Living and Growing (OCR Gateway) W Richards The Weald School
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 and there are LOTS of these in the liver and muscles 5) Cell Membrane – controls what comes in and out 3)
DNA Some facts: - Made up of paired bases - Contain instructions on what a cell does, how the organism should work etc - The instructions are in the form of a code - The code is made up from the four bases that hold the two strands together - The bases represent the order in which amino acids are assembled to make proteins - The sequence of bases determines the order in which a cell makes amino acids, which turn into proteins - There are about 20 amino acids in all, and different combinations produce different proteins
Making 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 5) Amino acids are then joined together to form a polypeptide (protein)
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
Watson and Crick We discovered the structure of DNA in 1953. We used data from other scientists (such as X-ray data showing that there were two chains wound in a helix) to come up with the double-helix structure. However, our discovery was not accepted by the scientific community until other scientists repeated and tested the work.
Proteins Proteins are basically long chains of amino acids: Every different protein has its own number and sequence of amino acids which results in differently shaped molecules with different functions. Some example proteins:
Enzyme use in nature 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. Enzymes are proteins that speed up chemical uses. Here are two important natural uses for them:
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 with high “specificity”: The enzyme’s shape helps another molecule “fit” into it: Substrate This shape can be destroyed by high temperatures or the wrong pH:
The “Active Site” Active site Enzyme Substrate
Enzymes Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity Rate at higher temperature Q10 = Rate at lower temperature 400C Temp pH pH Enzymes work best in certain conditions: The “Q10” value is a way of measuring the change to the rate of reaction:
Mutations Genes Cells contain a nucleus and the nucleus contains genes that carry instructions for what that cell should do: • Some facts: • Some genes are “switched off” and don’t do anything in that cell • Genes basically tell the cell which proteins they should be producing • Sometimes cells can “mutate” which may have a harmful effect on the cell and can be caused by natural or artificial means.
Mutations Mutations are changes in the base sequence of the DNA molecule. They can be passed on to daughter cells through cell division. They will result in the wrong proteins being produced. Mutations can be caused by: - Ionising radiation (UV, X-rays etc) - Radioactive substances - Certain chemicals Effects: - Mostly harmful - Causes death or abnormality in reproductive cells - Causes cancer in body cells - Some CAN be neutral or even beneficial (e.g. the peppered moth)
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.
(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 C6H12O6 + 6O2 6H2O + 6CO2 + 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
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.
Muscles and exercise Carbon dioxide produced RQ = Oxygen used When we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration. Respiration results in the production of ATP which is used as an energy source in cells. This process requires oxygen so the rate of respiration can be measured by measuring the rate of consumption of oxygen. The rate of respiration is controlled by enzymes. What are enzymes affected by?
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
Single celled or multi-celled? Advantages of being single-celled: Advantages of being multi-celled: Disadvantages of being single-celled: Disadvantages of being multi-celled:
Cell Growth There are three ways in which a cell might “grow”: 1) Cell division: 2) Cell expansion: 3) Cell specialisation:
Mitosis Each daughter cell has the same number of chromosomes and genetic information as the parent. Mammal cells are “diploid” – they have two copies of each chromosome
Making DNA copies 2) New bases pair up with the exposed bases 3) An enzyme bonds these bases together 4) Two identical pieces of DNA are formed 1) The double helix unzips
Meiosis Each daughter cell has half the number of chromosomes of the parent.
Mitosis vs. Meiosis • Mitosis: • Used for growth and repair of cells • Used in asexual reproduction • Cells with identical number of chromosomes and genetic information are produced • Meiosis: • Used to produce gametes for sexual reproduction • Each daughter cell has half the number of chromosomes of the parent
Sexual Reproduction The human egg and sperm cell (“ HAPLOID GAMETES”) contain 23 chromosomes each and are created by meiosis. When fertilisation happens the gametes fuse together to make a single cell called a DIPLOID ZYGOTE. The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis.
