IMMS Flashcards
(125 cards)
1
Q
what is the largest membrane bound organelle
A
nucleus
2
Q
function and structure of the nucleus
A
- stores and transmits genetic info for protein production
- home of DNA
- membrane bound, membrane has pores to allow passage of RNA out the pores
3
Q
what is chromatin
A
a mass of genetic material - DNA and proteins
condenses into chromosomes during mitosis
4
Q
function and structure of Golgi body apparatus
A
- parallel stacks of membrane
- processes and modifies macromolecules produced in the ER
- located close to the nucleus
5
Q
main sections of the golgi-body and their functions
A
3
- cis-face: nuclear facing and receives products from the ER
- medial: modifies products by adding sugars → production of complex oligosaccharides
- trans-face: proteolysis of peptides into active forms and budding off of vesicles containing complete products
6
Q
structure and function of smooth ER
A
- highly folded and flattened membrane sheet
- site of lipid synthesis
7
Q
structure and function of rough ER
A
- highly folded flat membrane sheets WITH ribosomes attached to surface
- site of protein synthesis and modification
- closely associated with the nucleus
8
Q
structure and function of ribosomes
A
- 2 subunits attached to the RER
- small =40s. Large =60s
- translates genetic code from RNA → a chain of amino acids which then fold into primary proteins
- deposits the protein into the RER for further modification
9
Q
cytoplasm function and key components
A
- site of glycolysis
- fluid that fills the cell
- 3 components
- cytoskeleton and thier motor proteins
- organelles
- dissolved solute
10
Q
structure and function of mitochondria
A
- double membrane organelle
- inner membrane = respiratory chain/electron transport chain and Krebs cycle within the matrix
- outer membrane = lipid synthesis and fatty acid metabolism
- intermembranous space = nucleotide synthesis
- site of oxidative phosphorylation for ATP production
11
Q
location, structure and function of nucleolus
A
- in the nucleus
- NOT membrane bound
- site of DNA transcription
- forms ribosomal RNA
12
Q
structure and function of vesicles
A
- membrane bound transport organelles
- many types:
- cell derived, golgi, ER, derived
- lysosomes and peroxisomes
13
Q
structure and function of vacuole
A
- membrane bound semi-permeable chamber
- holds solutions or materials
- only lets specific molecules through
14
Q
types and functions of cell junctions
A
-
tight junctions
- seals neighbouring cells together to prevent leakage
-
adherens
- joins an actin bundle in one cell to another in another cells
-
desmosomes
- joins intermediate filaments in one cell to a neighbour
-
gap junctions
- allows passage of small water-soluble ions and molecules and electrical impulses
-
hemi-desmosomes
- anchor intermediate filaments to the basal lamina
15
Q
plasma membrane structure and function
A
- phospholipid bilayer
- hydrophobic tail, hydrophilic head
- contains protein channel and transporters
- forms a physical barrier and controls entry of specific molecules only = selective permeability.
16
Q
components of the phospholipid bilayer
A
- membrane proteins
- cholesterol
- carbohydrate groups
- both attach to form glycoproteins and glycolipids
- phoshpolipids
- phosphate and glycerol head with 2 fatty acid tails and a phosphate
17
Q
structural components within a cell and their sizes
A
-
microtubules
- 25nm
- e.g. tubulin
- found in all cells except RBCs
- involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape.
