B2 Cells and simple transport: Part 1: cell, ribosomes, respiration, chemical reactions, protein, nucleus, cell membrane, chloroplasts, cell wall, mitochondrion, vacuole, photosynthesis, chlorophyll, sap, cytoplasm Animal cells: label the main parts. Cytoplasm Cell membrane nucleus ORGANELLE NUCLEUS CTOPLASM FUNCTION Controls all activities of the cell. Contains genes on the chromosomes. Carries the instructions for making new cells or organisms. Where chemical reactions take place Type of cell where found Plant Animal mitochondrion CELL MEMBRANE Controls the passage of substances into and out of the cell. Plant and algal cells: label the parts Cell wall MITOCHONDRIA RIBOSOMES Structures in the cytoplasm where oxygen is used and energy is released using respiration. Where protein synthesis takes place, all proteins needed for the cell are made here. Cell membrane CELL WALL Made of cellulose that strengthens and gives support to plant cells. N vacuole Chloroplast Cytoplasm nucleus CHLOROPLASTS LARGE PERMENANT VACUOLE Found in the green parts of plants. They are green because they contain chlorophyll. Chlorophyll absorbs the light energy to make food by photosynthesis. Is the space in the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant. N N
B2 Cells and simple transport Part 2: diffusion, nucleus, oxygen, cell wall, high, faster, cytoplasm, lower, cell membrane, es, concentration, no. Bacterial cells: Key fact: Although bacteria contain genetic material, they do not have a nucleus. A east cell Label the diagram: east cells o Cell membrane east o Nucleus is a single celled fungus. o Cytoplasm o Cell wall Cell membrane Cytoplasm nucleus Cell wall Cell wall Cell membrane Cytoplasm A east cell Label the diagram: Feature Animal Plant or algae Cell membrane Chromosome Bacteria east es es es es Nucleus es es No es Chloroplast No es No No Cell wall No es es es Cytoplasm es es es es Simple cell transport Dissolved substances move into and out of cells by diffusion. The net (overall) movement of particles is from a high concentration to a lower concentration (down a concentration gradient). The greater the difference in concentration, the faster the rate of diffusion. Example: Oxygen gas diffuses into cells through the cell membrane and is used during respiration.
B2 Specialised cells: mesophyll, surface area, haemoglobin, leaves, xylem, differentiate, energy, sugars impulses, chloroplasts, nucleus, water, oxygen, mitochondria, insulated, soil, phloem, root hair Mesophyll cells These are found in plant leaves. They contain many chloroplasts for photosynthesis. Specialised cells Cells of multicellular organisms may differentiate and become adapted for specific functions. Red blood cells. Unlike most animal cells, these do not contain a nucleus. This allows more space inside for haemoglobin which carries oxygen. The biconcave disc shape creates a larger surface area for faster diffusion of oxygen. Root hair cells. These are found on plant roots. They have a large surface area for rapid uptake of water and mineral ions from the soil. Xylem and phloem Xylem vessels are dead and hollow, allowing them to easily transport water and minerals up the plant. Phloem cells are long, thin tubes which transport sugars up and down the plant. Sperm cells These have many mitochondria. This allows faster respiration to provide energy for movement. Neurones (nerve cells) These are long and insulated. This allows them to transmit nerve impulses rapidly.
B2 Tissues, Organs and Organ systems Organs, outside, glandular, churn, organ, faeces, absorption, liver, tissue, inside, cells, muscular, digestive, epithelial, small, water, digests, function, digestion, bile, salivary, large, systems Tissues, organs and organ systems A group of similar cells working together to perform a function is called a tissue. The stomach: As an organ the stomach is made from several tissues, each with a specific function. Muscular tissue, contracts helping to mix and churn the food. Glandular tissue, makes digestive juices including protease and hydrochloric acid. Epithelial tissue covers the outside and inside of the stomach. An organ is made from several types of tissue working together. The digestive system Salivary glands make digestive juice. Organ systems are groups of organs that perform a particular function. eg digestive system. Liver makes bile. Pancreas a gland that makes digestive juice. Large intestine absorbs water from undigested food, producing faeces. Stomach digests proteins. Small intestine digestion and absorption of soluble food.
