cells Flashcards
What is the role and structure of the cell surface membrane?
Controls what goes in and out of the cell
Contains receptor molecules that allow it to respond to chemicals such as hormones
What is the role and structure of the nucleus?
controls the activity of the cell
large organelle surrounded by a nuclear envelope containing
many pores which allow the movement of substances
What is the role and structure of the mitochondria?
where aerobic respiration takes place, which produces ATP
have a double membrane
inner membrane is folded to form structures called cristae
Inside is the matrix, which contains enzymes
What is the role and structure of the chloroplasts?
where photosynthesis takes place
has a double membrane
contain membranes called thylakoids, which can be stacked together to form grana - can be linked together by membranes called lamellae
What is the role and structure of the Golgi apparatus?
processes and packages lipids and proteins, which
are stored and transported out of the vesicles, also produce
lysosomes
group of fluid filled membrane-bound flattened sacs, called cisternae.
What is the role and structure of the lysosomes?
contain digestive enzymes called lysozymes, which can digest/hydrolyse or break down invading cells
round organelles surrounded by a membrane,
that have no clear internal structure.
What is the role and structure of the rough endoplasmic reticulum and smooth endoplasmic reticulum?
RER- system of membranes that enclose a fluid filled space with ribosomes attached
responsible for folding and processing proteins that have been
made by the ribosomes.
SER- responsible for synthesising and processing lipids
What is the role of the cell wall and how does it differ in plant, fungal and bacterial cells?
provides support for the cell and prevents it from changing shape
plant- cellulose
fungal- chitin
bacterial- murein
What is the role and structure of the cell vacuole?
keeps the cell turgid by maintaining pressure
What is the role and structure of the ribosomes?
small organelles that are found floating freely in the cytoplasm, or
attached to the rough endoplasmic reticulum
in charge of protein synthesis
Features of prokaryotic cells
cytoplasm with no membrane bound organelles
smaller ribosomes
circular DNA
murein cell wall
plasmids
capsule
flagella
Description and structure of viruses
They are acellular and non-living
Include genetic material, capsid and attachemnt proteins
Name the features of an optical microscope
Optical microscope- uses light
Low magnification and resolution
Can view living species
Preperation is relatively easy
Compare features of TEM and SEM
TEM- use electromagents to focus beam of electrons
produce 2D images that can be falsely coloured
Hard preperation- speicmen has to be thin and prepared in vaccum
very high magnification and resolution
SEM-scan beam of electrons across surface of specimen
Image is 3D, but can be falsely coloured
lower resolution than TEM
What are artefacts? Give examples
Artefacts are things present on microscope slide that is not part of specimen e.g hair, fingerprints,dust, air bubbles
What is magnification?
How many times bigger the image is compared to actual specimen
What is resolution?
The ability to distinguish between two things that are close together
How to use the scale bar?
measure length of cell
measure length of scale bar
divide cell by scale bar
multiply by scale bar
What is cell fractionation?
the process of seperating cell organelles from each other
Describe the process of cell fractionation
Cells go through homogenisor- are broken up using pestle and mortar, blending or vibrations
Then placed into cold (slows down enzyme activity), isotonic (maintain water potential) buffer(maintain pH) solution.
then placed into homogen
solution then flitered through gauze to get rid of larger organelles
then placed into centrifuge machine at lowest speed. The densest organelles (nucleus) will create a pellet at bottom of tube first. The solution left over is called supernatant
Continued at higher speeds
What is mitosis?
A type of cell division in eukaryotes that results in 2 genetically identical daughter cells
In what part of the cell cycle does DNA replication occur?
interphase
What happens during interphase?
Cell begins to divide by making new organelles and proteins
DNA unravels and replicates doubling the genetic content in the cell
What happens during prophase?
Chromosomes condense and become shorter
Nuclear envelope breaks down and releases chromosomes into cytoplasm
Centrioles move to opposite sides of the cell and produce spindle fibres
What happens during metaphase?
chromosomes align across the equator of the cell
spindle fibres attach to centromere on chromosomes
What happens during anaphase?
Centromeres are pulled to opposite poles of the cell, dividing from the other chromatid
Chromatids appear v shaped
What happens during telophase?
Chromatids uncoil and become long again
new nuclear envelope is formed around both groups of cells
Cytoplasm pinches inwards called cytokinesis.
results in 2 genetically identical daughter cells
What is the equation for mitotic index?
number of cells with visible chromosomes/ number of cells observed x100
What is the result of uncontrolled cell division and what are its treatments?
Tumours and cancers
Treated using chemotherapy which distrupts G1 phase
Treated using radiotherapy with causes damage to DNA
Explain the process of binary fission
Circular DNA replicates everything in the cell
Cell grows, and DNA loops move to opposite ends
Cytoplasm divides and new cell wall forms
2 non-identical duaghter cells are produced due to different number of plasmids
Describe the root tip squash practical
Add 1M of hydrochloric acid to water bath at 60 degrees
Using scalpel cut 1cm of growing tip of root
Transfer to boiling tube and incubate for 5 mins
Use tweezers to remove, wet under water then pat dry
Place on cutting tile and cut 2mm then place on microscope slide
What is the fluid mosaic model?
