AQA Knowledge PowerPoint Unit 2 Biology 2 B2.1 Cells and simple cell transport • All living things are made up of cells. The structures of different types of cells are related to their functions. To get into or out of cells, dissolved substances have to cross the cell membranes. • B2.1.1 Cells and cell structure • B2.1.2 Dissolved substances No Higher Tier content PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.1.1 Cells and cell structure All living things are made up of cells. The structures of different types of cells are related to their functions Part Function Plant or animal Nucleus Contains genetic material, which controls the activities of the cell Both Cytoplasm Most chemical processes take place here, controlled by enzymes Both Cell membrane Controls the movement of substances into and out of the cell Both Mitochondria Most energy is released by respiration here Both Ribosomes Protein synthesis happens here Both Cell wall Strengthens the cell Plant ONLY Chloroplasts Contain chlorophyll, absorbs light energy for photosynthesis Plant ONLY Permanent vacuole Filled with cell sap to help keep the cell turgid Plant ONLY Yeast: Yeast is a single-celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall. Bacteria: Single-celled organism. A bacterial cell consists of cytoplasm and a membrane surrounded by a cell wall. The genes are not in a distinct nucleus. B2.1.1 Cells and cell structure - Specialised cells Cell Diagram Cells are specialised for a particular function. Structure helps them to carry this function out. Function Adaptations Leaf cell Absorbs light for photosynthesis. Lots of chloroplasts. Root hair cell Absorbs water and mineral ions from the soil. Large finger like shapes to increase surface area. Sperm cell Fertilises an egg Head contains an enzyme to help penetrate egg, lots of mitochondria so egg can swim to sperm. Red blood cell Carries oxygen to the cells. Thin outer membrane so oxygen diffuses easily, no nucleus so more room for oxygen. Goblet (mucus) and cilia cells are found in the lining of the gut and the tubes into the lungs. They are specialised to release and move mucus. Helps food slide down easily in the gut and helps trap dirt and bacteria before they enter the lungs. The cilia cells help move the mucus especially in the lungs. Cilia cells have lots of mitochondria. B2.1.2 Dissolved substances Concentration gradient A difference in concentration between two areas next to each other. Particles will move down the concentration gradient High to Low. The larger the difference in concentration the faster the rate of diffusion. Diffusion is the spreading of the particles of a gas or liquid, resulting in a movement of particles from a region where they are of a higher concentration to an area of lower concentration. Diffusion can occur in: Air - smells from perfume etc. Liquids – tea from a tea bag, dye in water etc. Through membranes – small intestines, blood cells etc. Location Small intestine Particles move From To Digested food products e.g. glucose Blood in Small capillary of intestine villus Oxygen Blood Alveolar air circulating space around the lungs Lungs AQA Knowledge PowerPoint Unit 2 Biology 2 B2.2 Tissues, organs and organ systems The cells of multicellular organisms may differentiate and become adapted for specific functions. Tissues are aggregations of similar cells; organs are aggregations of tissues performing specific physiological functions. Organs are organised into organ systems, which work together to form organisms. • B2.2.1 Animal organs • B2.2.2 Plant organs No Higher Tier content PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.2.1 Animal organs Organisation of a multicellular organism cells tissues organs organ systems A TISSUE is a group of specialised cells working together to carry out a particular function. Tissues in the stomach The stomach is an organ that contains: muscular tissue, to churn the contents glandular tissue, to produce digestive juices epithelial tissue, to cover the outside and the inside of the stomach. The digestive system An organ system which humans and other mammals have so they can exchange substances with the environment. Tissue Function Muscular tissue Contracts, bringing about movement Pancreas/ salivary glands Produce digestive juices Stomach Digests food Glandular tissue Produces substances such as enzymes and hormones Liver Produces bile Small intestine Epithelial tissue Covers some parts of the body Digest and absorb soluble food Large intestine Absorbs water/ produces faeces Part(s) Function B2.2.2 Plant organs Plants organs Stem support for the leaves and flowers. Water and glucose transported too. Leaves make the food for the plant where photosynthesis happens. Roots anchor the plant in the soil, take up water and mineral ions. Flowers are reproductive organs to attract insects. Tissue Definition Epidermal Covers the plant, contains stomata. Mesophyl Where photosynthesis takes place. Contains palisade cells and spongy layer. Xylem Carries water and mineral ions from roots. Phloem Carries glucose from the mesophyll to the rest of the plant. Stomata Pores on the underside of the leaf that allow gases to diffuse in and out. AQA Knowledge PowerPoint