L27 Metabolism & energy balance Flashcards
Define ‘nutrient’ and list the major classes and subclasses.
Nutrient
- a substance used in an organism’s metabolism or physiology;
- building blocks for maintenance, growth, and reproduction
Major classes:
- Carbohydrate
- 50-60% most total energy intake
- monosaccharides e.g.glucose
- disaccharides e.g. lactose(galactose+glucose), maltose(2glucose), sucrose (glucoss+fructose)
- polysaccharides e.g. starch,glycogen, fibre.
- Proteins
- Lipids
- Vitamins
- Minerals
- Water
Describe the difference between essential and non-essential nutrients
Essential (must be supplied in diet) non-essential (can be synthesized de novo)
For carbohydrates, proteins, lipids/fats, minerals, and vitamins provide details of their chemical composition and function in the body.
1. carbohydrate
- CnH2nOn
- used as energy source
2. Protein
- 20 amino acid to build protein and linked together by peptide bond
- large, complex organic molecules that are the building blocks of all animals & plant cells
3. Lipids
- comprised of fatty acid (FAs), but have short-chain, medium-chain and long-chain fatty acids (saturated and unsaturated)
- Large, organic, hydrophobic molecules that are an important form of energy storage; provide barrier function,e.g. main constituent of cell membranes
- Stored as triacylglycerol (triglyceride) in liver, muslce and adipose tissue
4. Vitamins
- Various function
5. Minerals
- Calcium, phosphorus, iron, copper, zinc 5
- serve a variety of function, such as: 5
1）Co-factors in enzyme-catalyzed reactions
2） regulation of acid-base balance
3）nerve conduction
4）muscle contraction
5）structure, i.e. skeleton
6. water
1) 60% we consume are water
2) No intrinsic energy value
3) Act as solvent for the other nutrient
Define digesiton
Breakdown of larger molecules into absorbable units (monomers)
Achieved by mechanical and chemical digestion
Chemical breakdown = hydrolysis (as H20 molecule added to each broken bond)
Define what is absorption
Uptake into the body
most nutrient absorption occurs in small intestine (with additional absorption of water, inons and some acids in large intestine )
Discuss the major digestive enzymes and their functions
Convert complex macromolecules into forms that can be absorbed and processed
1) amylases
- breakdown polysaccharides into oligosaccharides
2) Proteases
- breakdown proteins to shorter polypeptides
3) Lipase
- release fatty acids from triglycerides and phospholipids
4) Nucleases
- break down DNA into nucleotides
For carbohydrates, proteins, lipid/fats, minerals, and vitamins. Describe digestion and absorption
.
Define Assimilation, Gastrointestinal (GI) tract, and egestion.
Assimilation:
the sequential processes of nutrient breakdown and absorption
(GI) tract:
contigugous with the external environment
Egestion = elimination = expulsion of undigested food
What the the GI tract do in the system:
*mechanical breakdown of fodd: mouth, pharynx, oesophagus
* acid compartment: stomach
* most digestion and absorption: upper small intestine
*reclamation ot water: lower or larger intestine
* release of indigestible material (anus)
Explain the effects oh high and low-quality feed on transit rate and rate and extent of digestion
influence digestion time
High:
- minimal energy to capture and eat
- high rate of digestion
- releases lot of energy
Low
- more energy to capture and eat
- lower rate of digestion
- yield less energy
List the 3 major types of digestive tracts of vertebrate and the limitation:
Digestive tract (=alimentary canal) adapted to digest and absorb the nutrients from food
1) Carnivores (meat eater)
2) Herbivores (plant eater)
3) Omnivores (Meat & plant)
* the digestive tract (=alimerntary canal) is a tube adapted to digest and absorb the nutrient from food
* physiology (&anatomy) of the digestive tract is matched to the chemical and physical nature of diet
Appreciate and explain the variation in digestive tracts
.
List the major physiological roles of the organs and accessory organ in humans.
Stomach
liver
pancreas
4 layer of stomach
- mucosa
- submucosa (smooth muscle)
- circular
- longitudinal
What in the mucosa surface (1 TJ, 4 cells)
What do they do?
- mucosa surface composed of columnar epithelial cells
* tight junctions between cells prevent leakage
- mucous neck cells - secrete mucus
- parietal cells - secrete HCl acid
- Chief cells - secrete pepsin ( protease)
- Enteroendrocrine cells - secrete hormones into blood
what are 4 types of mucosa cells
1. Enterocytes: absorptive cells with microvilli
2. Globlet cells : secrete mucus
3. Enteroendocrine cells: secrete hormones
4. Paneth cells: Secrete antimicrobial molecule
GI tract specializations (Ruminants/foregut fermenters)
- Ruminant have a fore-stomach with specializations chambers
- cellulose converted to volatile fatty acids (VFAs) by bacteria, protozoa & fungi
- carbohydrate digestion in ruminants/hindgut fermenters - production of (VFAs) by symbiotic bacteria
- glucose requirements met by propionate conversion to glucose in the liver
Hindgut fermenters
- cellulose passes through into large intestine
- fermentation in large intestine: production of VFAs