-
intermediate filaments
- 10nm
- anchored transmembrane proteins
- provide structural support, regulate key signaling pathways
-
microfilaments
- 5nm
- assist with cell movement and are made of actin
18
Q
smallest and largest structural cell components
A
largest = microtubules
smallest= microfilaments
19
Q
structure and function of centrosome
A
- made from 2 centrioles which are microtubule rings
- pull chromatids apart during mitosis/meiosis
20
Q
lysosome structure and function
A
- golgi-derived - membrane bound organelle
- contain digestive enzymes
- used as a waste disposal system to breakdown molecules
21
Q
what is an peroxisome
A
- small membrane bound organelle
- contain enzymes that oxidise long-chain fatty acids
- involved in the generation of ATP from fatty acids
- involved in ROS detoxification
22
Q
what is an endosome and its function
A
- golgi-derived - membrane bound organelle
- they receive material from outside the cell and sort them
23
Q
describe DNA structure and how it is stored
A
DNA is a double helix structure with complimentary base pairing
it is stored by the helices coiling around histones to form nucleosomes which coil further → super coils → chromosomes
24
Q
how many chromosomes are there
A
46 in total - 23 pairs
- 22 autosome pairs
- 1 pair of sex chromosomes
25
define karyotype
the number and appearance of chromosomes in a cell - arranged in size order
26
describe the DNA found in mitochondria
maternal
27
describe a chromosome
2 identical chromatids joined together in the middle by a centromere
28
difference between prokaryotes and eukaryotes
* Eukaryotes have a membrane-bound nucleus, prokaryotes do not
* Eukaryotes strore their DNA within the nucleus, prokaryotes have theirs in a nucleoid region of the cell
29
what does DNA stand for
deoxyribonucleic acid
30
what are the building blocks for DNA
nucleotides
31
what are nucleotides / nucleic acids made of
* nitrogenous base
* Deoxyribose sugar
* phosphate group
* base
32
how do the nucleotides join together, what bond is formed
* via the phosphate groups in the nucleotide → formation of the sugar-phosphate backbone.
* a phosphodiester bond holds the molecules together.
33
what are the types of bases
1. adenine
2. thymine
3. cytosine
4. guanine
5. uracil
34
which bases pair up together
AT
GC
AU (in RNA)
35
what are the main enzymes involved in DNA replication
* DNA topoisomerase
* DNA helicase
* DNA primase
* DNA polymrease
* DNA ligase
36
describe the steps of DNA replication
1. before DNA replication starts, **topoisomerase** enzyme unwinds DNA
2. **DNA helicase** then breaks the hydrogen bonds between the base pairs → 2 seperate strands
3. si**ngle strand binding protein** binds to the exposed base pairs to prevent rejoining with its original base pair.
4. **DNA primase** uses the DNA sequence on the parent strand to form a primer from RNA
5. **DNA polymerase** synthesises the new strand using free floating nucleotides and proof reads the DNA as it replicates
* polymerase can only build in the direction of **5' → 3' [3-5 on parent]** hence this is the leading strand
* the lagging strand has its DNA produced in _okazaki fragments_ which are glued together by **DNA ligase**
6. RNA primers are removed from each fragment of the lagging stand then glued together by **ligase** to form a complete strand.
7. termination occurs when the replication forks meet or there is no more DNA to copy.
* 2 new DNA molecules formed each with 1 new and 1 old strand = _semi-conservative replication_
37
functions of DNA polymerase
* extension of the new DNA strand
* proof reads as it goes to avoid errors
* fills in gaps in new DNA strand between okazaki fragments
38
differences between DNA and RNA
1. DNA=deoxyribose sugar RNA=ribose sugar
2. same bases except uracil replaces thymine in RNA
3. DNA is double stranded RNA is single stranded
4. RNA is shorter than DNA
39
what is transcription
synthesis of mRNA from the template strand of DNA via the action of RNA polymerase
40
describe the steps of DNA transcription
* **Initiation**
1. transcription factors bind to the promoter region of genes to be copied for mRNA synthesis
2. RNA polymerase attaches to the DNA molecule and moves along till it finds a promotor sequence.
3. once at the sequence it unwinds the DNA to expose the bases of each DNA strand.
