Biochemistry Flashcards
1
Q
Oxidoreductases
Action?
Example?
A
Action: Oxidation reduction reactions
Examples: oxidase, dehydrogenase
2
Q
Transferase
Action?
Example?
A
Action: Transfers amino, carboxyl, acyl, carbonyl, methyl, phosphate and other groups between molecules
Example: transaminase
3
Q
Hydrolase’s
Action?
Example
A
Action: cleavage of bonds coupled with inserting water
Example: Esterase, amylase
4
Q
Lyases
Action?
Example?
A
Action: Cleavage of carbon-carbon, carbon-sulfur, and carbon-nitrogen bonds
Example: Decarboxylase
5
Q
Isomerase
Action?
Example?
A
Action: Rearrangement of bonds
Example: epimerise
6
Q
Ligases
Action?
Example?
A
Action: formation of bonds between C,O,S,N
7
Q
Irreversible inhibitor action
A
Bind to enzymes permanently, the cell must produce new proteins to resume function
8
Q
Reversible enzyme inhibitor action
A
Can bind and release enzymes, non-covalent bonds.
Includes competitive and non -competitive enzymes.
9
Q
Competitive inhibitors
A
Compete with substrate to bind to the active site
10
Q
Non-competitive inhibitor
A
Bind at different site from the substrate, changes the shape of the active site
11
Q
Feedback loops in enzymes
A
the product of the metabolic pathway often inhibits an enzyme early in the same pathway, preventing waste
12
Q
Allosteric regulation of enzymes
A
Allosteric enzymes control key points in metabolism, allosteric inhibitors bind to a regulatory site, altering the enzymes shape
13
Q
Post-translational modification
A
enzymes can be chemically modified after synthesis to alter activity, E.G. phosphorylation
14
Q
Membrane protein roles:
5
A
- transporters
- channels
- anchors
- receptors
- enzymes
15
Q
Percentage of membrane weight that is membrane proteins?
A
20-75%
16
Q
Membrane protein structure
A
- most form alpha helices, crossing the membrane
- Membrane inserted part is hydrophobic
17
Q
membrane permeability
2
A
- Molecules diffuse from high conc. to low conc.
- Not all molecules can diffuse across the membrane
18
Q
Transporter protein
3
A
- switches between two states, open on one side (binding), and open on the other side (releasing)
- also called a pump
- relatively slow, 10^2 - 10^4 molecules
19
Q
Protein channels (3)
A
- Only allow active transport
- Can be ligand-gated or voltage-gated
- Much faster than transporter
20
Q
Protein receptors and ligand examples (2)
A
- Proteins that bind to signalling molecules (ligands), producing a cellular response
- Ligands include; hormones, cytokines and neurotransmitters
21
Q
G-protein coupled receptors examples (5)
A
- Adrenaline receptors
- Glucagon receptors
- Odour molecule receptors
- Acetylcholine receptors
- photoreceptor
22
Q
G-protein coupled receptor action
A
- Ligand binding causes activation of the associated G protein, which binds on.
- Activated G-protein stimulates enzymes that produce a secondary messenger, amplifying the signal
23
Q
cAMP action
A
cAMP stimulates protein kinases, that phosphorylate various cellular proteins, causing changes in gene expression
24
Q
Enzyme-coupled receptors (3)
- Ligand binding
- RTK
- Examples
A
- Ligand binding causes dimerisation and activation of intracellular enzyme
- E.G. RTK phosphorylates proteins on the tyrosine
- Includes receptors for insulin, GH
- Cancer related
25
The nucleus (5)
- Contains
- Condension
- Membrane
- entry/exit
- nucleolus
- contains most of the cells DNA
- DNA is condensed as chromatin
- The nucleus is surrounded by a double membrane
- Nuclear pores allow proteins to enter/leave the nucleus
- Nucleolus is the site of ribosome assembly
26
mitochondria (2)
- ATP
- Structure
- Produce most of the cells ATP using oxidative phosphorylation
- Has a double membrane, oxidative phosphorylation occurs within the inner membrane
27
Rough endoplasmic reticulum (2)
- Bound by many ribosomes
| - Site of synthesis for proteins destined for section and membrane proteins
28
Smooth endoplasmic reticulum (2)
- No ribosomes bound
| - Site of lipid synthesis
29
The Golgi apparatus (2)
- Modification of proteins and lipids, e.g. addition of sugar groups (glycosylation)
- Sorting and packaging of proteins and lipids to other organelles
30
Vesicular transport (1)
- Transport vesicles bud off and fuse to allow exchange of material between Golgi, ER and other organelles
31
Lysosomes (3)
- Degradation of unwanted cellular components
- Low pH within lysosome, suited to hydrolyse enzymes
- Receives waste vesicles from Golgi
32
Peroxisomes (2)
- Contains oxidase enzymes that produce H2O2
| - H2O2 used to detoxify molecules and to kill bacteria
33
Protein targeting (3)
- Rough ER
- Transport vesicles
- Lysosomes
- Proteins destined for secretion are made in the rough ER
- Vesicles transport proteins to the Golgi for processing, then to the plasma membrane
- Misfolded, damaged or unwanted proteins are targeted to the lysosomes for degradation
34
Cytoplasm definition:
- All cell contents inside the plasma membrane
35
Cytosol definition:
- The fluid inside the cytoplasm
36
Cell polarisation:
- Many cells are arranged asymmetrically, different ends have different function/structure
37
The cytoskeleton:
| - A network of .....
