Presentation on theme: "OCR 21st Century Science Unit B4a Revision"— Presentation transcript:
1OCR 21st Century Science Unit B4a Revision Animal and Plant cellsRespiration and Photosynthesis
2Animal and Plant Cellsmitochondria contain enzymes for the reactions in aerobic respiration (in animals, plants and yeast)cell membrane allows gases and water to pass in and out of the cell freely while presenting a barrier to other chemicalsnucleus or circular DNA in bacteria contains DNA which carries the genetic code for making enzymes used in the chemical reactions of respirationcytoplasm where enzymes and proteins are madechloroplasts contain chlorophyll and the enzymes for the reactions in photosynthesis
4Uses for respiration summary Animals and plants have many uses for the energy they generate from respiration:To perform the life processes, such as moving, _____ etcTo build up body _______To maintain a constant body ___________ (warm-blooded mammals only)To build up sugars, ________ and other nutrients in plantsActive __________Words – nitrates, tissue, proteins, transport, growing
5Synthesis“Synthesis” means “making large molecules out of small ones”. Two examples:1) Glucose (sugar) can be used to make long chains of insoluble starch…Glucose moleculesStarch molecule2) Glucose can be combined with nitrates to make proteins (for growth)…Glucose moleculesProteins
6Aerobic Respirationall living things depend on chemical reactions within cells that require energy released by respirationRespiration is a series of chemical reactions that release energy by breaking down large food molecules in all living cellsglucose + oxygen carbon dioxide + water(+ energy released)C6H12O6 + 6O2 CO2 + 6H2O
7Glucose + oxygen water + carbon dioxide + ENERGY Aerobic respiration summaryAll living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy:Glucose + oxygen water + carbon dioxide + ENERGYThe glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells.Words – breathing, energy, grow, respiration, food, mitochondria
8Anaerobic Respiration anaerobic respiration takes place in animal, plant and some microbial cells in conditions of low oxygen or absence of oxygen, to include:In Animal Cells:glucose lactic acid (+ energy released)In Yeastglucose ethanol + carbon dioxide (+ energy released)Happens inroots in waterlogged soilbacteria in puncture woundshuman cells during vigorous exercise
9Glucose lactic acid + a bit of energy Anaerobic respiration summaryUnlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________:Glucose lactic acid + a bit of energyThis happens when the body can’t provide oxygen quick enough for __________ respiration to take place.Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much.Anaerobic respiration can also take place in other low-oxygen conditions, such as plant roots in _________ soil or bacteria in ________ wounds.Words – oxygen, aerobic, quicker, puncture, waterlogged
10In bacteria cells, this job is done by circular DNA Respiration in cells1)Cytoplasm - where enzymes are madeIn bacteria cells, this job is done by circular DNA2)Nucleus – carries genetic info for making enzymes3)Cell Membrane – controls what comes in and out4)Mitochondria – contain enzymes for respiration reactions
11OCR 21st Century Science Unit B4b Revision Enzymes, Osmosis and Diffusion
12Enzymes in respiration and photosynthesis Enzymes are proteins that speed up chemical uses. Here are two important natural uses for them:Cells use glucose to generate energy – this process is called “respiration”. Respiration happens in mitochodria and is catalysed by enzymes.Photosynthesis is catalysed by enzymes in the cells.
13Enzymes- The lock and Key Model enzymes are proteins that speed up chemical reactionscells make enzymes according to the instructions carried in genesmolecules have to be the correct shape to fit into the active site of the enzyme (the lock and key model)EnzymeSubstrate
14Factors affecting enzyme action (Denaturing) denaturednormalheatpHThe shape of the enzyme is vital to its function.The main factors affecting enzyme action are 1.) temperature and 2.) pH1.) High temperatures can destroy the enzymes ‘special shape’ so it becomes denatured.2.) Different enzymes work best at different pH values.
15Enzymes are denatured beyond 40OC Optimum conditionsEnzymes work best in certain conditions:Enzymes are denatured beyond 40OCCould be protease (found in the stomach)Could be amylase (found in the intestine)Enzyme activityTemppH400CEnzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.
