Topic 2 - Cells, Cell Transport + Immunity Flashcards
What type of cell are bacteria cells?
Prokaryotic.
What will a prokaryotic cell always contain?
Cell wall
Cell surface membrane
Circular DNA (in cytoplasm)
Ribosomes (smaller than in eukaryotes)
Cytoplasm
What may a prokaryotic cell contain?
Capsule surrounding cell wall
Plasmids
Flagellum
What type of ribosomes are present in a eukaryote?
80s.
What type of ribosomes are present in a prokaryote?
70s.
What does the cell wall in just prokaryotes contain?
Murein.
What does the cell wall of plants contain?
Cellulose microfibrils embedded in a matrix.
What does the vacuole contain in plants?
Soluble sugars, salts and sometimes pigment.
What surrounds the vacuole?
Tonoplast.
Describe the surface membrane in an epithelial cell
Folded into microvilli to provide a large surface area for absorption.
Name 4 components of a virus
Capsid
RNA genome
Envelope
Spikes
What does the nucleus do?
Contains the genetic material of an organism.
Controls protein synthesis.
Bound by a double membrane, nuclear envelopes and pores.
What do nuclear pores allow?
Communication with the cytoplasm.
What do ribosomes do?
Used in protein synthesis by joining together amino acids.
Made up of rRNA.
What does the rough endoplasmic reticulum do?
Contain 80s ribosomes that produce secretory proteins which are sent to the Golgi body for packaging.
What does the smooth endoplasmic reticulum do?
Lack ribosomes and produce and transport lipids.
What does the Golgi apparatus do?
Adds carbohydrates to proteins received from RER to produce glycoproteins.
Package proteins/glycoproteins in Golgi vesicles.
Produce lysosomes (a type of Golgi vesicle that contains lysozymes.
What do lysosomes contain?
Hydrolytic digestive enzymes.
Kept apart from rest of cell otherwise it would destroy it.
Produced by Golgi apparatus.
What do lysosomes do?
Digest material taken in by phagocytosis.
Non-functioning organelles within the cell are engulfed and digested within lysosomes.
Release enzymes outside of the cell.
What does a mitochondria contain?
Ribosomes
Cristae
Matrix
Inner membrane
Outer membrane
Enzymes
Intermembrane space
DNA
What do mitochondria do?
Involved in aerobic respiration which produces ATP.
Which organelle contains grana and stroma?
Chloroplasts.
What is the process of grinding up cells?
Homogenisation.
What 3 conditions of solution are usually maintained during cell fractionation?
Isotonic
Low temperature
Buffer solution
What does an isotonic solution help with during cell fractionation?
Prevents the osmotic movement of water in/out of organelles which might cause them to shrivel or burst.
What does a low temperature help with during cell fractionation?
Prevents the action of enzymes within the cells that might cause self-digestion of the organelles.
What does a buffer solution help with during cell fractionation?
Maintain the pH so that proteins (particularly enzymes) are not denatured.
Name the steps of cell fractionation
- Cells are first broken by grinding a tissue using a blender.
- Resulting suspension may be filtered to remove cell debris.
- Homogenate is then centrifuged at low speed, the densest organelles form a pellet at the bottom of the tube.
- Repeated at increases speeds.
- Isolated in order: Nuclei, chloroplasts (plant), mitochondria, endoplasmic reticulum, ribosomes
What is the order of isolated organelles during cell fractionation?
Nuclei
Chloroplasts (plant)
Mitochondria
Endoplasmic reticulum
Ribosomes
What microscope has a poorer resolution?
Light.
What microscope shows images in black/white?
Electron.
What is the advantage of electron microscopes?
Shorter wavelength provides a greater resolution.
What are the 2 types of electron microscopes?
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)
What are the disadvantages of electron microscopes?
As a vacuum is required, living specimens can’t be seen.
Preparation techniques can be complicated and may form artefacts.
Expensive to buy.
Expert training is required for use.
Why may a TEM be considering better than an SEM?
TEM allows you to see into organelles.
What type of image does a TEM produce?
2D.
What type of image does a SEM produce?
3D.
In which type of electron microscope do the sections have to be very thin?
TEM.
What is the formula for calculating magnification?
Image
———
Actual
What is the formula for calculating actual size?
Image
———-
Magnification
What is the formula for calculating image size?
