Biology unit 2

Biology unit 2

B2.1 Cells, tissues and organs
1. plant and algal cells have the same stuctures seen in animal cell but include a cell wall. Most plant cells also have a chloroplast and a permanent vacuole filed with sap
2. bacterial cells contain plasmids (small circular bits of DNA)
3. Yeast reproduces by asexual budding - involves a new yeast cell growing out from the original cell to form a new separate yeast organism
4. when yeast cells have plenty of oxygen they use aerobic respiration - use oxygen to break down the sugars to provide energy for the cells
5. when there is no oxygen yeast can use anaerobic respiration - yeast cells break down sugar in the absence of oxygen, they produce ethanol and co2
6. yeast is a single-celled organism - each cell has a nucleus, cytoplasm and a membrane surrounded by a cell wall
7. example of specialised cells: fat, cone, root hair, and sperm cells
8. dissolved substances and gases (oxygen) move in and out of cells by diffusion
9. diffuision is the net movement of particles from an area where they are at a high concentration to an area of low concentration
10. the greater the difference in concentration, faster the rate of diffusion
11. tissue = group of cells with similar structure and function
12. organs are made of tissues, one organ may contain several types of tissue
13. digestive system in a mammal is an example of a system where substances are exchanged with the environment
B2.2 Organisms in the environment
1. photosynthesis: co2 + h2o -----> glucose + o
2. during photosynthesis light energy is absorbed by chlorophyll in the chloroplasts of the green parts of the plant. It is used to convert co2 and h2o into glucose. O is released as a by-product
3. rate of photosynthesis may be limited by shortage of light, low temperature and shortage of co2
4. plant and algal cells use the soluble glucose they produce during photosynthesis in several different ways: - for respiration, to convert into insoluble starch for storage, to produce fats and oils for storage, to produce fats, protein or cellulose for use in the cells and cell walls
5. plant and algal cells need other materials including nitrate ions to make the amino acids with make up proteins
6. factors affecting the rate of photosynthesis: light levels, low temperature and co2 levels
7. physical factors affecting the distribution of living organisms: temperature, nutrients, amount of light, avaliability of water, avaliability oxygen and co2
8. you can get quantitative data on the distribution of organism in the environment using: random sampling with quadrats, sampling along a transect
B2.3 Enzymes
1. Protein molecules are made up of long chain of amino acids
2. Proteins act like a structural of tissues as hormones, antibodies and catalysts
3. Catalysts work to increase the rate of reaction without themselves changing. Enzymes are biological catalysts.
4. Enzymes are proteins. The amino acids chains are folded to form the active site
5. Enzyme activity are affected by temperature and ph
6. high temperature and the wrong ph can affect the shape of the active site of an enzyme and stop it working
7. enzymes made in the pancreas and the small intestines work best in alkaine conditions
8. bile produced by the liver neutralises acid and emulsifiers fat
B2.4 ENERGY FROM RESPIRATION
1. aerobic respiration involves chemical reactions that use oxygen and sugar and release energy: glucose + oxygen -> co2 + h2o (+energy)
2. energy released during respiration is used to build large molecules from smaller ones and allow muscles to contract
3. body responds to exercise: an increase in heart rate, breathing rate and in depth breathing, glyogen stores in the muscles are converted to glucose for cellular respiration
4. act to increase the supply of glucose and oxygen to the muscle and remove more carbon dioxide
5. anaerobic respiration is respiration without oxygen. Glucose is incompletely broken down to form lactic acid
B2.5 CELL DIVISION AND GROWTH
1. Chromosomes are found in pairs
2. body cells divide by mitosis to produce more identical cells for growth, repair and replacement or in asexual reproduction
3. cells in the reproductive organs divide by meiosis to form the gametes
4. in meiosis the genetic material is copied and then the cells divides twice to form four gametes, each with a single set of chromosomes
5. embryonic stem cells and adult stem cells can be made to differentiate into many different types of cells
6. stem cells have the potential to treat previously incurable conditions
7. gregor mendel was the first person to suggest separtely inherited factors which are now called genes
8. chromosomes are made of large molecules of dna
9. a gene is a small section of DNA that codes for a particular combination of amino acids which make a specific protein
10. genes can have different forms called alleles
11. cystic fibrosis is caused by a recessive allele of a gene and so must be inherited from both parents
B2.6 OLD AND NEW SPECIES
1. fossils are remains of organisms from many years ago in the rocks
2. extinction can be caused by new predators, new diseases or new, more successful competitors
3. extinction can be caused by environmental change over geological time
4. mass extinction may be caused by single castophic events such as volcanoes or asteroid strikes
5. new species arise when two populations become isolated
6. populations become isolated when they are seperated geographically such as on islands
7. there are natural cycles linked to environmental change when species form when species die out
8. in a isolated population alleles are selected that increase successful breeding in the environment
9. speciation takes place when an isolated population becomes so different from the original population that successful interbreeding can no longer take place

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