Cell Biology

• What are eukaryotes and some examples?

  Organisms with cells containing a nucleus

  • plants
  • animals
  • fungi.
• What does the Nucleus do?

  Contains the cell's genetic material (in the form of DNA), and so controls the cell's activities.
• What do ribosomes do?

  The ribosomes are where proteins are made. We sometimes call them the site of protein synthesis. 
• What is 'cytoplasm'?

  A jelly-like material containing nutrients and salts, where chemical reactions take place
• What is the role of the mitochondria? 

  Mitochondria are the site of aerobic respiration, so they release energy for the cell. 
• What are found in plant cells but not animal cells

  Cell wall

  Permanent Vacuole

  Chloroplast
• Chloroplasts carry out the process of photosynthesis, which involves using light energy from the sun to make glucose. 

  The green pigment that absorbs the light energy is called chlorophyll. This is what makes plants green.
• What is the vacuole?

  The vacuole is a large sac in the middle of the cell that contains a watery solution of sugars and salts (cell sap). It helps maintain the structure and shape of the cell.
• The cell wall is made of cellulose. This makes it strong and allows it to maintain the shape of the cell. 
• What are prokaryotic organisms and what are some examples?

  Organisms without a nucleus

  • bacteria
• Bacteria have :

  • cell membrane
  • cell wall.
  • Plasmids
  • Flagella
  • ribosomes
  • cytoplasm
  • circular strand of DNA
• What is the definition of magnification?

  How many times larger the image is than the object
• What is the pathway of light through a microscope?

  Light source ➔ stage ➔ microscope slide ➔ object ➔ objective lens ➔ body tube ➔ eyepiece lens ➔ eye
• What are advantages of light microscopes?

  • Cheaper to buy as electron microscopes require more energy
  • Easier to use
• What are advantages of electron microscopes?

  • Used to study sub-cellular structures (organelles)
  • Have a much higher resolution
• What's the formula for magnification?

  Magnification = Image size / object size
• Steps of mitosis & cytokinesis?

  1. DNA condenses to form chromosomes.
  2. Chromosomes line up along the centre of the cells.
  3. Cell fibres pull the two arms of each chromosome to opposite sides (poles) of the cell.
  4. Cytokinesis - the entire cell divides to form two identical daughter cells.
• What are the three reasons why new cells are required?

  • Growth (we need more cells as we grow)
  • Development (we need new cell types as we develop new tissues)
  • Repair (we need to replace the cells that we lose each day)
• What is the cell cycle and what are the three stages

  The series of steps that take place as a cell grows and then divides 

  • Interphase
  • Mitosis
  • Cytokinesis
• What happens during interphase?

  During interphase, the cell grows (ribosomes and mitochondria double), replicates its DNA, and prepares for cell division.
• What happens during mitosis

   The two sets of chromosomes line up at the centre and one set of chromosomes goes to opposite poles (due to cell fibres) of the cell and the nucleus reforms around each set of chromosomes.
• What happens during cytokinesis?

  The cell membrane divides and two new daughter cells are formed.
• Are the cells created by mitosis genetically identical to each other, or genetically different? 

  Genetically identical 
• Name the two types of stem cells found in animals?

  • Adult stem cells
  • Embryonic stem cells
• What are the two key features of stem cells?

  1. They can divide by mitosis to form more cells 
  2. They can differentiate into specialised cells
• 1. When a sperm cell fertilises an egg cell they form a single cell called a zygote.
  2. This cell then divides by mitosis to form a ball of cells which we call an embryo.
  3. The cells in this embryo are known as embryonic stem cells and can differentiate into any type of cell. 
• Adult stem cells can only differentiate into different types of blood cells, e.g. white blood cells, red blood cells and platelets. 

  Whereas embryonic stem cells can differentiate into all types of cells
• Where in the body are adult stem cells found?

  Bone marrow
• What do we call the plant tissues, stem cells and where are they found?

  Meristem

  • Tips of the roots
  • Tips of the shoots
• What are disadvantages and advantages of embryonic stem cells

  • Can form all types of cells
  • Risk of rejection
  • limited supply
  • Raise ethical issues as its destroying potential life
• What are advantages and disadvantages of adult stem cells?Doesn't raise ethical issues as the donor can consent

  • Can only form blood cells
  • have to be extracted from the bone marrow which is very painful 
  • won't cause rejection as they're taken from the patient themselves
  • taken from the patient so are not in limited supply
• Explain how a sperm cell is adapted for its role.

  • It has lots of mitochondria to provide the energy for movement
  • It has a flagellum to allow it to swim to reach the egg
  • It has digestive enzymes in its head to break through the wall of the egg
• What do nerve cells do?

  transmitting electrical impulses from one part of the body, to another
• What do muscle cells do?

  Muscle cells contract and relax to generate force and enable movement in the body.
• How are red blood cells adapted for its roll?

  • Large surface area
  • No nucleus to make from for oxygen
  • lots of haemoglobin to bind to oxygen
• How are root hair cells adapted for there role?

  -Tiny hairs which include surface area for osmosis

  -Lots of mitochondria to provide energy for active transport
• What are the steps of stem cell treatment

  1. Extract embryonic stem cells from early embryos.
  2. Grow them in a laboratory.
  3. Stimulate them to differentiate into whichever type of specialised cell that we want.
  4. Give them to the patient to replace their faulty cells.
• Give drawbacks of using embryonic stems cells in stem cell therapy?

  Stem cells have a limited supply

  The risk of rejection

  Ethical issues associated with stem cells 
• What are two risks of using stem cells in medicine?

  1. The stem cells could be infected with a virus whilst in the laboratory, which could then infect the patient.
  2. As stem cells divide quickly, there is a chance they could divide uncontrollably once they've been transplanted, and then develop into a tumour. 
• What is diffusion?

  Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.