All of studying cells Flashcards
Structure and function of the Nucleus
Nuclear envelope/double membrane and pores
Chromosomes/chromatin
Nucleolus
Stores genetic information for polypeptide production
site of DNA replication
site of production of mRNA and tRNA
Site of production for rRNA
Structure and function of mitochondria
Double membrane
inner membrane highly folded to form cristae
matrix containing mitochondrial DNA, ribosomes, proteins and lipids
Site of ATP production for aerobic respiration
cells that need a lot of ATP have lots of mitochondria such as muscle cells
Structure and function of RER
Highly folded membrane with 80s ribosomes embedded
membrane folded into flattened sacs called cisternae
joined to nucleus
synthesis and transport of proteins throughout the cell
Structure and function SER
Highly folded membranes flattened into sacks called cisternae
recombines glycerol and fatty acids to make triglycerides
packages triglycerides into vesicles and transports to Golgi body
Structure and function of cytoplasmic ribosome
made up of 2 subunits made of long strands of rRNA and ribosomal proteins
eukaryotic cells contain 80s ribosomes
site of protein synthesis for amino acids
Structure and function of Golgi body
Flattened sacs of membrane filled with fluid
golgi vesicles pinch off the main membrane
sorts, modifies and packages proteins and triglycerides into vesicles, can be used to form lysosomes
Structure and function of lysosome
membrane bound organelles that store and release many hydrolytic enzymes
contain hydrolytic enzymes that hydrolyse invading bacteria and pathogens
Structure and function of CSM
made up of phospholipids, specific transport proteins and carbohydrates arranged in fluid mosaic model
controls the passage of molecules into and out of the cell
Structure and function of centrioles
microtubules
form a network of spindle fibers onto which chromosomes attach, pull chromosomes apart during mitosis
not found in plant cells
Structure of the chloroplast and definitions
Granum- stack of thylakoid membrane
Thylakoid membrane- contains chlorophyll for photosynthesis and ATP synthase enzyme to produce ATP
Stroma- fluid filled part, some photosynthetic reactions occur here
starch grains- the energy storage molecule of a plants
DNA and ribosomes- contain their own DNA and 70s ribosomes for synthesis of enzymes needed for photosynthesis
plasmodium- connects cells
Plasmodesmata- gaps in cell walls that connect cell cytoplasm’s together to allow easy movement of water soluble molecules
What is the name of the cell wall found in Fungi
Chitin, not cellulose
Prokaryotic cells
No nucleus or membrane bound organelles
DNA free in cytoplasm- 70s ribosomes, flagellum, mesosome( highly folded section of inner membrane), plasmid, cell wall(Made from murein or peptido glycan- a blend of polypeptides and polysaccharides), cell membrane, capsule(slime layer)
Prokaryotic cell vs eukaryotic
DNA is circular and not associated with histones: DNA is linear and associated with histones
Contains no membrane bound organelles: Contains membrane bound organelles
DNA is free in cytoplasm: Has a nucleus, DNA contained within nuclear membrane
Contains 70s ribosomes: Contains 80s
Some have a capsule, one or more flagella, one or more plasmids: Do not have capsule
Have mesosomes for ATP synthesis: Foes not have mesosomes
Cell wall made of murein or peptidoglycan: Plants have a cell wall made of cellulose
Light microscope
Magnification is limited, low resolution- limited by the wavelength oflight
the shorter the wavelength of light, the better the resolution
electron microscopes
Both types use a beam of electrons, rather than light. Electrons behave like waves and focus using electromagnetics, detected using a phosphorous screen or photographic film. Electrons so have small wave length so higher resolution
TEM
Electrons pass through allowing to view internal structures
more dense areas absorb more electrons so appear darker
SEM
No sliced but electrons bounce off the surface. produces a 3D image.
Principles and limitations of TEM
Electrons pass through, denser parts absorb more electrons, denser parts appear darker, electrons have a short wavelength so give high resolution
cannot look at living material
must be thinly sliced
artefacts present
long preparation time
describe how you would make a temporary mount
add a drop of water to the microscope slide
get a thin section of plant tissue and float on the drop of water
stain with KI
lower the cover slip using a mounted needle to avoid air bubbles
describe how a student would use an eyepiece graticule
measure each sample using an eye piece graticule
calibrate the eyepiece graticule against a stage micrometer
take at least 5 measurements and calculate mean
scale factor measurements
1m= 1000mm
1mm=1000um
1um= 1000nm
Cell fractionation and differential centrifugation
Homogenise by placing sample in a blender
Place in an
Ice cold: to reduce the action of enzymes that would digest organelles
Isotonic- prevents osmosis of water in or out of organelles, prevent cell lysis
Buffered: stop ph changes that could cause enzyme to denature
solution
filter to remove debris
centrifuge at high speed. densest organelles settle at bottom in a pellet. supernatant removed and spun again at a higher speed
Phopsholipids
Form micelles when submerged in water. hydrophobic fatty acid tails point inwards towards the middle, hydrophilic heads point outwards towards the extracellular fluid. Forms the basis of a cell membrane- selectively permeable
Allow lipid soluble non polar molecules to pass through by simple diffusion and prevents the passage of small polar lipid isnoluble molecules
The fluid-mosaic model
Forms a phospholipid bilayer which is constantly moving around, giving a fluid structure. the selective permeability is related to distribution of specific proteins- mosaic
Role of cholesterol
Decreases permeability and increases stability of membrane
more cholesterol= less fluidity of membrane
Chanel proteins
pores within the membrane that allow only specific molecules to move across by FD. Intrinsic
Proteins have specific tertiary structure so are specific and can only transport molecules that are complementary to shape of channel proteins
carrier proteins
aid transport of polar ions by FD and AT. Allow diffusion of larger molecules- attaches to binding site and changes shape, releasing the molecule through to the other side of the membrane
Glycoproteins
Composed of carbohydrates and proteins, important in cell recognition as act as antigens. Immune cells detect the specific shapes of glycoproteins to help identify self and non self cells
Diffusion
Passive process- does not require ATP, will stop when there are equal numbers of that specific molecule on each side- when they have reached equilibrium. Involves small non-polar lipid soluble molecules
Definition: Net movement of molecules from an area of higher concentration to a lower concentration across a partially permeable membrane
factors affecting diffusion
temperature- increase in kinetic energy- faster rate of diffusion
Surface area- the larger the surface area the more space for molecules to pass through
Concentration gradient- as concentration difference increases, rate of diffusion increases
diffusion distance- the shorter the diffusion distance, the faster molecules will travel from one area to the next. Phospholipid bilayer are all the same thickness
Facilitated diffusion
specific proteins help specific molecules to pass through the phospholipid bilayer. All have binding sites not active sites
FD levels off when all the carrier proteins are saturated- number of carrier proteins will become a limiting factor
Osmosis
The net movement of water from higher water potential to lower water potential through a partially permeable membrane down a water potential gradient
WP- water molecules and their ability to collide with a membrane
The affects of osmosis- higher, lower WP and isotonic
high- causes swelling and cell lysis- causes increase in mass
low- results in shriveling of the cell- plant cell membrane pulls away from the cell wall
isotonic-no net movement of water into and out of the cells
AT
Movement of substances from low to high concentration moving against their concentration gradient. Requires carrier proteins. requires ATP- the hydrolysis of ATP allows protein to change shape and transport the molecule across the membrane
Other forms of Active transport
Bulk transport by exocytosis- uses golgi body to move large quantities of molecules