Cell Biology - Division Flashcards
Cell
The smallest structural and functional unit of an organism
Nucleus
A structure that contains genetic material and controls the activities of the cell
Chromosome
A thread like structure of coiled DNA found in the nucleus of eukaryotic cells
…and Jakub has an extra
DNA
A polymer made up of two strands forming a double helix
Gene
A section of DNA that codes for a specific protein or characteristic
Cell division (mitosis)
Cells divide in a series of stages. The genetic material is doubled and then divided into two identical cells.
Growth - Stage 1 of Mitosis
Increase the number of sub-cellular structures e.g. ribosomes and mitochondria
DNA Synthesis - Stage 2 of Mitosis
DNA replicates to form two copies of each chromosome
Mitosis - Stage 3
One set of chromosomes is pulled to each end of the cell and the nucleus divides. Then the cytoplasm and cell membranes divide to form two cells that are identical to the parent cell.
When does mitosis occur?
Mitosis occurs during growth, repair, replacement of cells.
Asexual reproduction occurs by mitosis in both plants and simple animals.
Undifferentiated cells of an organism
Divides to form more cells of the same type, and can differentiate to form many other cell types.
Human Embryonic stem cells
Can be cloned and made to differentiate into most cell types.
Therapeutic cloning uses the same genes so the body does not reject the tissue. Can be a risk of infection.
Adult bone marrow stem cells
Can form many types of human cells e.g. blood cells
Tissue is matched to avoid rejection, risk of infection. Only a few types of cells can be formed.
Meristems (plants)
Can differentiate into any plant cell type throughout the life of the plant.
Used to produce clones quickly and economically, e.g. rare species, crop plants with pest/disease resistance
Treatment using stem cells - why
Treatment with stem cells may be able to help conditions such as diabetes and paralysis. Soke people object to the use of stem cells on ethical or religious grounds (embryos in human embryonic stem cells, if you’re against abortion for some reason)
Rule of diffusion
The greater the difference in concentration, the faster the rate of diffusion.
Diffusion
No energy required
Movement of particles in a solution or gas from a higher to a lower concentration.
Example: Oxygen and Carbon dioxide in gas exchange.
Factors that affect the rate:
- concentration
- surface area
- temperature
Osmosis
No energy required
Movement of water from a concentrated solution to a dilute solution through a semi permeable membrane
Example: Plants absorb water from the soil by osmosis through their root hair cells. Plants use water for several vital processes, including photosynthesis and transporting minerals.
Active transport
Energy required
Movement of particles from a dilute solution to a more concentrated solution
Examples: movement of mineral ions into roots of plants, movement of glucose into the small intestines.
Adaptations for diffusion in Small Intestines
Villi - increase surface area
Good blood supply - to maintain concentration gradient
Thin membranes - short diffusion distance.
Adaptations for diffusion in the lungs
Alveoli - increase surface area
Good blood supply - to maintain concentration gradient
Thin membranes - short diffusion distance.
Adaptations for diffusion in the gills of fish (why we need to know this is a mystery)
Gill filaments and lamelia - increase surface area
Good blood supply - to maintain concentration gradient
Thin membranes - short diffusion distance.
Adaptation for diffusion in roots
Root hair cells - increase surface area.
Adaptation for diffusion in leaves
Large surface area
Thin leaves for short diffusion path
Stomata on the lower surface to let oxygen and carbon dioxide in and out.