Unit 2 Biology 2 B2.3 Photosynthesis Green plants and algae use light energy to make their own food. They obtain the raw materials they need to make this food from the air and the soil. The conditions plants are grown in can be changed to promote growth. • B2.3.1 Photosynthesis No Higher Tier content PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.3.1 Photosynthesis Plants convert glucose into starch and store it. Cover part of a leaf in black paper then test it for starch using iodine. Plant cells use some of the glucose produced during photosynthesis for respiration. Also use the glucose to make: oil for storage, cellulose for cell walls, proteins (also need nitrates for this from the soil). Photosynthesis Photo = light, Synthesis = making of (glucose) Photosynthesis = making glucose using light • • • • Factors that can limit the rate of photosynthesis Light intensity – not enough light no photosynthesis CO2 concentration - not enough light no photosynthesis Water availability – plants wilt, not enough no photosynthesis Temperature – too low temp enzymes don’t work well Greenhouses Farmers can use greenhouses to increase plant growth. Artificial light - allows photosynthesis to continue beyond daylight hours. Heating - allows photosynthesis to continue at an increased rate heater can also give off extra carbon dioxide released into the greenhouse this allows photosynthesis to continue at an increased rate. AQA Knowledge PowerPoint Unit 2 Biology 2 B2.4 Organisms and their environment Living organisms form communities, and we need to understand the relationships within and between these communities. These relationships are affected by external influences. • B2.4.1 Distribution of organisms No Higher Tier content PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.4.1 Distribution of organisms Quadrats: These are square frames, used to mark off specific areas of ground 0.5m X 0.5m The distribution of living organisms in a particular habitat may be affected by physical factors (abiotic) e.g. Temperature, amount of light, availability of water, availability of nutrients, availability of oxygen and carbon dioxide. They can also be affected by living factors (biotic) availability of prey, disease, predators. Line Transect:Measure out an area, good for investigating changing habitats, place quadrat at regular intervals, record organisms, repeat on different line to collect average Quadrats: Sample an area Random method generate numbers using a calculator. Take several samples Count number of organisms in each quadrat or count the % cover. Calculate an average from the samples Multiply the average by the area of the field Reproducible Improve results by taking more samples Another group are able to carry out the investigation and collect similar results Valid Data collection that is suitable to answer the investigation hypothesis AQA Knowledge PowerPoint Unit 2 Biology 2 B2.5 Proteins – their functions and uses Proteins have many functions, both inside and outside the cells of living organisms. Proteins, as enzymes, are now used widely in the home and in industry. • B2.5.1 Proteins • B2.5.2 Enzymes No Higher Tier content PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.5.1 Proteins - Enzymes 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: structural components of tissues e.g. muscles, hormones, antibodies, enzymes. Enzymes made of proteins they are biological catalysts substances that increase the rate of chemical reactions without being used up. Uses of enzymes: Biological detergents: Contain protease and lipase, break down protein and fats in stains. Baby food: Protease, Pre digest proteins. Diet products: isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter, can be used in smaller quantities in slimming foods To begin with heat will help increase collisions between the enzymes and substrates BUT too hot and it will denature (remember denature NOT die) DENATURED Enzymes are also easily affected by pH changes. Need specific conditions to keep them working at their best. OPTIMUM CONDITIONS! B2.5.2 Enzymes –Digestive enzymes Digestion and absorption occurs in the gut this goes from the mouth to the anus. Enzymes for respiration, photosynthesis and protein synthesis work inside cells. Other enzymes produced by specialised cells and released from them e.g. digestive enzymes. Catalyse means to speed up. Enzyme Reaction catalysed Where produced Amylase Starch → sugars Salivary glands, pancreas, small intestine Protease Proteins → amino acids Stomach, pancreas, small intestine Lipase Lipids → fatty acids + glycerol Pancreas, small intestine Digestion and pH: The stomach releases acid. The enzymes made in the stomach work best in acidic conditions. The 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. AQA Knowledge PowerPoint Unit 2 Biology 2 B2.6 Aerobic and anaerobic respiration Respiration in cells can take place aerobically or anaerobically. The energy released is used in a variety of ways. The human body needs to react to the increased demand for energy during exercise. • B2.6.1 Aerobic respiration • B2.6.2 Anaerobic respiration Higher tier content: HT - As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water. PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.6.1 