Foundations Of Medicine Flashcards
Define quaternary proteins
Fourth level of the structure, several polypeptides (subunits) interacting together to form a structure
Define a secondary protein
2nd level of structure, 3D spatial arrangement which relies on hydrogen bonding
What is a receptive field
Somatic sensory neuron activated by stimuli in a specific area
Explain the structure of a neuron
Cell body Dendrites (receive information) Initial segment - axon hillock (triggers action potential) Axon - (sends action potential) Axon - (release transmitter)
Why are barriers between fluid compartments important
Prevent too much secretion and absorption of waste and nutrients between compartments and maintain electrochemical gradient
Describe how an action potential works
Cell reaches threshold and then sudden massive depolarisation occurs, followed by repolarisation
What’s the structutre of skeletal muscle
Striated, multinucleate, bundles of fibres encased in connective tissue sheets
What is abnormally low levels of circulating plasma proteins called and what effect does it have
Hypoproteinaemia - oedema due to loss of on optic pressure
What is a non-competitive inhibitor
Binds to site other than active site, causing conformational change which prevents substrate from binding
What are the different types of glia and what are their functions
Astrocytes - maintains external environment of neurons, surround blood vessels & produce blood brain barrier
Oligodendrocytes - form myelin sheaths in the CNS
Microglia - phagocytosis hoovers mopping up infection
How are lipids transported around the body
Fatty acids - through the blood carried in lipoproteins
Triacyglycerols - hydrophobic so carried in lipoproteins which have hydrophobic core and hydrophilic surfaces
What are abnormal functions of glands
Over/under proliferation
Over/under secretion
Loss of cilia beat
Describe the epithelial components of the kidney
made from epithelial cells and organised into nephrons used for filtration of the blood and excretion of urine
What are leukocytes
White blood cells
Nucleated, large cells involved in defence against pathogens
Define the major carbohydrates in the body
The three main monsaccharides in humans are glucose, galactose and fructose
The three main disaccharides are maltose, lactose and sucrose
What are platelets
Membrane bound cell fragments, rarely nucleated and formation is governed by thrombopoietin. They adhere to damaged vessel walls and exposed connective tissue to mediate blood clotting.
Explain contraction and relaxation of smooth muscle
Smooth muscle contracts by an increase of calcium which activates the x-bridge cycle
Smooth muscle relaxes via the action of myosin light chain phosphatase
What is muscle fatigue
Repeated muscle stim causes fatigue, whch prevents muscles muscles using up vast amounts of ATP which would cause rigor. (Depends on fibre type, length of contraction and fitness of individual)
Describe the formation of urea
Urea is formed in the urea cycle
Excess glutamate is metabolised in the mitochondria of hepatocytes
Ammonia is re-captured via synthesis of carbamoyl phosphate
Nitrogen from carbamoyl phosphate enters the urea cycle
Urea is formed through a hydrolysis reaction of arginine
What is endocytosis
when the membrane forms a vesicle to take molecules in which eventually disintegrates on the inside surface of the membrane, releasing its contents
What is the autonomic nervous system
controls the things we do without thinking about them
Messages are sent from one nerve cell to another through a ganglion
Contracts and relaxes smooth muscle
Importance of maintaining homeostasis
Allows the body and its internal processes to function normally
What is pathogenesis
The way a disease develops
What is meant by an electrochemical gradient
The combined gradient of chemical and electrical which determines the direction of which ions will move. (charge and concentration)
What is erythopoiesis
Process for the formation of red blood cells
What is Vmax in terms of enzymes and kinetics
The maximum rate of reaction (although it increases to infinity)
What are the functions of blood
Clotting Defence Carriage of gas Thermoregulation Maintenance of ECF pH
What is a graded potential
Graded potentials decide whether or not an action potential is fired, by reaching a threshold which set the action potential off
How are interneurons used in the golgi-tendon organs?
Activation of inhibitory interneurons to the agonist muscle causes decrease in contraction strength. Activation of excitatory interneurons to antagonist muscles.