- A network of protein filaments that run throughout the cytoplasm of eukaryotic cells
38
3 parts of the cytoskeleton:
- Actin filaments
- Microtubules
- Intermediate filaments
39
Actin filaments (7nm diameter):
- Can change...
- Can grow or shrink by ...
- Involved in .....
- Can change cell shape and cause movement.
- Can grow or shrink by adding or removing actin subunits
- Involved in muscle contractions and forming cellular extensions
40
Microtubules (15nm diameter) (4)
- Hollow cylinders of ....
- Extend from c..... near the .....
- Pulls apart ...... during cell division
- Forms ..... and ......
- Provides tracks for ...... using ....... proteins
- Hollow cylinders of tubular subunits
- Extend from centrosomes near the nucleus
- Pulls apart chromosomes during during cell division
- Form cilia and flagella
- Provide tracks for transport of molecules using motor proteins
41
Intermediate filaments (10nm):
- Rope-like ....
- Provide ....
- Rope-like filaments found throughout cytoplasm
| - Provide mechanical strength for the cell, prevents shearing
42
Free energy (g): (2)
- Energy change associated with a reaction is known as a change in free energy (KJ/mol)
- When change in free energy is less than zero, the reaction can occur spontaneously
43
Adenosine triphosphate (ATP): (4)
- Metabolic purpose
- Hydrolysis
- Use
- Synthesis in animals
- ATP is a key intermediate in metabolism
- Hydrolysis of ATP to ADP is energetically favourable
- ATP hydrolysis is used to drive energetically unfavourable reactions
- In animals ATP is made using energy from food molecules, food molecules release energy by oxidation
44
Oxidation of food molecules:
- Carbon-based foods are oxidised to release energy
| - In aerobic respiration,
45
Activated carriers in metabolism (3)
- Role
- Coenzymes
- Derivation
- Biomolecules that store energy in the form of transferable chemical groups
- Often bound to enzymes
- Many are derived from vitamins
46
NADH and NADPH
- NAD+ can accept two electrons and a proton to form NADH
| - NADH can be phosphorylated to form NADPH
47
FAD and FADH2
- Transition
- Bond between FAD and enzymes
- FAD can accept two protons to form FADH2
| - FAD is covalently linked to the enzymes for which it acts as a coenzyme
48
Glycolysis: net result
| - Glucose = ......
GLUCOSE = 2 PYRUVATE + 2 ATP + 2NADH
49
Citric acid (Krebs) cycle:
- Location
- Acetyl CoA role
- desirable products
- Waste products
- Occurs in the mitochondrial matrix
- Acetyl CoA feeds Carbon atoms into the cycle
- Produces 3 NADH, FADH2 and GTP
- Carbon atoms released as CO2
50
Oxidative phosphorylation (3)
- Electrons from .... are passed to ....
- The energy released is used to ......
- H+ flows back .....
- Electrons from NADH and FADH2 are passed to 02
- The energy released is used to pump H+ out of the matrix into the inter membrane space
- H+ flows back down its concentration gradient, generating ATP from ADP
51
Physiology definition:
- The normal functions and phenomena of living organisms
52
Cell basics:
- Number of cells in a human
- ICF
- ECF
- fluid seperation
- Approximately 30,000,000,000
- ICF: intracellular fluid, fluid inside the cell
- ECF: extracellular fluid, fluid outside the cell
- ECF and ICF separated by a plasma membrane
53
Properties of living cells:
- They assimilate materials from ....
- They excrete waste products into......
- They g....
- They r.....
- They respond to .....
- They may exhibit m.....
