Module 2 Cells Flashcards
whats the structure of the nucleus
Nuclear envelope, nuclear pores, nucleolus, and chromatin
whats the functions of the nucleus
Controls the cells activity through transcription on mRNA
Nuclear pores allow substances to move between the nucleus and cytoplasm
Nucleolus makes ribosomes which are made up of proteins and ribosomal RNA
whats the structure of the CSM
Phospholipid bilayer with embedded proteins
whats the functions of the CSM
Selectively permeable – enables control of the passage of substances in and out of the cell
The barrier between the internal and external environment of the cell
whats the structure of the mitochondria
Double membrane – inner membrane folded to form cristae.
Matrix containing small 70S ribosomes, small circular DNA, and enzymes involved in aerobic respiration
whats the function of the mitochondria
Site of aerobic respiration producing ATP for energy release
whats the structure of the golgi apparatus
3 or more fluid filled membrane bound sacs with vesicles at edge
whats the function of the golgi apparatus
Receives protein from rough endoplasmic reticulum
Modifies protein
Packages into vesicles
Makes lysosomes
whats the structure of the lysosomes
Type of Golgi vesicle
whats the function of the lysosomes
Release of lysozymes to pathogens or worn out cell components
whats the structure of the ribosomes
1 large and 1 small subunit
whats the function of the ribosomes
Site of protein synthesis
whats the structure of the RER
Ribosomes bound by a system of membranes
whats the function of the RER
Folds polypeptides to secondary and tertiary structure
Packages to vesicles, transport to the Golgi apparatus
whats the structure of the SER
System of membranes
whats the function of the SER
Synthesises and processes lipids
whats the structure of the chloroplasts (plants and algae)
Thylakoid membranes are stacked up in some parts to form grana, which are linked by lamellae. These sit in the stroma (fluid) and are surrounded by a double membrane. Also contains starch granules and circular DNA.
whats the function of the chloroplasts (plants and algae)
Absorbs light for photosynthesis to produce organic substances
whats the structure of the cell wall (plants, algae and fungi)
Made of cellulose in plants and algae, and of chitin in fungi
whats the function of the cell wall (plants, algae and fungi)
Rigid structure surrounding cells in plants, algae and fungi.
Prevents the cell changing shape and bursting (lysis)
whats the structure of cell vacuole (plants)
Contains cell sap which is a weak solution of sugars and salts.
Surrounding membrane is called the tonoplast.
whats the function of cell vacuole (plants)
Maintains pressure in the cell (stop wilting)
Stores/isolates unwanted chemicals in the cell
whats a specialised cell
The most basic structural subunit in all living organisms; specialised for a particular function
whats a tissue
Group of organised specialised cells; joined and working together to perform a particular function
whats an organ
Group of organised different tissues; joined and working together to perform a particular function
whats an organ system
Group of organised organs; working together to perform a particular function
How prokaryotic cells differ from eukaryotic cells (6 points)
Prokaryotic cell cytoplasm contains no membrane bound organelles WHEREAS eukaryotic cell contains membrane bound organelles
Prokaryotic cell has no nucleus WHEREAS eukaryotic cell has a nucleus containing DNA
Prokaryotic DNA is circular and isn’t associated with proteins WHEREAS eukaryotic DNA is linear and is associated with proteins
Prokaryotic cell wall contains murein and peptidoglycan WHEREAS eukaryotic cell wall is made of cellulose
Prokaryotic cells have smaller 70s ribosomes WHEREAS eukaryotic cells have larger ribosomes
what might prokaryotes have
One or more plasmid, a capsule, and one or more flagella
what does acellular mean
Not made of or able to be divided into cells
what does non-living mean
Unable to reproduce without a host cell
principles of an optical microscope
Use light to form a 2D image
advantages of optical microscopes
Can see living organisms
disadvantages of optical microscopes
2D image
Only used on thin specimens
Low resolution; can’t see internal structures of organelles or organelles smaller than 200nm
Low magnification
principles of a TEM
Use electrons to form a 3D image
Electromagnets focus beam of electrons onto specimen
advantages of TEM
High resolution so can see internal structures of organelles
High magnification
disadvantages of TEM
2D image
Only used on thin specimens
Vacuum; can’t see living organisms
principles of an SEM
Use electrons to form a 2D image
Beams of electrons scan the surface, knocking off electrons from the specimen, which is gathered in a cathode ray tube to form an image
advantages of SEM
3D image High resolution; can see internal structures of organelles High magnification Used on thick specimens
