Topic One - Cell Biology

• Which types of cells are eukaryotes?

  Animal and plant cells
• Which organelles do eukaryotes have? How is their genetic information stored?

  Cytoplasm and a cell membrane surrounded by a cell wall. Their genetic material is not enclosed in a nucleus, instead is is a single, circular strand of DNA (and the cell may have more small rings of DNA called plasmids).
• Which cells are bigger, eukaryotes or prokaryotes?

  Prokaryotic cells are much smaller than eukaryotes.
• What type of cell are bacteria?

  Prokaryotes
• Nucleus


  Contains genetic material that controls the activities of the cell.
• Cytoplasm


  The gel-like substance where most of the chemical reactions happen in the cell. It contains enzymes that control these chemical reactions.
• Cell membrane


  It holds the cell together and control what goes in and out of the cell
• Mitochondria


  Contain the enzymes for respiration, and where most energy is released in respiration, the cell needs this energy to work.
• Ribosomes


  Where proteins are made in the cell.
• Chloroplasts


  Where photosynthesis occurs, makes food for the plant. Contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.
• Permanent vacuole


  Contains cell sap, a weak solution of sugar and salts, helps keep the cell turgid.
• What organelles do plant cells have?

  All of the organelles in animal cells (cytoplasm, nucleus, cell membrane, mitochondria and ribosomes) as well as a cell wall, vacuole and chloroplasts.
• What organelles do animal cells have?

  Cytoplasm, nucleus, cell membrane, mitochondria and ribosomes.
• How do you prepare a slide?

  1) Add a drop of water to the middle of a clean slide.

  2) Place sample onto slide. Add drop of iodine solution as stain.

  3) Place cover slip carefully with needle, avoiding bubbles.
• How do you use a light microscope?

  1) Clip the slide onto the stage and select the lowest-powered objective lens.

  2) Use a coarse adjustment knob to move the stage up to just below the objective lens.

  3) Look down into the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is in focus.

  1) Adjust the focus with the fine adjustment knob, until you get a clear image of what is on the slide.

  2) If you need greater magnification, swap to a higher-powered objective lens.
• What is a specialised cell?

  A cell that has a particular structure and composition of subcellular structures that help it perform a specific function.
• What is a sperm cell's function and how is it adapted for that function?

  The sperm cell's function is to get the male DNA to the female DNA in the egg. It has a long tail and a streamlined head to help it swim. It has a lot of mitochondria in the cell to provide the energy needed for swimming. It carries enzymes in its' head to digest through the egg's cell membrane.
• What is a nerve cell's function and how is it adapted for that function?

  Nerve cells' function is to carry electrical signals from one part of the body to another. They are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
• What is a muscle cell's function and how is it adapted for that function?

  Muscle cells' function is to contract quickly. They are long so that they have more space to contract and contain lots of mitochondria to generate energy needed for contraction.
• What is a root hair cell's function and how is it adapted for that function?

  Root hair cells' function is to absorb water and minerals from the soil. They grow into long 'hairs' that stick out into the soil to provide a large surface area for faster diffusion
• What is a xylem cell's function and how is it adapted for that function?

  Xylem cells' function is to transport water and mineral ions from the roots to the rest of the plant. Xylem cells are hollow in the centre so that they can flow through them.
• What is a phloem cell's function and how is it adapted for that function?

  Phloem transport food substances like dissolved sugars, made of columns of elongated living cells that have very few subcellular structures so that they are thin for diffusion.
• What is differentiation?

  Differentiation refers to the process by which unspecialized or less-specialized cells acquire specialized structures and functions, it is important as otherwise, multicellular organisms would not be able to have multiple types of tissues
• When does differentiation occur?


  Most differentiation occurs as the organism develops, in most animal cells the ability to differentiate is then lost at an early stage, after they become specialised.

  Many types of plant cells retain the ability to differentiate throughout life.
• What is differentiations' use in animals?

  In mature animals, cell division is mainly restricted to repair and replacement. As a cell differentiates it acquires different subcellular structures to enable it to carry out a certain function. It has become a specialised cell.
• Why are electron microscopes better?

  An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
• What is the magnification equation?


  magnification = size of image /size of real object
• What are chromosomes?

  The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes. In body cells the chromosomes are normally found in pairs. There are 23 pairs in the human body, 46 in total.
• What is the cell cycle?

  Cells divide in a series of stages called the cell cycle
• What are the three stages in the cell cycle?

  Interphase, mitosis and cytokinesis.
• What happens during interphase?

  In a cell that is not dividing, DNA is spread out in long strings. Before it divides the cell has to grow and increase the number of subcellular structures such as mitochondria and ribosomes. It then duplicates it's DNA so there is one copy for each cell. The DNA is copied and forms X-shaped chromosomes. Each arm is an exact duplicate of the other.
• What happens during cytokinesis?

  During cytokinesis, the cell membrane divides, and two new daughter cells are formed.
• What happens during mitosis?

  Mitosis is a stage in the cell cycle when the nucleus divides.

  1)Chromosomes line up at centre (equator) of the cell

  2) spindle fibres pull them apart; each arm goes to an opposite end (or pole) of the cell

  3) Membranes then form a round each of the sets of chromosomes these become the nuclei of the two new cells.

  4)Then cytokinesis occurs, and two new identical daughter cells have been produced, also identical to the parent cell.
• Give a brief summary of the cell cycle?

  During the cell cycle the genetic material is doubled and then divided into two identical cells. Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome. In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides. Finally, the cytoplasm and cell membranes divide to form two identical cells.
• What is mitosis important for?

  The growth and development of multicellular organisms?
• What is a stem cell?

  A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation
• Why are human embryos important?

  Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells. They are pluripotent.
• Where can stem cells be found in adult humans?

  The bone marrow. They can differentiate into many type of cells including red and white blood cells.
• What is therapeutic cloning?

  In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment. The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.
• What can stem cells help treat?

  Treatment with stem cells may be able to help conditions such as diabetes and paralysis.