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B2 Revision. All living things are made up of cells. The structures of different types of cells are related to their functions.

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Presentation on theme: "B2 Revision. All living things are made up of cells. The structures of different types of cells are related to their functions."— Presentation transcript:

1 B2 Revision

2 All living things are made up of cells. The structures of different types of cells are related to their functions.

3 PartFunction Nucleus Contains genetic material, which controls the activities of the cell Cytoplasm Most chemical processes take place here, controlled by enzymes Cell membrane Controls the movement of substances into and out of the cell MitochondriaMost energy is released by respiration here RibosomesProtein synthesis happens here Parts of cells which animal and plant cells have in common:

4 PartFunction Cell wallStrengthens the cell Chloroplasts Contain chlorophyll, which absorbs light energy for photosynthesis Permanent vacuole Filled with cell sap to help keep the cell turgid Parts of cells which only plant and algal cells contain:

5 Bacteria are single celled organisms which contain: cytoplasm cell membrane cell wall no distinct nucleus

6 Yeast is a single-celled organism, similar to bacteria, containing: Cytoplasm Cell membrane Cell wall But, they also have a nucleus.

7 Cells may be specialised for a particular function. Their structure will allow them to carry this function out. CellJobAdaptations Leaf cell: absorbs light for photosynthesis lots of chloroplasts Root hair cell: absorbs water and mineral ions finger like shape for large surface area Sperm cell: fertilises an egg head contains an enzyme to help penetrate egg Red blood cell: carries oxygen to the cells thin outer membrane so oxygen diffuses easily

8 Substances have to pass through the cell membrane to get into or out of a cell. Diffusion is a process that allows this to happen. Particles diffuse from an area of high concentration to an area of low concentration.

9 Diffusion happens in our: Gut:digested food particles diffuse from the gut cavity to blood in the villus Lungs:oxygen moves from the alveoli into capillaries around the lungs

10 A tissue is a group of specialised cells that have a similar structure and function. cells  tissues  organs  organ systems TissueFunction Muscular tissueContracts, bringing about movement Glandular tissue Produces substances such as enzymes and hormones Epithelial tissueCovers some parts of the body

11 Organ systems are groups of organs that carry out a particular function. For example, the digestive system:

12 Plants also usually contain differentiated cells, tissues and organs.

13 Leaves are adapted to absorb sunlight for photosynthesis

14 Three factors can limit the speed of photosynthesis: light intensity carbon dioxide concentration temperature

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16 Glucose is produced during photosynthesis and is used by the plant to make: Cellulose - which strengthens the cell wall Proteins - such as enzymes and chlorophyll Glucose is stored by plants as starch, fats and oils. Plants also need nitrates to do this

17 6 marks

18 Using what you know about photosynthesis and limiting factors, explain the difference in the growth of the two sets of seedlings (5 marks) Mark Scheme Plants in higher light intensity photosynthesise faster (therefore) produce more food and grow well Light will not limit them/is not a limiting factor CO2 or temperature may be limiting factors (plants in low light intensity) Light is a limiting factor on their growth

19 5-6 marks3-4 marks1-2 marks0 marks There is a clear, balanced and detailed explanation of most of the structures in the leaf and their functions The answer is coherent and in a logical sequence It contains a range of appropriate or relevant specialist terms used accurately The answer shows few errors in spelling, punctuation and grammar There is a clear description which includes the name of at least one tissue and at least one correct function described for an indicated part of the leaf The answer has some structure and organisation The use of specialist terms has been attempted, but not always accurately There may be some errors in punctuation, spelling and grammar There is a brief description of at least one tissue OR at least one function of an indicated part of the leaf The answer is poorly constructed with an absence of specialist terms or their use demonstrates a lack of understanding of their meaning The spelling, punctuation and grammar are weak No relevant content Examples of biology points made in the response: Describe the structure of the leaf and the functions of the tissue in the leaf (6 marks)

20 The distribution of living organisms in a particular habitat may be affected by physical factors, such as: Temperature Amount of light Availability of water Availability of nutrients Availability of oxygen and carbon dioxide

