2A-Cell structure and division Flashcards
What is a eukaryotic cell
Eukaryotic cells are complex and include all animal and plant cells as well as cells in algae and fungi
What is a prokaryotic cell
Prokaryotic cells are smaller and simpler like bacteria
What and where is plasmodesmata
It is channels for exchanging substances with adjacent cells in the cellulose cell wall
Describe algae cells
Similar to plant cells they have all the same organelles including cell wall and chloroplast
What are the two key differences between a fungal cell and a plant cell
In fungal cells the cell wall is made up of chitin not Cellulose
They also don’t have chloroplasts as they do not photosynthesise
What is the cell-surface plasma membranes description
Description – found on surface of animal cells, made up of mainly lipids and protein
What is the function of the cell surface plasma membrane
1-Regulates movement of substances in and out of cell
2-Has receptor molecules on it which allows it to respond to chemicals like hormones
Description of nucleus
Large organelles surrounded by nuclear envelope (double membrane )which contains many pores
Contains chromosomes made from protein-bound linear DNA
Contains nucleolus
Function of the nucleus
Control cells activities
DNA contains instructions for making proteins
pores allow substances e.g. RNA to move between the nucleus and the cytoplasm
nucleolus makes ribosomes
Description of mitochondrion
Oval shaped
double membrane-The inner one is folded to form structure called Cristae
inside is the matrix which contains enzymes involved in respiration
Function of mitochondrion
Aerobic respiration, where ATP is produced
Description of chloroplast
Small flat structure in plant and algal cells
surrounded by double membrane also has membranes inside called thylakoids membranes- these membranes are stacked in some parts of chloroplasts to form Grana
Grana linked together by lamellae
Function of chloroplast
Where photosynthesis takes place
parts photosynthesis happen in grana and other parts in stroma
description of Golgi apparatus
group of fluid filled membrane bound flattened sacs
function of Golgi apparatus
processes and packages new lipids and proteins
makes lysosomes
description of Golgi vesicle
small fluid filled sac in cytoplasm surrounded by membrane produced by Golgi apparatus
function of Golgi vesicle
stores lipids and proteins made by Golgi apparatus and transports them out of cells
description of lysosome
round organelle surrounded with membrane
type of Golgi vesicle
function of lysosomes
digestive enzymes called lysozymes contained which are kept separate from cytoplasm by membrane and used to digest invading cell,s or to break down worn out parts of cell
description of ribosome
very small
either floats in cytoplasm or attached to th rough endoplasmic reticulum
made proteins and rna
function of ribosomes
where proteins are made
description of rough endoplasmic reticulum
system of membrane enclosing a fluid filled space
covered with ribosomes
function of RER
folds and processes proteins which have been made at ribosomes
description of smooth endoplasmic reticulum SER
same as red but no ribosomes
function of SER
synthesises and processes lipids
description of cell wall
rigid structure
in plant and algae its made of carbohydrate- cellulose
in fungi its made up of chitin
function of cell wall
supports cell and prevents change in shape
description of cell vacuole
membrane bound
found in cytoplasm
contains cell sap-weak solution of sugar and salts
surrounding membrane called the tonoplast
function of cell vacuole
maintains pressure inside cell to keep it rigid
stops wilting
involved in the isolation of unwanted chemicals inside the cell
how are epithelial cells specialised
To absorb food efficiently in the small intestine
walls of small IN have villi (finger like projections)-increases surface area
Epithelial cells have microvilli(folds in cell membrane)-increase surface A even more
also has lots of mitochondria to increase energy for respiration
Explain cytoplasm of a prokaryotic cell
It has no membrane-bound organelles
It has ribosomes but they’re smaller than those in a eukaryotic cell
Explain the plasma membrane in prokaryotic cell
Same as in eukaryotic cell made of lipids and proteins controls movement in and out of cells
Explain flagellum in prokaryotic cell
Long hair like structure the rotates to make the cell move
not all prokaryotes have a flagellum
Explain how prokaryotes don’t have a nucleus
Instead they have DNA which floats free in cytoplasm
its circular DNA presents as one long coiled up strand it’s not attached to any histone proteins
Explain plasmids in prokaryotes
Plasmids are small loops of DNA
they contain genes for things like antibiotic resistance and can be passed between prokaryotes
Explain cell wall in prokaryotic cells
Supports the cell and prevents it from changing shape it’s made of polymer called murein
murein is glycoprotein
What is a glycoprotein
A protein with a carbohydrate attached
Explain prokaryotes with capsule
Prokaryotes like bacteria have capsule made ups of secreted slime
it helps protect bacteria from attacking cells
What are viruses
Acellular
Describe a virus
Nucleic acid surrounded by protein smaller than bacteria
How is a virus different to a bacterial cell
It has no cytoplasm no cell membrane and no ribosomes
Describe structure of virus
Contain core of genetic material either DNA or RNA protein coat around core is the capsid attachment protein stick out from edge of capsid these let viruses cling onto host cells
How does prokaryotic cells replicates
By binary fission
Explain steps of binary fission
One – circular DNA and plasmids replicate
2-cell gets bigger and DNA loops move to opposite poles of cell
