Biology Unit 2 – The Components of Life

1. Biology Unit 2 – The Components of Life EdExcel Additional Science N Smith St. Aidan’s

2. Topic 1 – The Building Blocks of Cells

3. A Typical Animal Cell Ribosomes – protein synthesis happens here 4) Cytoplasm - this is where the reactions happen and these are controlled by enzymes 1) Nucleus – controls the cell’s activities 2) Mitochondria - energy is released here during respiration 5) Cell Membrane – controls what comes in and out 3)

4. A Typical Plant Cell: Cell wall – made of cellulose which strengthens the cell Cell membrane – controls what comes in and out Chloroplasts(containing chlorophyll) – this is needed for photosynthesis Nucleus – controls what the cell does and stores information Large vacuole – contains sap and helps support the cell Cytoplasm – Chemical reactions happen here

5. Bacteria • The cell contains a number of features, including: • Chromosomal DNA, containing the genetic info of the cell • Plasmid DNA, containing extra information such as defence mechanisms • Flagella, which helps the cell move Bacteria – containing cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus. Consider a bacteria cell in more detail:

6. Using a light microscope 1. Eyepiece 2. Arm 7. Lenses 6. Stage 3. Focus adjustor 5. Mirror 4. Base

7. Magnification Calculations A “stereo” microscope An old microscope! These microscopes have different powers of magnification. Consider this image of velcro: If the “loop” on this image is measured to be 20cm tall at a magnification of 100x how big is it really? 2mm

8. Genes, Chromosomes and DNA

9. How genes work - DNA 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 - The bases represent the order in which _____ acids are assembled to make specific ________ Words – helix, amino, code, bases, proteins

10. DNA • Task: Find out how the structure of DNA was discovered, including: • An image of Crick and Watson with their original model • A brief desciption of what Crick and Watson did to discover DNA • How Franklin and Wilkins built on their work

11. The Human Genome Project In 1990 an international project was launched called the “Human Genome Project”. The aim was to map the _______ makeup of the human race and includes work from ______ in 18 different countries. • Possible benefits: • Improved genetic testing • Improved predictions and screening of ________ diseases • New gene ________ treatments • New knowledge of how ______ have changed Words – scientists, genetic, genes, inherited, therapy

12. Uses of Genetic Engineering • With genetic engineering I can produce milk that contains: • Extra protein • Lower levels of cholesterol • Human antibodies Basically, genetic engineering is when a gene is removed from one organism and inserted into another. Consider the example of making insulin:

13. Genetic engineering - Insulin Step 1: Using RESTRICTION ENZYMES “cut out” the part of the human chromosome that is responsible for producing insulin. Step 2: Using another restriction enzyme cut open a ring of bacterial DNA (a “plasmid”). Other enzymes are then used to insert the piece of human DNA into the plasmid. Step 3: Place the plasmid into a bacterium which will start to divide rapidly. As it divides it will replicate the plasmid and make millions of them, each with the instruction to produce insulin. Commercial quantities of insulin can then be produced.

14. Cell growth 1 - Mitosis Each daughter cell has the same number of chromosomes and genetic information as the parent.

15. Cell growth 2 - Meiosis Each daughter cell has half the number of chromosomes of the parent.

16. Mitosis vs. Meiosis During meiosis copies of the genetic information are made and then the cell divides twice to form four daughter cells. • Mitosis: • 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

17. Fertilisation The human egg and sperm cell (“GAMETES”) contain 23 chromosomes each and are created by meiosis. When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE (“diploid”). The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis.

18. Key words • Contains half the number of chromosomes • This is formed when an egg is fertilised by a sperm • A section of DNA • Contains the full number of chromosomes • An egg or a sperm are called this Gamete Zygote Diploid Haploid Gene

19. Cloning Animals Clone Host mothers Here’s how Dolly the sheep was cloned:

20. Pros and cons of cloning Medicinal - Cloning new organs for use when humans’ organs fail Creating new food supplies Cloning Ethical issues – is it right to clone animals or humans? Risk of creating deformed animals or humans

21. Cell specialisation Ciliated epithelial cell White blood cell Nerve cell (neurone) Egg cell (ovum) During the development of a multi-celled organism cells differentiate to form specialised cells: A “stem cell” is a cell that hasn’t yet become specialised and can be found in embryos or bone marrow. These cells can be used to treat certain conditions but the use of these cells is very controversial.

22. Stem cell research Stem cells are cells that have not yet specialised: These stem cells have the potential to develop into any kind of cell. In grown adults they can be taken from bone marrow or they can come from embryos from unused IVF treatments. They can be used to treat conditions such as paralysis. Embryo Egg and sperm Cloned embryos The ethical issue: Should these embryos be treated as humans?

23. Making proteins 1) DNA “unravels” and a copy of one strand is made 2) The strand copy is made to produce mRNA 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 specific amino acid 5) Amino acids are then joined together to form a polypeptide (protein)

24. Mutating DNA Each protein has its own specific number and order of amino acids. But what happens when DNA mutates? This mutation will cause different amino acids (and therefore different proteins) to be formed. These mutations can be beneficial, harmful or neutral.

