Topic 2 - Cells Flashcards
What is a cell?
A basic unit of structure and function in an organism
What does a eukaryote have? Example of some
A true nucleus with a nuclear envelope surrounding the chromosome and membrane bound organisms
Animal and plant cells
What does a prokaryote have? Example of one
Don’t have membrane bound organelle
Free floating DNA and plasmids, not a nucleus
What does a plant cell have?
Chloroplasts Nucleus Cell membrane Cell wall Vacuole Cytoplasm
What does an animal cell have?
Nucleus Plasma membrane Mitochondria Ribosomes Cytoplasm Golgi apparatus Smooth endoplasmic reticulum Rough endoplasmic reticulum Nuclear envelope Nucleolus Nucleoplasm Vesicles
What does a bacteria cell have?
Flagellum
Plasmids
Free floating DNA
Cytoplasm - containing ribosomes
What does a yeast cell have?
Cell wall Cell membrane Vacuole Cytoplasm Nucleus
Parts of a chloroplast
Double membrane
Thylakoid
Grana
Stroma
structure of Nucleus
Nucleus surrounded by a nuclear envelope (a double membrane)
Nuclear pores allow the passage of large molecules out of the nucleus
Nucleoplasm jelly makes up a bulk of the nucleus
Nucleolus within the nucleoplasm manufactures RNA
Chromosomes
Function of Nucleus
Store genetic information
Control centre of the cell
Structure of Ribosome
2 sub units (one small one big)
Each contain ribosomal RNA and protein
Function of ribosome
Site of protein synthesis
Difference between 70S and 80S ribosomes
80S – eukaryotic cells, 25nm diameter
70S – prokaryotic cells, mitochondria, and chloroplasts, slightly smaller than 80S
Structure of mitochondria
Bound by a double membrane
Outer membrane = Matric
Inner membrane = Cristae
Has its own strand of DNA
Function of mitochondria
Respiration
“Powerhouse of the cell”
Aerobic Respiration
Production of ATP
Structure of the cell membrane
Around the whole cell
The function of the cell membrane
Controls what diffuses in and out of the cell
Structure of Rough Endoplasmic Reticulum
Ribosomes present
The function of Rough Endoplasmic Reticulum
Protein synthesis
Pathway for the transport of materials (like proteins throughout the cell)
Endoplasmic Reticulum general info
‘ER’
Connected to the outer nuclear membrane
Structure of Golgi Apparatus
Stack of membranes = flattened sacs
Membranes contain small hollow structures called vesicles
The function of the Golgi Apparatus
Transport, modify and store proteins and lipids produced by the Endoplasmic Reticulum
Molecules transported to and from the Golgi by vesicles
Produces Lysosomes and secretory enzymes
Cell post office – receives, sorts and delivers
Structure of Smooth Endoplasmic Reticulum
No ribosomes
The function of smooth endoplasmic reticulum
Synthesize, store and transport lipids and carbohydrates
Cytoplasm
Between the membrane and nucleus, made up of mainly water
Lysosome
Membrane
Contained up to 50 enzymes
Chloroplast
Outer and Inner membrane
Open space in the stroma
Thylakoid stacks (Grana) provides surface area
Permanent Vacuole
Large membrane bound sacs
Cell wall
On top of the cell membrane, around the whole cell
Cytoplasm
Houses all the organelle
Where chemical reactions take place
Lysosome
Garbage disposal of the cell
Remove useless/dangerous material
Formed when vesicles produced by the Golgi contain useful enzymes
Contain digestive enzymes to break down waste
Chloroplast
Captures light for photosynthesis
Permanent Vacuole
Provides structure and support for the cell and holds sap/water
Cell wall
Provides structure and support for the cell
What are the 3 main adaptations a cell can have?
number of RER and Golgi
Number of mitochondria
Surface area
How does the number of RER and Golgi affect a cell? What cells would need this adaptation?
Increased protein synthesis and production as well as transport for these proteins (and hormones)
Useful for cells that need lots of proteins for example cells that produce enzymes
How does the number of mitochondria affect a cell? What cells would need this adaptation?
Increased respiration which in turn increases energy for cells that need a lot of energy
For example muscle of sperm cells
How does surface area size affect a cell? What cells would need this adaptation?
Increases room to diffuse but also space to carry things
Red blood cells have no nucleus, so, therefore, a bigger surface area, so that it can carry more oxygen and waste products
Which is bigger prokaryotes or eukaryotes?
Eukaryotes
Explain DNA in eukaryotes
Membrane-bound in a true nucleus
Explain DNA in prokaryotes
Free-floating or in plasmids, not membrane-bound
Which organelles are present in prokaryotes?
Plasmid
Free-floating DNA
Flagellum
Ribosomes
Which organelles are present in eukaryotes?
Nucleus Ribosomes Mitochondria Golgi Apparatus SER RER Vesicles Lysosomes
Are ribosomes membrane-bound?
No, but RER is
Is there any photosynthetic material present in prokaryotes? Why?
No, chloroplasts are too big, but some big bacteria’s do have some photosynthetic material
Which ribosomes are present in prokaryotes?
70S
Which ribosomes are present in eukaryotes?
80S
70S (in mitochondria and chloroplasts)
What are cell walls made of in prokaryotes?
murien
What are cell walls made of eukaryotes?
Cellulose
What is a capsule and where is it found?
Most, but not all, prokaryotes
It is a protective layer of mucus slime that helps group bacteria in biofilm (a mass of sticky cells)
What is a virus?
A microscopic intracellular parasitic organism that can infect other organisms
Is a virus a prokaryote or a eukaryote?
Neither
What is a parasite?
An organism that relies on a host for survival to the detriment of the host
Why do viruses require a host?