Aerobic respiration RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY. Aerobic Respiration The process of releasing energy from food in cells. Aerobic respiration uses oxygen. All chemical reactions inside cells are controlled by enzymes. Aerobic respiration (with oxygen) glucose + oxygen → carbon dioxide + water (+ energy) Glucose reacts with oxygen, producing carbon dioxide and water as waste products. To release energy. This takes place continuously in animals and plants. Released energy is used for: Mitochondria: Tiny organelles found in most To build up larger molecules using smaller ones. In animals, to enable muscles to contract. In mammals and birds, to maintain a steady body temperature in colder surroundings. In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins. plant and animal cells. Where the respiration reactions happen. More active cells have more mitochondria e.g. muscle cells, sperm cells. During exercise changes take place: the heart rate and breathing increases. Blood flow increases so more glucose and O2 to cells. Muscles store glucose as glycogen – the glycogen gets converted back to glucose during exercise. B2.6.2 Anaerobic respiration RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY. During exercise, too little oxygen is reaching the muscles they use anaerobic respiration to RELEASE energy. It is the incomplete breakdown of glucose and produces lactic acid. Anaerobic respiration (without oxygen) glucose → lactic acid (+ small amount of energy) Lactic Acid If muscles have long periods of exercise they get fatigued- they stop contracting properly. One cause is the build-up of lactic acid in the muscles. Lactic acid is poisonous. We can only tolerate small amounts in our body. Blood flowing through the muscles removes the lactic acid. Higher Tier OXYGEN dept: Anaerobic respiration results in an oxygen debt that has to be repaid in order to change lactic acid to carbon dioxide and water. The extra oxygen needed is called the oxygen debt. -The heart continues to pump faster. -The breathing rate remains high. -This delivers the extra oxygen to the muscles. -This pays back the oxygen debt. In yeast anaerobic respiration produces ethanol and carbon dioxide (which is why we used it to make beer and bread) we call this fermentation. AQA Knowledge PowerPoint Unit 2 Biology 2 B2.7 Cell division and inheritance Characteristics are passed on from one generation to the next in both plants and animals. Simple genetic diagrams can be used to show this. There are ethical considerations in treating genetic disorders. Higher Tier - construct genetic diagrams of monohybrid crosses and predict the outcomes of monohybrid crosses and be able to use the terms homozygous, heterozygous, phenotype and genotype. Foundation Tier - should be able to interpret genetic diagrams of monohybrid inheritance and sex inheritance. • B2.7.1 Cell division Higher Tier - When a cell divides to form gametes: ■ copies of the genetic information are made ■ then the cell divides twice to form four gametes, each with a single set of chromosomes. • B2.7.2 Genetic variation Higher Tier - Each gene codes for a particular combination of amino acids which makes a specific protein. • B2.7.3 Genetic disorders PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.7.1 Cell division Genetic information is in the nucleus of cells Inside the nucleus are chromosomes made up of DNA –BODY CELLS have two sets of chromosomes, SEX CELLS (gametes) have one set of chromosomes in humans body cells 46 chromosomes (23 pairs), sex cells (sperm/egg) 23 single chromosomes. MITOSIS cell division for growth and repair of cells (produces clones). 1 2 3 4 5 6 1. Parent cell 2. Chromosomes make identical copies of themselves 3. Line up along the centre 4. They move apart 5. Two daughter cells start to form. 6. Two new daughter cells with identical chromosomes to the parent cell. BODY CELLS DIVIDE BY MITOSIS (makes my toes) SEX CELLS DIVIDE BY MEIOSIS Higher Tier MEIOSIS cell division to produce sex cells for reproduction. Creates 4 daughter cells, genetically unique , makes gametes (sperm, egg), 23 chromosomes only Fertilisation: where gametes join. New cell divides by mitosis to form baby. B2.7.1 Cell division – STEM cells STEM CELLS: Cells that can become anything, they are undifferentiated Embryonic stem cells can be made into any type of cell (curing all sorts of disease) but come from aborted embryos (which can be a problem) We also don't know the long term effect of their use yet. Stem cells can be used in new treatments for Parkinson's disease and paralysis. They can be harvested from inside embryos, Adult bone marrow stem cells can also be used umbilical cords and bone marrow. but can’t be made into as many different things but you can give permission to have them taken the operation can be painful! Plant Cells: Most 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. There are social and ethical issues concerning the use of human embryonic stem cells. B2.7.2 Genetic variation Alleles -different forms of the same gene represented by two letters. For example, eye colour Recessive- characteristic only expressed when two of the