* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Science - B3 Revision
Biochemical cascade wikipedia , lookup
Organisms at high altitude wikipedia , lookup
Embryonic stem cell wikipedia , lookup
Cell culture wikipedia , lookup
Genetic engineering wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cell growth wikipedia , lookup
Human genetic resistance to malaria wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Chimera (genetics) wikipedia , lookup
Microbial cooperation wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell theory wikipedia , lookup
Somatic cell nuclear transfer wikipedia , lookup
State switching wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Cell (biology) wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Biochemistry wikipedia , lookup
History of genetic engineering wikipedia , lookup
Symbiogenesis wikipedia , lookup
DHFS Science a Molecules of life b Proteins and mutations c Respiration d Cell division e The circulatory system f Growth and development g New genes for old h Cloning Liver and muscle cells have large numbers of mitochondria due to large amounts of respiration taking place. Ribosomes are in the cytoplasm and are the site of protein synthesis Some structures in cells, such as ribosomes, are too small to be seen with the light microscope Structure of DNA: two strands coiled to form a double helix, each strand containing chemicals called bases, of which there are four different types, with cross links between the strands formed by pairs of bases. Watson and Crick used data from other scientists to build a model of DNA X-ray data showed that there were two chains wound in a helix Chemical data indicated that the bases occurred in pairs. New discoveries, such as Watson and Crick’s, are not accepted or rewarded immediately ◦ Shows the importance of other scientists repeating or testing the work to get the same results A chromosomes is a long, coiled molecules of DNA, divided up into regions called genes Each gene contains a different sequence of bases and codes for a particular protein Only some of the full set of genes are used in any one cell; some genes are switched off. The genes switched on determine the functions of a cell. For example, only pancreas cells switch on the gene for making the hormone insulin. Proteins are synthesised at the ribosomes in the cytoplasm An mRNA copy of the gene is made because the gene itself cannot leave the nucleus. The mRNA travels from the DNA to the ribosomes mRNA from DNA is called transcription (in nucleus) Proteins from mRNA is called translation (at ribosome) Protein structure is determined by the DNA base code The base sequence determines amino acid sequence and each amino acid is coded for by a sequence of 3 bases. DNA controls cell function by controlling the production of proteins, some of which are enzymes Proteins are made of long chains of amino acids. Each protein has its own number and sequence of amino acids, which fold into differently shaped molecules, which have different functions. The function of proteins includes: ◦ structural (e.g. collagen) ◦ hormones (e.g. insulin) ◦ carrier molecules (e.g. haemoglobin) ◦ enzymes Enzymes biological catalysts catalysing chemical reactions occurring in living cells: ◦ respiration, photosynthesis, protein synthesis having a high specificity for their substrate -the ‘lock and key’ mechanism. Changing temperature and pH, away from the optimum, will change the rate of reaction of an enzymecatalysed reaction. Enzyme activity is affected by pH and temperature: ◦ lower collision rates at low temperatures ◦ denaturing at extremes of pH and high temperatures ◦ denaturing as an irreversible change inhibiting enzyme function ◦ denaturing changing the shape of the active site. Q10 value for a reaction over a 10°C interval Q10 = rate at higher temperature rate at lower temperature For example, if rate of a certain reaction is 10 units/min at 20 °C and 24 units/min at 30 °C. What is its Q10? Q10 = 24 ÷ 10 = 2.4 Changes to genes alter, or prevent the production of the protein which is normally made. Cystic Fibrosis ◦ The sequences of DNA bases is changes which may lead to a different sequence of amino acids, which causes a different shaped protein Mutation may occur spontaneously but can be made to occur more often by radiation or chemicals. Mutations are often harmful but may be beneficial or have no effect. Production of ATP using energy from glucose ATP is the ‘universal energy currency’ and is used for all cellular processes that require energy such as active transport and muscle contraction Aerobic respiration C6H12O6 + 6O2→ 6CO2 + 6H2O Glucose + oxygen → carbon dioxide + water Energy released leads to production of 30-38 ATP molecules Production of ATP using energy from glucose ATP is the ‘universal energy currency’ and is used for all cellular processes that require energy such as active transport and muscle contraction Anaerobic respiration (in animals) C6H12O6 → 2C3H6O3 Glucose + oxygen → lactic acid Energy released leads to production of 2 ATP molecules Takes place when there is insufficient oxygen available due to hard exercise Incomplete breakdown of glucose Lactic acid (oxygen debt) accumulates in muscles causing pain and fatigue Recovery of oxygen debt ◦ continued panting replacing oxygen allowing aerobic respiration ◦ increased heart rate ensuring that blood carries lactic acid away to the liver Production of ATP using energy from glucose Rate of respiration is influenced by changes in temperature and pH because enzymes are involved The rate of oxygen consumption can be used as an estimate of metabolic rate (rate of chemical reactions in cells) because aerobic respiration requires oxygen Use the respiratory quotient (RQ) formula RQ = carbon dioxide produced / oxygen used Advantages of being multicellular: ◦ organism can be larger ◦ Allows for cell differentiation ◦ organism can be more complex Becoming multi-cellular requires the development of specialised organ systems: ◦ communication between cells (nervous system) ◦ supplying the cells with nutrients (digestive system) ◦ controlling exchanges with the environment (respiratory and excretory system) DNA replication must take place before cells divide (both mitosis and meiosis) ‘unzipping’ of the chromosome to form single strands new double strands forming by complementary base pairing. New