Cell structure & organisation Flashcards
are there any bonds holding the PL bilayer?
no. they naturally form this configuration due to their nature of hydrophilic and hydrophobic components
phospholipids remain in the same position and cannot move. is this correct?
no. they are able to move horizontally around the membrane. (just not vertically)
a phospholipid with more saturated fatty acids will have more fluidity. is this correct?
yes. the fact that they have a double bond that causes a bend in the structure means PLs are less able to pack tightly together, increasing fluidity
a PL bilayer which is less fluidity has more of which type of fatty acid in the PLs?
unsaturated
besides saturated fatty acids, what else helps with fluidity in PL bilayers? how?
cholesterol. this does so by binding to the hydrophobic regions of the PL and holding PLs apart from each other, so they are not tightly packed together
when the temperature increases, how does cholesterol maintain the PL bilayer structure?
it holds phospholipids together so they do not move too far apart
when the temp decreases, how does cholesterol ensure that the cell membrane doesn’t get too rigid?
prevents phospholipids from packing tightly together
cholesterol is only a polar molecule. t/f and explain
f.
it is amphipathic (both polar and non polar regions)
has a hydrophilic head that associates with the hydrophilic region of the PL and a hydrophobic tail
cell membranes are mosaic in appearance.. what does this mean?
contains a mixture of lipids and proteins, which has the appearance of a mosaic
types of membrane proteins
integral and peripheral
integral proteins are…
embedded in the bilayer and are permanently associated with the membrane- hydrophobic regions of molecule associate with hydrophobic region of bilayer
peripheral proteins are…
not permanently attached to the membrane, only found on one side of the membrane and are interacting with something attached to the membrane, such as a fatty acid
molecules that are……… ……… or ………. are able to pass easily through the membrane
small, uncharged, non polar
some molecules are still able to pass through the membrane but it is more difficult… what properties do they have?
they are small but charged/polar. large molecules are not able to pass through the membrane easily
purpose of enzymes on the surface of membrane
facilitates the conversion of one molecule to another
anchor molecules on the cell membrane…
associate with other cells (allows adhesion) or allow a cell to bind with an abiotic surface
endomembrane system…
divides the cell into different compartments, which allows for specific conditions within the cell
endomembrane system involves all but what organelles?
mitochondria, chloroplasts, peroxisome
function of the nucleus
it is where the majority of the cells dna is stored
transcription of proteins occurs here
what is the nucleolus?
a smaller, non membrane bound compartment in the nuclear envelope which codes for rRNA and the assembly of ribosomal subunits
types of ER
smooth-no ribosomes
rough- ribosomes
function of rough ER
production of proteins
smooth ER
does not produce proteins but metabolises carbohydrates, creates lipids, phospholipids and steroid hormones
function of vesicles
movement of molecules from the ER to golgi
exo and endocytosis
golgi apparatus
modifies and sorts proteins and lipids produced by the ER, ensures they get to their destination and is the site of synthesis of most carbohydrates in the cell
lysosomes
contain enzymes that degrade macromolecules. derived from the golgi
vacuoles
- only in plants or single celled animals
- stores ions, toxic waste products
- water storage and uptake
peroxisomes
detoxification
transfer hydrogen from various compounds to oxygen, forming hydrogen peroxidase
glyoxysomes
specialised peroxisomes in plants
break down fat reserves in seeds to produce sugars for seed growth
mitochondria
energy synthesis- conversion of sugars to ATP
chloroplast
photosynthesis in plants and algae
- creation of sugars from light and water
cytoskeleton
network of protein filaments involved in the movement of cells, vesicles, organelles, responsible for the overall structure of the cell and its shape