They replicate inside body cells
Name 4 viral structures
Nucleic acid (RNA or DNA)
Caspid
Attatchment proteins
An envelope
Purpose of nucleic acid (RNA or DNA)
holds genetic information and controls organism
Purpose of capsid
protein coat that protects the genetic material
Purpose of attachment proteins
Helps the virus attach to a host via the cells receptors
Purpose of a viruses envelopes
An outer phospholipid membrane surrounding the capsid
What is a reverse transcriptase?
An enzyme that helps replicate the viruses own DNA
What is a cells plasma membrane made out of?
Phospholipids
What does a eukaryotic cell have that viruses do not?
Mitochondria, Golgi, RER and SER
Because the virus doesn’t have mitochondria, Golgi, RER or SER what can’t it do? So what does it do instead?
It can’t respire or modify, transfer and produce proteins so instead it uses the host cells organelles for these functions
What will the virus use of the host cell and what for?
.Enzymes - metabolic processes
.Mitochondria - respiration - energy
.Ribosomes - protein synthesis
Explain how a virus works
- The virus binds its attachment proteins to the host cells receptors – they are complementary
- The capsid fuses with the membrane, the virus releases its genetic material into the cell where it incorporates with cell genetic material
- The genetic material gets replicated and multiplies in amount of copies, at the same time it takes over the RER, SER, Golgi and Mitochondria to create caspids, attachment proteins and RNA/nucleic acid
- The genetic material and parts created through the cells organelle join up to create viruses and they burst out the cell, via exocytosis, releasing the viruses into the blood so they can spread to other cells
What is it called when the viruses burst out of the cell?
Exocytosis
What are the cells receptors and attachment proteins?
Complementary
Name the 3 types of microscopes
Light microscope, transmission electron microscope, scanning electron microscope
Why are microscopes useful?
.Let us see microscopic things, subcellular etc, so we can see the differences between cells and help us understand how it works
Define magnification
Magnification is the act or process of enlarging the physical appearance or image of something
Define resolution
Resolution is the minimum distance apart two objects can be in order to appear as separate items
Sources - light
Light radiation
Sources - SEM
electrons
Sources - TEM
electrons
Magnification - light
Up to 1500x
Magnification - SEM
30,000x
Magnification - TEM
Up to 10,000,000x
Resolution - light
Poor resolution
Resolution - SEM
20-100nm
Resolution - TEM
0.1nm
Sample preparation - light
Sample needs to be thin Washed A chemical stain is added Covered with a coverslip Apply pressure
Sample preparation - SEM
Coat surface of the specimen with thin layer of gold
Must be in a vacuum
Sample preparation - TEM
Sliced and stained with heavy metal
Must be in a vacuum
How it works - light
Light passes through the specimen
How it works - SEM
Scan surface of the substance
Electrons reflected off the surface
Beam is observed
How it works - TEM
Electrons passed through the specimen
Only electrons that pass are seen/produce an image
Resulting image - light
Can’t see small cells or organelle
2d black and white
Resulting image - SEM
3d
Resulting image - TEM
2d black and white
Disadvantages - light
Low resolution and magnification
Disadvantages - SEM
Expensive
Can’t view anything alive
Difficult to use
Very big
Disadvantages - TEM
Expensive
Can’t view anything alive
Difficult to use
Very big
What is an artefact? In terms of microscopy
An artefact is something seen that is not naturally there
When does an artefact happen? In terms of microscopy
happens as when you prep the slide you might affect the subject
Example of an artefact in terms of microscopy
for example creating wrinkles in the cell
1km = x m
1000m
1m = x cm
100cm
1cm = x mm
10mm
1mm = x um
1000um
1um = x nm
1000nm
Magnification =
image size / actual size
Image size =
actual size / magnification
Actual size =
image size / magnification
What is a stage micrometer?
A slide with a small etched scale on it
What is an eye piece graticule?
A glass disc placed in the eyepiece with a small scale etched on it
What is cell fractionation?
the process where cells are broken up and the different organelles they contain are separated out
Before a cell fractionation begins it needs to be placed in a solution that is what conditions?
Cold, same water potential as the tissue and buffered
Why does the cell fractionation solution need to be cold?
to reduce enzyme activity that might break down the organelles
Why does the cell fractionation solution need to be same water potential as the tissue?
to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
Why does the cell fractionation solution need to be buffered?
so that the pH does not fluctuate, any change of the pH could alter the structure of the organelles or affect the functioning of enzymes
What are the two stages to cell fractionation?
Homogentation and ultracentrifugation
What is homogenation?
Cells are broken up by a homogeniser (blender) with waves. This releases organelles from the cell, the resultant fluid, known as homogenate, is then filtered to remove any complete cells and large pieces of debris.
What is ultracentrifugation?
This is the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speed in order to create a centrifugal force.
What is the process of ultracentrifugation?
. The homogenate is placed in the centrifuge and spun at a slow speed
. The heaviest organelle, the nuclei, are forced to the bottom of the tube, where they form a thin sediment or pellet
. The fluid at the top of the tube (supernatant) is removed, leaving just the sediment of the nuclei
. The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before
. The next heaviest granules, mitochondria, are forced to the bottom of the tube
. The process continues like this so that at each increase in speed, the next heaviest organelle is sediment and separated out
What is the first organelle to be separated out and at what speed of centrifugation?
Nuclei at 1000 revolutions/minute
What is the second organelle to be separated out and at what speed of centrifugation?
Mitochondria at 3,500 revolutions/minute
What is the third organelle to be separated out and at what speed of centrifugation?
Lysosomes at 16,500 revolutions/minute
What is lysis?
Breaking down of the membrane of a cell
Why are the cells placed inside a buffer solution for cell fractionation?
.Some Lysosomes are broken open
.Proteins inside the cell are exposed to the external solution
.Organelles are exposed to the external solution
.This could damage them
Order of organelle size (big to small)
- Nucleus
- Chloroplast
- Lysosome
- Nuclear Pore
- Microtubule
- Ribosome
- Cell membrane
Why is it important the homogenate is filtered before it is spun in the centrifuge?
