
39AllelesDifferent forms of the same gene For example, eye colour
40Determining sexHuman body cells have 23 pairs of chromosomes in the nucleus.One of these pairs controls the inheritance of gender - whether offspring are male or female.
41Dominant or Recessive?Alleles are dominant or recessive.
42Punnett SquaresShow the possible genotypes produced when two organisms breed.
43Evolution60 millionyears ago1 millionyears agoFossils are the remains of organisms which died thousands or millions of years ago.By looking at fossils, we can see that organisms have changed very slowly over time.
45Fossils form if an organism does not decay because: little oxygen was presentpoisonous gases killed of decay causing organismslow temperature
46Fossil Formation Trace or imprints are left behind by organisms. Isle of Wight, UK
47Fossil Formation Hard parts of organism replaced by minerals. This is the most common type of fossil.
48The fossil record is incomplete. Why?Early forms of life were soft bodied.Fossilisation requires very specific conditions.Many fossils are destroyed.Many fossils have not been found yet.
49Evolution by Natural Selection Individuals in a species show a wide range of variation. This is because of differences in genes. Individuals most suited to the environment are more likely to survive and reproduce. The successful genes are then passed to the offspring in the next generation.Charles Darwin
50Extinction What causes organisms to become extinct? Competition New predatorsNew diseasesEnvironmental changes
51Why did the dinosaurs become extinct? Volcanoes Rocks formed by huge eruptions 65 million years ago can be found in India today. Meteorite Impact The remains of a 180km-wide crater caused by a meteorite 65 million years ago can be found near Mexico. Disease This theory doesn’t explain why so many sea animals died at the same time.