B2 Plant tissues and organs: leaves, epidermis, stem, vein, tissues roots, phloem, water, mesophyll, xylem, photosynthesis, organ Plant Organs. Label the plant organs. Inside a leaf: As an organ the leaf contains several types of different tissues. Leaves Upper epidermis covers the plant The vein contains: a) xylem tissue which transports water and mineral ions. b) phloem tissue which transports sugars Stem Mesophyll tissue carries out photosynthesis. Roots Lower epidermis covers the plant
B2 Photosynthesis: mesophyll, respiration, chlorophyll, chloroplasts, walls, absorbs, carbon dioxide, insoluble, oxygen, storage, glucose, light, water, fats, proteins, oils, nitrate, cellulose Photosynthesis Plants and algae use light energy to make their own food. The word equation for photosynthesis is carbon dioxide + water glucose + oxygen The role of chlorophyll Inside the leaf, mesophyll tissue contains many chloroplasts. Chloroplasts contain chlorophyll which absorbs light energy needed for photosynthesis. Uses of glucose 1. Glucose may be converted into insoluble starch for storage. 2. Plant cells use some glucose during respiration. (glucose + oxygen 3. Some glucose can be made into fats and oils for storage. carbon dioxide + water) 4. Glucose can be used to make cellulose, which strengthens plant cell walls. 5. Glucose can used with nitrate ions from the soil to make proteins.
rate of photosynthesis B2 Photosynthesis and limiting factors Lighting, carbon dioxide, photosynthesis, limiting factor, temperature, increasing, yield, profit, light, increases, enzymes, Limiting factors The rate of photosynthesis may be limited by: 1. Shortage of light Light intensity 1 1. As the amount of light increases, so does the rate. The limiting factor is light. 2 2. Here, increasing the amount of light has no affect on the rate. The limiting factor is now carbon dioxide or temperature. 2. Low temperature 3. Shortage of carbon dioxide In reality all 3 factors interact and any one of them can be a limiting factor. Carbon dioxide 1 1. As the amount of carbon dioxide increases, so does the rate. The limiting factor is carbon dioxide. 2 2. Here, increasing the amount of carbon dioxide has no affect on the rate. Light or temperature is now the limiting factor. Greenhouses For optimum plant growth farmers may need to control light, temperature or carbon dioxide. This can be done by using artificial lighting, heaters/ventilation and addition of carbon dioxide. Increases in yield must be balanced against the costs involved if farmers are to make a profit. Temperature 1 0 o C temperature 45 o C 2 1 1. As temperature increases, so does the rate because photosynthetic enzymes work best in the warmth. Here, the limiting factor is temperature. 2. Most plant enzymes are destroyed at about 45 C. Here, photosynthesis stops and the rate falls to zero. 2
B2 Organisms in their environment Quadrats A quadrat is a square frame used to outline an area to sample plants or slow moving animals in their habitat. The number of each different organism in the quadrat are counted. This creates quantitative data which can be used to compare different habitats. Quadrats can be placed at random to avoid bias by using a table of random numbers as coordinates. A large sample size (above 10 quadrats) allows you to calculate a more reliable mean, making the data more valid and reproducible. Collecting fieldwork data This is more difficult than collecting data in a lab because it is hard to control some variables in the environment, for example genetic variation in plants, exposure to rain and sunlight and the concentration of soil mineral ions. our data is reproducible if another group get similar results/patterns. our data is valid if it allows you to answer the question or hypothesis in your experiment. Transects Transects are used to sample organisms along a line (from A B). The quadrats are NOT placed at random, but are placed at regular distances along the line, allowing organisms to be sampled. This data shows how the distribution of organisms changes along the transect eg. from under a shady tree, to open field. Maths skills Mean = sum of values number of values Median = middle value in the range Mode = most frequent value Find the mean, median and mode of the following numbers: 11, 7, 3, 6, 2, 7 Mean = 6 Median = 6.5 Mode = 7 Physical factors affecting organisms in their environment Temperature (eg plants grow slowly in cold climates) Light (most plants need high light for growth) Nutrients (eg plants need nitrates for protein) Water (essential for all living cells/life) Oxygen (low O 2 in water limits some animals) Carbon dioxide (a limiting factor for photosynthesis)