same alleles are present e.g. bb. Dominant- characteristic expressed when one or both alleles are present e.g. BB or Bb Sexual reproduction leads to variation: Meiosis ensures that all gametes contain the same genes, but have a different selection of alleles. Also, it is random which sperm fertilises which egg. All individuals (except for identical twins) produced sexually are genetically different DNA fingerprinting can identify individuals. Determining sex (gender): Human body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the inheritance of gender: XX=female XY=male HIGHER TIER: You must be able to draw for monohybrid crosses, these and identify genotype and phenotype of offspring. You must work out % of offspring with each characteristic. T – tall t – short What % of the offspring will be short? HIGHER TIER: Homozygous- two of the same allele e.g. bb or BB Heterozygous- two different alleles e.g. Bb Genotype- the genes present e.g. Bb or bb or BB Phenotype- the genes that are expressed in the physical characteristics. e.g., brown eyes, blue eye, blond hair, brown hair. Each gene codes for a particular combination of amino acids which makes a specific protein. B2.7.3 Genetic disorders Cystic fibrosis (a disorder of cell membranes) inherited from both parents. The parents can be carriers of CF but not have CF. Caused by a recessive allele so can passed on by parents who don’t have it. Causes thick, sticky mucus to accumulate in the lungs and the digestive system. This causes: Lung infections, problems with breathing, problems with digestion and absorption. Some genetic disorders are inherited e.g. polydactyly, cystic fibrosis. Embryos can be screened for the different types of disorders. Polydactyly: Extra fingers or toes - caused by a dominant allele can be passed on by only one parent who has the disorder. A genetic pedigree or Family trees can also be used to trace how a disease is inherited. On the right is an example for cystic fibrosis. B2.7.2 Genetic variation – Gregor Mendel Gregor Mendel (1822-1884) studied the inheritance of different characteristics in pea plants. • Found that when he bred red-flowered plants with white-flowered plants, all the offspring had red flowers. • If he bred these plants with each other, most had red flowers, but some had white. • This was because the allele for red flowers is dominant, and the allele for white flowers is recessive. Called the father of modern genetics. No one took his ideas seriously until after his death. FIRST CROSS: All the offspring have red flowers, even though they carry the recessive allele for white flowers SECOND CROSS: Three-quarters of the offspring have red flowers and a quarter have white flowers AQA Knowledge PowerPoint Unit 2 Biology 2 B2.8 Speciation Changes in the environment of plants and animals may cause them to die out. The fossil record shows that new organisms arise, flourish, and after a time become extinct. The record also shows changes that lead to the formation of new species. • B2.8.1 Old and new species Higher Tier - genetic variation – each population has a wide range of alleles that control their characteristics ■ natural selection – in each population, the alleles that control the characteristics which help the organism to survive are selected ■ speciation – the populations become so different that successful interbreeding is no longer possible. PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards B2.8.1 Old and new species OLD Fossils can be used to gather evidence for evolution. This is called a fossil record. FOSSILS – SHOW EVIDENCE OF EARLY LIFE FORMS. Can be formed by Mineralisation of the hard parts (shells, bones, teeth etc) Some soft parts do not decay/rot, because they are buried. Traces of the animals (footprints, burrows, faeces, etc) Extinction Permanent loss of all members of a species. Caused by a change: New predators New diseases Loss of habitat More successful competitor Can’t find evidence of all earlier life forms: Many were soft-bodied, so left few traces behind as many destroyed by geological activity. B2.8.1 Old and new species NEW New species arise as because of: Isolation – two populations of a species become separated e.g geographically. Species: A group of similar organisms that can breed to produce fertile offspring Higher Tier: Genetic variation – each population has a wide range of alleles that control their characteristics. Natural Selection Variation –populations of organisms have variations. Over-production –produce more young than will survive to adulthood. Struggle for existence – competition for survival between the organisms Survival – those with advantageous characteristics are more likely to survive Advantageous characteristics inherited – better adapted organisms are more likely to Reproduce successfully passing on the advantageous characteristics to their offspring in their genes. Gradual change – over a period of time the more individuals with the advantageous characteristics in the population. Endemic: A species that has evolved to live in only one place in the world. Higher Tier: Speciation Takes place when an isolated population becomes so different from the original population that a new species is produced.