- They assimilate materials from the internal environment that surrounds them
- They excrete waste products into the internal environment
- They grow
- They reproduce
- They may respond to changes in their surrounding internal environment or the environment external to their body
- They may exhibit motility
54
Distribution of water in a 70Kg man:
- Total body water
- ECF
- Intravascular fluid
- Interstitial
- ICF
- Total body water: 60% x 70L
- ECF: 20% X 70L = 14L
(- Intravascular fluid: 3L)
(- Interstitial fluid: 11L)
- ICF: 40% X 70L = 28L
55
Concentration of sodium ions in ECF and ICF
```
ICF = 10 mmol/L
ECF = 140 mmol/L
```
56
Concentration of potassium ions in ICF and ECF
- ICF = 120 mmol/L
| - ECF = 4 mmol/L
57
Concentration of calcium ions in ICF and ECF
```
ICF = 0.0001 mmol/L
ECF = 1.25 mmol/L
```
58
Homeostasis:
- The regulation of the internal environment within the body
| - E.g. temperature, pH, osmolarity, oxygen level, glucose concentration etc.
59
Simple diffusion (flux):
- PP
- Direction of movement (concentration gradient)
- By virtue of random ....
- Application to plasma membrane
- Passive process (doesn't require energy from metabolism)
- Down concentration (solutes) or partial pressure (gases) gradient
- By virtue of random thermal motion
- Lipid soluble substances such as oxygen and carbon dioxide cross the plasma membrane by simple diffusion
60
Fick's Law: the rate of diffusion of a gas across a membrane is ......
(1) proportional to the ............ ....... of the membrane
(2) proportional to the ................... .................. gradient
(3) Inversely proportional to the ................ .. ... membrane
(1) proportional to the surface area of the membrane (A)
(2) proportional to the partial pressure gradient (change in P)
(3) inversely proportional to the thickness of the membrane (x)
61
Partial pressure (P):
The total pressure exerted by a mixture of gases is made up of individual partial pressures of each gas present
62
How are gases carried in blood? (3)
- Dissolved in plasma
- Bound to protein
- Chemically altered
63
Purpose of bulk flow:
- Time for diffusion is proportional to the distance squared
- Diffusion cannot keep up with demand over long distances
64
Flow (Q) equation:
Q = change in Pressure / Resistance
65
Cardiac output (Q) equation:
```
Q = SV x HR
Q = (MAP - CVP) / TPR
```
66
Flow requires metabolic energy (explanation):
Pressure gradients are generated by respiratory and cardiac pumps which require the usage of metabolic energy
67
Bulk movement of water between ICF and ECF:
- How
- Effecting factors
- Occurs by osmosis
| - Depends on the total number of osmotically active solute particles in the ICF and membrane permeability
68
Tonicity definition:
- A measure of the effective osmotic pressure of a solution compared with that of ICF
- Cell volume will change if water enters or leaves via osmosis
69
Isotonic solution:
- No change in the size or shape of the cell
- No net movement of water into or out of the cells by osmosis
- E.g. 0.9% NaCl solution
70
Hypertonic solution:
- Cells have shrunk and became crenated (notched)
- Water has moved out of the cells via osmosis
- E.g. 2.7% NaCl solution
71
Hypotonic fluid:
- Cells become swollen and haemolysed (burst)
- Water has been sucked into the cell via osmosis
- e.g. distilled water, (pure solvent) never given intravenous
72
Skeletal muscle:
- Role:
- Structure:
- Innervation:
- Voluntary movement
- Striated
- PNS, voluntary
73
Cardiac muscle:
- Role
- Structure
- Innervation
- Generation of blood pressure
- Striated
- ANS, involuntary
74
Smooth muscle:
- Role
- structure
- Innervation:
- Contraction of hollow organs (blood vessels, gut, urinogenetal)
- Non-striated
- ANS, involuntary
75
Skeletal muscle structure: (5)
- Large, rod-like fibres
- Striations present
- Nuclei at periphery
- Fibres electrically separate
- Each fibre innervated singly
76
Cardiac muscle structure: (4)
- One/two nuclei
- Striations
- Cells connected electrically
- Typically not innervated
77
Smooth muscle structure: (5)
- Very small cells
- Single nucleus
- No striations (arrangement)
- Cells sometimes connected
- Hollow organs
78
```
Contraction process: cross bridge cycle:
1.
2.
3.
4.
```
1. ATP binds to myosin filament head
2. ATP is hydrolysed by the myosin, pulling the myosin head up
3. Myosin head attaches to the actin filament
4. ADP and phosphate group de-attach, myosin head reverts to original position, pulling the actin with it
79
Rigor mortis:
1. Cellular respiration ceases at death
2. ATP conc. falls
3. Cross bridges permanently attached
4. Rigor mortis occurs (muscular rigidity)
80
Role of sarcoplasmic reticulum (SR) in skeletal and cardiac muscle contraction
- SR is a calcium store
- T tubules conduct the action potential into a fibre
- T tubule AP stimulates Ca release from SR
- Released Ca stimulates muscle contraction
81
```
What is the action potential?:
(3)
- AP is a brief.....