B2 Proteins and their functions Enzymes, amino acids, respiration, antibodies, shapes, structural, muscle, speed, catalysts, antigen, hormones, photosynthesis, liver Proteins Proteins are long chains of amino acids. Functions of proteins 2: Some proteins act as antibodies. The specific shape of antibodies allows them to bind to one type of antigen (often found on the surface of pathogens, remember B1!). Functions of proteins 3: Some proteins have a structural role. eg. muscle tissue is made from proteins. These long chains are folded to produce specific shapes which enable other molecules to fit into the protein. This is important for the function of many proteins. Functions of proteins 1: Some proteins act as hormones eg insulin. The specific shape of insulin allows it to bind to its target cells in the liver. Functions of proteins 4: Some proteins act as catalysts. A catalyst increases the speed of chemical reactions. All enzymes are proteins. Enzymes speed up important reactions like digestion, respiration and photosynthesis. Label the diagram products Reactants (substrate) enzyme
B2 Enzymes part 1 Protease, denatured, cells, temperatures, ph s, catalysts, shape, hydrochloric acid, Enzymes Enzymes speed up chemical reactions, acting as catalysts. They can function inside or outside of cells. The effect of ph Different enzymes work best at different ph s. The stomach makes hydrochloric acid, helping the protease enzymes in the stomach to function rapidly. Making digestive enzymes Label the organs/glands which produce digestive enzymes. Salivary glands High temperatures change the shape of enzymes, so that they are no longer able to function. Enzymes damaged by high temperatures are said to be denatured. Stomach pancreas What is the ph optimum for each enzyme? Pepsin = ph 2; trypsin = ph 8 Where in the body does each enzyme function? Pepsin = stomach; trypsin = small intestine Small intestine
B2 Enzymes part 2: glands, neutralises, protease, gall bladder, gut, stomach, mouth, surface area, large, alkaline, small, digestion, enzyme, liver, small intestine, ph, lipase, fat, fatty acids + glycerol, starch, amino acids, amylase, salivary, pancreas, Digestive enzymes: These are produced by specialised cells in glands and in the lining of the gut. The enzymes pass out of the cells and into the gut where they breakdown large food molecules into small ones. This process is called digestion. Amylase Protease Lipase Enzyme Made in Reaction catalysed Where it works Amylase Protease Lipase Salivary glands, pancreas, small intestine Stomach, Pancreas, small intestine Pancreas, small intestine starch glucose Mouth + small intestine protein lipid Amino acids Fatty acids + glycerol Stomach + small intestine Small intestine Bile Bile is NOT an enzyme. Bile is made in the liver, stored in the gall bladder and released into the small intestine. Add the labels liver Gall bladder pancreas Small intestine Bile is alkaline. It neutralises acid from the stomach when it enters the small intestine, making the ph optimum for the enzymes present. Bile breaks down large fat droplets into smaller droplets. This makes a larger surface area for lipase enzymes to attack.
B2 Uses of enzymes Microbes, glucose, stains, sweeter, proteases, baby, temperatures, slimming, lipase, digest, protease, energy, carbohydrases, fructose, Some microbes produce enzymes that pass out of their cells. These enzymes have many uses in the home and industry. Biological detergents Biological detergents contain protease and lipase enzymes to breakdown and remove stains made from protein and fats or oils. Sugar syrups Carbohydrases are used to convert starch into glucose (sugar) syrup. Starch carbohydrase Glucose Isomerase enzyme is used to convert glucose syrup into fructose syrup. Baby foods Proteases are used to predigest some baby foods. This makes them easier for the baby to digest. Biological detergents are more effective at lower temperatures than ordinary detergents. Using them helps to save energy, as low temperature washes cost less. Glucose isomerase Fructose Fructose syrup is sweeter than glucose syrup. It can be used in smaller quantities, adding fewer calories to sweeten slimming products.
B2 Aerobic Respiration: temperature, water, plants, energy, contract, proteins, animals, amino, larger, colder, smaller, birds, mitochondria, day, enzymes, carbon dioxide, oxygen, glucose Aerobic respiration Like all chemical reactions respiration is controlled by enzymes. Aerobic respiration takes place continuously (day + night) in both plants and animals. Uses of energy Respiration releases energy used to 1. Build larger molecules from smaller ones. 2. Enable muscles to contract. Glucose + oxygen carbon dioxide + water (+ energy) Mitochondria Most of the reactions of aerobic respiration occur inside mitochondria found in the cytoplasm of cells. 3. Maintain a constant body temperature in colder surroundings (mammals + birds) 4. Plants, make amino acids from sugars and nitrate ions, so that proteins can be made.