.As debris and other unwanted parts need to be removed so that it doesn’t contaminate the sample or interfere with the results
What is the cell cycle?
The cell cycle is a regular cycle of cell division, separated by periods of cell growth
Why is the cell cycle needed?
.Differentiation, becomes lots of different cells form the first fertilised egg cell
.Growth and repair
What are the 3 main different parts of the cell cycle?
- Interphase
- Nuclear division
- Division of the cytoplasm (cytokinesis)
What happens in nuclear division?
Mitosis, new nuclei form
What happens in Cytokinesis?
Division of the cytoplasm, new membranes form
What is the interphase split up into?
G1, S and G2
What happens in G1?
The cell is growing and working normally
It needs to grow to allow for enough organelle for each daughter cell
Synthesis of DNA polymerase which is an enzyme to make DNA
Producing ribosomes and mitochondria to produce the DNA and DNA polymerase
What happens in S?
DNA replicates to allow for the cell to divide, it halves the DNA between the two daughter cells, (they need the right amount of chromosomes, 23 pairs each)
What happens in G2?
Replication of other organelle/prepare the cell for cell division
checkpoint – apoptosis (programmed cell death) occurs if there is an abnormality
What is G0?
Cell Arrest
When does G0 occur?
Some cells don’t divide at all (nerve cells)
.Some cells will stop dividing, for example when we each adult hood, due to overcrowding or differentiation (like nerve cells).
How long do most mammalian cell cycles last?
24 hours
How long does a liver cell cell cycle last?
one year
Why is mitosis important?
Growth and repair, it helps gametes grow into embryos after their DNA has mixed and helps helps if we cut ourselves we can create the needed cells to repair the cut
How many chromosomes does each body cell have?
23 pairs in every body cell, apart from gametes
What is a centromere?
Where the spindle fiber attaches during cell division
How does the s phase change the amount of chromosomes?
Before the s phase, there are 1 maternal and 1 paternal chromatid to make up one chromosome, during the s phase each chromatid is replicated and doubles so that each chromosome is made up of a pair of identical sister chromatids (be that paternal or maternal) which are connected by the centromere and still regarded as a single chromosome, even though they are made up of two strands of identical genetic material
What is mitosis?
Controlled nuclear division
What are the 4 main stages of mitosis?
Prophase, metaphase, anaphase and telophase
What happens in prophase?
This is the preparation phase, chromosomes condense and become more visible by shortening and thickening, the nuclear membrane breaks down
What happens in metaphase?
This is all about the middle, a microtubule spindle forms within the cell, all the chromosomes line up along the equator of the cell attached to the spindle fibers (which start at the poles)
What happens in anaphase?
This is all about being pulled apart, microtubules shorten/contract pulling apart the sister chromatids, chromosomes are pulled to opposite poles of the cells
What happens in telophase?
This is all about the two, two new nuclear membranes form, chromosomes condense to become longer, thinner and less visible, a nuclear envelope forms around each group of chromosomes/chromatids at each pole
What is cytokenesis?
Where the cell membrane divides
How to remember the order of the cell cycle?
I P MAT C
Interphase, prophase, metaphase, anaphase, telophase and cytokenesis
How does uncontrolled cell division come about?
.Result of mutated genes
.Most mutated cells die or are destroyed however some may continue to divide and form tumors
How do cancer treatments disrupt the cell cycle?
.Preventing DNA from replicating
.Inhibiting metaphase by inhibiting the formation of spindle fibers
What do mitotic indexes tell us?
The ratio between the number of cells in a population undergoing mitosis to the total number of cells
miotic index =
number of actively dividing cells in a field of view/total number of cells in a field of view
What usually causes a cell to go wild and start reproducing very quickly?
A genetic mutation
How do bacteria reproduce?
binary fission
What is binary fission?
A form of asexual reproduction and cell division, used by all prokaryotes
State what you know about asexual reproduction
.One parent .No mixture of genetic material .Identical offspring .Clones .Quick (quicker than sexual as it’s simpler)
Describe the process of binary fission
The Plasmids replicate at one end of the cell while the free floating DNA moves to the centre of the cell, unravels (uncoils) and replicates there. One plasmid and one strand of free floating DNA move to each pole of the cell , the cell grows longer and then the equatorial plate of the cell constricts and separates the plasma membrane. The free floating DNA then ravels back up in each individual cell, forming 2 identical clones of cells. The cell wall and capsule will now form, it the cell needs one.
Similarities between nuclear division in prokaryotes and eukaryotes
DNA replicates
Genetic material moves to the centre then the poles
Prokaryotes are asexual, eukaryotes are asexual
Cytoplasm and cell membrane split
Formation of two new cells
Two identical cells produced
differences between nuclear division in prokaryotes and eukaryotes
Membrane bound DNA in eukaryotes so a membrane needs to form around the DNA to produce a nucleus
Chromatids line up along the equator in eukaryote reproduction before being pulled by the spindle fibres to the poles
Replication of plasmids
Sister chromatid joined at the centromere
4 distinct stages (PMAT)
Formation of cell wall
Why is Binary Fission quicker than mitosis?
