Topic 2 cells Flashcards
Give the 5 key structure points of the nucleus
- Nucleus envelope - double membrane
- Nuclear pores
- Nucleoplasm - jelly like material
- Chromosomes - protein bound linear DNA
- Nucleolus - smaller sphere inside site of rRNA production and makes ribosomes
What is the function of the nucleus
(2)
Sure of DNA replication and transcription
Contained the genetic code for each cell
Give the structure of the endoplasmic reticulum
Rough and smooth endoplasmic reticulum both have folded membranes called CISTERNAE
Rough ER have ribosomes on the cisternae
Give the function of the Endoplasmic reticulum
Rough endoplasmic reticulum- protein synthesis
Smooth endoplasmic reticulum- synthesis and store lipids and carbohydrates
Give the structure of the Golgi apparatus
Folded membranes making cisternae
Secretary vesicles which pinch off from cisternae
Give the function of the Golgi apparatus
(7)
- Adds carbohydrates to proteins forming glycoproteins
- Produced secretory enzymes
- Secrete carbohydrates
- Transports, modifies and stores lipids
- Forms lysosomes
- Molecules are ‘labelled with destination
- Finished products are transported to cell surface in golgi vesicles where they fuse with membrane and release the contents
What is the structure of lysosomes?
Bags of digestive enzymes - contain 50 different enzymes
Give the function lysosomes
(4)
- Hydrolyse phagocytic cells
- Completely break down dead cells
(Autolysis) - Exocytosis - release enzymes outside cell to destroy material
- Digest work out organelles are reuse the materials
Give the structure of mitochondria
(4)
- Double membrane
- Inner members be called Cristae
3.fluid centre (mitochondrial matrix) - Loop of mitochondrial DNA
Give the function of mitochondria
(3)
- Site of AEROBIC respiration
- Site OF ATP production
- DNA to code for enzymes needed in respiration
Give the structure of ribosomes
Small
Made up of 2 sub units of protein and rRNA
80s which are larger found in eukaryotic cells
70s smaller found in prokaryotic cells as well as mitochondria and chloroplasts
What is the function of ribosomes
Site of protein synthesis
What is the structure of the vacuole
Filled with fluid surrounded by single membrane called tonoplast
What is the function of the vacuole
(3)
- Makes cell turgid providing support
- Temporary store of sugars and amino acids
- Pigment colours petals to attract pollinators
What is the structure of chloroplasts
Surrounded by a double membrane
Contains thylakoids
Fluid filled storms contains enzymes for photosynthesis
What is the function of chloroplasts
Site of photosynthesis
What is the structure of a cell wall
Plants - made up of microfibrils amid cellulose
Fungi - made of chitin
What is the function of cell walls
To provide structure an strength to the cell
What is the structure of the plasma membrane
Found in all cells
Contains phospholipid bilayer - molecules embedded within and attached on outside such as proteins, carbohydrates and cholesterol
What is the function of cell membrane
Controls the entrance and exit the molecule
What are the key differences in prokaryotic cells compared to eukaryotic
(5)
Much smaller
No membrane bound organelles
Smaller ribosomes
No nucleus
Cell wall made of murein
What 3 additional features Can a prokaryotic cell contain
- Plasmids
- A capsule
- Flagella
What is the structure of a virus?
Genetic material a capsid an envelope surrounding this and then attachment proteins
How do viruses replicate
Replicate inside of host cells
What are the 3 types of microscopes
Optical (light)
Transmission electron
Scanning electron
Define magnification
The magnification of a microscope refers to how many times larger the image is compared to the object
Define resolution
Minimum distance between the two objects on which they can still be viewed as separate, the resolution on an optical microscope is determined by the wavelength of light and the wavelength of beams of electrons in the electron microscopes
Give 5 properties of the optical microscope
- Bean of light condensed to create an image
- Poor resolution due to light having lower wavelength
- Lower magnification
- Colour images
- Can view living samples
Give 5 properties of electron microscopes
- Beam of electrons condensed to create image
- Higher resolution as electrons have shorter wavelength
- Higher magnification
- Black and white images
- Sample must not be living as it need to be in a vacuum
Why must specimens be kept in a vacuum for the electron microscope
As electrons are absorbed by air
Explain the difference between the scanning electron (SEM) and transmission electron microscope (TEM)
SEM creates 3D images as the electrons don’t go through the specimen they scatter in different ways producing a black and white 3D image
TEM has to have a think sample as electrons had to pass though specimen where some parts absorb electrons more and so are darker
What is the equation for magnification?