disadvantages of SEM
Vacuum; can’t see living organisms
Lower resolution than TEM
why is resolution high
Electrons shorter wavelength
why is resolution low
Visible light longer wavelength
results of SEM
more dense = more absorbed = darker appearance
whats magnification
how much bigger the image of a sample is compared to the real size
how to measure the magnification
magnification = size of image/actual size
whats resolution
how well-distinguished an image is between 2 points; shows the amount of detail
how to measure the size of an object viewed with an optical microscope
- Line up eyepiece graticule with stage micrometer
- Use stage micrometer to calculate the size of divisions on eyepiece graticule at a particular magnification
- Take the micrometer away and use the graticule to measure how many divisions make up the object
- Calculate the size of the object by multiplying the number of divisions by the size of division
- Recalibrate eyepiece graticule at different magnifications
how to prepare a ‘temporary mount’ of a specimen on a slide
- Use tweezers to place a thin section of specimen e.g. tissue on a water drop on a microscope slide
- Add a drop of a stain e.g. iodine in potassium iodide solution used to stain starch grains in plant cells
- Add a cover slip by carefully tilting and lowering it, trying not to get any air bubbles
what are the principles of cell fractionation and ultracentrifugation
- Homogenise tissue using a blender to disrupt cell membrane and break open cell to release organelles
- Place in a cold, isotonic, buffered solution
- Filter homogenate to remove large, unwanted debris
- Ultracentrifugation occurs so centrifuge homogenate in a tube at a low speed and remove pellet of heaviest organelle and spin supernatant at a higher speed then repeat at higher and higher speeds until organelles separated out,
Why is the solution placed in a cold, isotonic, buffered solution
- Cold reduces enzyme activity so organelles aren’t broken down
- Isotonic so water doesn’t move in or out of organelles by osmosis so they don’t burst or shrivel
- Buffered keeps pH constant so enzymes don’t denature
How are the organelles separated in ultracentrifugation
in order of mass/density
What’s the order in which organelles are separated
nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes
what happens in interphase
s phase
g1
g2
what happens in s phase
DNA replicates semi-conservatively leading to two sister chromatids
what happens in g1 and g2
Number of organelles and volume of cytoplasm increases, protein synthesis, ATP content increased
what’s the structure of a virus
DNA and RNA, capsid and attachment proteins
whats mitosis
a parent cell divides to produce two genetically identical daughter cells, containing identical copies of DNA of the parent cell.
mnemonic for mitosis stages
‘PMAT’
what happens in prophase
Chromosomes condense, becoming shorter and thicker so appear as two sister chromatids joined by a centromere
Nuclear envelope breaks down and centrioles move to opposite poles forming spindle network
what happens in metaphase
Chromosomes align along equator
Spindle fibres attach to chromosomes by centromeres
what happens in anaphase
Spindle fibres contract, pulling sister chromatids to opposite poles of the cell
Centromere divides
what happens in telophase
Chromosomes uncoil, becoming longer and thinner
Nuclear envelope reforms and forms two nuclei
Spindle fibres and centrioles break down
what happens in cytokinesis
The division of the cytoplasm producing two new cell
whats the importance of mitosis
Growth of multicellular organisms
Repairing damaged tissues
Asexual reproduction
what does uncontrolled cell division lead to
formation of tumours and of cancers
whats a malignant tumor
cancerous and spreads and affects other tissues
whats a benign tumor
non-cancerous
what are cancer treatments directed at
controlling the rate of cell division
how do cancer treatments work
Disrupt the cell cycle
Mitosis slows
Tumour growth slows
give 2 examples of how cancer treatments control the rate of cell division
Prevent DNA replication which prevents and slows down mitosis
Disrupts spindle activity so chromosomes can’t attach to spindle by their centromere and sister chromatids can’t be pulled to opposite poles of the cells which slows mitosis
give an advantage and disadvantage of cancer treatments
Drugs more effective against cancer cells because dividing uncontrollably
Disrupt cell cycle of normal cells too, especially rapidly dividing ones
explain the process of binary fission
- Circular DNA and plasmids replicate
- Cytoplasm expands as each DNA molecule moves to opposite poles of the cell
- Cytoplasm divides
- This produces 2 daughter cells, each with a single copy of DNA and a variable number of plasmids
wy do viruses not undergo cell division
they’re non-living
how do viruses replicate
- Attachment protein binds to complementary receptor protein on surface of host cell