1. one DNA strand = antisense which is used as the template to produce mRNA - 3'-5'
2. the other = sense and should be identical to the mRNA produced except for uracil replacing thymine
* **Elongation**
1. RNA polymerase moves along DNA 3'→5' and produces mRNA 5'→3' from free floating ribonucleotides.
1. RNA polymerase catalyses the production of phosphodiester bonds between the nucleotides
2. as RNA polymerase moves along, it zips the DNA strands back together so only 10-20 bases are exposed at once in the transcription bubble
* **Termination**
1. once RNA polymerase reaches a stop codon, transcription ends and it releases the DNA template stand
* **Modification**
1. the pre-mRNA molecule undergoes splicing in the spliceosome
2. this removes introns [non-coding] and leaves only introns [coding]
3. the mature mRNA leaves the nucleus through the nuclear pores
1.
41
what 3 components are required for DNA translation
ribosomes
tRNA
mRNA
42
what is tRNA
a molecule carrying an amino acid, with an anticodon region that it complimentary to mRNA
43
describe the stages of translation
* **Initiation**
1. the 5' end of mRNA codes for methionine. the mRNA and tRNA-methionine bind to the 40s ribosome.
2. Then the 60s ribosome binds to the tRNA-methionine to complete the initiation complex
* **Elongation**
1. the tRNA-methionine lies within the A site of the ribosome, it shifts to the P site and a new tRNA molecule enters the A site.
2. methionine bonds to the next amino acid and releases itself from tRNA → formation of a peptide chain. the empty tRNA leaves the ribosome through the E site.
3. the ribosome translocates along the mRNA molecule producing a longer and longer peptide chain
* **Termination**
1. translation ends once the stop codon on mRNA is reached.
2. no tRNA molecule binds to the ribosome at this point → the dissociation of the peptide chain and mRNA from the ribosome
3. the peptide chain is released into the cytoplasm to undergo further modification in the cell.
44
what is the start codon and where is it located
AUG
located on the 5' end
45
what are the sites in a ribosome
A site: **A**ccepts new tRNA molecules
P site: holds the tRNA in place for **P**eptide chain formation
E site: **E**xit site
46
how does DNA damage occur
mutations in DNA
physical breaks in the molecule
47
what causes DNA damagee
* spotaneous damage
* environmental factors
* radiation e.g. UV
* thermal
* mutagenic chemicals
* viruses
48
types of mutations
1. deletion mutations
2. splice-site mutations
3. mis-sense mutations
4. non-sense mutations
5. trinucleotide repeat mutations
49
what is a point mutation and what types are there
* a mutation of a single nucleotide
* can result in:
* silent mutations where the change doesn't affect the AA coded for
* non-sense mutations where the change → stop codon early in the sequence
* mis-sense where the change → different AA coded which may or may not → pathology
50
types of deletion mutations
* out of frame deletions
* 1 or 2 base deletions → frameshift
* the reading frame is disrupted, all codoons after the mutation are altered → non-functional protein
* in-frame deletions
* an entire codon is lost → loss of 1 AA
* 1 missing AA usually → mild consequences to protein function.
51
what is a splice-site mutation
* Affects accurate removal of introns
* Mutation to base sequence at boundary of exon and intron.
* Splice acceptor site changes and is no longer recognised by the enzyme
* Intron sequence not removed and so is translated into the protein
52
what is a non-sense mutation
* Changes a codon to a stop codon due to **substitution** or **frameshift**
* RNA detaches from ribosome too early and protein synthesis is not completed
53
what is a mis-sense mutation
* Single base substitution → different AA coded.
* May or may not be pathogenic depending on the nature of aa coded for
* May be a polymorphism of no functional significance
54
what is a trinucleotide repeat
* codon repeats → genetic disease
* e.g. huntingtons
55
what is anticipation
the expansion of trinucleotide repeats.
* the repeats increase in number when transmitted onto the next generation → earlier symptoms with greater severity
56
define haploid and diploid
haploid = 1 copy of each chromosome
diploid = 2 copies of each chromosome
57
describe the stages of the cell cycle
* G1
* cell growth
* duplication of cellular components
* S phase
* DNA duplication of each chromosome → 46 pairs of chromosomes
* G2
* further cell growth
* M phase
* mitosis followed by cytokinesis
* G0 = ooutside of the cell cycle
* most cells exit the cell cycle at this point to perform normal cell functions.
