Semester 1 Biology Flashcards
1
Q
What is a hydrophobic region
A
Interaction between non-polar section of the protein,
tend to exclude water and are side chains
2
Q
How do disulfide bridges form
A
As a result of an oxidation reaction between 2 cysteine molecules (covalent bonds between sulfur)
3
Q
Compare and contrast the shape and function of Fibrous and Globular proteins, give examples of each.
A
Fibrous
-Parallel polypeptide chain with cross-links
-Form rope-like fibres or sheets providing strength and flexibility
-Insoluble
E.G keratin in nails and collagen in bones
Globular
-Highly folded polypeptide to produce a complex specific tertiary structure
-Spherical shape
-Soluble
E.G enzymes, antibodies, receptors and hormones
4
Q
What will happen to Fibrous and Globular proteins when they become denatures
A
Fibrous-loses structural strength
Gloubular-Become insoluble and inactive
5
Q
4 shapes of bacteria
A
Cocci (spherical)
Bacilli (rod shaped)
Spirilla (spiral shaped)
Vibrio (curved shaped)
6
Q
Pilli
A
Helps with motility
7
Q
Capsule
A
-Consists of polysacharides/polypeptide
-Protects against phagocytosis and antibodies
-Prevents dehydration
8
Q
How does binary fission occur
A
-Cell elongation, circular DNA replicates attaches to mesosomes
-Septum is synthesised to divide the wall
-Septum grows across cell, divides genetic material. 2 daughter cells formed
-2 daughter cells separate and cycle begins again
9
Q
Mesosome
A
-Infoldings of cell surface membrane, has enzymes involved in respiration
-Plays a role in cell division, aid the separation of DNA in new cells,
10
Q
Define generation time
A
Time taken for a bacterial population to double in numbers
11
Q
Lag phase
A
-Little cell division occurs, cells may increase in size
-Cells synthesise RNA, proteins and enzymes
12
Q
Log/exponential phase
A
-Cells show maximum division (double exponentially)
-Nutrient levels, temperature and pH are at optimal levels
-No factor limiting
-Primary metabolites are formed and excreted during log phase of microorganims
13
Q
Stationary phase
A
-No increase in population, number of cells produced is equal to number dying
-Level of nutrients decrease, limiting growth, temp/pH has become unfavourable
-Increase in metabolic waste will limit growth
-Secondary metabolites that are not essential for growth and reproduction are produced & excreted here
14
Q
Death phase
A
-Unfavourable conditions (temp,pH, toxins) increase the death rate above reproduction rate
-Autolysis of cells may occur (self digestion)
15
Q
Define obligate aerobes
A
Microbes that only grow with oxygen present
16
Q
Define obligate anaerobes
A
Microbes that only grow in anaerobic conditiones
17
Q
Define Facultative anaerobes
A
Can respire aerobically when oxygen levels are high and anaerobically when oxygen levels are low
18
Q
Define aerotolerant aerobes
A
Grow well in anaerobic conditions but can tolerate and grow in presence of oxygen
19
Q
Define microaerophiles
A
Grow in aerobic conditions but require low conc of oxygen
20
Q
Halophiles adaptations
(grow in high salt concs)
A
-Maintain high conc of salt in cytoplasm to prevent water moving out of cells by osmosis
-Folding of protein to tolerate high salt conc, allows functioning of enzymes
21
Q
Alkalinophiles adaptations
(grow optimally at pH above 9)
A
-Have membrane lipids and cell walls that resist dissociation by alkali
-Their proteins and enzymes are adapted to work optimally at this pH
22
Q
Acidophiles adaptations
(grow optimally below pH 5)
A
-Acid-resistant cell walls and membranes
-Active pumping of excess protons
23
Q
Barophile adaptations
(grow at high hydrostatic pressure)
A
-Folded in a way that minimises pressure-related effects on their enzymes
-Lipid bilayer of cell membrane becomes more tightly packed at high pressure forms rigid structure that shields inside of cell
24
Q
Thermophiles adaptations
(optimum temp above 45 deg
Hyperthermophiles above 80 deg)
A
-More saturated fatty acids on lipid membranes, provide membrane stability
-Have more chemical bonds to maintain protein shape
25
Psychrophile adaptation
(optimum temp 15 deg or lower)
-Cold adapted enzymes that are active at low temps
-Have antifreeze proteins that bind to ice crystals preventing them from piercing cell membrane
26
Define total cell count
Total number of cells present, living and dead
27
Define viable count
Only living cells, cells that are capable of dividing
28
Which methods are used to calc total cell count
-Haemocytometry
-Turbidimetry
29
Why can turbidimetry be used to measure the growth of a culture of microorganisms
