cells + membranes Flashcards
plasma membrane
regulates movement of substances in and out of the cell
has receptors
made of phospholipids and proteins (carriers and channels)
glycoproteins and lipids
cholesterol
nucleus
surrounded by nuclear envelope containing nuclear pores
contains nucleolus
contains chromosomes (DNA on histones)
controls cells activities by
controlling transcription
contains DNA which has instructions to make protiens
pores allow substances to move between nucleus and cytoplasm
nucleolus makes ribosomes
mitochondria
double membrane (inner and outer)
inner membrane folded into cristae
inside is matrix
contains enzymes for respiration
site of aerobic respiration
where ATP released
chloroplast
found in plants and algae
double membrane
contains thylakoid membranes
stacked into grana
linked by lamellae (thin pieces of thylakoid membrane)
stroma - fluid (like cytoplasm)
site of photosynthesis
in stroma or grana
golgi apparatus and vesicles
fluid filled flattened sacs
processes and packages new lipids and proteins
makes lysosomes
makes vesicles
vesicles are fuid filled sacs in cytoplasm
stores lipids and proteins made by golgi
transports them out of cell
lysosomes
round surrounded by membrane
type of golgi apparatus
contains lysozymes
used to digest pathogens
break down worn out cell components
ribosomes
in cytoplasm or attached to RER
made of a small and large subunit
made of protein and rRNA
(no membrane)
site of proteinsynthesis
rough endoplasmic reticulum
fluid surrounded by membranes
has ribosomes on surface
folds and processes proteins
from ribosomes
smooth endoplasmic reticulum
same as RER but without ribosomes
synthesises and processes lipids
cell vacuole
in plant cells
membrane bound - tonoplast
in cytoplasm
contains sap
maintain pressure in cell to keep it rigid - no wilting
cell wall
rigid structure surround some
supports cells, keeps shape
plants and algae - cellulose
fungi - chitin
bacteria - murein
differences between prokaryotic and eukaryotic cells
DNA is circular not linear
DNA not is nucleus but free in cytoplasm
DNA not associated with proteins
have plasmids
have cell wall of murein
smaller ribosomes (70s)
no membrane bound organelles
structure of prokaryotic cells
plasma membrane
cell wall of murein (glycoprotein)
cytoplasm - no membrane bound organelles
just ribosomes (smaller)
plasmids - small loops of DNA
(not part of main circular DNA)
DNA free in cytoplasm
(no nucleus)
no histones (proteins)
circular
flagellum - makes cell move
capsule - made of smile to protect from attack
structure of a virus
acellular - not cells and not live
no plasma membrane
no cytoplasm
no ribosomes
survive and reproduce in host cells
core of genetic material (DNA or RNA)
capsid - protein coat round core
attachment proteins - stick out from capsid, allow to attach to host
cells to organs
tissues
a group of cells working together to perform a particular function
organs
different tissues working together
organ systems
organs working together to complete a function
how do prokaryotic cells replicate?
binary fission
- circular DNA and plasmids replicate
(DNA once but plasmid many times) - cell grows, DNA moves to opposite poles
- cytokenesis
= 2 daughter cells
one copy of DNA, variable number of plasmids
how do viruses replicate?
