Cell Biology

• What are the two types of cell?

  Eukaryotic (with a nucleus eg, animal, plant and yeast cells) and prokaryotic (no nucleus - bacterial cells only)
• Which cells are biggest/smallest?

  Plant cells are the largest, followed by animal cells, yeast cells and finally bacterial cells are the smallest.
• Where is the DNA in a eukaryotic cell?

  Eukaryotic cells have their DNA inside a nucleus. The DNA is coiled up into structures called chromosomes.
• Where is the DNA in a prokaryotic cell?

  Prokaryotic cells have their DNA in the cytoplasm. They have a single DNA loop, and may also have small rings of DNA called plasmids.
• What cell structures are in all eukaryotic cells?

  Cell membrane, cytoplasm, nucleus, mitochondria and ribosomes.
• What is the function of a cell membrane?

  Controls entry and exit of substances (cell transport).
• What is the function of mitochondria?

  To carry out aerobic respiration and release energy (in the form of ATP) for cell activities. The more mitochondria, the more energy the cell needs.
• What is the function of a ribosome?

  To carry out protein synthesis (making proteins). The more ribosomes, the more proteins the cell needs to make.
• What structures are only found in plant/algal cells?

  Chloroplasts, large vacuole and cell wall made of cellulose.
• What is the function of chloroplasts?

  Chloroplasts absorb light energy to carry out photosynthesis and produce glucose for the plant. The more chloroplasts, the more glucose a cell can make.
• What is the function of a large vacuole?

  To store water and solutes and help keep the cell upright.
• What is the function of the cell wall?

  Cellulose is strong and rigid. It strengthens the cell (this is important as plants do not have a skeleton to give them support).
• What are the only cell structures in a prokaryotic cell?

  DNA and ribosomes are the only cell structures in a prokaryotic (bacterial) cell.
• Why don't prokaryotic cells have mitochondria?

  Mitochondria are bigger than prokaryotic cells so they don't fit inside.
• What is a specialised cell?

  A cell that has a certain structure to help it carry out a particular function
• What examples are there of specialised animal cells?

  Sperm cells, nerve cells (neurones), muscle cells, glandular cells, epithelial cells.
• What examples are there of specialised plant cells?

  Root hair cells, xylem cells, phloem cells, palisade and spongy mesophyll cells.
• What is a stem cell?

  A cell that has not become specialised yet.
• What is cell differentiation?

  The process during development where a stem cell develops to form a specialised cell.
• When does differentiation happen?

  In animal cells, differentiation happens at an early stage (when the animal is an embryo), but in plants some cells can differentiate throughout the life of the plant.
• Where can stem cells be found in an animal?

  Early stage embryos are completely made of stem cells, but in adults, the only place stem cells exist is in our bone marrow (inside large hollow bones, eg. Thigh bone)
• Where can stem cells be found in a plant?

  Meristem tissue is made of stem cells. It is found near the xylem and phloem, and also in the root and shoot tips.
• Why do scientists think animal stem cells are so useful?

  Stem cells can be made to differentiate into different types of cell. We can use them to treat diabetes and paralysis as well as use them for research into other disorders.
• What are the risks of using animal stem cells?

  Infections caused by viruses could be tranferred. Also some people have ethical objections or religious reasons (as embryos are destroyed during treatments and research)
• Why do scientists think plant stem cells are so useful?

  Stem cells can be used to clone plants quickly and cheaply. This can save rare species from extinction, or produce crop plants with resistance to disease for farmers.
• What is a microscope?

  A piece of equipment that uses lenses to magnify cells so that we can see some of their structures.
• What types of microscope are there?

  Light microscope (uses light to make an image) and electron microscope (uses electrons to make an image)
• How have microscopes developed over the years?

  Lenses have improved now glass can be made without cracks or bubbles showing up. Also the electron microscope shows more detail than the light microscope.
• What is the equation for magnification?

  Magnification = image size / actual size (Remember this as I / AM)
• What are chromosomes?

  Structures in the nucleus, made of a chemical called DNA. They are normally found in pairs in body cells (one of each pair from mum, and one from dad).
• What are genes?

  A small section of DNA (in a chromosome) that is the code for one whole protein. Ribosomes read the code and then make a protein by joining lots of amino acids together.
• What is the cell cycle?

  The life of a cell, including it growing and carrying out it's functions and then replicating it's DNA before getting ready to divide by mitosis to form new cells.
• When does mitosis take place?

  When cells need to divide to grow or repair an organism. Adults do less mitosis as they are no longer growing, and only repairing tissues/replacing old cells.
• What are the new cells from mitosis like?

  Two genetically identical cells (identical to each other and to the parent cell that they came from).
• What are the three types of cell transport?

  Diffusion, osmosis and active transport all move molecules in and out of cells.
• What is the definition of diffusion?

  The spreading out of particles (molecules) in a solution or a gas, from an area of high concentration to an area of lower concentration. It is passive as it requires no energy.
• What factors affect the rate of diffusion?

  The concentration gradient, temperature and surface area of the membrane.
• What molecules move into cells by diffusion?

  Oxygen and glucose are the two most important molecules that enter cells by diffusion. They are both needed for aerobic respiration.
• What molecules move out of cells by diffusion?

  Carbon dioxide and urea are both removed as wastes from cells by diffusion - so they can be excreted by the lungs (CO2) and kidneys (urea).
• What is surface area to volume ratio? (SA:Vol)

  The larger the surface area compared to the volume of a cell or organism, the faster the rate of diffusion. It needs to be fast to allow enough molecules in/out for survival.