Mitosis and Transport in Cells Revision Past Paper PDF

LearnIT! KnowIT! Cell division Chromosomes Mitosis and the cell cycle Stem cells  Cell division - Chromosomes In human body cells the chromosomes are normally...

LearnIT! KnowIT! Cell division Chromosomes Mitosis and the cell cycle Stem cells  Cell division - Chromosomes In human body cells the chromosomes are normally found in pairs. The karyotype diagram below shows the 23 chromosome pairs for a female human. The nucleus of a cell contains the instructions for making proteins and new cells. In the nucleus there are structures called chromosomes. The Human have are around chromosomes are made of 24,000 genes and there are coiled strands of DNA up to 2,000 genes in one molecules. A section of DNA human chromosome. that codes for a specific protein  Cell division - Mitosis and the cell cycle In the cell cycle, cells divide in a series of stages. The genetic material is doubled and then divided into two identical Stage 1 – Growth: Before cells. a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. Stage 2 - DNA synthesis: The DNA replicates to form two copies of each chromosome. Stage 3 – Mitosis: One set of chromosomes is pulled to each end of the cell and the nucleus divides. Then the cytoplasm and cell membranes divide to form two cells that are identical to the parent cell. Mitosis occurs during growth and to repair or replace damaged cells. Asexual reproduction occurs by mitosis  Cell division - Stem Cells - animals Stem cells are undifferentiated cells within an organism. They can produce other stem cells that can then differentiate into many different types of cells. Human embryo stem cells: can be cloned and made to differentiate into most different types of human cells. Human adult stem cells: can form many (but not all) types of cells including blood cells. Human stem cells can be used to help Embryos treat produced diseases by therapeutic like diabetes and cloning have the same genes as the patient. This means stem cells from the embryo are not paralysis. rejected by the patient’s body. This is why they can be used for medical treatments. The risks of using stem cells risks such as transfer of viral infections. Some people have objections to stem cell use for ethical and religious reasons. During Fertility treatment doctors usually fertilise many more eggs than are going to be used. The embryos then formed are used to obtain stem cells. In the UK scientists can use  Cell division- Stem Cells - plants Most types of PLANT cells can differentiate throughout their life cycle. Undifferentiated stem cells in plants are grouped together in structures called meristems. The undifferentiated cells can then specialise e.g. root hair cell, xylem or Stem cells from phloem cells. in plants meristems can be used to produce clones of plants quickly and economically. Rare species: can be cloned to protect from extinction. Crop plants: with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers. e.g. potatoes, strawberries and dates Questio nIT! Cell division Chromosomes Mitosis and the cell cycle Stem cells  Cell Division– QuestionIT 1. What are chromosomes? 2. What is a gene? 3. What is DNA? 4. Where in a cell do you find chromosomes? 5. How many chromosome pairs do you find in a human body cell? 6. What are the three stages of the cell cycle? 7. What is mitosis and what is it used for in animals and plants? 8. What is a stem cell? 9. Which type of human stem cell can differentiate into  Cell Division– QuestionIT 10. What is therapeutic cloning? 11. What are the risks of therapeutic cloning? 12. State two reasons why people may object to the use of stem cells in therapeutic cloning. 13. What are meristems? 14. State two reasons that plants are cloned. AnswerI T! Cell division Chromosomes Mitosis and the cell cycle Stem cells  Cell Division– AnswerIT 1. What are chromosomes? Coiled strands of DNA molecules. 2. What is a gene? A section of DNA that codes for a protein. 3. What is DNA? A genetic material found in the nucleus that codes for proteins. 4. Where in a cell do you find chromosomes? In the nucleus of cells. 5. How many chromosome pairs do you find in a human body cell? 23 pairs 6. What are the three stages of the cell cycle? Growth, DNA synthesis and mitosis. 7. What is mitosis and what is it used for in animals and plants? Growth, repair and asexual reproduction.  Cell Division– AnswerIT 10. What is therapeutic cloning? Where patients are given stem cells containing the same genes as theirs. 11. What are the risks of therapeutic cloning? Viral infections. 12. State two reasons why people may object to the use of stem cells in therapeutic cloning. Ethical and religious reasons. 13. What are meristems? Structures in plants that contain stem cells. 14. State two reasons that plants are cloned? To clone LearnIT! KnowIT! Transport in cells Diffusion Osmosis Active transport  Transport in cells - Diffusion Diffusion is the spreading of the particles of a gas or substances in solution, resulting in a net movement of particles from a region where they are of a higher concentration to an area of lower concentration. Diffusion can occur in: Air – smells from perfume etc. Solution – tea from a tea bag, dye in water etc. Through membranes – small intestines, blood cells etc. Substances that are transported in and out of cells in humans Location Particles move From To Small Digested food e.g. Blood in Small Intestine glucose, amino capillary of intestine acids villus Blood Lungs Alveolar air circulating Oxygen space around the lungs Kidneys Urea Cells Blood plasma  Transport in cells - Diffusion Factors which affect the rate of diffusion: The larger the difference in concentration the faster the rate The concentration gradient: of diffusion. A difference in concentration between two areas next to each other. Particles will move down the concentration gradient from high to low. The temperature: As the temperature increases the particles in a gas or liquid gain more energy so they move faster. The hotter it is the faster the rate of diffusion. Beetroot in different temperatures of wate The surface area of the membrane: A single-celled organism has a large surface area compared to its volume. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.  