B2 Anaerobic Respiration + exercise: oxygen, carbon dioxide, lactic acid, rate, liver, oxidise, muscles, depth, circulation, glycogen, heart, blood, glucose, respiration, exercise, less, aerobic, oxygen debt, water Anaerobic respiration During exercise if not enough oxygen is reaching muscles they respire anaerobically to obtain energy. Glucose lactic acid (+ energy) Oxygen debt (HT only) In anaerobic conditions the breakdown of glucose is incomplete. Much less energy is released than during aerobic respiration. Vigorous exercise creates an oxygen debt. This must be re-paid after exercise. Extra oxygen is needed to oxidise lactic acid lactic acid + oxygen carbon dioxide + water Effect of exercise on muscles Long periods of vigorous exercise may cause a build-up of lactic acid. This can cause muscles to fatigue, stopping them from contracting efficiently. Massaging muscles helps to increase blood circulation and removes lactic acid from muscles. It is transported to the liver where it is oxidised (see oxygen debt). Effect of exercise on heart and breathing rates During exercise heart rate increases. The rate and depth of breathing also increases. These changes increase blood flow to muscles and so increases the supply of oxygen and glucose (sugar) allowing faster rates of respiration to provide extra energy needed during exercise. Increased blood flow also helps to remove waste carbon dioxide. Glycogen Muscles store glucose as glycogen. During exercise glycogen is converted into glucose for use in respiration. Glycogen glucose
B2 Comparing types of respiration and typical graph to show the effects of exercise: muscles oxygen, breathing, lactic acid, preexercise, blood, exercise Rapid increase in heart and breathing rates during exercise, increasing the circulation of glucose and oxygen to muscles. Breathing rate remains higher and deeper after exercise. This helps the blood absorb more oxygen in the lungs. This oxygen is used to repay the oxygen debt, helping to oxidise lactic acid. Substance Reactants Products Heart and breathing rates finally return to pre-exercise rates. Aerobic Anaerobic Aerobic Anaerobic carbon dioxide N N N lactic acid N N N oxygen N N N water N N N Complete the table with (yes) and N (no) to compare the types of respiration in humans. loads of energy N N N little energy N N N glucose N N
B2 Cell division: gametes, body, mitosis, once, repair, asexual, copied, growth, two, testes, twice, differentiate, four, fertilisation, gamete, genetic, random, ovaries, identical Mitosis Body cells divide by mitosis to form new cells needed for growth and repair. First each chromosome is copied (the DNA molecules replicate). The cell then divides once to make two genetically identical cells. Meiosis Gametes (sex cells) are made by meiosis. In humans sperm are made in the testes and eggs are made in ovaries. First each chromosome is copied (the DNA molecules replicate). The cell then divides twice to make four gametes, each with one set of chromosomes (23 in human gametes). Fertilisation Gametes join at fertilisation forming a single body cell. This cell then divides by mitosis repeatedly. Most types of animal cells differentiate at an early stage and become specialised cells (eg nerve cells, muscle cells) Asexual vs sexual reproduction Some organisms can reproduce using a single parent and no gametes. Cells of offspring made by asexual reproduction are produced by mitosis, so they are genetically identical to their parents (no variation in alleles). Sexual reproduction results in genetic variation because a) Gametes fuse at random. b) Every gamete is unique, with a different combination of alleles.
B2 Chromosomes and stem cells: DNA, cancer, nucleus, 46, helix, 23, gene, alleles, embryos, animals, medical, long, plant Chromosomes Most body cells have a nucleus containing two sets of chromosomes. Human cells have 23 pairs, making a total of 46. Stem cells Stem cells from human embryos and adult bone marrow can differentiate into many different types of cells. Chromosomes contain genetic information and are made from DNA. Each DNA molecule has a double helix structure. A short section of chromosome DNA which codes for a characteristic is called a gene. Treatment with stem cells may be able to help conditions such as paralysis. Genes can exist as different forms called alleles, eg. the eye colour gene has a blue (b) allele and brown (B) allele. Differentiation. When cells become specialised, they are said to have differentiated. In animals, most cells differentiate at an early stage (in the embryo). Many plant cells can differentiate throughout life. Say NO to stem cells: 1. Destroys embryos which have a right to life. 2. Unknown long term effects stem cells may cause cancer. 3. Money could be spent on other medical research Say ES to stem cells: 1. May cure paralysis. 2. Makes use of spare IVF embryos.
B2 Genetics: chromosomes; genes; DNA; recessive; heterozygous; death; phenotype; homozygous; genotype; allele; Mendel (1822-1884) Mendel studied inheritance in peas. His idea was that organisms passed on separate characteristics via inherited factors (we now call genes). He recognised that some inherited factors were dominant, whilst others were recessive. The importance of Mendel s work was not recognised until after his death because: 1. DNA, genes and chromosomes had not been discovered. (Chromosomes were first seen under a microscope in about 1900. The idea of genes being small sections of chromosomes which could be inherited then followed). Genetic crosses key terms (HT only) Homozygous = When an organism has two identical copies of the same allele. For example TT or tt. Heterozygous =When an organism has two different alleles of the same gene. For example Tt. Phenotype = The appearance or characteristics caused by a particular allele. Genotype = The combination of alleles found in the cell. For example TT, Tt or tt. Family trees: These can be used to track the inheritance of genetic diseases over several generations. If the disease shown is caused by a dominant allele, what are the genotypes of parents 1 and 2 (use the letters A and a for alleles)? State clearly if they are homozygous or heterozygous. 1 = Aa, heterozygous. 2 = aa, homozygous. Parents 2. People struggled to understand his theories.