Describe the structure and function of smooth muscle?
Smooth muscle has no striations, is spindle shaped, has thick myosin and thin actin filaments and is arranged diagonally across
Smooth muscle is used in organs and functions autonomically. e.g. blood vessels, bladder, etc.
What is an allosteric enzyme
An enzyme which contains many sub-units with many active sites. One substrate binding to an active site on the enzyme causes conformational changes to the other active sites on other sub-units
What does blood consist of
Plasma
Platelets
White blood cells
Red blood cells
What is lateral inhibition in relation to nerves
Receptors at the edge of a stimulus are more strongly inhibited than those in the centre
Allows precise localisation of a stimulus
What is the function of glycolysis
Glycolysis is a complex series of biochemical reactions, not requiring oxygen which splits glucose, glycogen and other carbohydrates into pyruvic or lactic acid
Do alpha 1 receptors relax or contract smooth muscle?
Contract
What is meant by diffusion
Process by which a gas or solution spreads to fill all available volume in a container (high concentration to low)
What is a common clinical problem that can arise from the urea cycle?
OTC - raised blood ammonia levels in birth which is toxic (inherited)
Which receptors are able to adapt?
Mechanoreceptors
proprioreceptors
NOT nocireceptors as important to respond to pain
How are proteins catabolised?
Proteins are broken down in exercising muscle to amino acids and transferred to the liver where it can then be converted into ammonia and excreeted as Urea
What is the average amount of blood in the average male?
5 Litres
Explain the sliding filament theory of muscle contraction?
When muscle shortens from its relaxed state, the muscle fibres slide together and so the bands inbetween the muscle shorten and the length of the muscle decreases.
Describe the reflex mediated by Golgi tendon organs?
Inverse stretch reflex is caused by afferent nerves from the Golgi tendon organs firing more action potentials. This causes a decrease in contraction strength and so the muscle relaxes.
What is the structure and function of eicosanoids?
These are unsaturated fatty acids that are synthesised throughout the body.
They are signalling molecules which exert control over inflammation or immunity
Describe the anaerobic properties of muscle?
During anaerobic excercise; the diameter of muscle increases as well as glycolysis increases.
What is a competetive inhibitor?
Competitive inhibitors block the active site of an enzyme and decreases the affinity for the substrate for the enzyme. (Km increases)
Define globular proteins?
globular proteins are compact and have a round shape, e.g. haemoglobin
Define the function of steroid lipids?
Steroid hormones are chemical substances that act as chemical messengers in the body.
What is a nociceptor?
Responds to painful stimuli, tissue damage and heat
Characteristics which favour diffusion through the lipid bi-layer?
Small
Hydrophobic
Uncharged
Explain the affinity and effect of a full agonist, partial agonist and an antagonist?
Agonist - high affinity, full effect
Partial agonist - High affinity, partial effect
Antagonist - High affinity, No effect
What are proteoglycans?
Macromolecules found on the surface of cells or inbetween cells in the extracellular matrix. They form part of many connective tissues in the body.
What is an isosmotic solution?
An isosmotic solution has the same number of particles as regular ECF.
Explain the process of excitation-contraction in muscle?
The myosin cross-bridge use energy to generate the force of contraction and consist of heavy chains and actin and ATP binding sites.
What is exocytosis?
Exocytosis is when a vesicle filled with molecules travels to the ICF releasing its contents.
What is glycogen?
It is used to store glucose in human cells and is extensively more branched than starch and so can hold much more glucose.
Explain the synthesis of glycogen?
Glycogenin begins the process by covalently binding glucose from uracil-diphosphate to form a chain.
Glycogen synthase takes over and extends the chain.
Finally, the chain is broken by glycogen-branching enzyme and re-attached via bonds to give branch types.
Describe the synthesis of free fatty acids?
Fatty acid is synthesised from acetyl CoA which requires ATP and NADPH.
What is an excitory and inhibitory neurotransmitter?