* some cells are constantly dividing and don't ever enter this phase
* some cells never divide and are only in this stage e.g. neurones
58
describe the stages of mitosis
1. **Prophase**
* the chromosomes condense and become visible
* the nucleolus disappears
* the centromeres nucleate and start moving towards opposite poles of the cell
2. **Pro-metaphase**
* the nuclear membrane breaks down
* the mitotic spindle fibres occupy the nuclear space
* the microtubules attach to the chromatids via the centromere
3. **Metaphase**
* the sister chromatids line up along the equator of the cell at the metaphse plate
4. **Anaphase**
* the spindle fibres pull the sister chromatids apart to opposite poles of the cell
5. **Telophase**
* the nuclear membrane reforms at both poles of the cell
* the chromosomes unfold into chromatin
* cytokinesis occurs
59
what stage of division is this
metaphase
60
what are the key differences between mitosis and meiosis
* Only in Gametes
* Recombination of genetic material generates diversity
* Two cell divisions
* 4 haploid daughter cells, each genetically different
61
describe the stages of meiosis
* the steps of meiosis are similar to mitosis, but they occur twice to produce 4 haploid daughter cells.
* the key differences increase genetic diversity and are:
* **prophase 1 - cross over**
* homologous chromosomes exchange parts of themselves so there is a mix of paternal and maternal DNa in 1 chromosome.
* **metaphase 1 - independent assortment**
* at the metaphase plate the homologous pairs arrange themselves on either side of the equator randomly → random allocation of maternal and paternal chromosomes.
62
what is gonadal mosaicism
a person with 2 or more populations of cells in their germline cells
* caused by mutation in a parent's germline during embryonic division → 1 population of normal cells and another of abnormal cells.
* this means the parent isn't affected
* BUT the mutation is passed down to their child as it is in the germline.
* thus the child will have 2 populations from 1 parent and 1 population from the other = 3 populations in total.
63
what type of inheritance pattern is gonadal mosaicism seen in
can be seen in any
most common in autosomal dominant
64
# define autosomal recessive
* disease only occurs in homozygous recessive genotype as 2 defective alleles are needed.
* 25% chance of having disease
* 50% chance of being a carrier
* e.g. cystic fibrosis
65
define autosomal dominant
* disease can occur in heterozygous genotype as only one dominant allele is required
* 50% chance of affected child
* Both parents can sometimes be unaffected E.g.:
* Gonadal mosaicism (don’t have genes for it)
* Mother has reduced penetrance
* Mother has variable expression
* e.g. Huntington's disease
66
define X-linked
* caused by a mutation on the X chromosome
* X chromosone always comes from mother, thus x-linked can't be from father to son
* all daughters from affected males are carriers
* Transmitted usually through unaffected female
* Can be recessive ( Duchenne’s muscular dystrophy) or dominant (Alport’s Syndrome)
67
define penetrance
Penetrance = the likelihood that a clinical condition will occur when a particular genotype is present
68
define Variable expressivity
Variable expressivity = the series of signs and symptoms that can occur in different people with the same genetic condition
69
define sex limitation
* the presentation of a disease in one sex only despite both sexes carrying the gene
* e.g. a male and femal both carry the gene for prostate cancer BUT only the male can develop prostate cancer due to females not having a prostate.
70
define phenotype vs genotype
**The genotype refers to the genetic material passed between generations, and the phenotype is observable characteristics or traits of an organism**.