- Inject nucleic acid (DNA/RNA) into host cell
- Infected host cell replicates the virus particles
whats the fluid-mosaic model of membrane structure
Molecules within the membrane can move laterally and is a mixture of phospholipids, proteins, glycoproteins, and glycolipids
what are the 5 parts of the cell membrane structure
phospholipid bilayer, embedded proteins, glycolipids, and glycoproteins, and cholesterol
how is the phospholipid bilayer arranged
Phosphate heads are hydrophilic so attracted to water – orientate to the aqueous environment
Fatty acid tails are hydrophobic so repelled by water – orientate to the inside
how does the phospholipid bilayer control how molecules can enter/leave a cell
Allows movement of non-polar small/lipid-soluble molecules down a conc gradient (simple diffusion)
Restricts the movement of larger/polar molecules
how do the channel proteins and carrier proteins control how molecules can enter/leave a cell
Allows movement of water-soluble/polar molecules / ions, down a concentration gradient (facilitated diffusion)
how do the carrier proteins control how molecules can enter/leave a cell
Allows the movement of molecules against a concentration gradient using ATP (active transport)
how is the phospholipid bilayer adapted for other functions
Maintains a different environment on each side of the cell or compartmentalisation of cell
how is the phospholipid bilayer is fluid adapted for other functions
Can bend to take up different shapes for phagocytosis / to form vesicles
how is the surface proteins / extrinsic / glycoproteins / glycolipids adapted for other functions
Cell recognition / act as antigens / receptors
how is cholesterol adapted for other functions
Regulates fluidity / increases stability
what the role of cholesterol
Makes the membrane more rigid by restricting the lateral movement of molecules making up the membrane
explain the movement across membranes by simple diffusion
Net movement of small, non-polar molecules across a
selectively permeable membrane, down a concentration gradient
does simple diffusion require ATP
no - passive
what are the factors affecting simple diffusion rate
surface area, concentration gradient, diffusion distance
explain the movement across membranes by facilitated diffusion
Net movement of larger/polar molecules across a selectively permeable membrane, down a concentration gradient through a channel/carrier protein
does facilitated diffusion require ATP
no - passive
what are the factors affecting facilitated diffusion rate
surface area, concentration gradients, number of channel/carrier proteins
what’s the role of carrier proteins
transport large molecules, the protein changes shape when molecule attaches
what the role of channel proteins
transport charged/polar molecules through its pore
what’s special about channels and carrier proteins
Different carrier and channel proteins facilitate the diffusion of different specific molecules
explain the movement across membranes by active transport
Net movement of molecules/ions against a concentration gradient, using carrier proteins and using energy from the hydrolysis of ATP to change the shape of the tertiary structure andpush the substances though
what are the factors affecting active transport rate
pH/temp (tertiary structure of carrier protein), speed of carrier protein, number of carrier proteins, rate of respiration (ATP production)
explain the movement across membranes by co-transport, illustrated by the absorption of sodium ions and glucose by cells lining the mammalian ileum
- Sodium ions actively transported out of epithelial cells lining the ileum, into the blood, by the sodium-potassium pump. Creating a concentration gradient of sodium (higher conc. of sodium in lumen than epithelial cell)
- Sodium ions and glucose move by facilitated diffusion into the epithelial cell from the lumen, via a co-transporter protein
- Creating a concentration gradient of glucose – higher conc. of glucose in epithelial cell than blood
- Glucose moves out of cell into blood by facilitated diffusion through a protein channel
explain the movement across membranes by osmosis
Net movement of water molecules across a selectively permeable membrane down a water potential gradient
whats water potential
Water potential is the likelihood (potential) of water molecules to diffuse out of or into a solution
what has the highest water potential
Pure water = 0
how to make water potential more negative
adding solutes to a solution lowers the water potential
what are the factors affecting osmosis rate
surface area, water potential gradient, diffusion distance
how might cells be adapted for transport across their internal or external membranes
- By an increase in surface area
- Increase in number of protein channels / carriers
whats the antigen definition
Molecules which, when recognised as foreign by the immune system, can stimulate an immune response and lead to the production of antibodies