The bilayer formed from phospholipids that is ‘fluid’
What movements occur across the plasma membrane + definitions ?
- simple diffusion (net movement of particles from high to low concentration, down concentration gradient)
- facilitated diffusion (larger molecules required channel/carrier proteins moving down concentration gradient)
- osmosis (net movement of water from higher water potential to lower through a partially permeable membrane) - active transport (movement of molecules from low to high concengtration, against concentration gradient)
- co-transport (proteins transporting 2 molecules at same time)
What can be found within the bilayer + description?
channel - used in simple diffusion
carrier- used in facilitated and active transport
co-transporter - used in active transport
glycoproteins - protein with carb attached
glycolipids - lipids with carbs attached
cholestrol- provides stability
What factors affect rate of movement across cell membrane?
surface area
number of channel or carrier proteins differences in gradients of concentration or
water potential
Describe the practical for cell permeability
Measure 5cm^3 of water and place into 5 boiling tubes
Place all tubes at different temp water baths and one in ice
Cut 5 equal sizes of beetroot using cork borer and scalpel
Rinse beetroot then place into boiling tubes with timed intervals for 20 mins
Remove beetroot and pour liquids into cuvettes
Fill one cuvette with distilled water and reset colorimeter
Record % of light absorbed and plot on graph
Describe the dilution series
a step by step dilution of a concentration in a solution
Describe practical for osmosis
Measures equal amounts of water and 4 different sucrose solutions then place in test tube
cut 5 equal pieces of potato,removing skin and patting them dry
measure mass of cylinders then place into solutions for 20 mins
take out,pat dry and measure mass
calculate change in mass and plot results on calibration curve
What are antigens?
Proteins on the plasma mebrane involved in cell recognition. They allow immune cells to recognise foreign cells
Describe the role of phagocytes in the immune response
Phagocytosis - phagocytes recognise foreign antigen and engulf pathogen, sotring in phagocytic vacuole. Lysosome fuses with vacuole releasing lysozymes that digest/break down pathogen. Phagocyte acts as antigen presenting cell.
Describe the role of T-cells in the immune response
They are another type of WBC with receptor molecules which bind to complementary antigens on pathogen. Helper t-cells release chemical signals that stimulate cytotoxic t-cells to kill foreign cells
Describe the role of B-cells in the immune response
Activated by helper T-cells, secrete antibodies
Covered with antibodies so form antigen-antibody complexes
Describe the process of antibody production in the immune response
B-cells divide by mitosis to form plasma cells which secrete antibodies (clonal selection)
T and B-cells produce memory cells (T remember antigens and B antibodies)
What is the structure of an antibody?
4 polypeptide chains bonded by disulphide bridges
It has variable and constant regions
What is agglutination?
When an antibody binds to 2 pathogens at once, causing them to be clumpred together and easier for phagocyte to engulf
What is active immunity?
When your own imune system produces antibodies. Can be both natural (catching disease) and artificial (vaccines)
What is passive immunity ?
When your immune system is given antibodies from different organism
Can be natural (babies) or artifical (injected with someone elses)
What are vaccines and their advantages ?
dead or inactive pathogens with the complementary antigens
Herd immunity- reduces trhe occurence of disease in population so reduces other peoples chances of getting it
What is antigenic variation?
When some pathogens e.g influenza have ability to change antigens
What is HIV and what is its sructure?
its a virus that attacks the human immune system
It has a spherical shape, with a core containing RNA
They have outer coatings called the capsid and envelope
On the outside they have attachment proteins
Describe HIV replication
attachment proteins attach to receptor molecules on T-cells
capsid is released into cytoplasm where RNA unravels
reverse transcriptase takes place and creates complementary strand of DNA
host cell enzymes make viral proteins which bud from cell and infect other cells
What is AIDS ?
when a persons number of helper t-cells gets critically low and the persons immune system deteriorates
What is the direct ELISA test?
they test for the presence of antigens
antigens from patient stuck to well
antibody with complementary binding site added
well is washed out to remove unbound antibodies
substrate solution added
enzyme causes colour change - meaning positive test
What is the indirect ELISA test?
tests for presence of antibody
antigens stuck to well of plate
antibody from patients blood added
well is washed out to remove unbound antibodies
secondary antibody + enzyme added
well washed out
substrate solution added
enzyme causes colour change - meaning positive test
How does a lateral flow test work?
used to detect presence of hormones or antigens
patients sample added to application area
if antigen present it will from antigen-antibody complexes
sample will move up absorbent strip carrying antibodies and the coloured beads
accumulation of antibodies with coloured bead causes a coloured line to appear at immobilised antibodies
What is herd immunity?
A type of disease immunity that occurs when a large proportion of a population are vaccinated against a disease which prevents the spread of the disease to unvaccinated individuals
Monoclonal antibodies have also been designed to treat cancer by
They recognise and find specific proteins on the cancer cells, working to kill it.
Drugs specifically target the cancer cells and can allow smaller doses of chemotherapy drugs to be used
This can reduce the side effects and reduce risk to healthy cells