.No nuclear envelope/nucleus
.Fewer/no membrane bound organelle to replicate
.Free floating DNA
.Simpler DNA (more condensed, doesn’t have all the junk DNA)
DNA VS DNA
Prokaryotes have a Single circular chromosome, eukaryotes have_____
Multiple linear chromosomes
DNA VS DNA
Prokaryotes have DNA condensed in the nucleoid, eukaryotes have_____
DNA condensed in the nucleus
DNA VS DNA
Prokaryotes have only one hard copy of each gene (haploid) , eukaryotes have_____
Two copies of each gene (diploid)
DNA VS DNA
Prokaryotes have plasmids commonly present , eukaryotes have_____
Plasmids not commonly present
DNA VS DNA
Prokaryotes have Little repetitive DNA , eukaryotes have_____
Large amounts of non-coding and repetitive DNA
Define antibody
Protein produced by white blood cells that help break down a pathogen
Define immune
When you are no longer able to catch a disease
Define fair test
When all variables other than the independent variable are controlled
Define plasmid
Circular pieces of DNA found in bacterial cells
Define vaccination
The insertion of a dead or weakened pathogen in order to cause an immune response
Define anomalous
When a result does not fit the pattern
Define optimum
The best conditions for a reaction to occur
Define active tranport
The movement of molecules from an area of low concentration to a high concentration against a concentration gradient
Define osmosis
The movement of water from a dilute to a concentrated area though a partially permeable membrane
Define diffusion
The movement of molecules from an area of high concentration to a low concentration down a concentration gradient
Describe the basics of an antigen
.On the surface of all cells are chemical markers called antigens
.Your body recognises the antigens on your cells as your own
.Anything with different antigens to yours stimulates an immune response
.In an immune response, your body will recognise the antigen as foreign and will attack it
Which molecules can act as anitgens?
. Proteins
. Glycoproteins
Why are antigens important?
. Initiate immune response to pathogens
. Allowing recognition of faulty cancer cells
. Recognition of cells from other organisms of the same species
How does antigenic variation work?
.Some pathogens can mutate which causes changes in the surface antigens
.The memory cells from the first infection won’t recognise the different antigens
.The immune system must carry out a primary response against the new antigens
What is phagocytosis?
Phagocytosis is when phagocytes (a type of white blood cell) engulf and break down an invading pathogen in order to protect the body, it is a part of the immune system.
What type of response is phagocytosis?
Phagocytosis is a non-specific response
Describe the steps of phagocytosis
- The phagocyte is attracted to the pathogen by detecting the toxins it is releasing
- The phagocyte moved towards one of the pathogens
- The phagocyte begins to surround the microbe. A vacuole forms around it.
- The phagocyte engulfs the pathogen
- The pathogen is inside a vacuole like phagosome in the phagocyte
- Lysosomes fuse with the phagosome and secrete digestive enzymes into the phagosome
- The pathogen inside the phagosome is digested by these enzymes and destroyed
What is a cell surface membrane made of? Why?
A bilayer of phospholipids, with the hydrophilic head facing out (attracted by the water on both sides) and the hydrophobic tail facing in (repelled by the water on both sides)
What are the functions of phospholipids in the membranes?
.Allow lipid-soluble substances to enter and leave the cell
.Prevent water-soluble substances entering and leaving the cell
.Make the membrane flexible and self-sealing
What two ways are proteins interspersed throughout the cell surface membrane?
.Some occur in the surface and never extend completely across it - these act to give mechanical support or in work in conjunction with glycolipids as cell receptors for molecules like hormones
.Other proteins span the phospholipid bilayer from side to side, for example:
- protein channels, form water-filled tubes to allow water-soluble ions to diffuse across the membrane
- carrier proteins, bind to ions or molecules like glucose and amino acids, then change shape in order to move these molecules across the membrane
State the functions of proteins in the membrane
.Provide structural support
.Act as channels transporting water-soluble substances across the membrane
.Allow active transport across the membrane through carrier proteins
.Form cell-surface receptors for identifying cells
.Help cells adhere together
.Act as receptors, for example, hormones
Where is cholesterol found in the cell membrane?
Within the phospholipid bilayer
Is cholesterol hydrophobic or philic?
Very hydrophobic so play a vital role in preventing the loss of water and dissolved ions from the cell
The function of cholesterol in the membrane:
.Reduce lateral movement of other molecules including phospholipids
.Make the membrane less fluid at high temperatures
.Prevent leakage of water and dissolved ions from the cell
Describe the structure of glycolipids
.Made up of a carbohydrate covalently bonded with a lipid
.The carbohydrate portion extends from the phospholipid bilayer into the watery environment outside the cell where it acts as a cell-surface receptor for specific chemicals
The function of glycolipids in the membrane:
.Act as recognition sites
.Help maintain the stability of the membrane
.Help cells attach to one another and so form tissues
Describe the structure of glycoproteins
Carbohydrate chains are attached to many extrinsic proteins on the outer surface of the cell membrane. These glycoproteins also act as cell-surface receptors
The function of glycoproteins in the membrane:
.Act as recognition sites
.Help cells to attach to one another and so form tissues
.Allows cells to recognize one another, for example, lymphocytes
In general, most molecules do not freely diffuse across the cell surface membrane because many are:
.Not soluble in lipids and therefore cannot pass through the phospholipid layer
.Too large to pass through the channels in the membrane
.Of the same charge as the charge on the protein channels and so, even if they are small enough to pass through, they are repelled
.Electrically charged (polar) and therefore have difficulty passing through the non-polar hydrophobic tails in the phospholipid bilayer
Why is the cell surface membrane described as a fluid mosaic model?
Fluid - because the individual phospholipid molecules can move relative to one another, this gives the membrane a flexible structure that is constantly changing in shape
Mosaic, because the proteins that are embedded in the phospholipid bilayer vary in shape, size, and pattern in the same way as the stones or tiles of a mosaic
What is diffusion?
The net movement of particles from an area of high concentration to low concentration, down a concentration gradient , until equilibrium is met.
What does diffusion being ‘passive’ mean?
It requires no energy
What 3 factors affect diffusion?
Temperature, surface area and concentration gradient
What substances move in and out of cells by diffusion?
