Revision questions - week 1 Flashcards
What are the definition, and difference between digestion and absorption?
Digestion
– Process of breaking down foods componets into the molecules that be can absorbed by
enterocytes and delivered into blood or lymphatic circulation. Macronutrients are turned into monomers, micronutrients are freed from larger food particles.
Absorption
– Uptake of monomers and micronutrients from the lumen of the GIT through the absorptive cells (enterocytes), into the blood or lymph for transport to organs / cells.
Trace a cheese and salad sandwich through the digestive processes, naming the various anatomical structures and naming secretions involved in the digestion, and their role
?
Describe the different forms of absorption
Passive
Facilitated
Active
Endocytosis
How are various nutrients being absorbed and transported into the body?
VIA THE CARDIOVASCULAR
SYSTEM
• Water-soluble nutrients transported via capillaries in villi to portal vein, into the liver and to other organs and tissues
VIA THE LYMPHATIC SYSTEM
• Fat-soluble nutrients and larger particles packed as chylomicrons, transported via lacteals into lymph vessels to the thoracic duct where they then enter the blood circulation
What occurs to indigested food compounds?
?
What are prebiotics?
non-digestible carbohydrates that “feed bacteria and promote their growth, and result in fermentation products (SCFA such as butyrate) e.g. inulin, fructans, resistant starch, pectin etc
What is the starting molecule in lipogenesis
acetyl coa
what in triglcerides can be used in glucose production
glycerol
Can fatty acids be used as substrate for gluconeogenesis
No, they can’t
Because:
• Gluconeogenesis starts from oxaloacetate
• Oxaloacetate is formed from glucogenic amino acids carbon
backbones( GGAACB), e.g. not fatty acids, or pyruvate.
• Pyruvate is formed from glucose or GGAACB, not fatty acids
• Fatty acids are oxidised to acetyl-coA (2 carbons molecules)
• Acetyl coA cannot be converted back to pyruvate
(irreversible reaction)
• Acetyl coA enters the CAC to form citrate with oxaloacetate.
The CAC is an open cycle /circuit, meaning that the
intermediates are formed from a variety of substrates coming
from other pathways, and carbons atoms are lost all along as
CO2 . Therefore the acetyl coA 2 carbons do not “exist” by
the time oxaloacetate is formed.
Key factors and their role in regulation of energy metbaolism
- liver - because most the reactions take place in the liver, major site of of nutirent conversion and metabolism,
- Substrate availability dictates whether the metabolism will be anabolic or catabolic.
- ATP levels in cell / tissue: determine activity of AMPK and whether
catabolic states are activated to make more ATP
- ATP levels in cell / tissue: determine activity of AMPK and whether
- Enzymes are necessary for reactions to take place. Mutation in
genes coding for these enzymes will impair energy metabolism
- Enzymes are necessary for reactions to take place. Mutation in
- Hormones dictate whether anabolic pathways (insulin) or
catabolic pathways (glucagon) take place
- Hormones dictate whether anabolic pathways (insulin) or
- Vitamins and minerals necessary for transfer of ions (NAD and FAD) and act as cofactors to metabolism enzymes
metabolic shifts occur in substrate utilisation for energy metabolism for maintenance of blood glucose level, and for sparing lean body mass when fasting from a few hours to several days
- ATP production relies on glycogen stores then lean body mas then fat stores and ketone bodies
- Maintenance of BGL – glucose used up, liver glycogen , lean body mass used in gluconeogenesis to continue supply of BGL.
- Long period of fasting result in using ketone bodies as energy source
therefore body does not need to provide as much glucose anymore and can spare the lean body mass from being used for gluconeogenesis - fat stores primary source of energy in extended fasting
What are probiotics
Live bacteria,identical to that found in the gut, consumed as supplement or via foods (yoghurt, sauerkraut,
kimshi). They populate the gut with good bacterial species.
Passive
- moves down the concentration gradient
- substrate concentration dependent
Facilitated
- requires a carrier protein; saturable
- moves down the concentration gradient
Active
- requires energy (ATP) + Na
- can transport against the concentration gradient
Endocytosis
- the cell wall engulfs a substance by surrounding it with the cell membrane
Entero-hepatic recirculation
recycling of bile
- save burden of making new bile by making new cholesterol
What is the difference between IBS and IBD? (definitions, location and characteristics)
– IBS: Causes are not well understood: genetic, stress, allergies, autoimmunity, dietary triggers, or dysregulation in gut microbiota species. Mainly functional in characteristic
– IBD: includes Crohn’s disease and ulcerative colitis. Damage of the structure of the intestine due to unclear causes (multiple: genetic, autoimmune, dietary and other lifestyle triggers, gut microbiota profile
What is the difference between diverticulosis and diverticulitis?
diverticulosis: pockets formed in the intestinal wall from extended constipation and strain
diverticulitis: inflamed and infected pockets formed in intestinal walls (serious condition)
What are the possible reasons for developing GORD?
– Lower esophageal sphincter that loses efficiency. Excess weight putting pressure on the sphincter. Large meals resulting in slow digestion
– When taking antacids medications: reliefs pain but impairs digestion, therefore nutrients absorption
What are the differences between food allergies and food intolerances?
intolerance - Intestinal flatulence, diarrhoea, bloating
versus
allergy - acute immune response.
intolerance - Dose-dependent
versus
allergy - acute response to the smallest dose
What is leaky gut? What does it result in?
space between enterocytes; gut integrity is
compromised resulting in systemic inflammation
AI
Adequate Intake
The average daily nutrient intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate
RDI
Recommended Dietary Intake
The average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in a particular life stage and gender group
- determined by EAR
