Cells Flashcards
Active immunity is…
immunity provided by the immune response of the body upon detection of a pathogen
Active transport is
the active movement of substances from a low concentration to a higher concentration against the concentration gradient with energy in the form of ATP.
Agglutination is …
the clumping together of cells caused by antibodies which assists phagocytosis
Antibodies are…
proteins produced by the immune system in response to foreign substances, such as viruses or bacteria.
Antigens are…
foreign substances which induce an immune response in the body
Binary fission is….
method of cell division used by prokaryotes
Function of chloroplast
Site of photosynthesis
Co transport is…
method of membrane transport where two substances are both transported across a membrane at the same time either in the same direction or opposite directions
Cytokinesis is
the division of the cytoplasm to produce two new cells
Function of flagella and where is it found
Found on bacterial cells and is used for cell movement
Why is the phospholipid bilayer described as a fluid mosaic model
Fluid as phospholipids allows for movement and mosaic because of the embedded proteins that resemble a mosaic pattern.
Function of Golgi Apparatus
Modification and packaging of proteins
Function of Helper T cells
Stimulates cytotoxic T cells, B - cells and phagocytes
Herd immunity is…
when a large proportion of a population is vaccinated against a disease which prevents the spread of the disease to unvaccinated individuals.
Function of lysosomes
Contain a hydrolytic enzyme calle lysozyme which can breakdown large waste products in the cytoplasm
Formula for magnification
M = I/A
Function of the mitochondria
Site of aerobic respiration
Monoclonal Antibodies are…
Identical antibodies that have been produced by an immune cell that has been cloned from a parent cell
Function of the nucleus
Stores genetic info of the cell as chromosomes and is surrounded by nuclear envelope
Osmosis is …
the passive diffusion of water molecules from a region of high water potential to a region of lower water potential down a concentration gradient through a selectively permeable membrane.
Passive Immunity is…
immunity provided by the introduction of antibodies to a disease into the body (vaccines)
Plasmids are…
a circular loop of DNA in bacterial cells
Phagocytosis is …
the process where phagocytes engulf and destroy material
Primary immune response is …
The response produced by the immune system when it encounters a pathogen for the first time.
Resolution is …
the ability to distinguish between two different points in a specimen
Function of ribosomes
Site of protein synthesis
Function of RER
Involved in the synthesis and packaging of proteins. Produces enough protein for the rest of the cell to function.
Secondary immune response is…
produced by the immune system when it recognises a pathogen it has encountered before
Function of SER
Involved in lipid and carbohydrates synthesis. Metabolism of exogenous substances like drugs and toxins
Vaccine is…
when dead or inactive pathogens are inserted to stimulate an immune response and provide long-term immunity.
How does TEM work?
A beam of electrons passes through a thin section of a specimen. Areas that absorb the electrons appear darker on the electron micrograph that is produced
How does SEM work?
A beam of electrons passes across the surface and scatter. The pattern of scattering builds up a 3D image depending on the contours of the specimen.
Limitations of SEM + TEM
System must be in a vacuum so no living specimens
Specimens must be very thin
SEM has a lower resolution than TEM
Process of Cell Fractionation
- The cells are blende in an homogeniser forming the resultant fluid called the homogenate. This is then placed in a cold , buffered and isotonic solution.
- It is then placed in a centrifuge and spun slowly. The heaviest organelles, the nuclei are forced to the bottom of the tube where the sediment forms
- The fluid at the top (supernatant) is removed and spun at a slightly higher speed . The next heaviest organelle forms at the bottom.
Why is the homogenate placed in a cold isotonic buffered solution
Cold - To prevent enzyme activity from breaking down organelles
Isotonic - To prevent the organelles from bursting under osmotic pressure
Buffered - To prevent fluctuation in pH which will denature the enzymes
Process of cell cycle
Interphase - Cell grows, chromosomes and so organelles are replicated + chromosomes condense
Prophase - Chromosomes become chromatids + spindle fibres form
Metaphase- Chromosomes align at the equator
Anaphase - Chromatids divide at the centromere and are pulled to opposite ends along the spindle fibres
Telophase -Nuclear membrane reforms and the chromosomes decondensed + spindle fibres disappear
Cytokinesis - cytoplasm divides and parent cell becomes 2 daughter cells
What happens during binary fission?
- Circular DNA replicates and attach to the cell membrane. Plasmids also replicate
- Cell membrane grows and cytoplasm begins to divide into two
3.New cell wall forms
Why are proteins important in the phospholipid bilayer?