An excitory neurotransmitter is when the cell depolarises and so is more likely to fire an action potential
An inhibitory neurotransmitter is when the cell hyperpolarises and so is less likely to fire an action potential.
What are the sources and effects of intracellular Ca2+ as a second messenger.
Sources;
internal stores in endoplasmic reticulum
voltage or ligand-gated channels
inhibition of Ca2+ transport out of the cell
Effects;
affects target protein
binds to calmodulin which then activates target protein
What are the main molecules in the body where nitrogen is found?
Amino acids and DNA
Descrbe negative feedback control?
Negative feedback control is the process of responding to homeosatic change from a signal (either nervous or endocrine) top return the body to its normal internal conditions.
Define Osmolarity?
Osmolarity defines the total number of particles in solution but not their nature (penetrating and non-penetrating).
Define fibrous proteins?
Fibrous proteins are made of long narrow strands, e.g. muscle fibres and connective tissue
What are erythrocytes?
Red blood cells
Highly flexible
non-nucleated
densely packed with haemoglobin
What is leukopoesis?
White blood cell formation controlled by a mix of cytokines
List the membrane proteins and describe their function?
Receptors - Penetrate the membrane and allow communication of extracellular signals.
Transporters;
Channel proteins - create a pore through the membrane for which molecules can flow through, usually water and ions.
Carrier proteins - Move larger molecules from ICF to ECF and only open to one at a time.
Enzymes - Catalyse chemical reactions on the cell membrane.
Structural proteins - Anchor the cell membrane to both the intracellular skeleton and extracellular matrix.
What are glycoproteins and why are they present in the cell?
They are proteins that have carbohydrates covalently atached.
This may occur so that proteins solubility is increased, to influence protein folding and conformation, protect it from degredation and act as communication between cells.
What is Feed Forward control?
This is when receptors can anticipate change in the body’s internal conditions and so activate the response earlier.
Where do the sympathetic and parasympathetic nerves stem from?
Sympathetic - middle of spinal cord
Parasympathetic - top and bottom of the spinal cord.
Define the term antagonist?
Blocks the normal response of the receptor.
Describe the processes of transmembrane signalling?
Receptors that act as ion channels
Receptors that functions as enzymes
Receptors that directly alters enzyme activity, but that enzyme is another protein
G-protein coupled receptors
What is myelination?
Allows the depolarisation at one node to spread as a local current so that the action potentials can be fired faster due to the current travelling further.
Explain the process of degredation of glycogen?
Glycogen monomers are removed one at a time from the non-reducing sugar ends.
Glycogen near the branch is removed by a de-branching enzyme.
Transferase activity removes a set of three glycogen residues.
Glycosidase activity then removes the final glycogen.
The unbranched chain can be further degraded.
How is glucose absorbed?
It is absorbed through an indirect ATP-powered process where an Na+ pump allows glucose to continually be moved into the epithelial cells.
What is an isotonic twitch?
An isotonic twitch is contraction with shortening length. e.g. running
What is aetiology?
The cause of disease
Which receptors does the sympathetic system act upon?
Nicotinic
Alpha or Beta
Explain the steps of the nueromuscular junction transmission?
- Motor neuron fires action potential
- Ca2+ enters through voltage-gated channels in presynaptic terminal
- Triggers fusion of vesicles
- Acetyl choline is released
- Diffuses across synaptic cleft
- Binds to acetylcholine receptors
- Na+ enters through open Na+ ligand-gated channels
- Evokes graded potential
- Depolarizes adjacent membrane to threshold
- Opens voltage-gated Na+ channels evoking a new action potential
- Acetylcholine is removed by acetylcholinesterase
How does concentration of an enzyme or substrate effect rate of reaction?
Increasing substrate concentration will increase the initial rate of reaction until all the active sites have been taken up.
Increasing enzyme concentration will increase the rate of reaction until all the substrates have been used up.
What does essential fatty acid mean?
Are essential in humans and deficiencies can lead to intestinal diseases, depression and ADHD.