Actual x Magnification
What is a centimetre equal to in standard form in terms of metres?
10 power -2.
What is a millimetre equal to in standard form in terms of metres?
10 power -3.
What is a micrometre equal to in standard form in terms of metres?
10 power -6.
What is a nanometre equal to in standard form in terms of metres?
10 power -9.
What is the alternative name for the cell-surface membrane?
Plasma membrane.
What does the cell-surface membrane mainly consist of?
Phospholipid bilayer.
Why is the cell-surface membrane also known as a fluid mosaic?
Fluid= Phospholipids are constantly moving in the bilayer.
Mosaic= Uneven distribution of protein molecules throughout the membrane.
Describe the orientation of the phospholipids within the bilayer
Hydrophilic heads orientated towards cytoplasm.
Hydrophobic tails attracted towards each other and point inwards.
What type of molecules can pass through the bilayer?
Lipid soluble molecules.
What is the exception molecule which can diffuse through the bilayer?
Water due to aquaporins between the phospholipids.
What is the role of cholesterol in the cell-surface membrane?
Provides strength to the membrane and restricts the movement of the phospholipids so that the membrane is less fluid and so less ions are lost from the cell.
What is the role of fatty acids in the cell-surface membrane?
Unsaturated FAs increase the permeability.
Saturated FAs decrease the permeability.
What is the role of carrier proteins in the cell-surface membrane?
Posses a specific tertiary structure complementary to polar molecules, aiding their transport by facilitated diffusion and active transport (glucose and amino acids).
What is the role of channel proteins in the cell-surface membrane?
Possess a specific tertiary structure which together with its charge and size determines which molecules can be transported across the membrane by facilitated diffusion (calcium, sodium potassium).
What is the role of branched carbohydrate chains in the cell-surface membrane?
Attach to lipids forming glycolipids or to proteins forming glycoproteins (which can act as receptors and be involved in cell-cell recognition).
Name as many components of the cell-surface membrane
Phospholipids
Cholesterol
Carrier proteins
Channel proteins
Un/saturated fatty acids
Glycolipids
Glycoproteins
Define diffusion
Net movement of molecules from a high concentration to a low concentration across a partially-permeable membrane.
Name 3 factors which affect the rate of diffusion
Surface area
Concentration gradient
Thickness of exchange surface
What is facilitated diffusion?
Allows the transport of polar molecules such as glucose and amino acids across membranes and involves channel/carrier proteins.
Define osmosis
Net movement of water molecules from a high water potential to a low water potential across a partially permeable membrane.
What is an isotonic solution?
When the solution has the same water potential as the variable.
What is a hypertonic solution?
A solution with a lower water potential than the cytoplasm.
What is a hypotonic solution?
A solution with a higher water potential than the cytoplasm.
Describe the DNA within prokaryote cells
Short, circular and not associated with protein, they don’t form chromosomes.
Describe the DNA within eukaryote cells
Very long, linear and associated with proteins called histones.
What does locus mean?
The position of genes and chromosomes.
What is formed as a result of mitosis?
2 identical daughter cells genetically identical to the parent cell.
What is an allele?
Different versions of the same genes.
What is a diploid number?
The total number of chromosomes in a normal body cell (2n).
What is a haploid number?
The single set of chromosomes (one member from each homologous pair) and is the number of chromosomes in a gamete (n).
Name the 6 stages of the cell cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Which stage takes up the highest proportion of the cell cycle
Interphase.
What happens in interphase?
Cell is carrying out its normal functions, but during late interphase:
1. Increase in protein synthesis
2. DNA content is doubled via DNA replication
3. Cell organelles are replicated
What happens in prophase?
Chromosomes form. Each chromosome then shortens and thickens
What happens in metaphase?
Centrioles form a spindle across the cell made up of protein microtubules.
Chromosomes move to the equator.
Spindle fibres attach to centromere.
What happens in anaphase?
Centromere splits and the sister chromatids separate.
They are then pulled to opposite poles of the cell by spindle fibres.
What happens in telophase?
Nuclear envelopes reforms around new set of chromosomes.
The two cells are genetically identical to each other and to the original parent cell.
What happens in cytokinesis?
The cytoplasm splits into two, cell-surface membrane forms and cell wall (if plant).
What is cancer?
A group of diseases caused by uncontrolled growth and rapid division of cells forming tumours.
