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OCR 21st Century Science Unit B4a Revision

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1 OCR 21st Century Science Unit B4a Revision
Animal and Plant cells Respiration and Photosynthesis

2 Animal and Plant Cells mitochondria 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 chemicals nucleus or circular DNA in bacteria contains DNA which carries the genetic code for making enzymes used in the chemical reactions of respiration cytoplasm where enzymes and proteins are made chloroplasts contain chlorophyll and the enzymes for the reactions in photosynthesis

3 Respiration

4 Uses for respiration summary
Animals and plants have many uses for the energy they generate from respiration: To perform the life processes, such as moving, _____ etc To build up body _______ To maintain a constant body ___________ (warm-blooded mammals only) To build up sugars, ________ and other nutrients in plants Active __________ Words – nitrates, tissue, proteins, transport, growing

5 Synthesis “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 molecules Starch molecule 2) Glucose can be combined with nitrates to make proteins (for growth)… Glucose molecules Proteins

6 Aerobic Respiration all living things depend on chemical reactions within cells that require energy released by respiration Respiration is a series of chemical reactions that release energy by breaking down large food molecules in all living cells glucose + oxygen  carbon dioxide + water (+ energy released) C6H12O6 + 6O2  CO2 + 6H2O

7 Glucose + oxygen  water + carbon dioxide + ENERGY
Aerobic respiration summary All 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 + ENERGY The 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

8 Anaerobic 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 Yeast glucose  ethanol + carbon dioxide (+ energy released) Happens in roots in waterlogged soil bacteria in puncture wounds human cells during vigorous exercise

9 Glucose  lactic acid + a bit of energy
Anaerobic respiration summary Unlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________: Glucose  lactic acid + a bit of energy This 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

10 In bacteria cells, this job is done by circular DNA
Respiration in cells 1) Cytoplasm - where enzymes are made In bacteria cells, this job is done by circular DNA 2) Nucleus – carries genetic info for making enzymes 3) Cell Membrane – controls what comes in and out 4) Mitochondria – contain enzymes for respiration reactions

11 OCR 21st Century Science Unit B4b Revision
Enzymes, Osmosis and Diffusion

12 Enzymes 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.

13 Enzymes- The lock and Key Model
enzymes are proteins that speed up chemical reactions cells make enzymes according to the instructions carried in genes molecules have to be the correct shape to fit into the active site of the enzyme (the lock and key model) Enzyme Substrate

14 Factors affecting enzyme action (Denaturing)
denatured normal heat pH The shape of the enzyme is vital to its function. The main factors affecting enzyme action are 1.) temperature and 2.) pH 1.) High temperatures can destroy the enzymes ‘special shape’ so it becomes denatured. 2.) Different enzymes work best at different pH values.

15 Enzymes are denatured beyond 40OC
Optimum conditions Enzymes work best in certain conditions: Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity Temp pH 400C Enzymes 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.

16 Diffusion and concentration gradients
high concentration low Diffusion 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 of a higher concentration to a region of lower concentration The greater the difference in concentration, the faster the rate of diffusion.

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18 Diffusion Summary Diffusion 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

19 Osmosis

20 Osmosis

21 Osmosis summary Osmosis 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, gradient Water

22 Which way does movement take place?
Strong sugar solution Medium sugar solution Which way does movement take place? Potato cells Weak sugar solution

23 Active transport

24 Active 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, nutrients Outside cell Inside cell Cell membrane

25 OCR 21st Century Science Unit B5a Revision
Animal & Plant cells and Stem cells

26 Specialisation of animal cells
During the development of a multi-celled organism cells differentiate to form specialised cells: White blood cell Egg cell (ovum) Ciliated epithelial cell Nerve cell (neurone)

27 and close to control exchange of gases and water loss
1. Guard cell – can open and close to control exchange of gases and water loss 2. Sperm cell – long tail providing movement s it can swim to and fertilise egg. Nucleus contains genetic material 3. Red blood cell – concave disc shape - increases area to carry more oxygen 4. Egg cell (ovum) – large – maximum exposure for sperm, has a large food store 6. White blood cell – can change shape to digest microbes 7. Neurone – long like wires to carry messages around the body 5. 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.

28 Cells, tissues and organs
Basically, all living things are made up of cells… A group of CELLS makes up a TISSUE A group of TISSUES makes up an ORGAN A group of ORGANS makes up a SYSTEM A group of SYSTEMS make up an ORGANISM

29 Adult stem cells It 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 cell Egg cell (ovum) Ciliated epithelial cell Nerve cell (neurone)

30 Adult stem Cells Cells 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.

31 Should these embryos be treated as humans?
Adult Stem cells As 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. Embryo Egg and sperm Cloned embryos The ethical issue: Should these embryos be treated as humans?