Transmitted light is proportional to number of cells
30
Describe end-point inhibition
(negative feedback)
-Occurs when end product of metabolic pathway accumulates (acts as an inhibitor)
-Product switches off it's own production
-Self regulatory, as product is used up its production switched on again
31
Equation for calculating dilution factor
DF=Total volume/Volume added
32
Give an example of end-point inhibition
Glycolysis (respiration)
33
What are immobilised enzymes
-Enzymes that can be trapped in a solid support that can be easily recovered from the reaction mixture
-Enzyme can be reused, reducing the cost of the process
34
Adavantages of immobilising enzymes
-Makes the enzyme more stable by restricting its ability to change shape and denature
-Allows for continuous production as reactants pass over enzyme and product is collected
-Enzymes don't become contaminated with product, held in a matrix
35
Examples of physical bonding (immobilising enzymes)
-Adsorbed onto insoluble matrix e.g collagen
-Held inside a gel e.g silica gel [gel entrapment]
-Held within semi-permeable membrane e.g polymer microspheres
-Trapped in micro capsule [microencapsulation] e.g in alginate beads
36
Example of chemical bonding (immobilising enzymes)
-Chemically binding enzyme to support medium but preparation is difficult
37
Features of Fungi
-Eukaryotes
-Filamentous fungi have hyphae that form masses (mycelium)
-Heterotrophic
-Use extracellular digestion
38
Function of cell wall
-Main component:chitin (nitrogen containing polysaccharide)
-Provides strength and rigid structure also allows enzyme secretion + absorption
39
Features of a cell wall
Main component: chitin (nitrogen-containing polysaccharide)
-Provides strength to wall and rigid structure
-Allows enzyme secretion + absorption
40
State aseptic techniques
-Use sterile syringes/ equipment
-Flame top of test tubes/ inoculating loops
-Minimise exposure to air (lift lid of Petri dish slightly)
-Avoid contact of sterile apparatus with skin/work surfaces
41
Culture media:
Complete/complex media
-Used to grow a wide range of microorganisms or when nutritional requirements of microorganisms are unknown
-Contains all nutrients required for growth e.g glucose, amino acids, water, vitamins
42
Culture media:
Selective/minimal media
-Suitable for growth of specific microrganisms
-If inoculated with mixed culture, only species that medium was designed for will grow
-Other microorganisms growth will be suppressed
43
Examples of sterilisation
-Direct heat; inoculating loop, neck of tubes
-Autoclaving (120°) glassware
-Putting things in alcohol and then placing on fire (Burning alcohol)
-Disinfectants (inanimate objects) e.g work surfaces
-Ultrafiltration
44
Bioassay
-Enables effectiveness of a compound (antibiotics) on the growth of microorganisms
-Screen microorganisms to determine if they produce effective antibiotics
-Measures ability to inhibit growth of bacteria on bacterial lawn
45
Antibiotics
Compounds that produce microorganisms that inbit or kill bacteria (not effective again viruses)
46
How can antibiotics work
Bactericidal- actually kill bacteria
Bacteriostatic- inhibit or prevent bacterial growth
47
Disinfectants
Chemical compounds that kill bacteria e.g Dettol
Can also use bioassay techniques to determine effectiveness
48
State the mechanisms of how antibiotics can work
-Inhibiting cell wall synthesis
-Cell membrane disruption
-Inhibiting mRNA translation
-Inhibiting nucleic acid synthesis
49
Broad spectrum antibiotics
Effective against wide range of bacteria, may be initially used in the treatment of undetermined bacterial infections
50
Narrow spectrum antibiotics
Effective against a small specific group of bacteria
51
Two ways that antibiotic-resistant bacteria can obtain this gene
-Spontaneous mutation
-Transfer of resistant genes from other bacteria
52
Vertical gene transmission (process)
-Resistance may arise due to random mutation
-Bacteria containing resistant gene survives when exposed to antibiotic
-These bacteria reproduce and pass their gene onto future generation
-Repeated exposure to antibiotics can lead to more bacteria surviving
-Can increase allelic frequency
53
Horizontal gene transmission (process)
-Conjugation
-Donor cell produces conjugation tube (pilus) that connects two bacterial cells
-Donor cell replicates its plasmid and passes the copy to other bacterium
-Recipient cell receives plasmid which may contain the gene for antibiotic resistance
54
Does horizontal gene transmission allow the gene to be transmitted to the next generation?
