studying cells Flashcards
(23 cards)
describe and explain how cell fractionation and ultracentrifugation can be used to isolate named organelle from a suspension of cells
cell homogenisation to break open cells and filter to remove whole cells/debris
isolation must be:
>isotonic-keep water potential same to stop organelles bursting
> ice cold-prevent enzyme activity
> buffered - pH kept constant preventing protein denaturation
centrifuge at high speed to separate nuclei
remove pellet(solid) containing nuclei
respin supernatant (solution) at a higher speed to get mitochondria/chloroplats in pellet
(repeat steps 3-5 at higher speed for smaller organelles)
what are the similarities of a chloroplast and mitochondria
both have double membrane
both contain circular dna
both have 70s ribosomes
what are the differences between chloroplasts and mitochondria
chloroplasts have thylakoids whereas mitochondria have cristae
chloroplasts have stroma where’s mitochondria have matrix
chloroplasts have pigments (chlorophyll) whereas mitochondria have no pigments
chloroplasts have starch grains whereas mitochondria have no starch grains
define acellular
no cell surface membrane,organelles or membrane
no metabolic reactions eg no respiration or protein synthesis or dna replication
define the properties of an electron microscope
electrons pass through/enter (very thin) specimen
denser parts absorb more electrons
so denser appear darker
electrons have short wavelength so give high resolution
state advantages of light microscope compared to TEM
advantages- can observe living specimens as stains are non toxic. can stain specific organelles with colour
give one advantage of using SEM over TEM
produce 3D image
see surface of specimen
give one advantage of using TEM over SEM
higher resolution
can see internal structures
describe the advantages of TEM over a light microscope
advantages
- small objects can be seen (ultrastructures/small organelles)
-TEM has higher resolution
- wavelength of electrons shorter
describe the ultrastructures of the nucleus
and function of nucleus
structure
-double membrane and pores
-chromatin (dna associated with histones)
function
-stores genetic information for polypeptide production
- site of dna replication
-site of production of mrna (Transcription) and trna
-site of production or rrna/ribosomes (nucleolus)
ultrastructures of mitochondria
function
structure
-double membrane
-inner membrane highly folded to form cristae(increase surface area)
-matrix(liquid part) containing mitochondrial dna,70s ribosomes,proteins,and lipids
function
-site of atp production by aerobic respiration
ultrastructure of rough endoplasmic reticulum
function
structure
-highly folded membranes with 80s ribosomes embedded
-membrane is folded into flattened sacked called cisternae
-joined to nucleus
function
synthesises and transport of proteins throughout the cell
ultra structure of smooth endoplasmic reticulum
function
structure
highly folded membrane flattened into sacks called cisternae
function
recombines glycerol and fatty acids to make triglycerides
packages triglycerides into vesicles and transports them into golgi apparatus
ultra structure pf cytoplasmic ribosomes
function
structure
-made up of two subunits that are made of long strands or rrna and ribosomal proteins
-eukaryotic cell contains 80s ribosomes(ans 70s ribosomes in mitochondria or chloroplasts)
function
site of protein synthesis from amino acids
ultra structure golgi apparatus
function
structure
flattened sacs made of membrane filled with fluid
golgi vesicles pinched off from main membrane
function
sorts modified packages proteins and triglycerides into vesicles
golgi vesicles used to form lysosomes
ultra structure lysosomes
function
structure
membrane bound organelle that stores and releases hydrolytic enzymes
function
contain hydrolytic enzymes that hydrolyse pathogens/damaged organelles once released into vesicles
ultra structure cell membrane
function
structure
-phospholipid bilayer(hydrophilic heads facing out and hydrophobic tails facing inwards) containing specific channel/carrier proteins,glycoproteins and cholesterol arranged into a fluid mosaic model
-fluid as position of molecules are constantly moving in their layer
-mosaic as made up of variety of proteins /molecules make a mosaic pattern from above
function
-controls passage of molecules in and out of cell
-channel proteins allow passage of large/polar molecules that are complementary to their binding site by facilitated diffusion
-carrier proteins allow passage or large/polar molecules that are complementary to their binding site by facilitated diffusion/active transport
-glycoproteins/glycolipids involved in cell recognition (antigens) and cell signaling
-cholesterol contains membrane fluid (more cholesterol =less fluid/ permeable)
ultra structure of centrioles
function
structure
microtubules
not in plant cells
function
form a network of spindle fibres which attach to the centromere of chromosomes
pull sister chromatids apart during mitosis
similarities of structures in plant/ animal cells
both have rough endoplasmic and smooth endoplasmic reticulum
both have golgi body
both have mitochondria nucleus
differences of structures in plant/ animal cells
plant cell has cellulose cell wall wheres animal cell has no cell wall
chloroplasts present(not in roots) or plant cell whereas no chloroplasts in animal cell
large central vacuole in plant cell whereas no large central vacuole in animal cell
carbohydrates stored as starch in plant cell whereas carbohydrates stores as glycogen in animal cell
no centrioles in plant cell whereas centrioles in animal cell
ultra structure of chloroplast
function
structure
thylakoid membranes contain chlorophyll that absorbs light (needed for photosynthesis)
function
site of photosynthesis
stage disadvantage of using light microscope compared to TEM
disadvantage- lower resolution as wavelength of light is longer so you cannot see smaller organelles/ ultrastructures
disadvantages of TEM over light microscope
disadvantages
-cannot look at living cells
–must be in a vacuum
-must cut section/thin specimen
-preparation may create artefacts(false image)