Ions, oxygen, food molecules, carbon dioxide, glycerol and fatty acids, amino acids and urea
What is Fick’s law
.Fick’s law states a relationship between the rate of diffusion at constant temperature and 3 variable:
.Concentration gradient
.Length of diffusion pathway
.Surface area over which diffusion occurs
Rate of diffusion is directly proportional to:
(Surface area x concentration gradient) / Length of diffusion pathway
Fick’s Law equation
Rate of diffusion is directly proportional to:
(Surface area x concentration gradient) / Length of diffusion pathway
Why are lungs adapted to optimum Ficks Law?
The lungs have lots of surface area, from the alveoli’s with folded surfaces, thin walls (alveoli are one cell thick), for a short diffusion pathway, and a great concentration gradient, from the continuous blood supply due to the lots of capillaries surrounding the alveoli
What is facilitated diffusion?
The diffusion of molecules through the membrane using an intrinsic protein
Does facilitated diffusion require energy?
no, it is passive
What 2 proteins does facilitated diffusion require?
carrier or channel proteins
What are the intrinsic proteins required in facilitate diffusion like?
.Proteins have a specific tertiary structure
.Ions/molecules have a specific shape
.The intrinsic proteins are specific to certain molecules
What are the roles of T cells?
.Produces memory T Cells
.Stimulates phagocytosis
.Kills infected cells – making holes in their membranes
.Stimulates B cells to divide
How does an antigen presenting cell come about?
B cells with an antibody that is complementary to the antigen of invading pathogens takes up the surface antigen
This antigen is presented on the surface of the B cell
What happens to an antigen presenting cell?
A T helper cell attaches to the processed antigens on the B cells thereby activating the B cell meaning it produces by mitosis to produce clones
When B cells divide by mitosis what is formed?
They can either become memory cells or plasma cells
Where are memory cells found and what are ready to do?
Memory cells circulate in blood and tissue fluid in readiness to respond to a future infection by the same pathogen whos antigen was used in the process of forming them
What do plasma cells do?
Plasma cells produce antibodies that exactly fit the antigens on the pathogens surface
What do antibodies do?
The antibodies attach to antigens on the pathogen and destroy them
If the same infection occurs again what do memory B cells do?
If the same infection occurs again the memory B cells divide and develop into plasma cells that produce antibodies
List 3 functions of antibodies
.Coat the pathogen with antibodies to make it easier for the phagocyte to engulf it
.Coat the pathogen with antibodies to prevent it from entering host cells
.Antibodies bind to and neutralise (inactivate) toxins produced by the pathogen
How are B cells and C cells both needed to remove a pathogen from the body?
The responses interact with each other
.T cells activate B cells and antibodies coat pathogens making it easier for phagocytes to engulf them
If you see the word humoral in the exam what do you think?
B cells
Why will facilitated diffusion plateau?
Because you reach saturation (Vmax), there is more particles needing to diffuse than intrinsic proteins available
Why is the rate of reaction faster at lower concentrations for facilitated diffusion?
There are more pathways into the cell
What is active transport?
Active transport is the movement of particles from an area of low concentration to high concentration, against the concentration gradient, using energy which is supplied from respiration.
What are channel proteins?
.Intrinsic protein
.Water filled tubes
What do channel proteins provide?
.A hydrophobic channel
.Allows water soluble ions and polar molecules to diffuse
Channel proteins are selective, what does this mean?
they only open for specific ions, as they are complementary in tertiary structure
What are channel proteins used in?
.Facilitated diffusion
What are carrier proteins?
Intrinsic proteins
What do carrier proteins do?
.Change shape to move molecules
Carrier proteins are selective, what does this mean?
, only open for specific ions, as they are complementary in tertiary structure
What are carrier proteins used in?
.Movement of larger molecules
.Facilitated diffusion and active transport
How does active transport happen?
The solute binds to the binding site on the complementary carrier protein, it is specific due to its tertiary structure. ATP, which is produced during aerobic respiration in the mitochondria, is hydrolysed to release ADP and a phosphate ion, which binds to the protein. The phosphorylation of the carrier protein changes the tertiary structure of the proteins binding site, which consequently pushes the solute out into the fluid outside of the cell, moving it against the concentration gradient into an area of higher concentration of the solute than that of the concentration in the cell.
Why is the cell membrane described as a fluid mosaic?
a. The structure of a membrane is described as fluid-mosaic since the individual molecules can move relative to one another which gives it a flexible structure that is constantly changing in shape and because the proteins that are embedded in the phospholipid bilayer vary in shape, size and pattern in the same way as stones or tiles of a mosaic.
What produces antibodies?
B cells, more specifically plasma cells
Are antibodies specific?
yes
Name 6 parts of an antibodies structure
- Antigen binding sites
- Variable region
- Constant region
- Light chains
- Heavy chains
- Receptor binding sites
Draw and label antibodies
idk check your revision guide or google if its right?
Why are the variable regions on antibodies called that?
As the binding sites differ
What gives the variable region its specific 3d shape in antibodies?
The sequence of amino acids
In antibodies, where does the constant region bind to?
receptors
Each binding site on an antibodie is c____________ to a specific antigen
complementary
When an antibodies binding site binds to an antigen what is formed?
forms an antigen-antibody complex
Roles of antibodies
.Antibodies do not directly destroy antigens
.Agglutination
.Markers
What happens in agglutination
Antibodies clump bacteria cells together which is helpful as it means they can be taken in by phagocytes for digestion much more easily since they are easier to locate as they are less spread out
How do antibodies act as markers?
They can act as markers that stimulate phagocytosis
What is a polyclonal antibodie?
.Pathogens can have many antigens on their surface that can activate many B cells
.Each of these B cells will clone copies and will produce different antibodies
.These are collectively known as polyclonal antibodies
What are monoclonal antibodies?
.It is useful to be able to produce antibodies outside of the human body
.It is even better if a single type of antibody can be isolated and cloned on mass
.These antibodies are known as monoclonal antibodies
Different between poly and mono clonal antibodies?
Poly -
.Made from a variety of B cells
Mono -
.Made from only one type of B cell
How do pregnancy tests work?
