cell structure and division Alevel P1

Mr J

what are the two main types of organisms

eukaryotes and prokaryotes

examples of eukaryotic organisms

animals, plants, algal and fungal

why is eukaryotic organisms different to prokaryotic

complex, multicellular, involves mitosis/meiosis

what are the extra organelles that plant cells have compared to animals 

cell wall, vacuole and chloroplast 

what can algal cells do that plants cant

can be unicellular or multicellular and can have different shape + sizes of chloroplast

what are the 2 main differences of a fungal cell

• cell walls are made of chitin not cellulose

• don’t have chloroplast (don’t photosynthesise)

what’s the function of cell surface membrane (plasma membrane)

regulates movement of substance in and out of the cell. Has receptor molecules on it which allow it to respond to chemicals like hormones.

what is the cell surface membrane mainly made of

proteins and lipids

what’s the nucleus function

controls cells activities (by controlling transcription of DNA)- DNA contains instructions to make proteins.

what do the nuclear pores do

allow substances like RNA to move between the nucleus and the cytoplasm

what does the nucleolus do

makes the ribosomes

describe the nucleus and its surroundings

a large organelle surrounded by a nuclear envelope (double membrane) which contains pores. The nucleus contains many chromosomes and one or more structure(s) called a nucleolus.

what’s the function of the mitochondrion

site of aerobic respiration producing ATP- used for energy.

describe the mitochondrion

usually oval shape, double membrane where inner one is folded to form cristae. inside is the matrix containing enzymes for respiration.

what’s the function of chloroplast

site of photosynthesis either in the grana or stoma

describe chloroplast

a small, flattened structure, surrounded by a double membrane as well as having a membrane inside called thylakoid membrane. thylakoid stacked up form grana which link together by lamellae.

what’s the function of golgi apparatus

it processes and packages new lipids and proteins- making lysosomes

describe the golgi apparatus

a group of fluid filled membrane bound flattened sacs. vesicles are often on the edges.

what’s the function of golgi vesicles 

stores lipids+ proteins made by the golgi apparatus and transports them out of the cell

describe the golgi vesicles

small fluid filled sac in the cytoplasm, surrounded by a membrane and produced by golgi apparatus

what’s the function of lysosomes

contains hydrolytic enzymes, kept separate from cytoplasm by surrounding membrane and used to digest invading cells or to break down worn out components of the cell. 

description of lysosomes 

a round oragnele surrounded by a membrane with no clear internal structure 

what is the function of ribosomes

site where proteins are made

description of ribosomes

very small organelle that floats free in cytoplasm or attached to rough endoplasmic reticulum. made of proteins and RNA 

function of rough endoplasmic reticulum

folds and processes proteins that have been made at the ribosomes

description of rough endoplasmic reticulum

system of membrane enclosing a fluid filled space, the surface is covered in ribosomes.

what’s the function of smooth endoplasmic reticulum 

synthesises and processes lipids 

function of the cell wall

supports cells and prevents them from changing shape

describe the cell wall

a rigid structure that surrounds cells, mainly made out of cellulose but in fungi its made of chitin

what is the function of the cell vacuole

helps to maintain pressure inside the cell and keep the cell rigid. Involved in the isolation of unwanted chemicals inside the cell

describe the cell vacuole

a membrane bound organelle found in the cytoplasm, contains cell sap. its surround membrane is called the tonoplast.

what structures do plasmids have that animals don’t

plasmids, flagellum and free DNA

do bacteria have a cell wall

yes

what are plasmids

small loops of DNA contain genes for things like antibiotic resistance.

what is the free DNA in bacteria 

circular DNA presented as one long coiled up strand 

what is the flagellum

long, hair like structure that rotates the cell making it move

how do prokaryotic cells replicate

through binary fission

how many stages are there in binary fission

4

what is the first step in binary fission

circular DNA replicates and plasmids reproduce 

what is the second step in binary fission 

The DNA moves to opposite poles (ends) of the cell

what is the 3rd stage in binary fission

cytoplasm begins to divide (new cell wall begins to form)

what is stage 4 of binary fission (last stage)

cytoplasm full divides and two daughter cells are produced- containing one copy of circular DNA and can vary in number of plasmids.