No
It increases the number of antibiotic-resistant bacteria in a population. Conjugation can occur between diff populations
55
Transduction
-Bacteriophage attaches to cell membrane of bacteria
-Inserts its DNA into host and is integrated into DNA of bacteria
-Bacteriophage DNA replicates and host DNA splits into bacteriophage-size pieces
-New bacteriophage assembled some with this DNA or bacterial DNA
-Bacteriophage w/ bacterial DNA attacks another bacterial cell
56
Transformation
-DNA from lysed bacterial cell is bound to DNA binding protein in host cell wall
-One strand of DNA enters host cell and the other is broken down
-Single strand bound to DNA of host cell
- Host cell is transformed
57
What are the membrane-bound organelles
Lysosome, Nucleus, Golgi body, SER + RER, Mitochondria and Chloroplast
58
What will bacteria cells always contain
Cell wall, cell membrane, circular genomic DNA, Ribosomes, cytoplasm
59
Densities of organelles in centrifugation
Nuclei (heaviest), chloroplast (if plant), mitochondria, ER and ribosomes
60
Advantages of TEM
and
Limitations of TEM
+ Higher resolution than SEM
+ Can see internal structures even molecular sizes e.g. proteins and nucleic acid
-Very thin sections of specimen must be used
-Does not show 3D arrangement of cellular components
-Specimen gradually deteriorates in the electron beam
61
Principles of TEM
-A beam of electrons is transmitted through the specimen
-Specimen must be thin and stained using heavy metal salts
-These substances deflect electrons in the beam, remaining electrons produce a pattern as they pass through the specimen which is converted to an image
62
Advantages of SEM
and
Limitations of SEM
+ Surface of structures are shown
+ Gives a 3D effect
+Much thicker sections can be examined than with a TEM
-Lower resolution than TEM
-Only the surface of an object can be viewed
63
Principles of SEM
-Specimen is coated with a thin film of heavy metal e.g. Gold
-Electron beam is scanned across specimen
-Electrons that are reflected from the surface are collected, produce an image on viewing screen
64
Structure of Mitochondrion, linked with respiration
-Folds of inner membrane are cristae and provide a large SA for the stalked particles they possess
-Stalked particles contain enzymes for ATP production by the ETC (for oxidative phosphorylation)
-Matrix contains enzymes of Krebs cycle (aerobic respiration) Mitochondrial DNA (FOR ITS REPLICATION) AND ribosomes
65
Ways that ribosomes can appear
Made of 2 subunits
-Singularly in cytoplasm
-In chains (polymers)
-Attached to ER
66
Golgi body structure + function
-Has cisternae that are continually being formed at one end and pinched off as vesicles at the other end
-Secretary cells have large Golgi bodies
FUNCTION
-Production of glycoprotein
-Packaging and secretion of protein
-Formation of cell walls in plant cells
-Lipid biosynthesis
67
Lysosomes
-Contain digestive enzymes e.g proteases, nucleases and lipases
-Enzymes must be kept apart from rest of cell or would destroy it
-Enzymes are synthesised for RER and transported to Golgi, which then bud off to form lysosome
68
Function of lysosome
-Digestion of material taken in by endocytosis, can release their enzymes into vesicles and digest material.
Products then absorbed by cytoplasm leaving undigested remains
-Autophagy, unwanted structures within cell are engulfed and digested within lysosome
-Release of enzymes outside cell e.g sperm releasing acrosome to digest path of cells surrounding egg before fertilisation
69
Define tissue
Aggregation of similar cells that perform a specific physiological function
e.g. epithelial, nervous, muscular tissues
70
Define Organ
A structure consisting of different tissues, which have specific physiological functions
e.g stomach has role of digestion
71
Structure of Palisade mesophyll cells
-Numerous chloroplasts
-Relatively thins walls to allow CO2 to diffuse in at faster rate
-Cylindrical (column) with relatively large SA which increase the rate of gaseous diffusion
- Few air spaces in between so maximum light can be absorbed
72
Types of epithelial tissue
Structure and function of one Epithelial cell
-Line inside or outside of organs e.g PCT, small intestines
-3 basic types: squamous, cuboidal and columnar
-Columna epithelial cells have cell membrane folded into microvilli for a large SA
-Numerous mitochondria provide ATP for AT of amino acid and sugars
73
Stem Cells
-Divide by mitosis and differentiate into range of different cells
(once they are specialised cells they cannot undergo mitosis)
74
Plant stem cells
-Totipotent so can differentiate into any kind of cell from that organisms
-Used for cloning plants for desireable traits
-Quickly produce mature plants
-Can regenerate whole plants from those that have been GM
75
Embryonic stem cells: Totipotent
-Cells which can differentiate into any kind of body cell, including extra-embryonic tissue. Then develop not complete organisms
76
Embryonic stem cells: Pluripotency
-Can give rise to all cells of the body but cannot produce the cells of extra-embryonic tissue.