16Diffusion and concentration gradients highconcentrationlowDiffusion is the spreading of the particles of a gas, or of any substance in solution.This results in a net movement from a region where they are ofa higher concentration to a region of lower concentrationThe greater the difference in concentration, the faster therate of diffusion.
18Diffusion SummaryDiffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______.Words – faster, low, gradient, temperature, energy
21Osmosis summaryOsmosis is a “special kind of ___________”. It’s when water diffuses from a __________ area to a less concentrated area through a partially permeable _________ (i.e. one that allows water to move through but not anything else):In this example the water molecules will move from left to right (along the concentration ______) and gradually _____ the sugar solution. Plants use osmosis to take in water through their roots.Words – membrane, concentrated, dilute,diffusion, gradientWater
22Which way does movement take place? Strong sugar solutionMedium sugar solutionWhich way does movement take place?Potato cellsWeak sugar solution
24Active transport summary In diffusion substances moved along a concentration gradient. In active transport, substances move against this gradient:This process takes ______ and this comes from ___________. It enables cells to take in substances even though there are in very small __________. Root hair cells take in ______ using active transport.Words – concentration, energy, respiration, nutrientsOutside cellInside cellCell membrane
25OCR 21st Century Science Unit B5a Revision Animal & Plant cells and Stem cells
26Specialisation of animal cells During the development of a multi-celled organism cells differentiate to form specialised cells:White blood cellEgg cell (ovum)Ciliated epithelial cellNerve cell (neurone)
27and close to control exchange of gases and water loss 1. Guard cell – can openand close to control exchange of gasesand water loss2. Sperm cell – long tail providing movement s it can swim to and fertilise egg. Nucleus contains genetic material3. Red blood cell – concave disc shape - increases area to carry more oxygen4. Egg cell (ovum) – large – maximum exposure for sperm, has a large food store6. White blood cell – can change shape to digest microbes7. Neurone – long like wires to carry messages around the body5. Root hair cell – large surface area to absorb water and minerals. Thin cell wall so minerals can pass through easily. Positioned close to xylem tissue.
28Cells, tissues and organs Basically, all living things are made up of cells…A group of CELLS makes up a TISSUEA group of TISSUES makes up an ORGANA group of ORGANS makes up a SYSTEMA group of SYSTEMS make up an ORGANISM
29Adult stem cellsIt is also possible to have adult stem cells – these are unspecialised cells that can become specialised later (but they can’t form ALL types of cell)Adult stem cells can be found in places like bone marrow.White blood cellEgg cell (ovum)Ciliated epithelial cellNerve cell (neurone)
30Adult stem CellsCells inside an organism contain the same genes. So how can cells specialise if they have the same genes and make the same proteins?The reason is that many of the genes in the nucleus are “switched off” so that the cell only produces the proteins it needs.It is possible to “switch on” different genes to make the cell produce different proteins – this is the basis of stem cell research.
31Should these embryos be treated as humans? Adult Stem cellsAs well as adult stem cells from bone marrow, stem cells can also come from...These stem cells have the potential to develop into any kind of cell. The rest of the embryo is destroyed. Most of these embryos come from unused IVF treatments.EmbryoEgg and spermCloned embryosThe ethical issue:Should these embryos be treated as humans?
32MeristemsPlant growth occurs in areas called meristems. These meristems are “mitotically active”:This meristem causes the plant to grow upwards.This meristem causes the plant to grow in width.Cells from the meristem behave like stem cells – they can develop into any kind of cell. Cloned plants can be produced from these cells.
34Plant hormonesShoots grow towards light (positive phototropism) and against gravity (negative geotropism).Roots grow away from light (negative phototropism) and in the direction of gravity (positive geotropism).The growth of roots and shoots is controlled by hormones:In the shoots the hormone auxin is “destroyed” by light, so the shoot will bend towards the light as the cells on the shaded side grow quickest.In the roots hormones slow down growth of the cells in the lower region, which makes the root bend down.