IAM
Magnification = Image size
Actual size
How do you convert from metres to millimetres
X1000
How do you convert from mm to micrometers
X1000
How do you convert from micrometers to manometers
x1000
What is the first step of cell fractionation
Homogenisation
What happens in homogenisation
(4)
- Cells are broken open to release contents and organelles then separated
- The cells must be prepared in a cold isotonic buffered solution
- Cell is then homogenised (broken up) using a blender
- The solution is then filtered to remove large cell debris
Why must cells be prepared in a cold solution for homogenisation?
To reduce enzyme activity
Why must cells be prepared in a isotonic solution for homogenisation?
Must be the same water potential to prevent osmosis as this could cause the organelles to shrivel or burst
Why must cells be prepared in a Buffered solution for homogenisation?
The solution had a PH buffer to prevent damage to organelles
Give the 2 steps of ultracentrifugation
- The filtered solution is spin at different speeds in the centrifuge
- Organelles separate according to densities
What is differential centrifugation
(3)
Centrifuge spine and creates a pellet of most dense organelles as bottom
Centrifuge is first spun at allow speed and increasingly gets faster after the removal of each pellet
Each time supernatant (liquid) removed leaving behind pellet or organelles
Give the order of organelles from most to least dense
(6)
Most dense
1. Nuclei
2. Chloroplasts
3. Mitochondria
4.lysosomes
5.endoplasmic reticulum
6.ribosomes
How do eukaryotic cells divide?
Mitosis or meiosis
How do prokaryotic cells replicate
Binary fission
What are the 3 Key stages in the cell cycle
Interphase
Nuclear division
Cytokinesis
What is interphase
The longest stage in the cell cycle
When the organelle doubles the cell grows and DNA replicates
What is nuclear division?
Can either be mitosis or meiosis creating 2 identical diploid cells or meiosis creating 4 t different haploid cells
Mitosis creates cells with identical DNA for growth and repair
What is cytokinesis
Final stage, division of cytoplasm to create new cells
What are the 4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What is a haploid cell?
The presence of a single set of chromosomes in an organisms cell
What is a diploid cell?
2 complete sets of chromosomes
Give the 4 key facts about mitosis
- One round of division
- Genetically identical cells are made
- Diploid cells are made
- Used for growth and repair
Explain the process of prophase
Chromosomes condenser and become visible
Nucleus disappears
Chromatin condense into chromosomes
Centrioles separate and move to opposite poles of the cell
These centrioles are responsible for creating spindle fibres
Explain the process of metaphase
Chromosomes align along the equator
The spindle fibres released form poles attach to centromere and chromatid
Explain process of anaphase
The spindle fibres retract pull away from centromere and chromatids they are bound to words opposite poles causing centromere to divide into 2 and individual chromatids pulled to each side
This stage requires energy in the form of ATP
Explain process of telophase
Chromosomes are now at each pole and elongate and thin out
Spindle fibres disintegrate
Nucleus reforms
Cytoplasm splits in 2 creating 2 genetically identical Cells
What is the mitosis index and how can it be calculated
Count how many visible cells are in a particular stage of mitosis
What is the equation for mitotic index
Number of cells in mitosis
The total number of cells x100
Give the 2 steps of binary fission
- Replication of the circular DNA and of plasmids
- Division of the cytoplasm to produce 2 daughter cells each single copy of circular DNA and variable number of plasmids
How do viruses replicate
They inject their nucleus acid into host and the host cell then replicated the virus particles
What model describes a plasma membrane and why?
Fluid mosaic model
As the mixture and movement of phospholipids create a mosaic like structure
What does the presence of cholesterol in the membrane do?
Cholesterol restricts lateral movement of other molecules
This can be useful as makes the membrane less fluid at high temps and prevents water and dissolved ions leaking out
What is the purpose of a peripheral protein?