-Are able to differentiate into all cells that arise from, the primary germ layers: ectoderm, endoderm and mesoderm. All animal cells are derived from these germ layers
77
Adult stem cells: Multipotency
-Found in mature mammals can differentiate into a limited number of types of cells
78
What does cholesterol do to Phospholipid membrane
Decreases the permeability of the cell membrane
79
Receptor proteins
-Have specific tertiary structures that allow specific hormones to attach. NOT an enzyme
E.g insulin binds to its specific receptor allowing the cell to respond
80
Diffusion
Net movement of molecules from a high conc to a low conc down a CG until molecules are equally distributed
Passive process
81
FD, properties of carrier proteins
Change shape as they move molecules across membrane
82
FD, properties of channel proteins
Have a fixed shape and transport ions
Charge determines what will bind, opposites attract
83
Factors that affect AT (same as factors affecting respiration)
-Lowering of temp
-Lack of O2
-Metabolic and respiratory inhibitors e.g cynide
84
The process of active transport and adaptation of cell
-Enzyme ATPase hydrolyses ATP, releasing energy
-Energy used to attach molecule to carrier protein and provide energy for carrier to change shape to move molecule across membrane
-Cells involved in AT have lots of mitochondria to provide ATP required via respiration
85
Define water potential
Potential (tendency) of water molecules to leave a solution by osmosis
86
Hypotonic (Hypo- too little)
Has low conc of solute molecules and a high conc of water molecules
87
Hypertonic (Hyper-too much)
Has high conc of solute molecules and low conc of water molecules
88
Isotonic
-When osmosis stops, water movement equal in both directions
89
Cell turgor
-As water enters the cell, vacuole enlarges, and then vacuole cytoplasm and cell membrane exert an outward turgor pressure on cell wall
-Essential in providing support in many plants
90
Pinocytosis (cell drinking) type of endocytosis
-Material taken up in liquid form, forms small vesicles
-Can be known as micropinocytosis as vesicles are micro pinocytotic
91
Phagocytosis (cell drinking) type of endocytosis
-Material taken up in solid form, using phagocytic cells (have been specialised)
92
How do pathogens produce disesase
-Damaging host tissue, reproducing inside cells
-Producing toxins
93
Factors affecting pathogenicity
-Attachment and entry
-Type of toxins
-Infectivity
-Invasiveness
94
Pathogenicity: attachment and entry
-Ligands and glycoproteins of bacterial cell wall attach to protein receptors in host cell membrane
-Enzyme produced by pathogen may damage the cell wall of host cell, causing entry of pathogen
Or endocytosis
95
Pathogenicity: types of toxins
-Exotoxins that are proteins secreted/leaked from bacteria. These cause the symptoms of the disease NOT the bacteria
[released in small amounts but have widespread effect]
-Endotoxins are lipopolysaccharides present in bacterial cell wall. can be released when cell wall of bacterium breaks up after death
[released in large amounts but have small effect]
96
Pathogenicity: Infectivity + EXAMPLE
Number of bacteria needed to cause the infection, varies widely from one type to another
e.g. Salmonella needs a large number of bacteria to cause food poisoning and typhoid fever only requires a small amount
97
Pathogenicity: invasiveness
Ability of the bacteria to spread, usually in hosts blood and lymph system
98
Transmission of disease
-Airborne/ droplets
-Foodborne
-Waterborne
-Contact, skin 2 skin, clothing 2 skin
-Sexual intercourse
-Vector-borne
99
Transmission of Cholera
-Transmitted by ingestion of water (rarely food) that has been contaminated with faecal matter containing pathogen
~Drinking water that's not properly purified
~Untreated sewage leaks into water courses
~Food is eaten that has been contaminated by those preparing and serving it
100
Course of infection of Cholera
-Produces a toxin that acts on epithelial cells of small intestines, this changes membrane permeability
-Receptor has specific tertiary structure and toxin is complementary to binding site on receptor
-Attachment of toxin causes ion channels to open, causing Cl- ions to diffuse into lumen of intestine
-This raises water potential of epithelial cells and lowers water potential of lumen
-So water moves from cells + blood into lumen by osmosis= watery faeces/diarrhoea
101
Symptoms of Cholera
Diarrhoea, dehydration, stomach cramps, vomiting and fever
102
Treatment of Cholera
-Oral rehydration solution (ORS), contains water, Na+, Cl- and glucose
-Ions and glucose taken up by co transport protein
-Water potential of epithelial cell is reduced and is lower than that of the lumen
-Water from ORS moves from lumen to cell by osmosis
-Water moves into blood and patient is rehydrated
103
Virus
-Intracellular parasite
-Damage host cells following entry and replication of virus
-Toxins produced in process of replication
104