A hormone called HCG is found in the urine of women only when they are pregnant, pregnancy tests can detect these hormones.
.Monoclonal antibodies that attach to HCG can be mass produced and stuck down to a test strip on a pregnancy test, while on a separate part of the pregnancy test antibodies attached to blue heads can be placed.
.If your pregnant and wee on it, the HCG in your urine will attach to the antibodies on the blue heads and the urine will carry them down to the test strip where they will attach to the stuck down antibodies and change the colour of the strip – showing a positive result.
.If you are not pregnant and wee on it, the urine still carries the blue beads and antibodies down the test to the test strip but they won’t attach to the stuck down antibodies, and so a colour change does not occur – a negative result.
How do monoclonal antibodies help diagnose PSA?
.men with prostate cancer tend to have high levels of the protein PSA (prostate specific antigen) in their blood due to the fact they produce so much of it
. Through the use of a monoclonal antibody that can interact with it, it is possible to get a measure of the level of PSA in a sample of blood.
Name 3 ethical implications of monoclonal antibodies?
.Use of mice
.Death of patients with MS
.Drug trials are dangerous
How is the use of mice in the production of monoclonal antibodies an ethical issue? Has any help been put in place?
.Production of monoclonal antibodies includes the use of mice
.The formation of tumour cells includes the deliberate inducing of cancer in mice
.Guidelines have been drawn up to reduce suffering but many people still believe it is unethical
How is the death of people with MS in treatment with monoclonal antibodies an ethical issue? Has any help been put in place?
.Monoclonal antibodies have saved many lives through diagnosis and treatment
.But they have also led to the deaths of some people with multiple sclerosis
.Informed consent is needed, where people know all the details of treatment including possible death before they consent to it
How are drug trials with monoclonal antibodies an ethical issue? Has any help been put in place?
.March 2006, 6 healthy volunteers underwent a test for a new monoclonal antibody in London
.They all suffered from organ failures, as a result of T cells overproducing chemicals that stimulate an immune response or attack body tissues
.All 6 survived, but it still raises questions about the ethics of drug trials
What is immunity?
The ability of an organism to resist immunity
What are the two types of immunity?
.Passive
.Active
What is passive immunity, with examples
.Antibodies introduced from an outside source
.Abs are not produced by the individual so they are broken down
.No memory cells
.Short lived
For example –
.Anti-venom
.Immunity acquired by a foetus from the mother
What is active immunity
.Production of abs is stimulated by the individual
.Direct contact with the pathogen/antigen
.Takes time to develop
.Long lasting
What two forms does active immunity come in?
.Natural – met the disease yourself, normal immune response
.Artificial – from a vaccine, induced immune response, few symptoms
How can vaccines be administered?
orally or subcutaneously (injection)
What does a vaccination do?
Generate an immune response
What do vaccines contain and what do they lead to?
.Vaccines contain antigens from the pathogens and lead to the formation of memory cells
When launching an effective vaccine programme, what needs to be thought about?
.Few side effects, as people can be easily discouraged
.Should be cheap enough to immunise all vulnerable populations
.Ability to produce, store and transport vaccine – requires hi-tech equipment, hygienic conditions and refrigeration
.Needs to be administered correctly at the appropriate time – trained staff required
.Vaccinate the majority of the population – best at one time so that for a period no individual carries the disease (transmission interrupted) – herd immunity
What is herd immunity?
.When a large enough proportion of a population is vaccinated which makes it difficult for the pathogen to spread
.The vaccinated population provide a measure of protection for individuals who have not developed immunity
Basically, what is herd immunity?
.Basically it’s harder for unvaccinated people to come into contact with the pathogen
When is herd immunity best carried out?
.Herd immunity is bet achieved when the vaccinations are carried out at one time
.This means that for a short period there are few infected individuals
.This interrupts its transmission
Why are vaccinations not 100% effective?
.Vaccinations don’t induce immunity in some individuals (immune system defects)
.Disease develops immediately after vaccination before immunity is established
.Pathogens can mutate frequently, rapidly changing their antigens (like with the flu)
.Each pathogen has many varieties (100 varieties of the common cold)
.Some pathogens can ‘hide’ in the immune system, they hide in cells or live in the gut where they are difficult to kill (e.g. cholera)
.Individuals object to vaccinations
- Religious, ethical, medical and safety concerns
What ethical problems arise with vaccinations?
.Animals used in development
.Side-effects can cause long term hard – risk against benefit
.Who should vaccines be tested on?
.Is it fair to test on a population where the target disease is common based on the idea they will gain the most benefit is its success – the vaccination is just a bit of a guess
.Is it right to make vaccinations compulsory?
.Should expensive vaccination programmes continue when the disease is almost vaccinated?
Name some cellular adaptations that increase the rate of transport, and how it does so
Increased surface area – greater sized surface to cross and for intrinsic proteins
Increased the number of channel or carrier proteins – prevent saturation (Vmax)
Mitochondria – increased rate of respiration so more energy for active transport
Increase the concentration gradient – increased rate of diffusion as greater difference
Where is the ileum?
The very end of the small intestine
What moves through the ileum?
Products of digestion not yet reabsorbed into the blood will be moving through here.
Glucose, minerals
Why is it important the ileum absorbs things?
It is important these substances are moved out of the ileum as it will be excreted if it moved past
Difference between villi and microvilli
Villi – 1mm projections of the cell wall
Microvilli – 0.6um projections of the epithelial cells
Explain how the ileum has increased surface area
Ileum wall has villi
Epithelial cells that line the cell wall have micro villi
Explain how the ileum has increased intrinsic proteins and what this does
A larger surface area gives more space for: .Channel proteins .Carrier proteins Decreased likelihood of saturation Increased rate of facility diffusion
Explain how the ileum has increased concentration gradient and what this does
.Muscle contracts and breaks the pieces of food down into smaller pieces
.Increase concentration gradient
.Increase substances SA:V ratio meaning enzymes will work faster
What is co-transport?