21 Sampling: Quadrat Square frame Used to sample a small area Samples chosen at random

22 Sampling: Along a Transect Not random Tape stretched between two points Samples taken along the line using a quadrat Shows how the distribution of organisms changes along the line

23 Enzymes Biological catalysts: speed up reactions. Enzymes are protein molecules, and so are made up of amino acids.

24 What happens at the active site? The enzyme is the lock, and the reactant is the key. enzyme reactant + enzyme-reactant complex ↔ products enzyme + ↔ + ↔↔ +

25 Key phrases: Catalyst: A substance which changes the rate of a chemical reaction without being changed itself. Enzyme: A biological catalyst. Active site: Where substrates bind to an enzyme and undergo a chemical reaction. Activation energy: The minimum amount of energy particles must have to be able to react. +

26 Temperature and enzymes Most enzymes in the human body work best at about 37 o C. Over 40 o C most enzymes will stop working. The amino acids they are made form start to unravel and the shape of the active site changes. We say that the enzyme is denatured.

27 pH and enzymes Changes in pH alter an enzyme’s shape. The best pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5 (alkaline). Enzymes in the stomach have an optimum pH of about 2 (acidic).

28 Amylase Made in the salivary glands, pancreas and small intestine. It breaks down starch into sugars. It works in the mouth and small intestine.

29 Protease Made in the stomach, pancreas and small intestine. It breaks down protein into amino acids. It works in the stomach and small intestine.

30 Lipase Made in the pancreas and small intestine. It breaks down lipids (fats and oils) into fatty acids and glycerol. It works in the small intestine.

31 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.

32 IndustryFunction of enzymes confectionery (sweets) change glucose into fructose, which is sweeter so less is needed and is used in 'slimming' foods (isomerase). baby foodstart off digestion of food (proteases and lipases) biological detergent break down stains (proteases and lipases). What do enzymes do for us?

33 Short Answer Questions 1.Enzymes are described as biological _______________ (1) 2.Enzymes molecules are made of ________________ (1) 3.The enzyme that digests starch is called _______________ (1) 4.The substance that neutralises stomach acid is called ____________ (1) 5.Glycerol is one of the products of the digestion of _____________ (1) 6.An enzyme works well in pH 7. o What happens to the enzyme when it is placed in an acid solution? __________________________________________________________ (1) o Give one other factor that will affect the acitivity of the enzyme __________________________________________________________ (1) o Explain what happens to starch when it is digested _____________________________________________________________ __________________________________________________________ (2)

34 Past Paper Question In this question, you will be assessed on using good English, organising information clearly and using specialist terms where appropriate The digestive system is a group of organs which changes food from insoluble into soluble molecules. Soluble molecules can be absorbed into the blood stream. Some food cannot be digested. Describe the functions (jobs) of the organs in the digestive system (6)

35 5-6 marks3-4 marks1-2 marks0 marks There is a clear, balanced and detailed explanation referring to most of the key organs in the digestive system and their functions The answer is coherent and in a logical sequence It contains a range of appropriate or relevant specialist terms used accurately The answer shows few errors in spelling, punctuation and grammar There is some description of at least three organs and their functions The answer has some structure and organisation The use of specialist terms has been attempted, but not always accurately There may be some errors in punctuation, spelling and grammar There is a brief description of the functions of at least two organs, which has little clarity and detail The answer is poorly constructed with an absence of specialist terms or their use demonstrates a lack of understanding of their meaning The spelling, punctuation and grammar are weak No relevant content Examples of biology points made in the response: Glands produce digestive juices Salivary glands Pancreas Digestion occurs in the stomach and small intestine The liver produces bile The soluble food is absorbed in the small intestine Water is absorbed from the undigested food In the large intestine Describe the functions (jobs) of the organs in the digestive system (6 marks)

36 Past Paper Question In this question, you will be assessed on using good English, organising information clearly and using specialist terms where appropriate Describe the roles of the liver and the pancreas in the digestion of fats (6)

