3.1-3.8 cell structure and microscopy unit 2 (not definition)

state 8 organelles found in animal cells

• nucleus

• mitochondria

• ribosomes

• rough endoplasmic reticulum

• smooth endoplasmic reticulum

• golgi body

• centrioles

• lysosomes

what is the function of the nucleus

to store and transmit genetic material

what is the function of the nuclear pores

to allow substances to enter and exit the nucleus

what is chromatin

DNA wrapped around histone proteins

describe the structure and function of the rough endoplasmic reticulum

• studded with ribosome

• made up of membranes folded into cisternae

• synthesises proteins destined to be secreted

describe the structure and function of the mitochondria

• double membrane folded into cristae

• fluid filled matrix inside

• contains its own DNA (mtDNA)

• site of ATP production through aerobic respiration

what is the function of lysosomes

contain hydrolytic enzymes that break down waste

what is the function of vesicles

to transport substances within cells

what is the structure and function of ribosomes

• two units made protein and rRNA (ribosomal ribonucleic acid)

• synthesise proteins

describe the structure of the golgi body

• it is a membrane bound organelle

• it is folded into cisternae

what is the function of the golgi body

it modifies and processes lipids and proteins and packages them into vesicles

describe the structure and function of lysosomes

membrane bound vesicles that contain hydrolytic enzymes that break down waste and toxins

describe the structure of centrioles

• a cylindrical bunch of protein called tubulin

• often found in pairs which makes up a structure called a centrosome

what is an intracellular enzyme

an enzyme that acts within cells e.g. catalase

what is an extracellular enzyme

an enzyme that is secreted by cells and functions outside of cells e.g. amylase

describe the steps involved in the production of an extracellular enzyme

• DNA transcribed to produce mRNA in the nucleus

• mRNA exits the nucleus and travels to a ribosome on the rough endoplasmic reticulum (rER)

• enzyme synthesises by the ribosomes on the rER in the process of translation

• enzyme is packaged into a vesicle and sent to the golgi apparatus where it is modified and repackaged

• the enzyme then leaves the golgi apparatus enclosed in a vesicle and undergoes exocytosis to exit the cell

what is the function of the flagellum

used to move the cell

what is the function of the pili

allow the bacteria to adhere to other cells or to surfaces

what is the function of plasmid DNA

to provide beneficial genes which aid in the survival of the prokaryote, for example, the genes which provide antibiotic resistance

what is the function of the bacterial capsule

• it prevents the cell from dry environments

• it acts as a virulence factor which helps it to resist phagocytosis

what is the magnification of a microscope a measurement of

how many times bigger in image appears compared to the original object

what is the purpose of staining specimens

• to visually distinguish different parts of a specimen

• to increase contrast as lots of cellular components are transparent

describe how light microscopes work

• lenses focus rays of light and magnify the image

• different structures absorb different amounts and wavelengths of light

• reflected light is transmitted to the observer via the objective lens and eyepiece lens

describe how a transmission electron microscope (TEM)

• high energy beam of electrons passed through a thin slice of specimen

• more dense structures absorb more electrons so appear darker

• image focussed onto a fluorescent screen or photographic plate using magnetic lenses

describe how a scanning electron microscope (SEM) works

• beam of electrons focussed onto the surface of a specimen using electromagnetic lenses

• reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate

why do electron microscope have a higher resolution than light microscopes

electrons have a much shorter wavelengths than light and so can distinguish much smaller structures

what type of a microscope typically produces naturally coloured images

light microscopes produce accurately coloured images as visible light is used to visualise the specimen

what type of electron microscope produces two dimensional images

transmission electron microscopes produce 2D images as electrons are passed through the specimen

give 5 advantages of light microscopes

• they are cheap

• they are easy to use

• they can visualise living cells

• they are portable and do not always require electricity to operate

• they can visualise whole specimens

give 2 advantages of electron microscopes compared to light microscopes

• they have a much higher resolution and depth of field

• they have a much higher magnification