71
what types of communication do the cells of the body use
1. **autocrine**: cell talks to itself
2. **paracrine**: cells talks to neighbouring and close by cells
3. **endocrine:** cells talking to other cells far away in the body via hormones
72
describe paracrine communication
* Signal diffuses across gap between cells
* Inactivated locally, so doesn’t enter the blood stream
* e.g. signalling in between WBCs in the immune system
73
types of hormones
hormones are classed based on their composition:
1. steroid hormones
2. peptide hormones
3. amino-acid derivative hormones
74
which amino acid is synthesised into AA derived hormones
tyrosine
75
what are peptide hormones made of, where are they stored and what type of reaction do they cause? hydrophobic or hydrophilic. example
* made of short chain AAs or small proteins
* stored in cells until needed for signalling
* produce a quick reaction in the body
* hydrophilic, dissolves in blood
* e.g. TSH
76
what are amino acid hormones made of, what type of reaction do they cause? hydrophobic or hydrophillic. example
* derived from tyrosine
* fast response reactions
* hydrophilic
* adrenaline
77
what are steroid hormones made of,
where are they stored
what type of reaction do they cause?
hydrophobic or hydrophilic.
example
* cholesterol
* not stored, produced when required
* produce a slow reaction over time - e.g. puberty and sex hormones
* can directly affect DNA
* hydrophobic, so require a transport protein to travel through the blood
* however, dissolves in lipids so can cross the cell membrane without transportation is needed
* e.g. oestrogen and testosterone
78
types of feedback loop
* Positive: amplifies the signal e.g. oxytocin in labour.
* Negative: the basis of homeostasis as it maintains a steady state
79
how is the total volume of body. fluid divided
* intracellular fluid ICF
* extracellular fluid ECF
* intravascular fluid [plasma]
* interstitial fluid
80
what are the similarities and difference between interstitial fluid and plasma
both are extracellular fluid
plasma circulates around the body while inteerstital fluid surrounds the cells of the body
81
Why don’t we give water intravenously?
water is hypo-osmolar to the blood cells, so the RBCs have a lower water potential → water moving by osmosis into the RBCs → them bursting = haemolysis
82
what happens during water deprivation / dehydration
* an increase in the osmolality of ECF →:
* the thirst centre in the hypothalamus is stimulated → drinking water
* release of ADH from the posterior pituitary → water retention in the renal system
* water moves from ICF → ECF
83
where does ADH take effect
distal convoluted tubule and the collecting ducts
84
name 3 causes of water depletion
* decreased intake
* sweating
* vomiting, diarrhoea and diuresis
85
what is the main consequence of water deprivation
dehydration
86
symptoms of dehydration
* thirst
* inelastic skin
* raised haematocrit
* confusion - brain cells affected
* sunken eyes
* hypotension
* dry mouth
* weight loss
87
what happens in water excess
* ECF osmolality decreases →
* water moving into the intracellular fluid
* inhibition of release of ADH from posterior pit gland to facilitate fluid loss in kidneys
* no stimulation of thirst centre in the hypothalamus
88
what are the main consequences of overhydration
* hyponatremia
* cerebral overhydration = water intoxication
* headache
* convulsions
* confusion
* coma
* death
89
define hydrostatic pressure
Pressure difference between plasma and interstitial fluid
Water moves from **plasma into interstitial fluid**
90
define oncotic pressure
Pressure caused by the difference in protein concentration between the plasma and interstitial fluid. It normally pulls water towards the proteins
Water moves from **interstitial fluid into plasma**
91
how do oncotic and hydrostatic pressure interact
at the arterial end of a capillary, water moves out of the plasma in to the interstitial place, down the pressure gradient - hydrdrostatic pressure
at the venous end of the capillary, water is drawn into the capillary due to the oncotic pressure exerted by the proteins in the blood, namely albumin.
this means there is no net change as the blood passes though the capillaries.