37 5-6 marks3-4 marks1-2 marks0 marks There is a clear, balanced and detailed description of both the roles of the liver and the pancreas The answer is coherent and in a logical sequence It contains a range of appropriate or relevant specialist terms used accurately The answer shows few errors in spelling, punctuation and grammar There is some description of the roles of both the liver and pancreas which lacks some details The answer has some structure and organisation The use of specialist terms has been attempted, but not always accurately There may be some errors in punctuation, spelling and grammar There is a brief description reference to the role of either the liver or pancreas The answer is poorly constructed with an absence of specialist terms or their use demonstrates a lack of understanding of their meaning The spelling, punctuation and grammar are weak No relevant content Examples of biology points made in the response: Liver produces bile Bile neutralises acid Acid produced by stomach Pancreas produces lipase Lipase is an enzyme Lipase works best in neutral/alkaline conditions Lipase catalyses the breakdown of fat To fatty acids and glycerol Allow reference to, or a description of emulsification Describe the roles of the liver and the pancreas in the digestion of fats (6 marks)

38 Mitochondria: tiny organelles found in most plant and animal cells. Where the respiration reactions happen. More active cells have more mitochondria.

39 Aerobic respiration (with oxygen) glucose + oxygen → carbon dioxide + water (+ energy) When too little oxygen reaches the muscles during exercise, they use anaerobic respiration to obtain energy. Anaerobic respiration (without oxygen) glucose → lactic acid (+ energy)

40 During exercise, the muscle cells respire more than they do at rest. This means that: Oxygen and glucose must be delivered to them more quickly Waste carbon dioxide must be removed more quickly This is achieved by increasing: depth of breathing rate of breathing heart rate

41 Short Answer Questions 1.Respiration is a chemical process. a)Where does respiration take place? Circle the correct answer. (1) chloroplasts mitochondria nuclei ribosomes b) Which food material is used in respiration? _________________________________________________________________ (1) c) Name the two waste materials that are produced in respiration. _________________________________________________________________ (2) d) Respiration is important in muscle contraction. Explain why. _________________________________________________________________ (2) 2. a) Copy and complete the word equation for aerobic respiration. Oxygen + __________ -> Water + __________ (+ energy) b) i) Which substance is missing in anaerobic respiration? _________________________________________________________________ (1) ii) What is made during anaerobic respiration? _________________________________________________________________ (1) iii) Muscles get tired during anaerobic respiration. Explain why. _________________________________________________________________ (1)

42 Past Paper Question – Longer Answer In this question, you will be assessed on using good English, organising information clearly and using specialist terms where appropriate The bar charts show what happens in an athlete’s muscles when running in two races of different distances. The equations show two processes that occur in muscle cells. Use all the information to explain what happens in the athlete’s muscles when running in the two races (6) Aerobic Respiration Glucose + Oxygen -> Carbon Dioxide + Water Anaerobic Respiration Glucose -> Lactic Acid 100m race 1500m race Rate at which muscles transfer energy (average) Rate at which muscles produce carbon dioxide (average)

43 5-6 marks3-4 marks1-2 marks0 marks There is a clear, balanced and detailed explanation about the differences between the two races in terms of aerobic and anaerobic respiration The answer is coherent and in a logical sequence It contains a range of appropriate or relevant specialist terms used accurately The answer shows few errors in spelling, punctuation and grammar There is some attempt to explain the differences between the two races in terms of respiration The answer has some structure and organisation The use of specialist terms has been attempted, but not always accurately There may be some errors in punctuation, spelling and grammar There is a brief description of the differences between the two races, which has little clarity and detail The answer is poorly constructed with an absence of specialist terms or their use demonstrates a lack of understanding of their meaning The spelling, punctuation and grammar are weak No relevant content Examples of biology points made in the response: Use all the information to explain what happens in the athlete’s muscles when running in the two races (6 marks) Energy is transferred faster in the 100m race Carbon dioxide produced faster during the 1500m race/more Carbon dioxide produced Correct reference to twice/half as fast in either/both cases Respiration during 100m race (mainly) anaerobic Respiration during 1500m race (mainly) aerobic Aerobic respiration produced carbon dioxide Anaerobic respiration produced lactic acid

44 Inside each cell is a nucleus. Inside the human nucleus are 46 chromosomes (two sets of 23, one set from Mum, one set from Dad). Chromosomes are made from DNA. A section of DNA is called a gene. Where is the genetic information in a cell?