B2 Genetic disorders: carriers, lungs, recessive, two, dominant, screening, mucus, phenotype, faulty, fingers, polydactyly, termination, one, toes, healthy, (letters and outcomes of crosses not included) Genetic disorders Genetic disorders can be inherited. They are caused by faulty alleles. The presence of disease causing alleles can be confirmed by embryo screening. Parents can then make informed decisions about termination of a pregnancy. Polydactyly This is caused by a dominant allele so can be passed on by only one parent who has the disorder. Sufferers have extra fingers or toes. Show the outcome of a cross between two parents, one of which is healthy, whilst the other has one copy of the disease causing allele. Let d = healthy allele, D = polydactyly allele Parents phenotype: healthy x polydactyly Parents genotype: dd x Dd Offspring: gametes d d D Dd (polydactyly) Dd (polydactyly) d dd (healthy) dd (healthy) Cystic fibrosis This is caused by a recessive allele, so sufferers need to inherit two copies, one from each parent. The parents may be suffers of the disease or symptomless carriers. The disorder affects the cell membranes, especially in the lungs, causing a build up of sticky mucus. Show the outcome of a cross between two parents, both of which are healthy, but carriers of cystic fibrosis. Let F = healthy allele, f = cystic fibrosis allele Parents phenotype: healthy x healthy (carrier) (carrier) Parents genotype: Ff x Ff Offspring: gametes F f F FF (healthy) Ff (carrier) f Ff (carrier) ff (cystic fibrosis 1 healthy : 1 polydactyly ½ (50%) chance of healthy baby, ½ (50%) chance of baby with polydactyly. 3 healthy : 1 cystic fibrosis ¾ (75%) chance of healthy baby, ¼ (25%) chance of baby with cystic fibrosis.
B2 Genetics terms, sex chromosomes, genetic code and genetic fingerprinting: related, 12, XX, protein, gene, father, fingerprinting, dominant, alleles, recessive, X, females, unique, 16, 23, amino, sex, males. (No outcome values listed). Sex chromosomes In human body cells one of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX), in males they are different (X). Parents phenotype: male x female Parents genotype: X x XX Offspring: Genetic terms Gene = small section of DNA. Alleles = different forms of the same gene. Dominant = an allele that controls a characteristic even if present on only one chromosome. Recessive = an allele that controls a characteristic only if the dominant allele is absent. Genetic fingerprinting: Each person (except identical twins) has unique DNA. Genetic fingerprinting is used to identify people. Related people share some bands eg the child and Man B share bands 10 + 16, 12 + 20 so Man B is likely to be the child s father. gametes X X XX (female) XX (female) X X (male) X (male) Ratio 1 male : 1 female ½ (50%) chance of male baby, ½ (50%) chance of female baby. Genetic code (higher tier) Each gene codes for a particular combination of amino acids which makes a specific protein.
B2 Old and new species: decay; isolated; asteroid; oxygen; minerals; soft; millions; competitors; natural; rocks; warmth; diseases; interbreeding; extinction; evolved; predators; billion; geological; variation; Fossils Fossils are the remains of organisms from many (often, millions) of years ago, often found in rocks. Fossils can be formed 1. From hard parts of animals that do not decay. 2. From parts of animals that did not decay due to a lack of oxygen, warmth or moisture. 3. When parts of an organism are replaced by other materials (such as rock minerals) as they decay. 4. From preserved traces of organisms eg footprints. Extinction The permanent loss of all members of a species from the planet is termed extinction. Causes of extinction include. 1. New predators 2. New diseases 3. New, more successful competitors 4. Asteroid collisions/massive volcanic eruptions 5. Changes to the environment Using fossils Scientists cannot be certain about how life on earth began 3-4 billion years ago because a) Early life forms were soft-bodied, so few became fossils. b) Most early fossils have been destroyed by geological activity. By comparing fossils of different ages and living organisms, scientists can see how much or little organisms have evolved. Speciation (formation of new species) (HTonly) Two populations of the same species get isolated (eg mountains) Genetic variation exists in each population. Natural selection occurs in each population and the most successful alleles and characteristics allow survival. Each population becomes so different that interbreeding between them is not possible.