3-cytoplasm divides, new cell wall begins forming
4-cytoplasm divides and two daughter cells are produced
each daughter cell has one copy of circular DNA but can have variable number of copies of plasmids
How do viruses use host cells to replicate themselves
1 – viruses use attachment proteins to bind to complimentary receptor proteins on surface of Host cell
2-as viruses are a cellular viruses, can’t undergo cell division instead they inject their DNA or RNA into host cell and then host cell replicates the viral particles
Magnification formula
Size of image/size of real object
Define resolution
How well a microscope distinguishes between two points that are close together
Describe optical microscopes
1– use light form image
2– maximum resolution of 0.2 micro metres
3– maximum useful magnification times 1500
Describe electron microscopes
1 – use electrons to form image
2 – have higher resolution than optical microscopes
3– maximum resolution of 0. 0002 micro metres
4 – the maximum useful magnification is 1,500,000
Two types of electron microscopes
Transmission electron microscope or scanning electron microscope
Describe TEM
1-Use electromagnets to focus beam of electrons which then transmits through the specimen
2 – denser part of specimen absorb more electrons which makes them look darker
3 – advantage they give high resolution images so you see internal structure of organelles like chloroplast
4 – can only be used on thin specimens
Describe SEM
1 – scan beam of electrons across specimen this knocks off electron from the specimen these are gathered in cathode ray tube to form image
2 – image shows the surface of specimen, can be 3D
3– advantage can be used on thick specimens
4– but they give lower resolution image than TEM
PRACTICAL how to view specimens on the optical microscope using slide
Pipette small drop of water onto slide, use tweezer place a section of specimen on water, add drop of stain, finally add coverslip
what stains show what
IODINE-starch
EOSIN-cytoplasm
What are the three stages of cell fractionation
1 – homogenisation
2-filtration
3-ultracentrifugation
CELL FRACTIONATION- explain homogenisation
1-grind cells up in blender, breaking up plasma membrane releasing organelles into solution
2-solution must be ice cold to reduce enzyme activity which breaks down organelles
3-solution must be isotonic(same concentration of chemicals as cell being broken dow to prevent damage of organelles through osmosis)
4-buffer solution added to maintain PH
CELL FRACTIONATING- explain filtration
Filtered through goes to separate large debris or tissue debris
CELL FRACTONATION- ultracentrifugation
1-cell fragments poured to tube, put in centrifuge, spun at low speed, heaviest organelles(nuclei)go to bottom(pellet), rest of organelles stay suspended at top (supernatant)
2-supernatant drained and added to another tube to repeat process at higher speed this time the pellet is mitochondria
What are the three phases of interphase
S-synthesis cell replicates DNA
G2-Cell keeps growing and proteins needed for cell division are made
M- mitosis
G1-cell grows and new organelles and proteins are made
Explain interphase
cell carries out normal functions, DNA unravelled and replicated, organelles replicated, ATP increased so it has enough energy
four stages of Mitosis
1- Prophase
2-Metaphase
3-Anaphase
4-Telophase
MITOSIS- explain prophase
Chromosomes condense getting shorter and fatter, central start moving to opposite ends of cells forming protein fibres called spindle, nuclear envelope breaks down, chromosomes lie free in cytoplasm
MITOSIS- explain metaphase
Chromosomes each with two chromatids line up along middle of cell becoming attached to the spindle by their centromere
MITOSIS- explain Anaphase
CentROMERES divide separating each pair of chromatids ,spindles contract pulling chromatids to opposite poles ,this makes chromatids appear V shaped
MITOSIS- explain Telophase
Chromatids reach opposite poles on spindle, they uncoil and become long and thin, now chromosomes again, nuclear envelope forms around each group of chromosomes so there are two nuclei, the cytoplasm divides (cytokinesis) – now two daughter cells that are genetically identical to original cell
Explain how cancer is the result of uncontrolled cell division
Mitosis and cell cycle are controlled by genes, if there is a mutation in a gene that control cell division the cells grow out of control, cells keep dividing which form a tumour, cancer is a tumour that invades surrounding tissue
Explain cancer treatment which targets G1
Chemotherapy prevents the synthesis of enzymes needed for DNA replication when these are produced cell is unable to enter synthesis phase forcing cell to kill itself
Explain cancer treatment which targets the S phase
Radiation and some drugs damage to DNA at several points in cell cycle DNA is checked for damage if damage is detected the cell will kill its self
How to prepare optical slide
1- clip prepared slide onto stage 2-select lowest power objective lens 3-use coarse adjustment knob to move stage up the adjust to best focus 4-refine focus with fine adjustment knob 5-swap to higher power obl if needed
mitotic index formula
number of cells with visible chromosomes/total number of cells observed
where is EPG fitted
eye piece graticule fits onto eyepiece
where is stage micrometer fitted
on the stage
what are artefacts
things you see down the microscope which aren’t part of specimen eg. dust bubbles or fingerprint or inaccuracies caused by squashing/staining sample
why are artefacts especially common in electron microscopes
specimens need a lot of preparation before being able to view under electron microscope
how did first scientists stop artefacts
prepare samples in multiple ways and compare