25. Introduction to Enzymes Enzyme Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. An enzyme is basically a protein molecule made up of long chains of amino acids. These molecules are then “folded” to create a certain shape. Proteins are used in DNA replication, protein synthesis and digestion. The enzyme’s shape helps another molecule “fit” into it (“lock and key”): Substrate This shape can be destroyed (“denatured”) by high temperatures or the wrong pH:

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

27. Topic 2 – Organisms and Energy

28. Respiration Introduction I enjoy taking samples using quadrats. In order to do this, I need energy. Where does this energy come from? Our energy comes from a process called respiration, which basically involves turning food and oxygen into energy and this reaction is controlled by enzymes.

29. Diffusion The “scent particles” from this hamburger are in high concentration here: Eventually they will “diffuse” out into this area of low concentration: Diffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger… Oxygen passes into cells by diffusion

30. 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

31. O2 Diffusion in the lungs Oxygen diffuses in and carbon dioxide diffuses out of blood in the lungs: CO2

32. (Aerobic) Respiration 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

33. Uses for this energy Animals and plants have many uses for the energy they generate from respiration: • To build up sugars in ______ • To build up body _______ • To maintain a constant body ___________ (warm-blooded mammals only) • To build up sugars, ________ and other nutrients in plants • To build up amino acids and ________ Words – nitrates, tissue, proteins, respiration, plants

34. The Effect of Exercise Heart rate/min Breathing rate/min 100 225 Rest Exercise Recovery 75 175 50 125 25 75 5 mins 10 mins 15 mins 20 mins During exercise the following things happen: heart rate increases, breathing increases and arteries supplying muscles dilate. These three things all help muscles to get the oxygen and glucose they need.

35. Cardiac Output and Heart Rate The electrical impulses from the heart can be monitored using an electrocardiogram: Using this information and the volume of blood pushed by the heart (the “stroke volume”) you can calculate the cardiac output of the heart: Cardiac output = stroke volume x heart rate

36. Muscles and exercise When we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration. Muscles store glucose as glycogen which can then be converted back into glucose during exercise.

37. Anaerobic respiration Glucose lactic acid + a bit of energy Unlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________: 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. Lactic acid is also produced, and this can build up in muscles causing ______ and “excess post-exercise oxygen consumption” (“EPOC”), which explains why breathing and heart rates remain high after exercise. Words – debt, oxygen, fatigue, aerobic, quicker

38. Photosynthesis Basically, photosynthesis is the process through which a plant makes its own food using carbon dioxide and water: That’s a nice plant. I’m going to put it in the sun and give it lots of water and air… CO2 H2O

39. Photosynthesis – the 4 things you need SUNLIGHT Gives the plant energy CHLOROPHYLL The green stuff where the chemical reactions happen WATER Travels up from the roots CARBON DIOXIDE Enters the leaf through small holes on the underneath

40. Photosynthesis equations Sunlight Carbon dioxide + _____ glucose + _____ 6CO2 + 6H20 C6H12O6 + 6O2 Chlorophyll Sunlight Chlorophyll The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________. Words – respiration, starch, water, oxygen, energy

41. Structure of the Leaf Large surface area Lots of chlorophyll Transparent Thin structure Packed with chloroplasts Network of veins Lots of air spaces Holes

42. Limiting Photosynthesis What factors could limit the rate of photosynthesis? • Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down • CO2– if there is more carbon dioxide photosynthesis will happen quicker • Light – if there is more light photosynthesis happens faster

43. Drawing graphs of these factors Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C Photosynthesis increases at first but is then limited by a lack of increase in temp or light Photosynthesis increases at first but is then limited by a lack of increase in temp or CO2 1. Temperature 2. Carbon dioxide 3. Light

44. Encouraging Photosynthesis Using knowledge of limiting factors, explain how plant growth is encouraged in a greenhouse:

45. Water loss Water loss through the stomata is biggest on a hot, dry, windy day. Plants that live in these conditions often have a thicker waxy layer.

46. Transpiration 1) Water evaporates through the stomata 2) Water passes back into the leaf through xylem vessels by osmosis 3) Water is then pulled upwards through the xylem tissue 4) This is replaced by water entering from the root tissue 5) Water enters root hair cells by osmosis to eventually replace the water lost through respiration

47. Xylem and Phloem Xylem are used by the plant to transport water and soluble mineral salts from the roots to the stem and the leaves. Phloem are tubes used by the plant to transport dissolved food to the whole plant for respiration and storage.

48. Root hair cells Root hair cells Thin cell membrane Large surface area Plant roots are made of “root hair cells” which have two features that help them to take in water and nutrients (“active uptake”):

49. More on Active Transport In diffusion substances moved along a concentration gradient. In active transport, substances move against this gradient: Outside cell Inside cell 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 Cell membrane

50. Diffusion and Active Transport in plants Carbon dioxide diffuses into the leaf through holes in the bottom surface. Mineral Less concentrated More concentrated …while plant nutrients are taken in by root hair cells using active transport.