Structural features of virus
-DNA/RNA
-Capsid (subunits called capsomere)
-Enzymes
-Lipid envelope (some)
-Glycoprotein, represent antigens that antibodies may possess
105
Symptoms of Influenza
-Incubation period~ 2 days
-Headaches, sore throats, backaches, joint pain, shivering, sweating (symps can last for 7 days)
-Coughing may continue due to epithelial damage to trachea and bronchi
106
Transmission of Influenza
-Droplets during coughing and sneezing, enter respiratory passages
-Overcrowding and poor ventilation enhance spread
107
Influenza: course of infection
-Virus attack generally localised on epithelial lining of respiratory passage
-Individual remains infective for more than 6 days
108
Replication of Influenza
-Virus particles enter epithelial cells, molecules in outer coat of virus bind to receptor molecules in CM of epithelial cells
-Virus coat removed releasing viral RNA and RNA polymerase
-Viral RNA enters hosts nucleus and controls protein synthesis in cell
-RNA polymerase activated and synthesises viral mRNA strands
-Viral proteins + lipids formed in cytoplasm and assembled into viral coats
-Viral RNA and coats assembled into new virus particles
-Lysis of cell occurs, releases viral particles which infect other cells
109
Difficulty of treating viruses
-Are intracellular, drugs don't penetrate cells so they are difficult to treat
-Antibiotics may be given to treat secondary infections
110
Coronavirus symptoms
-Continuous cough, high temp, change in sense of taste/smell, lack of energy, headaches , stuffy/runny nose
111
Transmission of Coronvirus
-Zoonotic (transmitted between animals and people and between people)
-Spreads through close contact of people with virus, even if they don't show symptoms
-Small droplets released when someone breathes, speaks, coughs or sneezes
-Catch virus if droplets breathed in or touched
-Risk of transmission highest indoors + crowded places
112
Replication of Coronavirus
-In humans able to attach to epithelial cell receptors (of respiratory tract) by having complementary glycoproteins
-Release RNA genome into host cells cytoplasm
-RNA genome acts like mRNA so directly translated by ribosomes into new viral particles
113
HIV course of infection
Stages of infection
-4 phases,
1)asymptomatic (no symptoms)
2)Antibody positve phase, period between infection and onset of clinical signs
3)Aids-related complex (ARC) , may contract opportunistic bacterial, viral and fungal infection. Loss of weight and reduction in T cells
-4th stage: opportunistic infections of organs, development of secondary cancers, HIV wasting syndrome. May die from pneumonia if immune system collapses
114
Structural features of HIV
-AIDs caused by infection of HIV
-Has RNA AND reverse transcriptase that produces DNA in host
-Has nucleocapsid, inner and outer protein capsid
-Nucleopcapsid had glycoprotein on surface allowing it to attach to host cell helper t cell
115
Transmission of HIV
-Transmitted by introduction of blood, semen or vaginal secretions from an infected individual into bloodstream of another individual
-Sexual transmission
-Blood transfusions of infected blood
-Sharing of needles (drug users)
-Mother to baby via placenta
116
Replication of HIV
-Viruses attach to CD4 helper T cells by glycoproteins binding to receptor sites
-Viral RNA + reverse transcriptase release and enter T cell
-Reverse transcriptase converts viral RNA into cDNA, using viral RNA as template
-cDNA enters nucleus attaches to host DNA, replicates
-Viral DNA can remain inactive (latent) up to 10 yrs
-Once activated viral DNA controls synthesis of viral proteins and RNA within T cell
-HIV particles assembled and T cell destroyed. Virus infects other T cells as it reproduces T helper cells in blood decrease
-T cells stimulate B cells (antibodies) to combat infection
-Immune response breaks down, individual suffers from opportunistic infections e.g pneumonia, kaposi's
117
How does HIV cause AIDs (simple terms)
-A pathogen is identified in body
-T lymphocytes are HIV infected so produce more HIV
-HIV released as T cells die
-HIV infect more helper T cells so NO IMMUNE REPSONSE
-So no destruction of pathogen
-Opportunistic infection
118
Structural Features of Ebola Virus
-Glycoprotein
-Nucleoprotein
-Transcription Factor VP30
-Polymerase cofactor VP35
-Polymerase (L)
-Matrix
-VP24
119
Structural features of bacteriophage
-DNA or RNA
-Head
-Collar
-Tail
-Long Tail fibres
-Base plate
120
Possible cycles for when bacteriophage attaches to host cell
-Virulent phages, often follow the lytic pathway resulting in the lysis of prokaryotic cell
-Temperate Phages enter a state (lysogeny), where viral DNA is incorporated into DNA of prokaryote host. Remains dormant but is replicated every time the host cell divides
121
Define Parasite
An organism that lives in or on living tissue of a host organism at expense of that host
122
Transmission of Malaria
