Biological Membranes Flashcards
membranes 3 main roles
cell signalling, site of chemical reactions & barrier to X’s environment
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example of membranes as sites for chemical reactions: chloroplasts
thylakoids contain chlorophyll = photosynthesis
true or false facillitated diffusion uses ATP
false
True or False carrier proteins can do both facilitated diffusion & active transport
True and false - carrier proteins collectively can do both, but individual ones are specialized do one or the other;.
why is chemical signaling important
for cell to stay in contact with the environment & adjacent cells
Why can chemical signals trigger a response
in some cells and not others?
Only target cells carry the complementary receptor molecule for the
signal
what factor increases the number of different types of cell signaling receptors on a plasma membrane in the fluid mosaic model, other than proteins amino acids & shape?
carbohydrate chains attached to glycoprotein & glycolipid receptors increases variation
what is the total thickness of a cell membrane
5-10nm
who proposed the fluid mosaic model
Singer & Nicolson
what is the diameter of a water-filled protein channel
0.8nm
what are the 2 types of diffusion
facilitated & simple
crenated cell meaning
an ANIMAL cell that has lost water by osmosis
plasmolysis meaning
the process in which cells lose water in a hypertonic solution
hypertonic meaning
lowER solute concentration
turgid meaning
refers to cells or tissues that are swollen from water uptake
hypotonic meaning
low solute concentration
cytolysis meaning
IN ANIMAL CELLS ONLY: when cell swells due to water uptake, causing plasma membrane to burst releasing the cells contents into the extracellular environment
plasmolysed definition
a word to describe the shape of a plant CELL after water loss: cytoplasm of cell shrinks and membrane pulls away from cellulose cell wall
what are transport proteins
protein carriers & channels
name 2 passive transport processes
simple diffusion & facilitated diffusion
what is the difference between facilitated diffusion & simple diffusion
in facilitated molecules move across a partially permeable membrane (1) via protein channels/carriers
what are the similarities between glycolipids & glycoproteins in function and structure
- both are antigens
- both have attached carbohydrate chains
what other functions do glycoproteins do that glycolipids don’t
- receptors for chemical signalling
- cell adhesion
cholesterol function
stablailes phospholip bilayer & regulated fluidity
does an increase in cholesterol increase fluidity or decrease it
decreases permability & fluidity
what moleculues can pass through membrane freely in fluid mosaic model
water, oxygen & co2, steroid hormones
name 2 intrinsic proteins
carrier proteins & protein channels
are lipids soluble in phospholipid bilayer?
true, soluble
how is the concentration gradient maintained in a cell
molecules entering the cell are passed onto organelles to use in metabolic reactions = lowering their concentration in the cytoplasm
where does active transport occur at the cell membrane
carrier proteins e.g aqua porins for water
how do carrier proteins work
large molecules bind to carrier proteins (1) which changes shape to allow molecules to pass through
true or false carrier proteins can carry out facilitated diffusion on any molecule
false- specific to the molecule
name 5 things impacting the rate of simple diffusion
- temperature
- diffusion distance
- surface area
- size of diffusing molecule
- concentration gradient
Do smaller molecules diffuse faster than larger molecules
Yes, only applicable for partially permeable membrane
how do (organic) solvents affect the rate of simple diffusion
increase in solvents = dissolves & disrupts cell membrane = increase in fluidity & permeabliliyty
give an example of an organic solvent
benzene (non-polar alcholol)
intrinsic proteins defintiion
embedded through both layers of a partially permeable membrane
extrinsic proteins defintiion
present in 1 side of bilayer & could move between layers
true or false extrincis proteins are fixtated in their position in the phospholipid bilyayer
false
PAG what is the pigment that is released from beetroot
betalain
what does ethanol do to cell membranes
dissolves lipids in cell membrane
what impact does increase in temperature have on membrane
creates temproary pores
active trnasportdefinition
movement of particles across a plasma membrane (1) against a concentration gradients (2) energy is recquiresd (3)
what organelle is used in active transport across a cell surface membrane
carrier protein
what organelle is used in facilitated diffusion across a cell surface membrane
channel protein
what does ATP stand for
adensosine triphosphaye
what does ADP stand for
adenosine diphosphate
give exampels of active transport usages
glucose in small intestine into cappilaries
what is bulk transport
used got transporting molecules that are too big for protein carriers
what are vesicles
small membrane-bound sacs
Name 2 times when ATP is needed during exocytosis
to form vesicles and to move them to the cell surface mambrane
give the 3 step process to endocytosis
segment of cell surface membrane surrounds & encloses the particles (1) & brings it into the cell (2), enclosed in a vesicle(3)
how are vesicles transported along the cytoskeleton
motor proteins along the cytoskeleton move vesciles
endocytosis process (3)
a membrane-bound vesicle is transported towards the cell membrane (1) membrane and vesicle fuse together (2), fused site opens up, secreting the large particle (3)
example of exocytosis process
vesicles in synapses got transmitting chemical signals
In endocytosis what is the process called when a solid molecule is engulfed? give an example
phagocytosis, e.g white blood cell engulfing bacteria
In endocytosis what is the process called when a liquid molecule is engulfed?
pinocytosis
what are aquaporins
protein channels specifically for water, to allow fasterd iffusion into the cell
what is flaccid
an adjective to describe plant TISSUE with plasmolyzed cells
difference ebtween flaccid and plasmolyzed?
plasmolyzed talks about cell, flaccid talks about tissue
do carrier proteins use facilitated diffusion or active transport
both
water potential defintion
the pressure exerted by water molecules as they collide with a membrane or container
what is water potential units
Pascals or Kilo pascals (KPa)
what is the water potential of pure water?
0KPa
True or false all solutions have a positive water potential?
false, all are under 0Kpa
Complete the phrase: the higher the solute concentration in a solution the ___ the water potential
lower the water potential
hydrostatic pressure definition
the pressure created by water in a closed system e.g in a cell; measured in KPa
How do multicellular animal cells prevent crenation or cytolysis occuring?
make sure cells are continuously surrounded by solutions with equal water potential