The coupled movement of one molecule with the concentration gradient and another molecule against the concentration gradient.
How does the sodium potassium pump work?
- 3 sodium ions move into the sodium – potassium pump and bind as well as an ATP molecule
- The ATP molecule releases a phosphate group into the pump which changes the tertiary structure and pushes the sodium ions out of the cell
- Sodium ions are released from the pump and two potassium ions enter instead
- The phosphate group is released from the pump (dissociates), changing the tertiary structure again back to normal so the potassium ions are brought into the cell and released into it
Is the sodium potassium pump a form of co-transport?
no
What happens inside the ileum?
Digestion of our food
What is the ileum membrane lined with?
epithelial cells
How does glucose move into the epithelial cells?
facillitated diffusion
What moves which way in co-transport in the ileum?
Na+ down its concentration gradient and glucose against its concentration gradient
How co-transport work? And what is it a form of?
- Na+ is actively transported out of the cell using the sodium-potassium pump, while potassium is taken in
- This creates a low concentration of Na+ in the ileum cells
- Diffusion occurs and Sodium is pulled down its concentration gradient into the cell, dragging a glucose molecule with it against its concentration gradient in coupled transport through a carrier protein after it has been digested from starch or another carbohydrate
- The glucose then goes through facilitated diffusion out of the cell into the blood capillary
- This is indirect active transport
Define osmosis
The net movement of water molecules though a partially permeable membrane from a region of high water potential to a region of lower water potential.
What is osmosis a form of?
Diffusion
Does osmosis require energy?
no, it is passive
What is water potential?
The pressure created by water molecules
Lots of water molecules = ___ =___
Lots of water molecules = high pressure = high water potential
Fewer water molecules = ___ =___
Fewer water molecules present = less pressure = low water potential
What is water potential measured in?
kPa
Pure waters water potential
0kPa
Is a higher or lower water potential value higher or lower water potential?
The number closer to zero is closer to pure water, which has a very high water potential
The lower the number (the further away from water) the less pure and so less water potential
What do all solutions have in terms of water potential?
A negative value
Define hypertonic
Concentration of solutes in the solution surrounding the cell is higher than inside the cell (less water)
Define hypotonic
Concentration of solutes surrounding the cell is lower than inside the cell (more water)
Define isotonic
Concentration of solutes in the solution surrounding the cell is the same as inside the cell
Define osmotic lysis
damage to the membrane during osmosis
What does an animal cell do in a hypotonic solution?
.Hypotonic has burst the cell since too much water has entered via osmosis, it has become lysed
What does an animal cell do in a hypertonic solution?
.Hypertonic has shrivelled the cell since too much water has left via osmosis, it has become shrivelled
What does an animal cell do in an isotonic solution?
.Isotonic has kept the cell the same, it is normal, the movement of water in and out is equal
What does a plant cell do in a hypotonic solution?
.Hypotonic has filled the cell since too much water has entered via osmosis (its swelled up), it has become turgid, it has become plasmolyzed, the vacuole is bigger and cell way fatter and harder
What does a plant cell do in a hypertonic solution?
.Hypertonic has shrivelled the cell since too much water has left via osmosis, the vacuole is shrivelled and the cytoplasm pulling away from the cell wall
What does a plant cell do in a isotonic solution?
.Isotonic has kept the cell the same, it is flaccid, the movement of water in and out is equal, the vacuole is a normal shape and cell wall okay
What is HIV?
human immunodeficiency virus
What does HIV cause?
AIDS – Acquired immune deficiency syndrome
What does HIV do?
Cause aids and HIV gradually destroys the sufferer’s immune system
When did AIDS epidemic start?
1980’s
As of 2015, how many people were living with HIV globally?
36.7 million people
How many people died of HIV last year?
1.1 million
Where did HIV come from?
HIV arose as a human infection:
.Western central Africa
.The virus ‘jumped’ the species barrier transferred from primates to humans
.Possibly due to eating or slaughtering chimpanzees
How can HIV infect us?
The virus can enter the body via infected body fluids:
.During sexual intercourse
.Drug-taking using infected needles
.Blood infection wounds
.Blood transfusion and blood products
.Mother to child across the placenta during pregnancy and via breast milk or birth
Symptoms of HIV
.Fever .Sore throat .Body rash .Tiredness .Joint pain .Muscle pain .Swollen glands (nodes)
Symptoms of AIDS
.Weight loss .Chronic diarrhoea .Night sweats .Skin problems .Recurrent infections .Serious life threatening illness
Name the 7 parts that make up HIV virus?
- Transmembrane glycoprotein
- Attachment glycoprotein
- Lipid envelope
- Reverse transcriptase
- Matrix
- Capsid
- Genetic material (RNA)
What is reverse transciptase?
enzyme that catalyses the production of DNA from RNA
Because HIV can produce DNA from RNA, what group is it apart of?
retroviruses
Because HIV is a virus what cant it do? So what does it do instead?
.As HIV is a virus, it is unable to replicate on its own
.It uses its genetic material to instruct the host cell’s biochemical mechanisms to produce the parts needed to make new HIV
How does HIV infect host cells? (8 steps)
- p120 molecules on the HIV bind to CD4 receptor proteins on T helper lymphocytes and macrophages
- The protein capsid fuses with the cell membrane
- HIV RNA + enzymes enter T cell
- HIV reverse transcriptase converts the viruses RNA to DNA
- The new DNA is moved into the helper T cell’s nucleus where it is inserted into the cell’s DNA
- The HIV DNA in the nucleus creates mRNA using the cells enzymes. This mRNA contains the instructions for making new viral proteins and the RNA from new HIV
- The mRNA leaves the nucleus of the host cell through nuclear pores and uses the cell’s protein synthesis mechanisms to make HIV particles
- The HIV particles bud away from the helper T cell with a piece of its CSM surrounding them which forms their lipid envelope
What does HIV specifically target?
helper T cells
How does HIV lead to aids?
