Macronutrients Flashcards
What is macronutrients?
•Macronutrients in dietary patterns can be considered as part of food groups or food choices
Complete the diagram on types of carbohydrates
What is the role of starch and glycogen?
Starch and glycogen - Energy Store
What are the non-starch polysaccharides?
Non-Starch Polysaccharides
Insoluble – cellulose
Soluble - Pectin
What are the 3 carbohydrates absorbed through the small intestine?
Monosaccharides -
Glucose
Fructose
Galactose
What are the biological features of carbohydrates?
What are the functions of carbohydrates?
What are the 2 types of unsaturated fats?
Single double bond = monounsaturated
More than one double bond = polyunsaturated
What are dietary fats made of?
•Triacylglycerol (TAG)
What are the polyunsaturated fatty acids?
Label the polyunsaturated fatty acids
Name the dietary sources of these polysunsaturated fatty acids
What are the functions of dietary fat?
TAG is the primary energy substrate stored in adipose tissues to sustain animals during fasting
How do TAG enter adipose tissue?
- Influx of TAG into adipose tissue largely mediated by the action of adipose tissue lipoprotein lipase (LPL) (103)
- This is upregulated in the presence of Insulin, fatty acids during fasting
Complete the diagram on the uses of protein within the body
Do younger or older adults need more protein?
Dynamic nature of protein
In health requirements 0.8g/kg/day
Older adults 1.2g/kg/day
When do our protein requirements increase?
Acute illness demand can exceed this – negative nitrogen balance due to inflammation induced catabolism (COVID19)
Are these amino acids essential, conditionally non-essential or non-essential?
Essential
Are these amino acids essential, conditionally non-essential or non-essential?
Non-essential
Are these amino acids essential, conditionally non-essential or non-essential?
Conditionally non-essential
What are conditionally non-essential amino acids?
Essential precursor missing – tyrosine requires phenylalanine
Rapid growth Arginine and proline synthesised from glutamate and glutamine in intestines
Hyper catabolic states (sepsis, Burns ?COVID19) - glutamine is depleted
What are essential amino acids?
Not synthesised in body – dietary requirement
What adaptions of the GI tract is there?
Stomach
Small intestine
Sphincters
Stomach – acid environment – mucous and bicarbonate ions
Small intestine - peristalsis becomes segmentation to squeeze food against intestinal wall and maximise digestion and absorption
Sequence of sphincters – cardiac, pyloric, ileocaecal valve, internal and external sphincters
Which nervous system is important for GI function?
Parasympathetic NS important for GI function
What happens in the buccal cavity during digestion?
Mastication
Swallowing
Taste – sweet, sour, bitter, salty and umami
Which digestive processes happen in the buccal cavity?
CHO digestion – Salivary amylase – limited activity
Initiates breakdown of starches by catalysing the hydrolysis of polysaccharides into disaccharides
Fat - lingual lipase secreted by serous glands
How are fats digested in the stomach?
Stomach –gastric lipase secreted by gastric cells in the fundic mucosa. An acid enzyme that does not require bile acid (from liver) or colipase (from pancreas) for optimal functioning
These enzymes are important
- in neonates contributing to up to 50% of lipid hydrolysis
- in adults up to 30% of lipid hydrolysis
How are proteins digested in the stomach?
Chief cells produce pepsinogen converted to pepsin in presence of HCL – Proteins -> Peptides
Acid environment – de natures protein
Reduces bacterial load
What bile acids are produced from the liver?
cholic and chenodeoxycholic acid.
Molecules are amphipathic - act as a detergent has both hydrophobic and hydrophilic properties - to solubilize lipids to form mixed micelles
What is the role of pancreatic lipase in fat digestion?
- Small intestine – pancreatic lipase secreted from the pancreas alongside the cofactor pro-colipase
- Pro colipase is activated in the intestinal lumen by trypsin to form colipase
- Colipase stabilises pancreatic lipase increasing its efficiency
- Pancreatic Lipase hydrolyses TG to form monocyglycerol, fatty acids and glycerol
How are pancreatic proteases activated?
- The two primary pancreatic proteases are trypsin and chymotrypsin. They are synthesized and packaged within secretory vesicles as inactive pro enzymes: trypsinogen chymotrypsinogen
- The pro enzymes are activated by an enteropeptidase - enterokinase secreted by the mucosal membrane of duodenum
The secretory vesicles also contain a trypsin inhibitor to serve as a safeguard against trypsinogen converting to trypsin within the pancreas or pancreatic ducts
Which pancreas peptidase digests which amiono acid?
Draw the mechanism for activation of peptidases in the stomach
Draw out exocrine pancrease peptidases secretions into the small intestine
Which peptidase is secreted by the brush border of the small intestine?
Aminopeptidases
Which are endopeptidases and which are exopeptidases?
What 2 things is starch made of?
Starch is made up of Amylose (30%)
Amylopectin (70%)
What is the role of pancreatic α amylase in carbohydrate digestion?
___ litres of fluid enter GI tract with ____ litres absorbed through small intestine
9
8
Why does the small intestine have a large surface area?
Large surface area to maximise secretion and absorption
How are dissacharides digested in the small intestine?
Further digestion occurs by actin of brush border enzymes – gluco-amylase, α-dextrinase, sucrase, and maltase to form monosaccharides – glucose, fructose and galactose
Which carbohydrates are absorbed in the small intestine?
- Absorption of CHO is limited to the monosaccharides - glucose, galactose and fructose.
- It occurs in the small intestine
- Capacity to absorb fructose is limited
How is fat absorbed in the small intestine?
Water soluble mixed micelles pass through the ‘unstirred water’ overlying the microvillus
Monocylglycerol and fatty acids cross apical membrane of microvilllus through passive diffusion and lipid protein transporter mechanisms
How are proteins absorbed in the small intestine?
Di and tripeptides absorbed in enterocytes
Human peptide transporter 1 (PEPT1)
sodium–hydrogen exchanger 3 (NHE3)
What does microbial fermentation of non starch polysaccharides lead to?
- Gas – CO2-H2-CH4
- Short chain fatty acids - acetate (enters peripheral circulation ), propionate (taken up by the liver) and butyrate (used by colonic cells)
•This also enhances microbial growth
How are non-starch polysaccharides digested?
- NSP (Fibre) resistant starch and most oligosaccharides are not digested and absorbed in the small intestine
- Soluble fibres (pectin/gum) are fermented by bacteria in the colon
What are non-starch polysaccharides?
•Insoluble fibres make up the cellulose ‘roughage’ in the diet