-Mosquito(vector) picks up Plasmodium from infected human when it feeds. Females feed on human blood to obtain protein required to develop their eggs
-Plasmodium reproduces in gut of females, produces thousands of plasmodium which move to salivary glands of female
-When mosquito feeds again on healthy individual plasmodium pass into blood along with anticoagulant in saliva
-Travel to liver, enter cells + multiply
-Leave liver and enter RBCs of the infected person, multiply further
-Once multiplied they cause cells to burst, releasing more plasmodium for further infection. Coincide with malaria symptoms
123
Treatment of malaria
-Vaccination
-Avoid being bitten, cover arms + legs, insect repellent, mosquito nets
-Use insecticides
-Antimalarial drugs prior to and after travel
[Parasite remain in bloodstream for 30 mins so immune system cant react]
124
Describe and explain one adaptation of the malaria parasite which causes it to be unaffected by the body immune system
Lives inside host cell so avoids attack by host, production of antibodies slow
125
State infectious pathogens
Bacteria, viruses and fungi
126
Transmission
When a pathogen is transferred from one individual to another
127
Non-specific defence mechanism
Act against all types of micro organisms, prevent them from gaining access to living cells
128
Non-specific defence mechanism: skin
-Outer layer of epidermis consists of dead ,tough cells (non-hospitable environment) containing indigestible Keratin that provide resistance to bacterial invasion
-Secretion from sebaceous glands have antiseptic properties against some bacteria
-Commensal bacteria compete more successfully than pathogenic bateria
129
Non-specific defence mechanism: Tears
Contain lysozyme which breaks down cell walls of bacteria
130
Non-specific defence mechanism: Saliva
Also has lysozyme. Chewing stimulates salivation increasing amount of lysozyme present in mouth
131
Non-specific defence mechanism: Mucus
-Secreted by epithelial cells lining nasal passage and respiratory tract
-Traps bacteria and dust particles entering air passage, also contains lysozyme other antibacterial substances
132
Non-specific defence mechanism: Cillia
-Minute hairs on epithelial cells in upper respiratory tract
-Cillia beat which create current moving mucus + trapped particles to pharynx (throat)
-Swallowing carries microbes to stomach, killed off by HCl or enzymes
-Coughing and sneezing also removes trapped particles and microbes
133
What happens if non-specific defence mechanisms are breached
Internal mechanisms step in
134
Process of phagocytosis (non-specific mechanism)
-Detection, phagocyte (neutrophils + macrophage) detects microbes by chemicals(chemotaxis) they give off + sticks microbes to its surface
-Ingestion, Microbe is engulfed by phagocytes, forms a vesicle
-Phagosome forms, this encloses microbes in a membrane
-Fusion with lysosome, phagosome fuses with lysosome
-Digestion, microbes are broken down by enzymes into chemical constituents
-Dishcharge, indigestible material is discharged from phagocytes
Soluble products are absorbed
135
Role of phagocytic WBCs in preventing spread of microorganisms
-Phagocytes destroy micro organism which enter blood, prevent their spread to other parts of body
-Can also act as APCs, using pathogens antigen on their cell surface membranes for T cells
136
B lymphocytes
-Involved in antibody-mediated immunity (humoral response)
-Produce specific antibodies (immunoglobulins) when exposed to specific antigen
-Antibody destroys or neutralises antigen
137
T lymphocytes
-Mainly involved in cell-mediated immunity e.g attack pathogens + foreign tissue
-Thymus gland activates T lymphocytes
-Have molecules on CSM (receptors) that recognise specific antigens then destroy the foreign cell/tissue [cytotoxic + killer T cells]
-Helper T cells and suppressor T cells, help regulate antibody production in B cells
-T Memory cells
138
Forms and location of antigens
-Proteins or glycoproteins, appear as foreign to organism
-May be present on surface of pathogen,
on cell surface of tissue or organ transplant,
or free molecule e.g toxin
139
Where are antibodies found
Plasma, tissue fluid, breast milk, B cell surface
140
What do B cells attach to
-Viruses (neutralisation), bacteria, cancer cells (protein toxins), foreign RBCs
141
Structure of antibody
=4 polypeptide chains (2 heavy + 2 light)
-Joined together by disulphide bonds (underneath intersection of Y)
-ig/G/M/A/D/E
-Constant region the sequence of AA is same in all molecules of same antibody
-Variable region sequences of AA is diff in diff molecules of same antibody
-Variable regions form 2 antigen binding sites w/ specific tertiary structure
-Antigen binding sites bind to 2 separate antigen molecules , can form a lattice = antibody-antigen complex
142
Functions of antibodies
-Agglutination of antigens
-Stimulation of phagocytosis
-Precipitation of soluble toxins
-Preventing pathogens attaching to cell membranes
143
Agglutination
