1.1 cell biology Flashcards
cell theory states that
- all living organisms are made of one or more cells
- the cell is the basic unit of structure and organization in organisms
- all cells come from other cells
what are 3 exceptions to cell theory?
Striated muscle fibres, Aseptate fungal hyphae, and giant algae
why are striated muscle fibers an exception to cell theory?
- Muscle cells fuse to form very long fibres (>300mm)
- multi-nucleated
- Challenges the idea that cells always function as autonomous units
why is Aseptate fungal hyphae an exception to cell theory?
- continuous cytoplasm
- challenges the idea that cells are individual units
why is giant algae an exception to cell theory?
- giant, grow up to 100mm in length w only 1 nucleus
- challenges the idea that larger organisms are always made of many microscopic cells
acronym for functions of life
mr h gren
functions of life
metabolism
response
homeostasis
growth
reproduction
excretion
nutrition
metabolism
all the enzyme-catalyzed reactions in the cell or organism. this includes respiration
response
the ability to respond to and interact with the environment
homeostasis
the maintenance and regulation of internal cell conditions
growth
changing size/shape
reproduction
producing offspring by sexual or asexual reproduction
excretion
the removal of metabolic waste
nutrition
obtaining organic molecules via absorption (eg feeding) or synthesis (eg photosynthesis)
heterotroph
an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter (consumers, not producers)
functions of life in paramecium
M - metabolic reactions mostly in cytoplasm, respiration in mitochondria
R - cilia feel particles in the surrounding environment
H - contractile vacuole regulate water content by expelling water from the cell membrane
G - gain biomass
R - cell division (mitosis)
E - the cell membrane regulates excretion. vesicles release materials (exocytosis)
N - the cell membrane surrounds food and takes it into the cell (endocytosis)
paramecium
genus of unicellular heterotroph protozoans
chlorella
photosynthetic unicellular organism
functions of life in chlorella
M - metabolic reactions in cytoplasm, photosynthesis in chloroplast, respiration in mitochondria
R - adapts to light and concentrations of solutes in environment
H - large central vacuole to store and regulate water content
G - gain biomass
R- mitosis
E - cell membrane regulates transport out of the cell (ex: exocytosis)
N - photosynthesis produces organic carbon compounds (biomass)
why is sa:vol ratio important in the limitation of cell size?
- more surface area means more surfaces for transport across the membrane
- less volume means particles can move thru-out the cell in a shorter time
- small cells tend to have a large sa:vol ratio
- transport (ex: diffusion) is more efficient when a cell has a high sa:vol ratio
structure of multicellular organisms
atoms → molecules → cells → tissues → organs → organ systems → multicellular organism
why are multicellular organisms’ cells differentiated?
to carry out diff functions
examples of differentiated cells
red blood cells, nerve cells, female reproductive/egg cell, male reproductive/sperm cell
function & special features of red blood cells
function: to carry oxygen
features:
* large sa for oxygen to pass thru
* contains haemoglobin, which joins w oxygen
* no nucleus
function & special features of nerve cells
function: to carry nerve impulses to diff parts of the body
features:
* long
* connections at each end
* can carry electrical signals
function & special features of egg cells
function: to join w male cell, and then to provide food for the new cell that’s been formed
features:
* large
* contains lots of cytoplasm
function & special features of sperm cells
function: to reach female cell, and join it
features:
* long tail for swimming
* head for getting into female cell
how to cells become different?
- not all genes are activated in all cells
- only some genes are expressed. ex: the set of genes expressed in a skin cell will differ from the genes expressed in a red blood cell
stem cells
unspecialized cells that continuously divide and specialize into diff cells
3 types of stem cells
totipotent, pluripotent, multipotent
totipotent stem cells
can form any cell type, as well as extra-embryonic (placental) tissue (e.g. zygote)
pluripotent stem cells
can form any cell type (e.g. embryonic stem cells)
multipotent stem cells
can differentiate into a number of closely related cell types (e.g. haematopoeitic adult stem cells)
unipotent stem cells
can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)
potential uses of stem cells
- replacing/repairing damaged tissues, particularly nervous tissue, heart tissue and blood cells in leukemia patients
- treatment of diseases such as Parkinson’s and diabetes
- testing effects of toxins or drugs on various tissues
- testing gene therapy techniques
- growing new organs
why is the use of embryonic stem cells controversial?
it results in the destruction of the embryo which may be considered a living organism
induced pluripotent stem cells (iPSC)
the turning of adult cells into stem cells via nuclear transfer
Stargardt’s macular dystrophy
- an inherited disease that results in the eventual loss of vision in young people
- a mutation in the gene causes a transport protein to malfunction in retinal photoreceptors (light sensitive cells)
use of stem cells to treat Stargardt’s macular dystrophy
- recent clinical trials have used embryonic stem cells to create retinal cells that are injected in the retina. these cells attach to the retina, become functional, and improve vision
- still undergoing clinical trials
leukemia
originates in the bone marrow. production of a high number of abnormal leukocytes (white blood cells). risk factors include ionizing radiation, chemicals (benzene), chemotherapy
what stem cells are used in the treatment of leukemia?
multipotent (adult) hematopoietic stem cells from a bone marrow donor, who needs to have the same antigens on their leukocytes as the host
how do the stem cells function in the treatment of leukemia?
- recipient’s immune system is destroyed (radiation or chemotherapy)
- stem cells are transplanted into the bone marrow and proliferate
- after a few weeks blood cell counts normalize and the immune system regenerates
benefit + risks of using stem cells to treat leukemia
benefit: a chance to cure or provide long-term remission, with increasing survival rates
risk to donor: drug interactions, pain from procedure
risk to recipient: can lead to death from infection (before or after transplant), or rejection of host cells
typical size of bacteria
1 micrometer
typical size of plant/animal cell
100 micrometers
typical size of virul
100nm