92
how do responses to ECF osmolality and ECF volume differ
* osmolality is tightly regulated and changes → rapid response
* change in volume → slower response via RAAS system
93
what is the most likely cause of hypo or hypernatraemia
gain or loss of water
94
causes of hypernatramia and clinical effects
* water deficit
* diabetes insipidus, reduced intake, sweating
* sodium excess - mineralocorticoid excess
* cerebral intracellular dehydration → confusion, tremors and irritability
95
causes of hyponatramia and clinical effects
* excess water intake
* sodium loss - diuretics
* cerebral over hydration → confusion, convulsions, headaches and coma
96
what is oedema
excess water in interstital fluid
97
what is serous effusion
excess water in body cavity
98
what are the steps of energy production
1. glycolysis
2. krebs cycle
3. electron transport chain
99
where does glycolysis take place
in the cytosol of the cell
100
where does the krebs cycle take place
matrix of the mitochondria
101
where does the electron transport chain take place
on the inner membrane of the mitochondria
102
why does glycolysis occur
* energy production in anaerobic conditions
* generation of precursors for biosynthesis
* pyruvate
* G6P
* Glycerol-3-P GLAP
103
what is the net yield of glycolyisis
* 2 ATP
* 2NADH
* 2 pyruvate
104
what can pyruvate be converted into
lactic acid
Acetyl CoA
105
how is pyruvate converted into lactic acid
using lactic dehydrogenase
106
how is pyruvate converted to acetyl coA
oxidation
produces 2 NADH
107
what is the rate limiting step of glycolysis
fructose-6-phosphate → fructose-1,6-bisphosphate
regulated by phosphofructokinase
PFK efficiency is controlled by allosteric activators/inhibitors
108
summarise the eqn fo glycolysis
Glucose + 2NAD+ + 2Pi + 2ADP → 2Pyruvate + 2NADH + 2ATP + 2H2O
109
draw the steps of glycolysis including the enzymes and products
110
what conditions does glycolysis occur in
anaerobic
or aerobic
used for anaerobic respiration to produce ATP
111
what conditions does Krebs occur in
aerobic
112
why does the krebs cycle happen
* produce lots of ATP
* produce precursors for further metabolic pathways
* Provides final common pathway for oxidation of carbohydrates, fat & protein via acetyl coA
113
what is the rate limiting step of the Krebs cycle
isocitrate → alpha-ketoglutarate
controlled by isocitrate dehydrogenase
114
what is the overall energy gain from Krebs cycle
* one cycle →
* 3 NADH
* 1 FADH2
* 1 ATP
* total energy gain from 1 glucose = x2
* **6 NADH**
* **2 FADH**
* **2ATP**
115
draw the krebs cycle including all the enzymes and products
116
how can the rate of citric cycle be regulated
* by controlling isocitrate dehydrogenase via ATP NADH and FADH2
* high levels inhibit the Krebs cycle
117
which enzyme is responsible for forming ATP
ATP synthase
118
what is the final electron acceptor in the ETC
oxygen → formation of H2O
119
why does the electron transport chain happen
* majority of energy production occurs here
* oxidation of NADH and FADH2 and their electrons are passed to the components of the electron transport chain
* final acceptor = oxygen
* the energy released is used to form ATP via ATP synthase
120
describe the process of the electron transport chain
* components of the ETC accept electrons and pass them on to the next component - thus they are reduced then oxidised
* electrons are passed along the chain until the final electron acceptor = oxygen
* H+ ions are passed into the intermembranous space using the free energy generated by the ETC
* this forms a proton gradient across the inner membrane of the mitochondria
* ATP is generated as the protons pass through ATP synthase down the electrochemical gradient
121
what is beta oxidation
the production of acetyl-CoA from fat sources
122
where does fatty acid oxidation take place
the liver
123
how is acyl coA formed
is energy required
fatty acids are converted to Acyl coA using Acyl coA synthetase
2ATP molecule needed
124
what are the main physiological ketones
* Acetone
* Acetoacetate
* B-hydroxybutyrate
125
which tissues can use ketones
muscle and heart muscles in starvation
brain too in severe starvation - to allow RBCs to use glucose
