bio topic one cell bio

• Animal and plant cells are eukaryotic.

  They have a:

  . Cell membrane

  . Cytoplasm

  . Nucleus containing DNA
• Bacterial cells are prokaryotic and are much smaller. They have a:

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids (small rings of DNA found in the cytoplasm)
• In animal and plants cell:

  Stucture:

  • Nucleus

  Function:

  • Contains DNA coding for a particular protein needed to build new cells.
  • Enclosed in a nuclear membrane.
• Structure:

  • Cytoplasm

  Function:

  • Light substance in which chemical reaction occur
  • Contains enzymes (biological catalys, I.e. protein that speed up the rate of reaction).
  • Organelles are found in it
• Structure:

  • cell membrane

  Function:

  • Controls what enters and leaves the Cell
• Structure:

  • Mitochondria

  Function:

  • Where aerobic respiration reactions occur, providing energy for the cell
• Structure:

  • Ribosomes

  Function:

  • Where protein synthesis occurs.
  • Found on a structure called the rough endoplasmic reticulum.
• Only in plant cell:

  Structure:

  • chloroplasts

  Function:

  • Where photosynthesis takes place, providing food for the plant
  • Contains chlorophyll pigment (which makes it green) which harvests the light needed for photosynthesis.
• Structure:

  • Permanent vacuole

  Function:

  • Contains cell sap
  • Found within the cytoplasm
  • Improves cell's rigidity
• Stucture:

  • cell wall (also present in algal cells)

  Function:

  • made from cellulose
  • provides strength to the cell
• In bacteria cells

  • cytoplasm
  • cell membrane
• Structure:

  • cell wall

  Function:

  • Made of a different compound (peptidogylcan)
• Structure:

  • Single circular strand of DNA

  Function:

  • As they have no nucleus, this floats in the cytoplasm
• Structure:

  • plasmid

  Function:

  • small rings of DNA
• Prefix:

  • centi

  Multiply units by….

  • 0.01
• Prefix:

  • Milli

  Multiply units by…

  • 0.001
• Prefix:

  • Micro

  Multiply units by….

  • 0.000,001
• Prefix:

  • Nano

  Multiply units by

  • 0.000, 000, 001
• Examples of specialised cells in animals:

  1. Sperm cells:

  • specialised to carry the male's DNA to the egg cell (ovum) for successful reproduction
  • Streamlined head and long tail to aid swimming
  • Many mitochondria (where respiration happens) which supply the energy to allow the cell to move
  • The acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell
• 2. Nerve cells:

  • specialised to transmit electrical signals quickly from one place in the body to another
  • The axon is long, enabling the impulses to be carried along long distances
  • Having lots of extensions from the cell body (called dendrites) means branched connections can form with other nerve cells
  • The nerve endings have many mitochondria which supply the energy to make special transmitter chemicals called neurotransmitters. These allow the impulse to be passed from one cell to another.
• 3. Muscle cells:

  • specialised to contract quickly to move bones (striated muscle) or simply to squeeze (smooth muscle, e.g found in blood vessels so blood pressure can be varied), therefore causing movement
  • Special proteins (myosin and actin) slide over each other, causing the muscle to contract
  • Lots of mitochondria to provide energy from respiration for contraction
  • They can store a chemical called glycogen that is used in respiration by mitochondria
• Examples of specialised cells in plants

  • Root hair cells:.
  • specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots
  • Have a large surface area due to root hairs, meaning more water can move in
  • The large permanent vacuole affects the speed of movement of water from the soil to the cell
  • Mitochondria to provide energy from respiration for the active transport of mineral ions into the root hair cell
• 2. Xylem cells:

  • specialised to transport water and mineral lons up the plant from the roots to the shoots
  • Upon formation, a chemical called lignin is deposited which causes the cells to die. They become hollow and are joined end-to-end to form a continuous tube so water and mineral ions can move through
  • Lignin is deposited in spirals which helps the cells withstand the pressure from the movement of water
• 3. Phloem cells:

  • specialised to carry the products of photosynthesis (food) to all parts of the plants
  • Cell walls of each cell form structures called sieve plates when they break down, allowing the movement of substances from cell to cell
  • Despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of the companion cells.
• Light microscope:

  • It has two lenses, an objective and eyepiece
  • The objective lense produces a magnified image, which is then magnified and directed into the eye by the eyepiece lense
  • It is usually illuminated from underneath
  • They have, approximately, a maximum magnification of ×2000 and a resolving power (this affects resolution: the ability to distinguish between two points) of 200mm (the lower the RP, the more detail is seen)
  • Used to view tissues, cells and large sub-cellular structures
• Electron microscope:

  • enabling scientists to view deep inside sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids.
• Electron microscope:

  • Electrons, as opposed to light, are used to form an image because the electrons have a much smaller wavelength than that of light waves
  • There are two types: a scanning electron microscope that create 3D images (at a slightly lower magnification) and a transmission electron microscope which creates2D images detailing organelles
  • They have a magnification of up to x2,000,000 and resolving power of 10mm (SEM) and 0.2m (TEM)
• Common calculation:

  • Magnification of a light microscope: magnification of the eyepiece lens x magnification of the objective lens
  • Size of an object: size of image/magnification = size of object (this formula canbe rearranged to obtain the other values, make sure you are in the same units!)
• Chromosomes:

  The nucleus contains your genetic information.

  • This is found in the form of chromosomes, which contain coils of DNA.
  • A gene is a short section of DNA that codes for a protein and as a result controls a characteristic- therefore each chromosome carries many genes.
  • There are 23 pairs of chromosomes in each cell of the body, as you inherit one from your mother and one from your father - resulting in 46 chromosomes in total in each cell.
  • Sex cells (gametes) are the exception: there are half the number of chromosomes, resulting in 23 chromosomes in total in each gamete cell.
• Mitosis and the cell cycle:

  • The cell cycle is a series of steps that the cell has to undergo in order to divide. Mitosis is a step in this cycle- the stage when the ceil divides.
• Cell cycle:

  • Stage 1 (Interphase): In this stage the cell grows, organelles (such as ribosome and mitochondria) grow and increase in number, the synthesis of proteins occurs, DNA is replicated (forming the characteristic 'X' shape) and energy stores are increased
  • Stage 2 (Mitosis): The chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the 'X' to either side of the cell.
  • Stage 3 (Cytokinesis): Two identical daughter cells form when the cytoplasm and cell membranes divide
• Stem cells:

  • A stem cell is an undifferentiated cell which can undergo division to produce many more similar cells, of which some will differentiate to have different functions.
• Types of stem cells:

  1. Embryonic cells

  • Form when an egg and sperm cell fuse to form a zygote. They can differentiate into any type of cell in the body
  • Scientists can clone these cells (though culturing them) and direct them to differentiate into almost any cell in the body
  • These could potentially be used to replace insulin-producing cells in those suffering from diabetes, new neural cells for diseases such as Alzheimer's, or nerve cells for those paralysed with spinal cord injuries
• 2. Adult stem cells

  • If found in bone marrow they can form many types of cells including blood cells
• 3. Meristems in plants

  • Found in root and shoot tips
  • They can differentiate into any type of plant, and have this ability throughout the life of the plant
  • They can be used to make clones of the plant- this may be necessary if the parent plant has certain desirable features (such as disease resistance), for research or to save a rare plant from extinction
• Therapeutic cloning:

  • involves an embryo being produced with the same genes as the patient.
• Therapeutic cloning:

  • The embryo produced could then be harvested to obtain the embryonic stem cells.
  • These could be grown into any cells the patient needed, such as new tissues or organs.
  • The advantage is that they would not be rejected as they would have the exact same genetic make-up as the individual.
• Benefit of research with stem cells:

  • Can be used to replace damaged or diseased body parts.
  • Unwanted embryos from fertility clinics could be used as they would otherwise
  • Research into the process of differentiation.
• Cell division: A process whereby a cell divides into two or more daughter cells. There are three main stages involved in cell division: interphase, mitosis and cytokinesis.
• Differentiation: The process whereby a single cell divides repeatedly until there are two identical daughter cells. These divide again and continue to do so until there are thousands of genetically identical cells. Some of these cells begin to specialise and become more complex than others. This results in a variety of differentiated cells within the organism.