cells for growth are produced by mitosis ◦ genetically identical because they contain the same genetic information ◦ Body cells are DIPLOID (contain two copies of each chromosome). in mitosis the chromosomes: ◦ line up along the centre of the cell ◦ they then split ◦ the copies move to opposite poles of the cell. Produces Gametes Gametes are HAPLOID (contain one chromosome from each pair) Chromosome number is halved and each cell is genetically different because: ◦ one chromosome from each pair separate to opposite poles of the cell in the first division ◦ chromosomes divide and the copies move to opposite poles of the cell in the second division. Fertilisation results in genetic variation because: ◦ gametes (1 sperm and 1 egg) combine to form a diploid zygote ◦ genes on the chromosomes combine to control the characteristics of the zygote. Structure of a sperm cell is adapted to its function: ◦ many mitochondria to provide energy ◦ an acrosome that releases enzymes to digest the egg membrane Feature Reason Small size Lets red blood cells pass through narrow capillaries Increases SA:V allowing rapid diffusion of oxygen Flattened disc shape (biconcave disc) Provides a large surface area, allowing rapid diffusion of oxygen Contains haemoglobin Reacts with oxygen in the lungs to form oxyhaemoglobin. In tissues the reverse of this reaction happens. Does not contain a nucleus Increases amount of space inside the cell for haemoglobin Plasma transports dissolved substances around the body, including: ◦ Hormones ◦ Antibodies ◦ Nutrients, such as water, glucose, amino acids, minerals and vitamins ◦ Waste substances, such as carbon dioxide and urea Arteries transporting blood away from the heart thick muscular and elastic wall in arteries Veins transporting blood to the heart - large lumen (inside diameter) and presence of valves in veins capillaries exchanging materials with tissues permeability of capillaries atria receive blood valves prevent back flow ventricles pump blood One circuit links the heart and lungs The other circuit links the heart with the rest of the body The advantage of the double circulatory system in mammals, means it can withstand higher pressures and therefore greater rate of flow to the tissues Plant cell Animal cell Bacterial cell Cell wall NO cell wall Sometimes has a cell wall chromosomes. chromosomes. single circular strand of DNA presence of a nucleus presence of a nucleus Absence of a nucleus, mitochondria and chloroplasts Advantages and disadvantages of measuring growth ◦ length ◦ wet mass ◦ dry mass. Height and wet mass can be measured when an organism is alive, but dry mass can only be measured when an organism has had all its water removed and is dead. However, dry mass is the best measure of growth. growth of parts of an organism may differ from the growth rate of the whole organism ◦ e.g the head of a human foetus in the womb grows faster than the rest of the body for the first two months. Undifferentiated cells called stem cells can develop into different cells, tissues and organs. Stem cell research in humans/animals. ◦ adult and embryonic stem cells. Human embryos (embryonic stem cells) Parkinson’s disease Paralysis Adult bone marrow (adult stem cells) Leukaemia Feature Plants Animals Pattern of growth Often can grow continuously Tend to grow to a maximum size How growth happens Mainly by cell enlargement (increase in cell size) Increasing the number of cells Where cell division happens Mainly at meristems – found at the tips of shoots and roots In most tissues Cell differentiation Many cells can differentiate Most cells lose the ability to differentiate at an early stage Selective breeding has been used to produce plants and animals with useful and desirable characteristics for human use ◦ Dairy cows with high milk yield ◦ Pugs with a friendly nature ◦ Wheat with large seeds Selective breeding may lead to inbreeding, which can cause health problems within the species due to a build up of recessive alleles ◦ Diabetes in Labradors Select desired characteristics Isolate genes responsible Insertion the genes into other organisms Replication organisms Organisms display characteristic Take the genes from carrots that control beta-carotene production Put them into rice Rice produce beta-carotene Humans can then convert the betacarotene from rice into Vitamin A Aimed at solving the problem of parts of the world relying on rice but lacking vitamin A Aimed at preventing vitamin A deficiency and blindness Take a gene out of an organism that has resistance to: ◦ Herbicides ◦ frost damage ◦ disease Insert into crop plants Grow plants that display characteristic The production of human insulin by genetically engineered bacteria advantage – organisms with desired features are produced rapidly risks – inserted genes may have unexpected harmful effects Ethics – unknown health risks and harm Changing an individuals genetic code in order to prevent disease ◦ Inserting or deleting sequences of DNA ◦ E.g. Attempts to cure cystic fibrosis by inserting healthy gene Controversial if the therapy is carried out on embryos or gametes ◦ Possible unknown effects for future generations ◦ Requires trials on embryos Status of the embryo nucleus removed from an egg cell egg cell nucleus replaced with the nucleus from an udder cell egg cell given an electric shock to make it divide embryo implanted into a surrogate mother sheep embryo grows into a clone of the sheep from which the udder cell came. Some possible uses of cloning include Possible risks Ethics ◦ Mass producing animals with desirable characteristics ◦ Producing animals that have been genetically engineered to provide human products ◦ Producing human embryos to supply stem cells for therapy and organ replacement ◦ Animal viruses could be introduced into humans if using genetically modified animals to supply replacement organs for humans ◦ Animal clones may age prematurely ◦ Status of the embryo ◦ Psychological issues if used for human reproduction (illegal) Advantages of cloning plants Can be sure of the characteristics of the plant since all plants will be genetically identical It is possible to mass produce plants that may be difficult to grow from seed Disadvantages of cloning plants If plants become susceptible to disease or to change in environmental conditions then all plants will be affected Lack of genetic variation.