use attachment proteins to bind to complementary receptors in hosts
(different viruses have different attachment proteins, require different hosts, viruses only affect certain cells)
inject genetic material into host
uses hosts enzymes and ribosomes to replicate
how to calculate magnification
size of image
over
size of real object
optical microscopes
use light to form an image
low magnification - up to x1500
low resolution - 0.2 micrometres
how to prepare a slide for an optical microscope
pipette small drop of water onto slide
use tweezer to place thin specimen
add a drop of stain
carefully lower cover slip, one side then the other to avoid air bubbles
transmission electron microscopes
uses beam of electrons
transmitted through specimen
denser parts absorb more - darker
+ highest resolution - see internal organelles
- only used on thin specimins
scanning electron microscopes
scan beam of electrons across specimen
knocks of electrons to form image
+ 3D
+ thick specimens
- lower resolution then TEMs
light vs electron microscopes
electron requires vacuum
electron has more complex preparation
electron has higher magnification and resolution
electron requires dead specimens
(compared to optical)
outline cell fractionation
homogenisation - breaking up cells
filtration - removing large pieces
utracentifugation - seperating organelles
homogenisation
vibrating or grinding up cells
breaks up plasma membrane
releases organelles into solution
solution should be:
ice cold - reduce enzyme activity that break down organelles
isotonic - same water potential as organelles, stops damage from osmosis
buffer solution - maintain pH, prevent damage
filtration
filtered through gauze
separate large debris
organelles pass through
ultracentrifugation
used to separate organelles from solution made
pour in tube and put in centrifuge
- spin at low speed
densest organelles flung to bottom
eg nucleus
= pellet
rest of organelles stay suspended
= supernatant - supernatant drained of into another tube
spun at higher speed
densest organelles form pellet
eg mitochondria
(or chloroplasts then mitochondria in plant cells)
supernatant drained again
spun at faster speed
repeated to separate denser organelles
how does temperature affect membrane permeability?
very cold, damages membrane = more permeable
lower temperature = less kintetic energy, less permeable, increases with temperature
0-45
- as temperatures increase, have more kinetic energy
- phospholipids more fluid, less closely packed = more permeable
above 45
- phospholipid bilayer melts, breaks down, more permeable
- water inside expands, more pressure on membrane
- proteins deform, cant control movement, more permeable
fluid mosaic structure of a membrane
acts as a barrier between cell and environment
- controls which substances enter and leave, partially permeable
made of lipids, proteins and carbohydrates
phospholipids arrange in bilayer
fluid - constantly moving
mosaic - pattern of transport proteins
carbohydrates can join proteins and lipids = glycoproteins/lipids
role of phospholipids in membrane
hydrophilic head
hydrophobic tails
centre = hydrophobic
doesn’t allow water soluble water stances though (eg ions)
role of cholesterol in membrane
type of lipid
fit between phospholipids = more closely packed
less fluid and more rigid
= maintains shape and provide support
what type of substances can move through the membrane
oxygen and CO2 - small so pass between phospholipids
non-polar/lipid soluble
- dissolve in hydrophobic bilayer
water soluble CAN’T
- due to hydrophobic tails
water can as small
outline diffusion
simple - molecules diffuse directly through membrane
for larger or charged (polar):
FD - molecules diffuse through channel/carrier proteins
different proteins transport different molecules
carrier
- molecule binds to one side
- protein changes shape
- released on other
channel
- create pores for polar molecules
factor affecting simple vs FD
simple:
- concentration gradient
- thickness of surface
- surface area (microvilli)
FD:
- concentration gradient
- number of channel/carrier proteins
outline osmosis
movement of water from high to low water potential across partially permeable membrane
move directly across membrane, small molecules
more - means lower water potential (0=pure)
affected by:
water potential gradient
thickness of surface
surface area
effects of osmosis on plant cells
placed in high water potential
- water enters by osmosis into vacuole
- creates pressure, plant cell turgid
lower water potential
- leaves by osmosis, vacuole shrinks
- pulls away from cell wall
(plasmolysis)
effects of osmosis on animal cells
lower water potential
- water leaves, cells shrivels
high water potential
- water enters
- cells bursts
has no cell wall to support it (unlike plant)
outline active transport
movement of molecules against gradient using ATP through carrier proteins
molecule binds to carrier
protein changes shape
released on other side
ATP binds and it hydrolysed
= ADP and Pi = energy
affected by:
- number of carrier proteins
- rate of respiration = ATP produced
- speed of individual carriers
outline co-transport
concentration gradient of one molecule used to move another against its own
- through co-transporters
eg absorption of glucose with sodium in ileum
co-transport of glucose
Na+ actively transported out of ileum epithelial cells into blood
by sodium potassium pump
= higher concentration of Na+ in lumen then epithelial cell
Na+ diffuse from lumen into epithelial
though co-transporter proteins
= glucose transported with sodium
increase concentration of glucose inside epithelial cells = diffuses into blood