What is the formula for the mitotic index?
Cells in mitosis
———————
Total cells
What type of reproduction is binary fission?
Asexual.
Name the stages of binary fission
- Cell elongation
- Replication of circular DNA and plasmids
- Septum starts to synthesise to divide cell
Name 3 types of pathogens
Bacteria
Fungi
Viruses
Name the non-specific defence mechanism
Phagocytosis.
Name the specific defence mechanisms
Humoral response
Cellular response
Name 4 places in where antigens can be present
Surface of a pathogen
Cell-surface membrane of other organisms
Abnormal body cells
As a toxin
Where are B and T lymphocytes produced?
Bone marrow.
Where do B lymphocytes mature?
Bone marrow.
Where do T lymphocytes mature?
Thymus.
Describe what happens in phagocytosis
- Phagocyte moves up concentration gradient towards intruder.
- Phagocyte extends around the pathogen and engulfs it (via its cytoplasm) forming a phagosome.
- Lysosomes containing lysozymes fuse with the phagosome and enzymes hydrolyse the pathogen.
Describe the structure of an antibody
Consists of 4 polypeptide chains (2 heavy and 2 light).
Each polypeptide consists of a constant and variable region.
The variable regions have of the heavy and light chains form 2 antigen-biding sites.
What is agglutination?
The clumping together of cells possessing the antigen against which the specific antibodies react to.
Which of humoral or cell mediated produces antibodies?
Humoral.
What do B lymphocytes secrete in humoral response?
Specific antibody into the blood plasma to destroy or neutralise the antigen and the pathogen.
Name 3 locations where antibodies are found
Blood plasma
Tissue fluid
Breast milk
What happens when a complementary antigen attaches onto an antibody?
T Helper cells stimulate B lymphocytes to divide by mitosis.
What is the name of the process where a large volume of identical plasma cells are formed?
Clonal selection.
What is formed in humoral response?
Antibody-antigen complex which leads to the destruction of the pathogen.
What do some of B cells divide into in humoral response?
Memory B cells.
What happens in a secondary humoral response?
Plasma cells secrete antibodies quicker at a higher concentration.
What is antigenic variation?
When microorganisms with a high mutation rate so that the person is no longer immune from multiple strains of that microorganism because B cells do not recognise the pathogen.
What type of cells are involved in cellular response?
T cells.
What do the T cell receptors recognise?
Specific antigens.
What happens to the antigen in cellular response?
Presented to a helper T cells by an antigen presenting cell (phagocyte).
What happens after the phagocyte has engulfed the pathogen in cellular response?
The phagocyte removes the antigens and embeds them in its cell-surface membrane.
After the Th cells divide by mitosis what do the cloned Th cells do?
- Activate cytotoxic T cells
- Develop into more helper T cells
- Develop into memory T cells
What do cytotoxic T cells do?
Attach to the specific antigen on the pathogen and secrete chemicals (perforin) to destroy it.
What do the developed helper T cells do?
Stimulate B lymphocytes to divide into plasma cells and secrete antibodies.
What do memory T cells do?
Remain in the blood after in the infection and produce a quicker response if a future infection occurs with the same antigen/pathogen.
What are the 4 types of immunity?
Natural passive
Artificial passive
Natural active
Artificial active
What is passive immunity?
Where an individual receives pre-formed antibodies from an outside course and is not exposed to the antigens.
What is natural passive immunity?
When the antibodies are obtained across the placenta and through breast milk and provides short-term protection.
What is artificial passive immunity?
When the pre-formed specific antibodies are injected usually following exposure to a pathogen or toxin, providing short-term protection.
What is active immunity?
When an individual is exposed to the antigen and produces antibodies and memory cells, providing long-term immunity as the body has produced its own antibodies and memory cells.
What is natural active immunity?
When an individual is infected and is exposed to the specific antigen, developing long-term immunity as memory cells are formed.
What is artificial active immunity?
When an individual is vaccinated and the immune system produces its own antibodies and memory cells, providing long-term immunity.
What is a vaccine?
Contains antigens from a specific pathogen. The antigens may be present in the form of a dead pathogen, a weakened strains or just antigens removed from the pathogen.
What does the injection from a vaccine result in?
A stimulated immune response with the production of plasma cells which release specific antibodies, memory B and T cells providing long-term immunity.