45 The genetic material is copied The cell divides once to form two genetically identical body cells Mitosis is used for growth or to replace cells. Mitosis

46 Meiosis Forms gametes (sex cells). The cell divides twice to form four gametes. Each daughter cell contains half of the chromosomes of the original cell.

47 Stem Cells Unspecialised - they can become any type of cell in the human body. As the cells of an embryo divide (by mitosis) and the embryo develops, the cells become differentiated.

48 Stem cells can be used in new treatments for Parkinson's disease and paralysis. Can be harvested from inside embryos, umbilical cords and bone marrow. There are social and ethical issues concerning the use of human embryonic stem cells.

49 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.

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52 Alleles Different forms of the same gene For example, eye colour

53 Determining sex Human body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the inheritance of gender - whether offspring are male or female.

54 Dominant or Recessive? Alleles are dominant or recessive.

55 Punnett Squares Show the possible genotypes produced when two organisms breed.

56 Questions 1.Rat fur colour is controlled by 2 genes. Black is dominant over white. What possible offspring could one black rat (Bb) have with a white rat (bb)? 2.Red sweet peas are recessive to white sweet peas, complete a genetic cross to show two white pea plants, both carry the red allele. 3.If a red pea plant is crossed with a white pea plant (with 2 dominant alleles), could any of the offspring be red?

57 Evolution Fossils are the remains of organisms which died thousands or millions of years ago. By looking at fossils, we can see that organisms have changed very slowly over time. 60 million years ago 1 million years ago

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59 Fossils form if an organism does not decay because: – little oxygen was present – poisonous gases killed of decay causing organisms – low temperature

60 Fossil Formation Trace or imprints are left behind by organisms. Isle of Wight, UK

61 Fossil Formation Hard parts of organism replaced by minerals. This is the most common type of fossil.

62 The fossil record is incomplete. Why? Early forms of life were soft bodied. Fossilisation requires very specific conditions. Many fossils are destroyed. Many fossils have not been found yet.

63 Evolution by Natural Selection Individuals in a species show a wide range of variation. This is because of differences in genes. Individuals most suited to the environment are more likely to survive and reproduce. The successful genes are then passed to the offspring in the next generation. Charles Darwin

64 Extinction What causes organisms to become extinct? Competition New predators New diseases Environmental changes

65 Why did the dinosaurs become extinct? Volcanoes Rocks formed by huge eruptions 65 million years ago can be found in India today. Meteorite Impact The remains of a 180km-wide crater caused by a meteorite 65 million years ago can be found near Mexico. Disease This theory doesn’t explain why so many sea animals died at the same time.

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68 Natural selection can result in the formation of new species… The formation of new species is know as ‘speciation’. Speciation can occur in a number of ways… This is evidence for natural selection in action!

69 Formation of new species The African and Asian elephants are two separate but very closely related species.

70 Formation of new species This speciation has arisen due to geographical isolation: A single population has become separated into two groups. A geographical (land) barrier has stopped them being all together in one group.

71 Formation of new species This speciation has arisen due to geographical isolation: A single population has become separated into two groups. Over time, each population of the separate group evolves differently due to genetic variation.

72 Formation of new species This speciation has arisen due to geographical isolation: A single population has become separated into two groups. Over time, each population of the separate group evolves differently due to genetic variation. The longer they are separated, the more different they become.

73 Formation of new species This speciation has arisen due to geographical isolation: A single population has become separated into two groups. Over time, each population of the separate group evolves differently due to genetic variation. The longer they are separated, the more different they become. Eventually, the two sub-populations have changed so much they can no longer interbreed.

74 Formation of new species This speciation has arisen due to geographical isolation: A single population has become separated into two groups. Over time, each population of the separate group evolves differently due to genetic variation. The longer they are separated, the more different they become. Eventually, the two sub-populations have changed so much they can no longer interbreed. They have formed separate but closely related species (speciation).

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