where are antigens found
as proteins on the surface of cells
why are antigens specific
proteins have a specific tertiary structure allowing different proteins to act as specific antigens
what do antigens allow the immune system to identify
Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins
outline the process of phagocytosis
- Phagocyte recognises foreign antigens on the pathogen and binds to the antigen
- Phagocyte engulfs pathogen by surrounding it with its cell surface membrane
- Pathogen contained in phagosome in cytoplasm of phagocyte
- Lysosome fuses with phagosome and releases lysozymes into the phagosome
- These hydrolyse the pathogen
- Phagocyte becomes antigen presenting and stimulates specific immune response
outline the cellular response process
T lymphocytes recognise antigen-presenting cells after phagocytosis and specific T helper cell with receptor complementary to specific antigen binds to it, becoming
activated and dividing rapidly by mitosis to form clones
What clones are formed and what do they do
a) Stimulate B cells for the humoral response
b) Stimulate cytotoxic T cells to kill infected cells by producing perforin
c) Stimulate phagocytes to engulf pathogens by phagocytosis
outline the humoral response process
Clonal selection occurs:
a) Specific B cell binds to antigen presenting cell and is stimulated by helper T cells which releases cytokines
b) Divides rapidly by mitosis to form clones (clonal expansion)
- Some become B plasma cells for the primary immune response – secrete large amounts of monoclonal antibody into blood
- Some become B memory cells for the secondary immune response
what is the primary response – antigen enters the body for the first time (role of plasma cells)
Produces antibodies slower and at a lower concentration because:
- Not many B cells available that can make the required antibody
- T helpers need to activate B plasma cells to make the antibodies (takes time)
- So infected individual will express symptoms
what is the secondary response – same antigen enters body again (role of memory cells)
Produces antibodies faster and at a higher concentration because:
- B and T memory cells present
- B memory cells undergo mitosis quicker / quicker clonal selection
what are antibodies
Quaternary structured protein
Secreted by B lymphocytes
Binds specifically to antigens forming an antigen-antibody complex
Describe and explain how the primary structure of an antibody relates to its function
Primary structure of protein = sequence of amino acids in a polypeptide chain
- Determines the folds in the secondary structure as R groups interact
- Determines the specific shape of the tertiary structure and position of hydrogen, ionic and disulfide bonds
Describe and explain how the quarternary structure of an antibody relates to its function
comprised of 4 polypeptide chains (tertiary structured) held together by hydrogen, ionic, and disulfide bonds
- Enables the specific shaped variable region (binding site) to form which is a complementary shape to a specific antigen
- Enables antigen-antibody complex to form
How do antibodies work to destroy pathogens
agglutination
whats agglutination
Binds to two pathogens at a time at variable region forming an antigen-antibody complex
- Enables antibodies to clump the pathogens together
- Phagocytes bind to the antibodies and phagocytose many pathogens at once
whats the hinge region
antibody can bind to antigens different distances part
What is a vaccination?
Injection of antigens
From attenuated pathogens
Stimulates the formation of memory cells
how can a vaccine lead to symptoms
some of the pathogens might be alive, the pathogen could reproduce and release toxins, which can kill cells
how does the use of vaccines to provide protection for individuals against disease
On secondary exposure to the same antigen, the secondary response produces antibodies faster and at a higher concentration
- Leading to the destruction of a pathogen before it can cause symptoms = immunity
what herd immunity
Large proportion but not 100% of population vaccinated against a disease
how does the vaccine make it more difficult for the pathogen to spread through the population
More people are immune so fewer people in the population carry the pathogen-infected
- Fewer susceptible so less likely that a non-vaccinated individual will come into contact with an infected person and pass on the disease
how does active immunity occur
Initial exposure to antigen e.g. vaccine or primary
infection
are memory cells involved in active immunity?
yes
where do the antibodies come from in active immunity
produced and secreted by (B) plasma
cells
give an advantage of active immunity
Long term immunity so antibody can be produced
in response to a specific antigen again
give a disadvantage of active immunity
Slow so takes time to develop
how does passive immunity occur
No exposure to antigen needed
are memory cells involved in passive immunity?
