Cell biology 2 (B1) Flashcards
cell
smallest structural and functional unit of an organism
nucleus
a structure that contains genetic material and controls the acuity of the celll
chromosome
a thread like structure of coiled DNA found in the nucleus of a eukaryotic cell
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
stage one cell Division
growth
increase number of sub-cellular structures e.g ribosomes and mitochondria
stage 2 of cell division
DNA synthesis
DNA replicates to form two copies of each chromosomes
stage 3 of cell division
Mitosis
- 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
during growth, repair, replacement of cells
when does asexual reproduction occur
by mitosis in both plants and simple animals
how are the small intestines adapted for diffusion
villi- increase surface area, good blood supply to maintain concentration gradient , thin membrane- short diffusion distance
how are the lungs adapted for diffusion
Alveoli- increase surface area, good blood supply to maintain concentration gradient , thin membrane- short diffusion distance
how are the gills in fish adapted for diffusion
Gill filaments and lamella - increase surface area, good blood supply to maintain concentration gradient , thin membrane- short diffusion distance
how are the roots adapted for diffusion
root hair cells - large surface area
how are the leaves adapted for diffusion
large surface area, thin leaves for short diffusion path, stomata on the lower surface to let oxygen and carbon dioxide in and out
Diffusion
movement of particles in a solution from a higher concentration to a lower concentration
does diffusion require energy
NO
Osmosis
movement of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane
e.g plants absorbing water from soil
Active transport
movement of water molecules from a dilute solution to a more concentrated solution
e.g movement of mineral ions into roots
does osmosis require energy
no
does active transport require energy
yes
adaptions for diffusion
the greater the difference in concentrations the faster the rate of diffusion
human embryonic stem cells
can be cloned and made to differentiate into most cells types
adult bone marrow stem cell
can form many types of human cells e.g blood cells
meristems
can differentiate into any plant cell type throughout the life of the plant