-Clumping together of cells possessing antigen (agglutinogen) for antibody(agglutins) to react
-Antibody antigen complex forms an agglutinated mass of cells, which are then destroyed
-Agglutination of donor RBCs occurs when individual is given wrong blood group this can lead to blood clots/death
144
Stimulation of phagocytosis
-Antibodies (opsonins) label foreign cells for destruction by phagocytic WBCs by attaching to antigen on surface of microorganism
-Phagocytes have receptors in CSM which match opsonins, enables them to recognise, bind and engulf the bacteria
145
Precipitation of soluble toxins
-Similar process to agglutination but on a molecular level
-Antibodies (precipitins) attach to soluble toxins (antigen) causes them to grow together forming a precipitate
-Neutralises action of the toxin molecules which are then destroyed
146
How to prevent the attachment of pathogens
(Immunnology)
-Use antibodies that are produced against antigens on surface of micro organism this prevents pathogen attaching to cell membranes
-Antigens (glycoproteins in particular) normally aid the entry of microbe into the host cell
147
Difference between DNA + RNA
DNA=2 polynucleotide strands but DNA=single polynucleotide strand
148
Where are phosphodiester bonds formed
Covalent bond between phosphate group of one nucleotide and pentose of the next
149
Purines
Adenine + Guanine
150
Pyrimidine
Thymine + Cytosine
151
Role of double helix in DNA
Protects bases
Makes molecules more stable
152
Role of H bonds in DNA
-Gives stability
-Prevent code from being disrupted
-Allows chain to unzip easily for replication and transcription
153
Role of sequence of bases in DNA
Provides genetic code for protein synthesis
154
Role of complementary base pairing in DNA
Enables info to be replicated accurately
155
Production of antibodies in humoral response
-Body has large number of different B cells, each type produces a diff specific antibody
-B cells secrete small amount of specific antibody onto CSM
-Macrophage becomes APC after phagocytosis
-If specific antigen attaches to B cell, these divide by mitosis, results in large pop of identical plasma cells
-Helper T cells stimulate B cells to divide
-Antibodies bind specifically to antigens, form an antibody antigen complex, antigen/source is destroyed or neutalised
## Footnote
Extra info
Primary response is slow requires 72hrs so disease symptoms may arise
-Following exposure some B cells develop into memory cells which divide into plasma cells. Which produce antibodies upon secondary infection=immunity
-T cells regulate this process, Helper T cells stimulate B cells to divide and suppressor T cells inhibit this process
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Cellular response
-Cytotoxic T cells uses its receptor to attach to antigen and secretes chemicals to destroy pathogen/ foreign cell
-Helper T cells stimulate B cells to divide and produce antibodies
-Memory T cells that remain in blood and produce a quicker response upon secondary infection with same pathogen
## Footnote
Extra info:
-Vast number of T cells, each one responds to different antigen
-Antigen presented as APC to T cell
-Stimulates T cell to divide by mitosis and form clones w/ same receptors, then develop into different type of type of cells
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Give an example of Antigenic variation
-Influenza has high mutation rate (as do other micro organisms)
-So individuals will not have immunity to new strains as not recognised by B cells and other antibodies
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Passive immunity/ artificial active immunity
-Vaccine that contains antigen is injected
-Stimulates an immune response, B cells release antibodies. some divide to form memory B cells, T cells divide to form memory T cells
-Boosters can be given to give a more effective response
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Natural passive immunity
-Preformed antibodies obtained across placenta and through breast milk
-Short-term protection as no production of own antibodies and memory B cells
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Artificial passive immunity
-Involves injection of preformed specific antibodies usually following exposure to particular virulent antigens e.g rabies, snake venom
-Provides short-term protection
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Ways to reduce rejection if transplant
-Ensure tissue of the recipient + donor are genetically similar
-Irradiation of areas producing WBC e.g bone marrow to reduce number of T cells
-immunosuppressive drugs to reduce number of T lymphocytes
-Recipient must be kept in sterile conditions after operation due to risk of infection
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Define transplant
Replacement of diseased organs by healthy ones
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Agglutinogen(antigen) and agglutin (antibody) on different blood groups
BG. Antigen. Antibody.