Why are boosted vaccines given?
To ensure a more effective secondary response due to exposure to more antigen.
What is herd immunity?
When a higher proportion of the population vaccinated against a particular infection is less at risk of an epidemic, because the probability of encountering someone unprotected is lower.
What does HIV stand for?
Human immunodeficiency virus.
What does HIV contain?
RNA and the enzyme reverse transcriptase.
In HIV, what does surrounds the RNA and enzyme?
Capsid (protein coat).
In HIV, what surrounds the capsid?
The viral envelope, which contains spikes (glycoproteins) specific to the host helper T cell.
How may HIV be transmitted?
Sexual transmission
Blood products/transfusions of infected blood
Sharing of needles
Mother to baby
What do viruses attach to? (stage 1 HIV replication).
CD4 helper T cells by glycoproteins on their surface binding to receptors on the membrane of helper T cells (lymphocytes).
What enters the T lymphocyte? (stage 2 HIV replication).
Viral RNA and reverse transcriptase.
What forms in the helper T cell? (stage 3 HIV replication).
Viral DNA by reverse transcriptase using the viral RNA as a template.
What does the viral DNA do? (stage 4 HIV replication).
Enters the nucleus and attaches to the host DNA, which then replicated with the host DNA.
What does the activated viral DNA control? (stage 5 HIV replication)
Controls the synthesis of viral proteins and viral RNA within the T cell.
What occurs in the final stage? (stage 6 HIV replication?)
HIV particles are assembled and the T helper cell is destroyed as viruses are released (budding).
What happens to the number of T helper cells (lymphocytes) in the blood as viruses reproduce?
Decrease.
What are the symptoms from HIV in the first phase?
Short flu-like illness
Skin rash
Swollen glands
What are the symptoms from HIV in the second phase?
Antibody-positive phase
Symptoms stop
What are the symptoms from HIV in the third phase?
AIDS-related complex
Contracting a variety of opportunistic bacterial, viral and fungal infections (not life threatening)
Loss of weight
What are the symptoms from HIV in the fourth stage?
Infections of body organs
Secondary cancers
HIV wasting syndrome
Dramatic weight loss
Immune system collapses
What drug prevents the replication or viruses?
Reverse transcriptase inhibitors.
What are monoclonal antibodies?
Identical antibodies having the same tertiary structure from a single clone of antibody-producing B cells.
Name 2 occasions in which monoclonal antibodies are used
- To target medication to specific cell types by attaching a therapeutic drug to an antibody.
- For medical diagnosis:
To detect the presence of specific antigens in body fluids.
To detect the presence of specific antibodies produced by a person against an antigen.
What does ELISA stand for?
Enzyme linked immunosorbent assay.
What is the ELISA test used for?
Measures the amount of antigen in a sample.
What does the direct ELISA test detect?
Antigens, therefore determining if a pathogen is present in a sample.
What does in the indirect ELISA test detect?
Antibodies, determining if an individual has a current or previous infection.
What happens in stage 1 of the direct ELISA test?
Coating each well with a specific monoclonal antibody that is irreversibly bound to the plastic surface of the well
It is then washed
What happens in stage 2 of the direct ELISA test?
A fluid sample is added to the well
If molecules of the specific antigen are present, they will bind to the monoclonal antibodies to form antibody-antigen complexes.
It is then washed to remove any unbound antigens
What happens in stage 3 of the direct ELISA test?
A second monoclonal antibody which has an enzyme attached is added to the well
This can only bind to the specific antigen
It is then washed to remove any unbound second antibodies
What happens in stage 4 of the direct ELISA test?
A suitable substrate for the enzyme is added
If the enzyme is present, the enzyme will convert the colourless substrate into a coloured product
Coloured product = antigen present (positive)
What happens in stage 1 of the indirect ELISA test?
The well is coated with an antigen
It is then washed
What happens in stage 2 of the indirect ELISA test?
Specific antibodies to antigen are added in a sample
It is then washed to remove any unbound antibodies
What happens in stage 3 of the indirect ELISA test?
Add another sample (made by lab) that are enzyme linked and specific to the antibody
It is then washed to remove any further unbound antibodies
What happens in stage 4 of the indirect ELISA test?
Substrate is added and converted by the enzyme into a coloured product
The rate of colour formation is proportional to the amount of specific antibody.
