Cell structure Flashcards
describe the function and structure of the cell-surface membrane
function is to regulate movement of substances into and out of cell
- phospholipid bilayer - is lipid soluble so allows hydrophobic substances to diffuse through the membrane
describe the function and structure of the nucleus
function is to control chemical reactions within the cell, is the site of DNA replication and transcription and contains the genetic code
- has a double membrane and nuclear envelope
- has pores so substances can move in and out
- nucleolus - site of rRNA production and assembles ribosomes
- nucleoplasm - jelly-like material
- contains chromosomes - linear DNA
describe the function and structure of the mitochondrion
site of aerobic respiration, site of ATP production and has mitochondrial DNA which codes for enzymes needed in respiration
- has a double membrane
- has a folded inner membrane called cristae
- inner fluid is called matrix
- loop of mitochondrial DNA (similar to prokaryotic DNA)
describe the function and structure of the chloroplast
function is to absorb light energy during photosynthesis
- has a double membrane
- folded inner membrane called thylakoid
- proteins such as chlorophyll are embedded within thylakoid
- liquid is called stroma
- thylakoid stack to form grana
describe the function and structure of the Golgi apparatus
function:
- adds carbs to proteins to form glycoproteins
- transports, modifies and stores lipids
- produces secretory enzymes for exocytosis
- makes lysosomes
- a stack of fluid-filled membrane-bound sacs
describe the function and structure of the lysosomes
function is to hydrolyse unwanted material using hydrolytic enzymes
- a vesicle containing enzymes
- lots in one cell for faster breakdown
describe the function and structure of the ribosomes
function is for protein synthesis during translation
- made up of 2 sub-units
- consist of proteins and rRNA
- no membrane so sub-units can move
- 80s in plant cells and 70s in prokaryotic cells
describe the function and structure of the RER
function is to transport and package polypeptides, needed for protein synthesis
- a fluid-filled membrane covered in ribosomes, has a large SA
describe the function and structure of the SER
function is to process, synthesise and store lipids and carbohydrates
- fluid-filled membrane with a large surface area
describe the function and structure of the cell wall
function is to support and maintain shape of cell - structural support
- made from chitin in fungal cells, cellulose in plant cells, and murein in bacteria
describe the function and structure of the cell vacuole
function is to maintain the shape and pressure of the cell which makes it turgid, moves chemicals and stores sugars/amino acids
- membrane-bound (tonoplast) within the cytoplasm and contains cell sap
describe how a lysosome can break down eg. proteins
- the lysosome will fuse with the faulty protein and the phospholipid biolayers will join together to become 1
- the hydrolytic enzymes within the lysosome are released which will break down the protein into amino acids
- exocytosis then occurs (when the waste molecules leave the cell)
name the structures found within prokaryotic cells
- cell wall made from murein
- no membrane bound organelles
- no nucleus - DNA loop instead
- 70s ribosomes
some contain:
- plasmids, flagella, capsules
describe how light microscopes work
- light from a mirror is reflected up through the object into the objective lens
- the image produced is magnified by the eyepiece lens
describe how an electron microscope works
- a beam of electrons is produced at the top of the microscope by an electron gun
- electrons are focused into a thin beam
why can electron microscopes give a higher resolution?
electrons have a shorter wavelength than visible light so produce higher resolution images
what are the advantages and disadvantages of light microscopes?
advantages:
- cheap to purchase and operate
- simple and easy sample preparation
disadvantages:
- low magnification
- lower resolution than electron microscopes
what are the advantages and disadvantages of SEM microscopes?
advantages:
- higher magnification and resolution than light microscopes
- can look at 3D structures
disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- lower resolution than TEM’s
what are the advantages and disadvantages of TEM microscopes?
advantages:
- high magnification and resolution
- can see internal structures
disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- can only be used with very thin objects
what are artefacts in microscopy and give some examples
they are things that can be seen under the microscope which are not meant to be there
eg. foreign bodies such as eyelashes, clumps of stain/dye
what is the formula for magnification
magnification = image size divided by actual size
how do you convert from nm to mm
divide by 1,000,000
how do you convert from micrometers to mm
divide by 1000
what is cell fractionation?
the process of separating different organelles of a cell, so they can be studied in detail
What are the steps in ultracentrifugation?
- homogenise tissue to break open cells and release organelles
- filter to remove cell debris
- use a cold solution to prevent enzyme activity
- use a solution with an equivalent water potential to prevent osmosis (isotonic)
- buffer solution to stop proteins/enzymes denaturing
- centrifuge at a low speed so higher density organelles eg. nucleus sink to the bottom to form a pellet