37OCR 21st Century Science Unit B5b Revision DNA and Mitosis & Meiois
38Inside the nucleusthe genetic code is in the cell nucleus of animal and plant cells but proteins are produced in the cell cytoplasm
39DNA DNA has a double helix structure both strands of the DNA molecule are made up of four different bases which alwayspair up in the same way: A with T, and C with Gthe order of bases in a gene is the genetic code for the production of a protein
40DNA and coding for proteins the order of bases in a gene is the code for building up amino acids in the correct order to make a particular protein
41Building proteins 1) DNA “unravels” and a copy of one strand is made 2) The strand copy is made to produce RNA3) The copy (with its code) then moves towards the ribosome4) The ribosome “decodes” the code which tells the ribosome how to make the proteinIn other words, genes do NOT leave the nucleus but a copy of the gene (the mRNA) carries the genetic code to the cytoplasm.
43DNA summary Some facts: - DNA has a “double ______” structure - This contains instructions on what a cell does, how the organism should work etc- The instructions are in the form of a ______- The code is made up from the four ____ that hold the strands together with hydrogen bonds; A always pairs with T and C with G- The bases represent the order in which _____ acids are assembled to make specific ________Words – helix, amino, code, bases, proteins
44Chromosomes in body cells In body cells the chromosomes are in pairsBody cells have two sets of chromosomes;Sex cells (gametes) have only one set.Sex cells (gametes) are made by meiosis
46Mitosis parent cell mitosis daughter cells cell division by mitosis produces two new cells that are genetically identical to each other and to the parent cella fertilised egg cell (zygote) divides by mitosis to form an embryo
47Mitosis The chromosomes are copied… Each daughter cell has the same number of chromosomes and genetic information as the parent – it’s a “clone”.The chromosomes separate…The nucleus divides…
49Meiosis meiosis is a type of cell division that produces gametes in meiosis, it is important that the cells produced only contain half the chromosome number of the parent cella zygote contains a set of chromosomes from each parent.
50Each daughter cell has half the number of chromosomes of the parent. MeiosisEach daughter cell has half the number of chromosomes of the parent.
52Mitosis Vs Meiosis Mitosis: Meiosis: Used for growth and repair of cellsUsed in asexual reproductionCells with identical number of chromosomes and genetic information are produced (“clones”)Meiosis:Used to produce haploid gametes for sexual reproductionEach daughter cell has half the number of chromosomes of the parent
53OCR 21st Century Science Unit B6a Revision Nervous system and Reflex actions
54The nerve cellThe CENTRAL NERVOUS SYSTEM (CNS) enables us to react to changes in our surroundings (“stimuli”). It consists mainly of the brain, the spinal chord, nerve cells (“neurones”) and receptors.
55Receptor cells Types of receptor: Light receptors in the eyes Sound receptors in the earsTaste receptors on the tongueSmell receptors in the noseTouch, pressure and temperature receptors in the skinChanges of position receptors in the ears (balance)
56The nerve cellNerve cells (neurons) are elongated with branched endings to connect to many muscles fibres and aid the transmission of electrical impulses:Axon – a long extension of cytoplasm surrounded by a membraneMuscle strands (effector)NucleusFatty sheath to increase the speed of transmission and to insulate the neuron from surrounding cells
57CNS and PNS There are two types of neurone we need to consider: The Central Nervous System (CNS) is the spinal cord and brain:The Peripheral Nervous System (PNS) is the collection of neurones connected to the CNS:There are two types of neurone we need to consider:1) Sensory neuroneImpulseThese carry impulses from the receptors to the CNS2) Motor neuroneImpulseThese carry impulses from the CNS to effectors
58Synapse summaryNeurones never ____ each other – there is a small gap between them called a _____. A signal is sent from one _______ to the next by a _______ transmitter across the synapse (called a “neurotransmitter”). These transmitters are then ________ back into the sensory neurone to be used again. This process only reacts with specific chemicals that bind to the receptor molecules.Words – chemical, synapse, neurone, touch, reabsorbed
59A Conscious actionA conscious action is one where the brain makes a considered response. Here’s what happens:4) The brain decides to move away the hand3) Here another sensory neurone carries the signal to the brain5) This impulse is sent by MOTOR NEURONES to the hand muscles (the effectors) via the spinal chord…2) The impulse is carried by SENSORY NEURONES to the spinal chord1) Receptors in your skin detect a stimulus6) Which then moves the hand awayStimulus Receptor Sensory Neurone CoordinatorMotor Neurone Effector Response
64Simple reflexes Babies can demonstrate simple reflexes: Stepping reflex (legs step back if you hold the baby up)Startle (or moro) reflex (when a baby hears a loud noise it spreads its arms and legs out)Grasping reflex (gripping your finger with their hands)Rooting reflexSucking reflex (for breast feeding)
66OCR 21st Century Science Unit B6b Revision Learning and memory
67Drugs and the nervous system Drugs are classed as “a substance that affects the central nervous system, causing changes in psychological behaviour and possibly addiction”. They do this by affecting the transmission of impulses. Consider Ecstasy for example:Ecstasy (MDMA) blocks the sites in the brain’s synapses where the transmitter substance serotonin is removed.Beta blockers and Prozac can also affect the transmission of impulses.
