Alimentary Flashcards
Active transport of Na+ out of the cell with corresponding import of K+
- consumes approximately ¼ of the bodies total energy expenditure
- occurs via a symporter located in the plasma membrane
- occurs at a greater rate than these ions pass back over the membran
- is driven by potential energy created by an excess extracellular negative charge, resulting from active Cl- ion export.
- consumes approximately ¼ of the bodies total energy expenditure
Endocytosis delivers substances to endosomes and lysosomes, and
- often relies on the presence of a protein coat which collects relevant occupied receptors into a pit
- is always a chance event in which material is randomly taken up into vesicles at the cell surface
- is used for the import of all material into cells
- does not require energy input since it occurs down a concentration gradient and the forming of a vesicle is a spontaneous process
- often relies on the presence of a protein coat which collects relevant occupied receptors into a pit
The inherent free energy change of a reaction (DGf)
- determines whether a reaction will be spontaneous or not
- indicates the potential direction of a reaction under conditions of set concentrations of products and reactants
- is decreased by the addition of a catalytic enzyme
- becomes more negative, and the reaction becomes less likely, with increasing substrate levels
- becomes more positive if the ratio of products to substrates increases
- indicates the potential direction of a reaction under conditions of set concentrations of products and reactants
Metabolism is controlled to reflect body conditions, mainly levels of food intake which affects the level of blood sugar. This control is mediated in part by
- the ratio of products to substrates of metabolic pathways i.e. mass action
- the release of hormones – namely glucagon and insulin – when blood sugar levels are high and low, respectively
- allosteric mechanisms in which products tend to stimulate pathways
- the ratio of products to substrates of metabolic pathways i.e. mass action
Proteins that are secreted from cells are
- often modified in the ER and Golgi with the addition of sugars, for example
- translated from free ribosomes in the cytosol
- transported to the cell surface and then released to the cell exterior through pores in the plasma membrane
- taken up into secretory vesicles by an active translocation process which occurs after translation is complete
- often modified in the ER and Golgi with the addition of sugars, for example
A cross section of the GIT wall, from lumen to peritoneal surface, passes through the layers in which order?
- epithelium, submucosa, lamina propria, circular smooth muscle, longitudinal smooth muscle, serosa
- epithelium, serosa, submucosa, lamina propria, circular smooth muscle, longitudinal smooth muscle
- epithelium, lamina propria, submucosa, circular smooth muscle, longitudinal smooth muscle, serosa
- epithelium, submucosa, lamina propria, serosa, circular smooth muscle, longitudinal smooth muscle
- epithelium, lamina propria, submucosa, circular smooth muscle, longitudinal smooth muscle, serosa
The cephalic phase of gastric secretion:
- is transmitted to the stomach by the parasympathetic nervous system, via the vagus nerve
- decreases the rate of secretion of acid and pepsinogen from the stomach lining
- is responsible for a decrease in acid secretion from gastric pits in response to low duodenal pH
- is inhibited by parasympathomimetic drugs
- is transmitted to the stomach by the parasympathetic nervous system, via the vagus nerve
Why is it more difficult to swallow with the ventral aspect of the neck fully extended?
- M. geniohyoideus pulls the hyoid rostrally.
- M. sternohyoideus pulls the hyoid caudally
- M. palatopharyngeus cannot contract
- M. cricopharyngeus cannot contract
- Epiglottis cannot close
- M. sternohyoideus pulls the hyoid caudally
Which germ layer(s) form the oral cavity and oral pharynx linings respectively?
- Both endoderm.
- Endoderm and ectoderm
- Ectoderm and endoderm
- Both ectoderm
- Both mesoderm
- Ectoderm and endoderm
With which part of the nasal cavity do the paranasal sinuses communicate directly?
- middle nasal meatus
- dorsal nasal meatus
- ventral nasal meatus
- gutteral pouch
- common nasal meatus
- middle nasal meatus
Which part of the mandible articulates with the temporal bone?
- ramus
- coronoid process
- retroarticular process
- symphysis
- condylar process
- condylar process
The histological structure of the omasum of the ruminant stomach differs from other nonglandular compartments by possessing one of the unique histological features. Which one of the five features listed below best fits that unique characteristic?
- extension of the lamina muscularis into laminae.
- extension of the tunica muscularis into laminae.
- the presence of papillae
- the presence of keratinised stratified squamous epithelium.
- the presence of a very thick tunica muscularis
- extension of the lamina muscularis into laminae.
Which of the following statements concerning chylomicrons is FALSE?
- They contain mostly triacylglycerol with some cholesterol, phospholipid and protein
- They are assembled inside intestinal cells
- They are secreted directly into the blood
- They contain triacylglycerol synthesised inside intestinal cells from monoacylglycerols and fatty acids
- They enable fat soluble compounds to be transported in the blood
- They are secreted directly into the blood
Bile consists of bile salts, cholesterol, bile pigments and bicarbonate ions, along with other constituents. Identify the one statement that is correct.