A. A b
B B a
AB. A+B -
O. None. a+b
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Rhesus positive/negative individuals
-Rhesus positive individuals have antigen D on surface of RBC membrane but rhesus negative individuals do not
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Haemolytic disease
-When rhesus negative mother recieves rhesus positive blood from her child
-Develops rhesus antibodies against rhesus-positive blood cells, first child not affected
-Memory B cells remain in mother
-During second rhesus-positive pregnancy antibodies pass through placenta and cause lysis of rhesus positive RBCs in foetus
-Child born with severe anaemia
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Prevention for haemolytic disease
-Rhesuse negative mothers are injected with rhesuse antibodies (anti-D) soon after birth
-Anitbodies will destroy fetal rhesuse positive RBCs in mother before she becomes sensitised and develops an immune response
-Must be repeated after every rhesus positive pregnancy
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Monoclonal antibodies
-Identical antibodies w/ same tertiary structure
-Have same antigen binding site
-B cell fused with cancer cell
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Uses of monoclonal antibodies
-Target medication to specific cell types
-Medical diagnosis
~Detect presence of specific antibodies (Indirect ELISA) or antigens( direct ELISA)
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Direct ELISA test
| Normal Elisa test
-Monoclonal antibody coated well
-Antigen binds to antibody
-Second monoclonal antibody,w/ enzyme binds to immobilised antigen
-Substrate added which causes colour change
-Washing of the well between each stage (especially the final washing) is important in preventing false positives
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Indirect ELISA test
-Antigen coated well
-Specific antibody binds to antigen
-Enzyme-linked antibody binds to specific antibody
-Substrate added which causes colour change
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What does rate of colour formation tell you in the ELISA test
-Rate of colour formation is proportional to the amount of antigen or antibody present depending on the test
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Evidence for SCR (method)
-Cells of E.Coli were grown on a medium, in which14N was replaced with 15N
-Cells were allowed to divide, bacteria then transferred into medium with 14N (normal isotope), allowed to divide
-Samples of bacteria taken after each generation, DNA was extracted and spun in centrifuge
-DNA containing heavy isotope 15N is slightly heavier than DNA containing 14N
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The results for SCR method
-1st generation, each DNA molecule contains 1 strand of 15N (heavy) and 1 strand of 14N (light)
-2nd generation, 50% of cells contain 14N
the other half contain hybrid DNA
-3rd generation, 25% contain hybrid DNA
75% contain DNA with 14N
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Define discontinuous replication
The synthesis of a new strand of a replicating DNA molecule, by a series of shorter fragments that are subsequently joined together.
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Define continuous replication in DNA replication
-DNA polymerase can only add nucleotides in the 5' to 3' direction as it synthesises a complementary strand
-So synthesis proceeds immediately along the leading strand
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Bases in RNA
-Uracil replaces Thymine
-Also Guanine, Cytosine and Uracil
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Regulation of transcription (gene tech)
-Transcription factors move from cytoplasm into nucleus
-TF binds to promoter region on DNA
-Allows RNA polymerase to transcribe the gene
If inhibitor blocked promoter region gene expression is prevented
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Regulation of translation
-Can be prevented by breaking down mRNA before the ribosomes translate it
-Small double stranded RNA molecules (siRNA) carry this out
-Enzyme cuts RNA into fragments forming siRNA
-One strand combines with restriction endonuclease enzyme, becomes integrated into its active site
-siRNA binds via complementary base pairing
-This signals restriction endonucleases enzyme to cut mRNA at the position which siRNA binds
-mRNA is now unable to be translated into a polypeptide
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Define epigenetics
Involves inheritable changes in gene expressions without changes to their DNA base sequences
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Acetylation
Unwinds DNA to histones, can be transcribed easier
(Active acetylation)
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Methylations
Winds DNA closer to histones, so less likely to be transcribed