68Drugs and the nervous system summary Some drugs stop the impulse from passing across the ………………………Drugs such as strychnine cause all the muscles in the body to go into a continuous spasm of contraction. This also stops the person from ……………………….Serotonin is a chemical released in the brain that gives feelings of pleasure. Lack of this chemical can lead to feelings of ……………………….Prozac is an ……………………… ……………drug that causes serotonin concentration to build up in synapses.The Prozac molecule blocks the re-uptake of serotonin from a synapse.Beta blockers are drugs that can help people who suffer from angina (chest pain due to a ……………………… condition). They work by blocking the receptor sites on heart muscle cells so impulses from nerves which would speed up the heart are ……………………… from passing to the heart.WORDS: synapse. Breathing depression anti-depressant heart prevented
69The cerebral cortexThe cerebral cortex is the part of our brain most concerned with intelligence, memory and consciousness. By studying the effects (e.g. memory/sight loss) when different parts of the brain are damaged scientists have been able to identify which parts of the brain control which functions.
70EEG and MRI1) An electroencephalogram (EEG) is a visual record of the electrical activity generated by neurons in the brain. It works by amplifying and detecting the electrical signals from the brain.2) Magnetic resonance imaging (MRI) scanning is a new technique that produces images of different cross sections of the brain and uses colours to represent activity.
71Conditioning- Pavlov’s dogs Ivan Pavlov,I won the Nobel Prize in 1904 and am most famous for investigating “conditioned responses”:Steak + dog = salivaSteak + bell + dog = salivaBell + dog = salivaNotice that the final response (saliva) has no direct relation to the stimulus (the bell). Conditioned reflexes can increase an animal’s chance of survival!
72Underline the primary stimulus Circle the secondary stimulus Bird finds a black caterpillar and tastes it. It tastes good so it is eatenBird finds a black and orange caterpillar and tastes it. It is poisonous and tastes bad so it is not eatenBird finds a black and orange caterpillar but avoids it because it is poisonousBird finds a hairy black and orange caterpillar, this one is harmless but the bird still avoids it.Underline the primary stimulusCircle the secondary stimulusPut a box round the conditioned responseExtension:Answer the following questions in your exercise book:Which organisms benefit? For each one explain how.Which caterpillar would you expect to find in the highest numbers? Explain your answer.Draw a cartoon
73Complex behaviour PET scan showing areas “activated” by doing algebra. When the brain is asked to do certain tasks different areas are “activated”. New experiences cause new neuron pathways to develop, while pathways that are not used are eventually destroyed. This is why we become better at certain tasks when we practice them more often.
74Memory Our memory is divided into two types: short term and long term. Short-term memory lasts for about 30 seconds. This is why, when you look up a new telephone number, by the time the call has ended you have forgotten the number. If more information arrives than can be held in the short-term memory then some is lost (forgotten).Long-term memory may last the whole of your life. When you sing the words of a favourite song, you are using your long-term memory. Although we often complain about how hard it is to learn new things, there is no limit to how much information you can store in your long-term memory.Ways of improvingshort term memory,e.g. a phone numberWays of improvinglong term memorye.g. exam revision
75Multistore modelScientists have produced models to help explain how memory works. So far, none of these models has provided an exact explanation.The multistore memory model can be used to help explain some steps involved in long-term and short-term memory.