- bile salts and bile pigments are re-absorbed as part of the entero-hepatic circulation
- bile salts and cholesterol aid in the absorption of fat-soluble vitamins
- reabsorbed cholesterol forms part of chylomicrons which enter the blood in intestinal villi
- the main effect of secretin is to induce gall bladder contractions whilst CCK increases HCO3- secretion from the bile duct
- bile salts and cholesterol aid in the absorption of fat-soluble vitamins
The enteric nervous system:
- facilitates voluntary control of the gut via the myoenteric and submucosal plexuses
- is modulated by the autonomic nervous system, with ACh generally inhibiting activity whereas noradrenaline is stimulatory
- controls the release of gastrin from the stomach lining during the intestinal phase of gastric secretion
- acts to initiate deglutition, elevating the tongue
- receives efferents from the gut mucosa, which respond to stretch
- receives efferents from the gut mucosa, which respond to stretch
The hormones insulin and glucagon antagonise each other through regulating the phosphorylation status of key controlling enzymes of metabolism. Which one of the following statements is correct.
- insulin acts on cell surface receptors to activate a protein phosphatise, which reduces phosphorylation of these key enzymes
- the effect of phosphorylation of these enzymes is to increase their activity
- glucagon binds to receptors on muscle cells to stimulate glycogen breakdown
- the intracellular protein kinase, PKA, phosphylates key enzymes in response to insulin action
- insulin acts on cell surface receptors to activate a protein phosphatise, which reduces phosphorylation of these key enzymes
The reaction catalysed by pyruvate dehydrogenase (PDH) (pyruvate + CoA + NAD+à acetyl CoA + CO2 + NADH + H+) links glycolysis to the citric acid cycle. Predict which 3 of the following compounds would stimulate PDH activity.
Select one or more:
- Pyruvate
- acetyl CoA
- Ca2+
- ATP
- Insulin
- NADH
- Pyruvate
- Ca2+
- Insulin
The title oxidative phosphorylation arise because:
- oxygen activates a protein kinase, PKA, which phosphorylates ATP synthase
- oxygen accepts electrons from the electron transport chain, generating NADP from NAD+ + Pi
- The oxidation of electron carriers pumps protons out of the mitochondrial matrix
- The electrochemical proton gradient over the inner mitochondrial membrane is used to generate ATP from ADP + Pi by ATP synthase
- oxidation of electron carriers is linked to ADP phosphorylation via the electrochemical proton gradient over the inner mitochondrial membrane
- The oxidation of electron carriers pumps protons out of the mitochondrial matrix
The protein thermogenin:
- spans the ER membrane in brown fat cells
- accelerates metabolic reactions, generating heat as a by-product
- allows the free passage of K+ over membranes
- is used to maintain body temperature in reptiles
- generates heat through the movement of protons down their gradient
- accelerates metabolic reactions, generating heat as a by-product
Glycogen synthesis and breakdown are regulated in a reciprocal manner:
- by the hormones glucagon and adrenaline
- through allosteric effects on the key enzymes, phosphofructokinase and glycogen synthase
- by opposing actions of protein kinases and phosphatases
- through concurrent dephosphorylation of glycogen synthase and phosphorylation of phosphorylase
- by opposing actions of protein kinases and phosphatases
Glycogen deposits in muscle are broken down:-
- in response to glucagon presence
- to release glucose that buffer blood sugar levels
- to provide fuel for short bursts of strenuous muscle activity
- to power long distance flights of migratory birds
- to provide fuel for short bursts of strenuous muscle activity
The gluconeogenic pathway would be stimulated under all of the following conditions, except:
- in an omnivore, between meals
- in a carnivore, between meals
- in a horse, after eating oats and chaff
- in a ruminant, whilst ruminating
- in a carnivore, shortly after a meat meal
- in a horse, after eating oats and chaff
Acetyl CoA levels increase in the liver during a fast for all of the following reasons, except:
- the supply of fatty acids increases, generating more acetyl CoA from b-oxidation
- the usage of acetyl CoA for fatty acids synthesis is decreased
- the usage of acetyl CoA in the citric acid cycle is decreased
- oxaloacetate decreases the activity of citrate synthase, the first enzyme of the citric acid cycle
- gluconeogenesis decreases the level of oxaloacetate in the cells
- oxaloacetate decreases the activity of citrate synthase, the first enzyme of the citric acid cycle
Ketogenesis occurs in the liver of fasting animals, in response to increased acetyl CoA levels, for all of the following reasons, EXCEPT:
- The relative deficiency of glucose stimulates gluconeogenesis, which depletes the citric acid cycle of intermediates
- muscle-derived ketogenic amino acids are converted into acetyl CoA
- the rate of b-oxidation in the liver falls, since the citric acid cycle is producing a lot of ATP
- glucagon activates hormone-sensitive lipase, increasing fat mobilisation from adipose tissue, much of which is taken up and metabolised by the liver
- glucagon inactivates acetyl CoA carboxylase, inhibiting fatty acid synthesis in the liver
- b-oxidation is accelerated, so its reciprocal pathway (fatty acid synthesis) would be inhibited, through hormone action (glucagon)
- the rate of b-oxidation in the liver falls, since the citric acid cycle is producing a lot of ATP