Eggs and sperm An acrosome that releases enzymes to ______ its way through the egg Nucleus Strong tail for ________ The female egg cell and the male sperm cell are examples of ____________ cells: The ______ cell is specialised in two ways: The egg cell is basically an enlarged cell with massive _____ reserves Words – food, swimming, sperm, specialised, digest
The Circulatory system The circulatory system is responsible for pumping ______ around the body. We need blood to be taken around the body because blood contains ________ and _______. These are needed so that all the ____ in our bodies can produce _____ through _________. The main organs in the circulatory system are the _____, the lungs and the kidneys. Words – energy, heart, blood, glucose, respiration, oxygen, cells
The four parts of blood 1. RED BLOOD CELLS – contain haemoglobin and carry ______ around the body. They have no _______ and a large surface area. 2. PLATELETS – small bits of cells that lie around waiting for a cut to happen so that they can ____ (for a scab). 3. WHITE BLOOD CELLS – kill invading _______ by producing _________ or engulfing (“eating”) the microbe. These three are all carried around by the PLASMA (a straw-coloured liquid). Plasma transports CO2 and ______ as well as taking away waste products to the ______. Words – antibodies, clot, kidneys, oxygen, nucleus, glucose, microbes.
The role of haemoglobin 1) Red blood cells are packed with haemoglobin. When they are pumped to the heart the haemoglobin picks up oxygen (“oxyhaemoglobin”) 2) After the oxygen and glucose have been removed for respiration the blood is sent back to the heart and then to the lungs to start again
The Double Circulatory System 1) Blood gets pumped from the heart to the lungs and picks up oxygen 2) The blood is then taken back to the heart… 3) The heart pumps the blood to the intestine (where oxygen and glucose are removed)… 5) After the oxygen and glucose have been removed for respiration the blood is sent back to the heart and starts again 4) … and to the rest of the body (where oxygen is removed) Having a double circulatory system enables mammals to pump blood at higher pressure and with a greater flow rate.
Arteries, veins and capillaries Arteries carry high pressure blood away from the heart. They have smaller lumen and no valves. Capillaries have thin walls (one cell thick) to allow glucose and oxygen to pass through. Also used to connect arteries to veins. “Lumen” Veins carry low pressure blood back to the heart. They have thinner, less elastic walls and have valves to prevent backflow of blood.
The Heart 1. Deoxygenated blood (i.e. blood without oxygen) enters through the vena cava into the right atrium 4. Oxygenated blood from the lungs enters through the pulmonary vein into the left atrium 2. It’s then pumped through the tricuspid valve into the right ventricle 5. It’s then pumped through the bicuspid valve into the left ventricle 3. It’s then pumped through the semi-lunar valve up to the lungs through the pulmonary artery 6. It’s then pumped out of the aorta to the rest of the body
Revision of 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 5) Cell Membrane – controls what comes in and out 3)
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
Plant cells vs. Animal cells 4) 1) 2) 5) 3) 6) Only plant cells have these: Both types of cell have these: Cell wall Cytoplasm Nucleus Chloroplasts Cell Membrane Large Vacuole
Bacteria Bacteria contain cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus and bacterial cells do not have mitochondria or chloroplasts. Consider a bacteria cell in more detail:
Measuring Plant Growth I’m bored of using quadrats now. I think I’ll measure the growth of this plant instead. How can I do it? • There are a number of ways to measure plant growth, including measuring: • Length/height • Wet mass • Dry mass What are the advantages and disadvantages of each?
Measuring Human Growth Growth rate (cm/year) Age
Adult Stem Cells Ciliated epithelial cell White blood cell Nerve cell (neurone) Egg cell (ovum) 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.
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. The rest of the embryo is destroyed. Most of these embryos come from unused IVF treatments unless the stem cells are taken from bone marrow in adults. Embryo Egg and sperm Cloned embryos The ethical issue: Should these embryos be treated as humans?
Human Growth vs Plant Growth There are many differences between the way humans grow and the way plants grow: • Plants grow continually and won’t stop until they die • Plant cells retain their ability to differentiate whereas animal cells lose it at an early stage • Plant cell division is restricted to areas called meristems • Humans have two main stages of growth: straight after birth and during adolescence • Human growth occurs throughout the human
Plant Growth Introduction Plants grow due to their cells dividing through mitosis. The cells then specialise into root hair cells, palisade cells etc. Unlike animals, plants continue to grow for the rest of their lives.
Plant Growth - Meristems This meristem causes the plant to grow upwards. This meristem causes the plant to grow in width. Plant growth occurs in areas called meristems. These meristems are “mitotically active”: Cells from the meristem behave like stem cells – they can develop into any kind of cell. Cloned plants can be produced from these cells.