Provides mechanical support or connected to proteins or lipids to make glycoproteins and glycolipids act as receptors
What is the purpose of integral proteins
Protein carriers or channel proteins
What is the difference between Carrier proteins and channel proteins
Channel proteins from tubes that fill with water allowing water soluble ions to diffuse
Carrier proteins will bind to other ones and large molecule such as glucose and change shape in order to transport them across the membrane
What’s meant by membrane partially permeable
Only lipid soluble molecules and very small molecules can pass through the membrane
What are the 4 key types of transport across membranes
- Diffusion
- Facilitated
- Active transport
- Osmosis
What is simple diffusion?
A net movement of molecules from area of high concentration to an area of lower concentration until equilibrium is reached
Does not require ATP
What is facilitated diffusion?
Proteins used to transport molecules they movement of ions and polar molecules are transported via channel and carrier proteins
What is osmosis
Movement of water from an area of higher water potential to area of lower water potential across a partially permeable membrane
What is meant by isotonic?
Water potential is same as the solution and the cell within the solution
What is meant by hypOtonic
The water potential of a solution is more positive (closer to 0) than the cell
Plump cells full of water
What is meant by hypERtonic
Water potential of a solution is more negative than the cell
Shrivelled cell as all water has left it
What is active transport?
The movement of a substance from a low concentration to a high concentration using metabolic energy and a CARRIER protein
Give the 5 steps of active transport
- Transport through carrier protein
- Molecule bonds to complementary receptor on Carrier protein
- ATP bonds to the carrier protein from inside cell and is hydrolysed
- Causes carrier protein to change shape and release molecule on other side
- Phosphate ion released and protein returns to its original shape
Explain why co transport is needed for glucose and sodium
To absorb glucose from the lumen to the gut requires high concentration of glucose in the lumen compared to epithelial cell
But there is more glucose in the epithelial cells
Explain co transport of glucose and sodium in 5 steps
- Sodium ions actively transported out of epithelial valley into the blood
- This reduces the sodium ion conc in epithelial cell
- Sodium ions can diffuse from Lumen down their conc gradient into epithelial cell
- Protein the sodium ions diffuse through is a co-transported protein so glucose or amino acids are also attached and transported into epithelial cell against their concentration gradient
- Glucose moves by facilitated diffusion from epithelial cell into blood
What are the 2 main adaptions for rapid transport
An increase in surface area
An increase in number of carrier and channel proteins
What are lymphocytes
Cells that can identify the presence of pathogens and foreign harmful substances and deftly them
How can lymphocytes distinguish between pathogens and self - cells
Each type of cell has specific molecule on its surface that identifies it, these molecules are proteins as true 3D tertiary structure enables lots of unique and identifiable shapes
What are the 4 different non-self cells that lymphocytes can recognise
- pathogens
- Cells from tiger organisms
- Abnormal body cells such as cancer
- Toxins
What is an antigen
Molecules that generate an immune response by lymphocyte cells when detected in the body
What is antigen variability
Pathogenic DNA mutates so shapes of the antigen will change so any previous immunity will no longer be effective
Give 2 examples of physical Barrier
Eyelashes and skin
Give 2 examples of chemical barrier
Stomach acid and tears
What are the 2 responses of white blood cells?
Phagocytosis - non-specific
Lymphocytes- specific
What is a phagocyte?