32 Meristems Plant 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.

33 Phototropism ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

34 Plant hormones Shoots 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.

35 Phototropism summary

36 Cuttings ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

37 OCR 21st Century Science Unit B5b Revision
DNA and Mitosis & Meiois

38 Inside the nucleus the genetic code is in the cell nucleus of animal and plant cells but proteins are produced in the cell cytoplasm

39 DNA DNA has a double helix structure
both strands of the DNA molecule are made up of four different bases which always pair up in the same way: A with T, and C with G the order of bases in a gene is the genetic code for the production of a protein

40 DNA 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

41 Building proteins 1) DNA “unravels” and a copy of one strand is made
2) The strand copy is made to produce RNA 3) The copy (with its code) then moves towards the ribosome 4) The ribosome “decodes” the code which tells the ribosome how to make the protein In other words, genes do NOT leave the nucleus but a copy of the gene (the mRNA) carries the genetic code to the cytoplasm.

42 Building proteins ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

43 DNA 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

44 Chromosomes in body cells
In body cells the chromosomes are in pairs Body cells have two sets of chromosomes; Sex cells (gametes) have only one set. Sex cells (gametes) are made by meiosis

45 Asexual and sexual reproduction

46 Mitosis parent cell mitosis daughter cells
cell division by mitosis produces two new cells that are genetically identical to each other and to the parent cell a fertilised egg cell (zygote) divides by mitosis to form an embryo

47 Mitosis 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…

48 Mitosis summary

49 Meiosis 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 cell a zygote contains a set of chromosomes from each parent.

50 Each daughter cell has half the number of chromosomes of the parent.
Meiosis Each daughter cell has half the number of chromosomes of the parent.

51 Meiosis summary

52 Mitosis Vs Meiosis Mitosis: Meiosis:
Used for growth and repair of cells Used in asexual reproduction Cells with identical number of chromosomes and genetic information are produced (“clones”) Meiosis: Used to produce haploid gametes for sexual reproduction Each daughter cell has half the number of chromosomes of the parent

53 OCR 21st Century Science Unit B6a Revision
Nervous system and Reflex actions

54 The nerve cell The 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.

55 Receptor cells Types of receptor: Light receptors in the eyes
Sound receptors in the ears Taste receptors on the tongue Smell receptors in the nose Touch, pressure and temperature receptors in the skin Changes of position receptors in the ears (balance)

56 The nerve cell Nerve 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 membrane Muscle strands (effector) Nucleus Fatty sheath to increase the speed of transmission and to insulate the neuron from surrounding cells

57 CNS 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 neurone Impulse These carry impulses from the receptors to the CNS 2) Motor neurone Impulse These carry impulses from the CNS to effectors

58 Synapse summary Neurones 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

59 A Conscious action A conscious action is one where the brain makes a considered response. Here’s what happens: 4) The brain decides to move away the hand 3) Here another sensory neurone carries the signal to the brain 5) 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 chord 1) Receptors in your skin detect a stimulus 6) Which then moves the hand away Stimulus Receptor Sensory Neurone Coordinator Motor Neurone Effector Response

60 A conscious nervous pathway
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

61 Copy and complete

62 3 types of neurons

63 The reflex arc ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

64 Simple 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 reflex Sucking reflex (for breast feeding)

65 Summary

66 OCR 21st Century Science Unit B6b Revision
Learning and memory

67 Drugs 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.

68 Drugs 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

69 The cerebral cortex The 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.

70 EEG and MRI 1) 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.

71 Conditioning- Pavlov’s dogs
Ivan Pavlov, I won the Nobel Prize in 1904 and am most famous for investigating “conditioned responses”: Steak + dog = saliva Steak + bell + dog = saliva Bell + dog = saliva Notice that the final response (saliva) has no direct relation to the stimulus (the bell). Conditioned reflexes can increase an animal’s chance of survival!

72 Underline the primary stimulus Circle the secondary stimulus
Bird finds a black caterpillar and tastes it. It tastes good so it is eaten Bird finds a black and orange caterpillar and tastes it. It is poisonous and tastes bad so it is not eaten Bird finds a black and orange caterpillar but avoids it because it is poisonous Bird finds a hairy black and orange caterpillar, this one is harmless but the bird still avoids it. Underline the primary stimulus Circle the secondary stimulus Put a box round the conditioned response Extension: 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

73 Complex 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.

74 Memory 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 improving short term memory, e.g. a phone number Ways of improving long term memory e.g. exam revision

75 Multistore model Scientists 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.

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