AQA B2 1.5 terms max Exam in Jan 2013
Guide timings • Cells • Diffusion • Organs & Tissues • Digestive System EASTER • B1 revision and exam • Photosynthesis ISA • Photosynthesis re-cap 2 • Distribution of organisms 2 SEPT • Proteins (enzymes) 3 • Respiration 3 • Cell division 3 • Genetics 3 • Speciation 2 HALF TERM
Name the cell…… • Cell A has a cell membrane and a cell wall and its genes aren’t in a distinct nucleus • Cell B has a cell wall containing cellulose and a permanent vacuole • Cell C has a nucleus, cell membrane and a cell wall • Cell D has no cell wall.
Specialised cells…… • Relate structure to function
Dissolved Substances • Move by diffusion low conc high conc
Diffusion • Diffusion is the spreading of the …………….. of a gas,or of any substance in ……………….., resulting in a ………movement from a region where they are of a ………………concentration to a region with a …………….concentration. • The greater the ………………… in concentration, the ………………. the rate of diffusion.
Diffusion of Oxygen What is the name of the process that happens in all living cells and uses oxygen?
Organisation • Cells • Tissues • Organs • Organ systems • Organism
Tissues • Muscular • Glandular • Epithelial
Digestive System • glands, such as the pancreas and salivary glands, which produce digestive juices • the stomach and small intestine, where digestion occurs • the liver, which produces bile • the small intestine, where the absorption of soluble food occurs • the large intestine, where water is absorbed from the undigested food, producing faeces.
Write the word equation____________+_____ _____+____________
Chlorophyll • Green plants and algaephotosynthesise. • They both contain chlorophyll. • This is a green substance which absorbs light energy.
Limiting factors • Light • Carbon dioxide • Temperature What would the ideal conditions be in a greenhouse? What are the disadvantages of growing food in greenhouses?
What is the glucose used for? 1. Stored as starch: glucose may be converted into insoluble starch for storage. 2. Respiration: plant cells use some of the glucose for respiration. 3. Making new substances: some glucose in plants and algae is used ■ to produce fat or oil for storage ■ to produce cellulose, which strengthens the cell wall ■ to produce proteins. To produce proteins, plants also use nitrate ions that are absorbed from the soil.
Distribution of organisms Physical factors that may affect organisms are: ■ temperature ■ availability of nutrients ■ amount of light ■ availability of water ■ availability of oxygen and carbon dioxide.
Measuring distribution Quantitative datacan be obtained by: ■ random sampling with quadrats. ■ sampling along a transect.
Belt transect • Looking at change along a line e.g. along a river bank, beach, hillside….
Sample Size • Number of quadrats over what size area? Valid Need to consider what a reasonable and valid sample size would be. and Reproducible What is reasonable in terms of time/cost. Could it be done again?
Mean, Median, Mode • Mean: add up and divide by how many • Median: put in order and find the middle one • Mode: most frequent one 2, 5, 8, 3, 5, 4, 8, 9, 2, 1, 1, 6, 7, 8, 6, 3, 5, 2, 8, 7, 8, 2, 8, 1, 9, 4, 3, 5, 4, 7
Proteins • Protein molecules are made up of long chains of amino acids. • These long chains are folded to produce a specific shape that enables other molecules to fit into the protein.
Proteins act as….. ■ structural components of tissues such as muscles ■ hormones ■ antibodies ■ catalysts (enzymes)
Enzymes • Catalysts increase the rate of chemical reactions. • Biological catalysts are called enzymes. • Enzymes are proteins. The shape of an enzyme is vital for the enzyme’s function.
Effect of temperature • High temperatures change the shape. (denature)
Digestive enzymes The digestive enzymes are produced by specialized cells in glands and in the lining of the gut. The enzymes then pass out of the cells into the gut where they come into contact with food molecules. They catalyse the breakdown of large molecules into smaller molecules.
pH and enzymes Different enzymes work best at different pH values • Stomach pH ? • Mouth pH ? • Intestine pH ?
Stomach acid The stomach also produces hydrochloric acid. The enzymes in the stomach work most effectively in these acid conditions.
Bile • The liver produces bile, which is stored in the gall bladder before being released into the small intestine. • Bile neutralises the acid that was added to food in the stomach. This provides alkaline conditions in which enzymes in the small intestine work most effectively.
3 types of digestive enzymes…… 1. The enzyme amylase is produced in the salivary glands, the pancreas and the small intestine. This enzyme catalyses the breakdown of starch into sugars in the mouth and small intestine. 2.Protease enzymes are produced by the stomach, the pancreas and the small intestine. These enzymes catalyse the breakdown of proteins into amino acids in the stomach and the small intestine. 3. Lipase enzymes are produced by the pancreas and small intestine. These enzymes catalyse the breakdown of lipids (fats and oils) into fatty acids and glycerol in the small intestine.