A macrophage (white blood cell)
Describe the process of phagocytosis in 6 steps
- Any chemicals or debris released by pathogens attract phagocytes
- Many receptor binding points on surface of phagocytes they will attach chemicals or antigens on the pathogen via these receptors
- Phagocyte changes shape to move around and Engulf the pathogen
- Once engulfed the pathogen is contained in a phagosome vesicle
- A lysosome within phagocyte will fuse with the phagosome and release its contents
- Lysozyme enzyme released into phagosome which then hydrolysed the pathogen destroying it and so liable products are then absorbed
Where do T cells mature
Thymus
What response involves T cells
Cell mediated
What is an antigen presenting cell
Give 4 examples
Any cell that presents a non self antigen on their surface
Infected body cells present these viral antigens
A macrophage which has engulfed and destroyed a pathogen will present these
Cells that have been transplanted
Describe the cell mediated response in 4 steps
- Once pathogen engulfed and destroyed by phagocyte antigens are now cell surface antigens
- Helper T cells have receptors on their surface and attach to the antigens of APC
- Once attached activated the helper T cells to divide by mitosis
- Cloned helper T cells differentiate
Some remain as helper T cells and active B lymphocytes
Others stimulate macrophages to perform phagocytosis
How do cytotoxic T cells destroy cells
They release a protein called perforin which embeds into cell surface membrane makes a pore so substances can enter or leave the cell
What are B lymphocytes
White blood cells that mature in the bone marrow
What is the response involved with B lymphocytes
Humoral
How are B cells activated
There’s 10 million different B cells in your body which are complementary to 10 million different antigens
Antigens in the blood collide with their complementary antibody on a B cell B cell then takes in the antigen by endocytosis and presents it on its cell surface membrane
When B cells collide with helper T cells activated B cells to go through clonal expansion and differentiation
What can B cells differentiate into
Plasma cells or memory B cells
What is the role of plasma cells
To make antibodies
What is the role of memory B cells
Divide rapidly into plasma cells when re infected with the same pathogen
Can live decades
Don’t make antibodies
This is a form of active immunity
Explain the graph you would see for primary and secondary immune response
So when your initially exposed to a new pathogen the number of antibodies your body makes would be small as it’s a new foreign pathogen and then you would eventually make more and overcome the illness but he number of this specific antibody wouldn’t go to 0 it would just lower so that when you are reinfected with a secondary exposure your body creates lots of specific antibodies to fight the illness before you get ill
What is an antibody
A protein produced in response to counteracting a specific antigen
What is agglutination
Antibodies are flexible and so can bind to multiple antibodies and so can clump together
What is passive immunity
When antibodies are introduced to body
Give an example if passive immunity
Breast milk
What is active immunity
Immunity created by your own immune system following exposure to pathogen
What is natural active immunity
Following infection and creation of antibodies and memory cells
What is artificial active immunity
Vaccine
What is a vaccine
A small amount of weakened antigen introduced usually by injection
What is herd immunity
If enough of population is vaccinated pathogen cannot spread easily amongst the population
What is the core of HIV
Genetic material (RNA) and the enzyme reverse transcriptase which is needed for viral replication
What is the capsid of HIV
Outer protein coat
What is the envelope for HIV
Extra outer layer made from membrane of host cell
What are the protein attachments on HIV
Exterior of envelope allows virus to attach to host helper T cells
How does HIV replicate in helper T cells
(4)
1.HIV transported around in blood until attached to a CD4 protein on helper T cell
- HIV protein capsule fuses with helper T cell membrane enabling RNA and enzymes from HIV to enter
- HIV enzyme reverse transcriptase copies thee viral RNA into DNA copy and moves to helper T cell nucleus
- mRNA is transcribed and helper T cell starts to create viral proteins and make new viral particles
What is AIDS
when a replicating virus in the helper T cells interfere with normal functioning immune system left vulnerable to cancer and infections
What are monoclonal antibodies
Single type of antibody that can be isolated and cloned
How can cancer be treated by monoclonal antibodies
Some monoclonal antibodies complementary to the shape of the antigens on outside of cancer cells so they will attach preventing chemicals binding to inhibit uncontrollable cell division
What does the ELISA test stand for
Enzyme linked immunosorbent assay
How does the pregnancy test work
- First mobile antibody, complementary to the antigen being tested for and has coloured dye attached
- A second antibody complementary in shape to the antigen immobilised in the test
- A third antibody is immobilised and complementary in shape to the first antibody
How does ELISA test work
(7)
- Add sample at bsd if beaker
- Wash to remove unbound test sample
- Add antibody complementary in shape to the antigen you are testing the presence of
- Wash to remove unbound antibody
- Add 2nd antibody that is complementary to the first antibody and binds to the first.
The 2bd antibody has an enzyme attached to it rinse any unbound antibodies - Substrate for enzyme is added (colourless) this substrate produces coloured products with the enzyme
- Presence of colour indicates presence of antigen
What are the ethical issues of monoclonal antibodies
Animal testing