if viruses are not eukaryotic or prokaryotic - what are they

acellular meaning they are not cells/not alive

give an example of some viruses

HIV, influenza and rhinoviruses.

when viruses invade and reproduce inside cells of other organisms what are the cells called

Host cells 

what structures do viruses not have

no ribosomes, cell surface membrane and no cytoplasm

what is the capsid of a virus

a protein coat with attachment proteins sticking out from it

what do the attachment proteins allow

let viruses cling onto host cell

what do viruses inject into host cell

DNA or RNA

how do viruses attach to host cell surface 

by the attachment proteins binding to complementary receptor proteins on cell surface membrane

what are the 5 stages of viral replication

1- virus attaches to host cell receptor proteins. 2-genetic material is released into host cell. 3- genetic material and proteins are replicated by host cell. 4- viral components assemble. 5-replicated viruses released from host cell. 

what is the calculation for magnification

magnification= size of image/ size of real object

define magnification

is a value that tells us how much larger an image is when compared to the original object

show how you would covert m into nm

metre X100 = centimetre X10= millimetre X1000= micrometre X1000 = nanometre

what are the 3 main lenses that make up the optical system

eyepiece lens, objective lens, condenser lens

define resolution

the smallest distance between two particles which allow them to be distinguished from one another 

if there is a shorter wavelength what does this mean for resolution 

greater resolution/clarity 

what is an optical microscope 

a light microscope 

describe an optical (light) microscope, how it works/functions

• oldest, simplest and cheapest

• use light to form image, specimen is illuminated with light, focused using glass lenses 

• requires staining with colour 

• magnification is low 1500X 

what are the two types of electron microscopes

Transmission electron microscope (TEM) or scanning electron microscope (SEMs)

describe an electron microscope, how it functions

• uses beam of electrons produced using a hot wire

• focused using electromagnets

• has a short wavelength allowing a high resolution 

• magnification is much higher than optical (max magnification is X500000) 

Describe how a TEM (transmission electron microscope) works

• transmits a beam of electrons through specimen produced by a cathode gun which is directed by anode down the TEM column 

• denser parts of specimen absorbs more electrons making image look darker (seen on a screen or film)

• short wavelength= high resolution 

• specimen must be viewed in a vacuum so easier if dead and thin

describe how a SEMs (scanning electron microscope) works

• scans a fine beam of electrons across the specimen which knocks of electrons from specimen and gathered in a cathode ray tube to form an image 

• provide a 3D image and can be used on thick specimen

what is the ADV and DISAD of using a TEM

adv- high resolution, shows small objects

disad- only used on thin specimen, only be used on non living specimen

what is the ADV and DISAD of SEMs

adv- used on thick specimen, gives 3D image

disad- lower resolution than TEM, only used on non living specimen 

what is the ADV and DISAD of a light microscope

adv- view whole live specimen under low magnification

disad- low resolution does not allow much smaller subcellular detail

what is a temporary mount on a microscope

where the specimen is suspended in a drop of liquid on a slide

what is cell fractionation

separating different parts and organelles of the cell so they can be studied in detail

what is ultracentrifugation

a technique used to extract and isolate pure samples of cell organelles.

what are the 3 different stages of ell fractionation called

1- homogenisation (breaking up the cell)

2- Filtration (getting rid of the big bits)

3- Ultracentrifugation (separating the organelles)

what happens in the first stage of cell fractionation = homogenisation

homogenisation can be done by vibrating the cells or grinding cells up in blender which breaks up plasma membrane and release organelles into solution. They must be kept in a Isotonic solution at 2C to reduce activity of enzymes that break down organelles. Must be isotonic as it’ll have same concentration of chemicals as the cells being broken down which stops cells shrivelling or bursting due to osmosis. A buffer solution should be added to maintain the PH. 

what happens in the second stage of cell fractionation= Filtration

homogenised solution if filtered through a gauze to separate any large cell debris

what happens in the third stage of cell fractionation= Ultracentrifugation

the tub is then put into a centrifuge (machine that separates materials by spinning) and is started to be spun at a low speed- the heaviest organelles collect at the bottom of the tube forming pellets and rest of organelles stay suspended in solution = supernatant. 

supernatant is drained off, poured into another tube and spun at a higher speed and the process happens again at higher speeds until all organelles are separated out.