HIV leads to AIDs by destroying/interfering with T cells normal functioning
How many helper T cells does a healthy human have?
800-1200 helper T cells per mm^3 of blood
How many helper T cells does an AIDS sufferer have?
less than 200 helper T cells per mm^3 of blood
If someone doesn’t have enough T cells what problems arise?
- B cells cannot be stimulated to produce Ab
- Cytotoxic T cells cannot be stimulated
With AIDS/HIV can memory cells be affected? What effect does this have?
Memory cells are also sometimes infected and destroyed
This results in an inadequate immune response leaving the body vulnerable to infections and cancer
What are AIDS sufferers prone to?
AIDS sufferers are therefore prone to infections of the lungs, intestine, brain and eyes
Diarrhoea and weight loss are common
What type of illness is HIV, why?
It is a secondary illness, not HIV that causes death
How to produce monoclonal antibodies
.Irradiate mouse to induce formation of tumours
.Tumours form inside mouse, the cells are removed
.Inject different mouse with non-self antigens
.B-cells which produce antibodies against the antigens are removed from the spleen
.Mix tumour cells with B cells and add detergent
.Detergent causes cells to fuse
.Fused cells are separated and cultured
.Fused cells have features of tumour and B cells – ‘immortal’ and produce antibodies
.Culture cells to form clones
.Test each clone to identify which one is producing the required antibody
.Culture the selected cells on a large scale
Define huminisation
making the monoclonal antibodies suitable for human use (since they come from mouse tissue)
Uses of monoclonal antibodies
.Separating chemicals from mixtures
.Immunoassay (detecting concentrations of macromolecules in solutions)
.Cancer treatment
.Transplant surgery
What can antibodies be used to identify?
Antibodies can be used to identify flu, hepatitis, chlamydia and types of cancer
What is a non-specific response?
immediate and same for all pathogens
What are the two nonspecific responses?
.Physical Barrier (skin)
.Phagocytosis
What is a specific response?
slower and pathogen specific
What are the two specific responses?
.Cell – mediated response (T-Lymphocytes)
.Humoral response (B-Lymphocytes)
Where do T cells mature?
.T Lymphocytes mature in the thymus gland
What do T cells respond to?
own cells altered by viruses/cancers (foreign material inside body cells) or transplanted tissues
How can different cells display antigens on their surface?
- Phagocytes that have engulfed and hydrolysed a pathogen present some of the pathogens antigens on their surface
- Body cells invaded by a virus present viral antigens on their surface as a distress signal
- Cancer cells are different from normal cells and present antigens on their surface
- Transplanted cells from the same species have different antigens on their cell surface
What are cells that display foreign antigens known as?
antigen-presenting cells
How do T cells become activated?
The phagocyte places antigens from the pathogen on its own cell-surface membrane
Receptors on certain helper T-cells fit exactly onto these antigens
This activates other T cells to divide rapidly by mitosis and form a clone
What do cloned T-cells do?
.Develop into memory cells that allow a fast future response to the same pathogen
.Stimulate phagocytes to engulf pathogens via phagocytosis
.Stimulate B-cells to divide and secrete their antibody
.Activate cytotoxic T cells
What do cytotoxic T cells do?
.Cytotoxic T cells kill abnormal body cells
How do cytotoxic T cells kill abnormal body cells?
.They produce a protein called perforin that makes holes in the cell surface membrane
.This makes the cell freely permeable, killing it
What are cytotoxic T cells effective against?
.This action is very effective against viruses as they replicate inside cells
What is the ELISA test?
Enzyme linked immunosorbent assay
.It uses antibodies to detect the presence and amount of protein in a sample
.Highly sensitive
ELISA test method
.Apply sample to surface
.The antigens in the sample will attach to this surface
.Wash the surface to remove any antigens that aren’t attached
.Add the antibody that is specific to the antigen we are trying to detect
.Leave to allow binding
.Rinse to remove excess antibody
.Add a second antibody that will bind with the first antibody
.The second antibody has an enzyme attached to it
.Add the substrate to the enzyme (must be colourless)
.The enzyme acts on the substrate
.The substrate is converted into coloured products
.The amount of antigen present is relative to the intensity of colour that develops
Define pathogen
Disease causing microbe
Define phagocyte
WBCs that travel in the blood and tissues, destroying pathogens
Define phagocytosis
Mechanism where phagocytes engulf pathogens and hydrolyses them using enzymes
Define immune
Resistant to a particular infection or toxin owing to the presence of specific antibodies
Define antigen
Molecule that triggers an immune response
Define antibody
A protein made by lymphocytes in response to the presence of an antigen
Define t lymphocyte
Type of WBC produced in the bone marrow but matures in the thymus. Coordinates immune response and kills infected cells – cell mediated response
Define helper t cell
Bind to antigens presented by antigen presenting cells. This binding stimulates T cell to divide rapidly.
Define antigen presenting cell
Cells that display foreign antigens on their cell-surface membrane.
Define b lymphocyte
Type of WBC produced by and matures in the bone marrow. Present in bodily humour. Humoral immunity. Produce antibodies.
Define memory cell
Produced by B cells. Live for decades. Provide long-term immunity. When they encounter the same pathogen again they divide rapidly into more plasma and memory cells to immediately fight the infection - secondary immune response
Define plasma cell
Secrete antibodies into blood plasma. Survive for only a few days. Destroy pathogens and toxins. Immediate defence only - primary immune response
Define cytotoxic T cell
Kills infected cells by introducing perforin molecules into their CSM, causing them to take in water and burst.
Define vaccination
Introduction of a vaccine subcutaneously or orally that contains pathogen antigens capable of initiating an immune response.