Transport in cells – Surface area to volume ratio The surface area to volume ratio can be calculated by dividing an object’s surface area (SA) by its volume Cube A represents a small Cube B represents a larger animal like a mouse the sides are 1 cm animal like a dog the sides are 6cm each and there are 6 sides. B A each and there are 6 sides. To calculate the volume: To calculate the volume: volume B = length x width x height volume A = length x width x height volume B = 6 x 6 x 6 volume A = 1 x 1 x 1 volume A = 216cm 3 volume A = 1cm 3 To calculate the area of one surface: To calculate the area of one area = height x width surface: area = 6 x 6 = 36cm2 area = height x width To calculate the surface area of B: area = 1 x 1 = 1cm2 area of one surface x the number of To calculate the SA of A: surfaces area of one surface x the number surface area = 36 x 6 = 216cm2 of surfaces surface area = 1 x 6 = 6cm2 SA:V ratio = 216/216 = 1 So as ratio SA:V you can see = 6/1 = 6the mouse has a much larger surface area compared to its volume.  Transport in cells – Adaptations in animals Adaptations of the small intestines: Internal surface is covered in millions of folds called villi. Villi increase the surface area. Villi have a very good blood supply. This maintains the concentration gradient. Membranes of the villi are Adaptations of the lungs: very Lungsthin to allow contain for aofshort millions tiny air diffusion sacs calleddistance. alveoli. Alveoli increase the surface area. Alveoli have a very good blood supply. This maintains the concentration gradient. Membranes of the alveoli are very thin to allow for a short  Transport in cells – Adaptations in animals Adaptations of gills in fish: Each gill is made of lots of thin plates called gill filaments, water with low oxygen flows over them (however, the oxygen in the blood surrounding the gills is lower). Gill filaments increase the surface area. Gill filaments are covered with lamella that increase the surface area more. Lamella have a very good blood supply. This maintains the concentration gradient as water flows in the opposite direction. Membranes of the lamellae are very thin to allow for a short diffusion distance. http://kids.britannica.com/kids/assembly/view /87782  Transport in cells – Adaptations in plants Adaptations of the roots: The root surface is covered in millions of root hair cells. Root hair cells increase the surface area. Present on the mature parts of the roots. Adaptations Absorb water of the and leaves: minerals from Large surface area to absorb the soil. more light. Thin so short distance for carbon dioxide to diffuse into leaf cells. Chlorophyll absorbs sunlight for photosynthesis. Xylem and phloem to support the leaf and transport water and glucose. Stomata on the lower side of  Transport in cells - Osmosis Osmosis in plant and Osmosis is the diffusion of animal cells: water from a dilute solution to a concentrated solution through a partially permeable membrane. Hypertonic – more concentrated solution The rate of osmosis changes than in the cells. depending on the concentration Isotonic – same gradient and temperature. concentration as the Partially permeable membrane – solution in the cell. a membrane that lets some but Hypotonic – more dilute  Transport in cells – Active transport Active transport occurs in root Active transport moves hair cells. substances from a more dilute solution to a more concentrated solution (against a concentration gradient). The energy is provided by respiration. The minerals are at a higher concentration in the root hair cell than in the soil. So the minerals move transport Active into the cell also against occurs inthe the concentration gut gradient. (small intestines) sugar (glucose) molecules are absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. The glucose is used for respiration. Questio nIT! Transport in cells Diffusion Osmosis Active transport  Transport in cells – QuestionIT 1. Define ‘diffusion’. 2. State three places where diffusion occurs in the body. 3. What is a concentration gradient? 4. What three factors affect the concentration gradient? 5. What is surface area to volume ratio? 6. Which has the largest surface area to volume ratio, an elephant or a meerkat? 7. State how the following are adapted for diffusion: a. The small intestines b. The lungs c. Gills in fish d. Root e. Leaves  Transport in cells – QuestionIT 8. Define ‘osmosis’. 9. What is a ‘partially permeable membrane’? 10. What happens to an animal cell in a hypertonic solution? 11. What happens to an animal cell in a hypotonic solution? 12. Define ‘active transport’. 13. Why does active transport need to occur in root hair cells? 14. Why does active transport need to occur in the gut? AnswerI T! Transport in cells Diffusion Osmosis Active transport  Transport in cells – QuestionIT 1. Define ‘diffusion’? The spreading of the particles from a region where they are of a higher concentration to an area of lower concentration. 2. State three places where diffusion occurs in the body. Small intestines, lungs, kidneys 3. What is a concentration gradient? The difference in concentration between two areas next to each other. 4. What three factors affect rate of diffusion? Concentration gradient, temperature, surface area. 5. What is surface area to volume ratio? The size of a surface compared to its volume. 6. Which has the largest surface area to volume ratio an elephant or a meerkat? The meerkat.  Transport in cells – QuestionIT 7. State how the following are adapted for diffusion: a. The small intestines. Have villi to increase surface area, good blood supply, thin membranes. b. The lungs. Have alveoli to increase surface area, good blood supply, thin membranes, they are ventilated. c. Gills in fish. Have gill filaments and lamella to increase surface area, good blood supply, thin membranes. d. Roots. Have root hair cells to increase surface area. e. Leaves. Large surface area, thin and stomata. 8. Define osmosis? Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.  Transport in cells – QuestionIT 10. What happens to an animal cell in a hypertonic solution? It will lose water by osmosis and shrivel. 11. What happens to an animal cell in a hypotonic solution? It will absorb water by osmosis and get bigger/burst. 12. Define active transport. Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient) using energy from respiration. 13. Why does active transport need to occur in root hair cells? Because the minerals are at a higher concentration in the roots than in the soil. 14. Why does active transport need to occur in the gut? Because the glucose in the blood is at a higher concentration than in the gut.