cell biology

• diffusion

  movement of particles from an area of high concentration to an area of low concentration
• concentration gradient

  change in the concentration of a substance from one region to another
• osmosis

  movement of water through a partially permeable membrane into a solution with a lower water concentration
• active transport

  movement of substances against a concentration gradient and requires energy
• chromosomes

  long molecules in the nucleus of all cells

  made from DNA
• DNA

  nucleic acid molecules that contain genetic information and make up chromosomes
• gene

  part of a chromosome

  made of DNA which codes for a protein
• cell cycle

  the series of growth and division events during a cell's life
• mitosis

  cell division that forms two daughter cells, each with the same number of chromosomes as the parent cell
• stem cell

  cells that have not undergone differentiation
• embryonic stem cells

  cells in an embryo that can differentiate into any type of cell
• adult stem cells

  cells that can differentiate into limited types of cell
• therapeutic cloning

  clones that are produced to treat diseases and will not be allowed to develop into new offspring
• meristems

  areas of cells in plants that can divide to form new cells
• resolution

  the smallest distance apart two objects can be and still be seen as separate objects
• electron microscope

  a device that fires electrons at a specimen to obtain a high resolution image
• magnification

  how many times larger an image is than the real thing
• nucleus

  the control centre of a cell
• cytoplasm

  substance outside the nucleus where chemical reactions take place
• cell membrane

  holds the cytoplasm and controls what enters and leaves the cell
• mitochondria

  structures in the cytoplasm where energy is produced
• ribosomes

  small structures in the cytoplasm where protein synthesis occurs
• cell wall

  a protective layer that helps to support the cell
• cellulose

  a carbohydrate that makes up the cell wall of plants
• vacuole

  a fluid-filled cavity in a cell that is used for storage and support

  only in a plant cell
• chloroplast

  a structure containing chlorophyll found in plants and algae

  absorb light to make food by photosynthesis
• prokaryotic

  organisms without a nucleus or organelles such as mitochondria
• eukaryotic

  cells with a nucleus and sub-cellular organelles such as mitochondria
• plasmid

  a small circle of DNA separate from the main bacterial chromosome
• magnification

  magnification= size of image \size of real image
• chromosomes

  each chromosome carries hundreds-thousands of genes
• humans have 23 pairs of chromosomes
• flagella

  tail-like structures that rotate to help some bacteria move

  ONLY IN BACTERIA CELLS
• stages of mitosis

  1. one set of chromosomes is pulled to each end of the cell.
  2. the nucleus divides.
  3. the cytoplasm and cell membranes divide to form two identical cells.
• mitosis makes new cells for:

  growth and development of multicellular organisms

  repairing damaged tissues

  asexual reproduction
• adult stem cells are found in bone marrow
• stem cells can help to treat conditions where cells are damaged or not working properly 


  diabetes

  paralysis
• some people are concerned about using stem cells from cloned embryos as:

  they may be infection risks

  they may have ethical or religious objections
• examples of diffusion in living organisms

  1. oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves.
  2. urea diffuses from cells into the blood plasma for excretion by the kidney.
  3. digested food molecules from the small intestine diffuse into the blood
• active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil.

  also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood, which has a higher concentration.