Aid movement across the membrane (carrier + channel proteins)
Provide mechanical support
Act in conjunction with glycolipids as receptors
What are glycoproteins + why are they important in the phospholipid bilayer?
Carbohydrates that attach to extrinsic proteins an acts as a cell-surface receptors and neurotransmitters. These allow cells to recognise on another and form tissues
Why is cholesterol important in the phospholipid bilayer?
Makes membrane more rigid + reduce the lateral movement of the phospholipids
Prevents the leakage of water and dissolved ions from the cell.
What are glycolipids and why are they important in the phospholipid bilayer?
Made up of carbohydrates that are bound to lipids.
Act as a cell surface receptors for certain molecules
Allow cells to adhere to each other to form tissues
Exocytosis is…
when vesicles containg large particles are fused with the cell membrane + released from the cell
Endocytosis is…
when the particles are enclosed in vesicle made from the cell membrane and transported into the cell
Explain how glucose and amino acid are transported in and out of the cell by co transport
- Na+ is actively transported out of the epithelial cells by the sodium-potassium pump into the blood (in a carrier protein). This helps maintain a higher con. of Na+ in the lumen than inside the epithelial cell (ACTIVE TRANSPORT)
2.Na+ diffuse into the epithelial cells down this concentration gradient through a co-transport protein carrying either an amino acid/ glucose molecule into the cell with them
3.Glucose/amino acid passes into the blood plasma by FACILITATED DIFFUSION
When is the rate of diffusion the fastest ?
- SA increases
- Diffusion pathway decreases
- Temperature increases
- Diffusion gradient becomes more steep
Differences between viruses and bacteria
Bacteria are prokaryotic so genetic info is stored in a circular strand of DNA whereas viruses consist of just nucleic acid enclosed in a protein coat.
Viruses are smaller than bacteria
Bacteria don’t require a host whereas viruses do
Bacteria has structures like pili, flagella, cell wall, ribosomes and cytoplasm whereas viruses don’t
Example of viral infection and bacterial disease
B = Tuberculosis
V = HIV
Symptoms of HIV
fevers, tiredness and headaches
Examples of non-specific responses of the body to infection
inflammation
phagocytosis
lysozyme action
Specific immune response of the body to infection is…
Humoral response (B-cells)
Cell mediated response (T-cells)
Cell mediated response is…
- Pathogens are taken in by phagocytosis. The phagocyte becomes antigen presenting.
- Helper T- cells become stimulated and recopter on the helper t-cells bind to the antigens
- This activates t-cells to divde by mitosis and form clones of genetically identical cells
- Cloned T-cells :
a. develop into memory cells that enable a rapid response to future injections
b. stimulate phagoctes to engulf pathogens by phagocytosis
c. stimulate B cells to divide and secrete their AB
d. activate cytotoxic T-cells
Humoral response is …
- The surface antigens of an invading pathogen are taken up by a B-cell and B-cell process the antigens and presents them on its surface
- Helper t-cells attach to the processed antigens and activate B-cells to divide by mitosis to give a clone of plasma cells
- Plasma cells produce and secrete the specific AB that exactly fits the antigen on the pathogen’s surface
- Antibodies attach and destroy the pathogen
- Some B-cells form memory cells which can help with future infections
Differences between plasma and memory cells
Plasma:
primary immune response
secretes antibodies
lasts only few days
responsible for the immediate defence of body
Memory:
secondary immune response
dont secrete AB
lasts for decades
divide rapidly into new memory and plasma cells
Why is HIV a retrovirus?
It has reverse transcriptase , so has the ability to make DNA from RNA
How is HIV treated?
With antiretroviral drugs which keeps the level of HIV in the blood low, reducing impact on the immune system. Antibiotics dont work because they prevent cell wall from forming in bacteria preventing them from controlling what enters and leaves the cell but viruses dont have a cell wall
How does HIV replicate?
- HIV binds to CD4 protein receptors
- Caspid then fuses with the cell surface membrane and the RNA and the reverse transcriptase enter the cell
- Reverse transcriptase converts RNA to DNA, which then moves into the nucleus of the cell
- Cell now has the instructions to begin producing viral HIV components.
Uses of monoclonal antibodies other than pregnancy testing
Diagnosis
Direct therapy (target cancerous cells)
Indirect therapy (used to direct drugs to cells that are antigen presenting)
Ethical considerations about vaccines
- Production and testing may be done on animals
- Risks of vaccine must be balanced to the benefits
3.Vaccinations are expensice
- Vaccine must be tested on humans before being distrubuted