no
where do the antibodies come from in passive immunity
Antibody introduced into the body from another
organism e.g. breast milk / across the placenta from
mother
give an advantage of passive immunity
Fast-acting
give a disadvantage of passive immunity
Short term immunity (antibody broken down and not replaced)
what are the ethical issues associated with the use of vaccines (4 points)
- Tested on animals before use on humans, have CNS so feel pain
- Tested on humans and volunteers may put themselves at risk of getting disease, think they protected, and then vaccine not work
- Have side effects
- Expensive
whats can antigen variability cause (3 points)
- New vaccines against a disease need to be developed more frequently
- Vaccines against disease hard to develop or can’t be developed
- Experience a disease more than once
what’s the effect of antigen variability on disease
- Change in antigen shape
- Not recognized by B memory cell so no antibody made
- Not immune
- Re-undergo primary immune response which is slower and releases a lower concentration of antibodies
- Disease symptoms felt
Explain the effect of antigen variability on disease prevention (vaccines)
- Change in antigen shape
- Existing antibodies with specific shape unable to bind to changed antigens and form an antigen-antibody complex
- Memory cells won’t recognise different antigens
whats the features of a successful vaccination program
Produce suitable vaccine that is:
- Effective – make memory cells
- No major side effects - side effects decrease uptake
- Low cost
- Easily produced / transported / stored / administered
- Provides herd immunity
whats a monoclonal antibody
antibody produced from a single group of genetically identical B cells/plasma cells with an identical structure
what are the useful features of a monoclonal antibody
- Only bind to specific target antigens
- Antibodies have a variable region with a specific tertiary structure
- is complementary to a specific antigen which can bind to the antibody
what can the use of antibodies in the ELISA test to determine if a patient has
a) Antibodies to a certain antigen
b) Antigen to a certain antibody
whats the ELISA test used for
Used to diagnose diseases or allergies
Why use controls when performing the ELISA test?
- Controls enable a comparison with the test
To show that: - only the enzyme and nothing else caused color change
- washing is effective and all unbound antibody is washed away
Explain why the secondary and detection antibody must be washed away
Enzyme attached to antibody reacts with substrate turns solution diff colour; positive result
- Not washed out so enzymes react with the substrate
- Gives a positive result even if no antigen present (false positive)
what are the ethical issues associated with the use of monoclonal antibodies
- animals involved in production of monoclonal antibodies have CNS so feel pain and unfair to give them a disease
- major side effects possible so patients need to be informed of risk and benefits before treatment so they can make informed decisions
The structure of HIV – human immunodeficiency virus
capsid, lipid envelope, attachment protein, reverse transcriptase, and RNA
outline the replication of HIV in helper T cells
- HIV infects T helper cells (host cell)
- HIV attachment protein (GP120) attaches to a receptor on the helper T-cell membrane - Virus lipid envelope fuses with cell surface membrane and capsid released into the cell which uncoats, releasing RNA and reverse transcriptase into the cytoplasm
- Viral DNA is made from viral RNA
- Reverse transcriptase produces a complementary viral DNA strand from a viral RNA template
- Double-stranded DNA is made from this (DNA polymerase) - Viral DNA integrated into host cell’s DNA (by enzyme integrase)
- This remains latent for a long time in the host cell until activated
- Host cell enzymes used to make viral proteins from viral DNA (within human DNA) → viral
proteins assembled with viral RNA to make a new virus - New virus bud from the cell (taking some of cell surface membrane as an envelope)
- Eventually kills helper T cells
- Most host cells are infected and process repeat
How HIV causes the symptoms of AIDS
- Infects and kills helper T cells as it multiplies rapidly
- T helper cells then can’t stimulate cytotoxic T cells, B cells, and phagocytes so impaired immune response
- Immune system deteriorates
- More susceptible to infections
- Diseases that wouldn’t cause serious problems in a healthy immune system are deadly
Why antibiotics are ineffective against viruses
- Antibiotics can’t enter human cells
- Viruses don’t have their own metabolic reactions
- If we did use the - act as a selection pressure + gene mutation = resistant strain of bacteria via natural selection - reducing the effectiveness of antibiotics and waste money