- Once initiated.....
- A very fast change of ....
```
- AP is a brief all or none depolarisation of the neuronal membrane
- Once initiated, it propagates without detriment
- A very fast change of membrane potential from - to + to - again
82
Ionic basis of AP:
- Na+ are responsible for depolarisation
| - K+ are responsible for repolarisation
83
Saltatory conduction in axons: (3)
- Insulation
- Uninsulated parts
- Effects
- Axons of many neurones are insulated with layers of myelin
- The AP jumps between the uninsulated parts (nodes of ranvier) as an electrical field
- This greatly accelerates AP propagation and saves much energy
84
Variation of myelinisation:
| 3
- Speed of conductance depends on the degree of myelinisation (thickness)
- Axons with thick myelin insulation are generally much faster
- Loss of myelin occurs in many diseases (e.g. multiple sclerosis) and can be fatal
85
Neuromuscular junction action:
(6)
1. AP reaches....
2. .... enters .....-gated channels
3. ...... released into the synaptic cleft
4. ..... binds to receptors in the end plate, opening ..... channels (.........)
5. Local current between ....... end plate and adjacent ........
6. Muscle fibre ...... ........ and .......
1. Action potential reaches presynaptic axon terminal
2. Ca2+ enters voltage-gated channels
3. Acetylcholine released into the synaptic cleft
4. Acetylcholine binds to receptors in the motor end plate, opening Na+ channels `(depolarisation)
5. Local current between depolarised end plate and adjacent muscle plasma membrane
6. Muscle fibre AP initiated and propagated
86
Termination of the trans-synaptic signal:
- Caused by acetylcholinesterase (AChE) degrading acetylcholine
87
Sub-divisions of the ANS (efferent):
| 2
- Parasympathetic
| - Sympathetic
88
Parasympathetic NS:
- Controls;
- Synapses:
- Signal molecules used:
- Endocrine:
- Dominates at fight or flight systems
- Synapses outside of the effector organ
- ACh used at the first synapse, NA (noradrenaline) used at the effector organ
- Effected by the adrenal gland
89
Fight or flight effects triggered by the sympathetic NS: (4)
- Pupil dilation
- Trachea and bronchi dilation
- Increased HR and force of contraction
- Re-distribution of blood by arterioles (favours critical organs)
90
sympathetic nervous system:
- Dominates at rest and during sleep
- Synapses inside the effector organ
- ACh used at both synapses
91
Rest and digest effects triggered by the parasympathetic system: (4)
- Constriction of pupils, reduces light reaching the retina
- Increases curvature of the lens to focus on close objects
- Increases secretion of glands in GI tract, increasing motility
- Decrease in HR and force of contraction
92
Visceral afferents:
- Conduct messages from the organs to the CNS
93
Karyotype:
- Definition:
- Heterochromatin:
- Euchromatin:
- Number and appearance of chromosomes of a cell
- Heterochromatin: dark bands
- Euchromatin: light bands
94
Aneuploidy:
- Definition
- Trisomy
- Monosomy
- Abnormal number of chromosome
- Trisomy: additional chromosome
- Monosomy: loss of a chromosome
95
Results of aneuploidy:
- Only 3 autosomal trisomies compatible with life (+21,+18,+13)
- Most cases result in miscarriage
96
Meiotic non-disjunction:
- Then failure of homologous chromosomes to segregate properly to opposite poles during meiosis
- Can occur in meiosis 1 or 2
- Causes trisomy and monosomy
97
Balanced chromosomal translocations:
- Defintion
- Clinical impacts
- Exchange of DNA regions between non homologous chromosomes
- If no DNA is lost, patient is clinically normal
- Increased chance that offspring will have an unbalance chromosome set
98
Dosage compensation:
- One copy of the X chromosome is randomly inactivated in females
- Preventing an inequality in X-chromosome expression between the sexes
99
Stem cells: 3 types
- Totipotent
- Pluripotent
- Multipotent
100
Totipotent stem cells:
- Can form all the cell types in a body, plus the extra embryonic and placental cells
101
Pluripotent stem cells:
- Can only make cells of the embryo proper, but this is all cells
102
Multipotent stem cells:
- Can only make cells within a given germ layer and derivates
- Adult stem cell
- maintain and repair the tissue where they're found
103
Cell fate determination:
- Transcription factors (cell specific regulatory proteins) determine cell differentiation by inducing expression of different proteins
