Test 3: Energy Principals and Material Metabolism Flashcards
What is digestion? What is its function? Where does it occur? How does it occur? What is broken down into what? What is it controlled by?
- breakdown of large molecules into smaller ones (hydrolysis)
- allows nutrients to be absorbed
- occurs in the gastrointestinal tract
- action of enzymes, bile and hydrochloric acid
proteins –> amino acids
fats –> fatty acids, monoglycerides
starch –> glucose
- controlled by the nervous system and hormones
State the different pancreatic enzymes, their substrates and digestive products.
trypsin, lipase, phospholipase, alpha amylase
enzyme - substrate - digestive product
trypsin - protein - smaller fragments
chymotrypsin - protein - smaller fragments
carboxypeptidase - protein - smaller fragments
lipase - fats - fatty acids & monoglycerides
phospholipase - lecithin & related compounds - free fatty acids
alpha amylase - starch - maltose & glucose
What is absorption? Its function? How are things absorbed?
- passage of nutrients from the gut into the blood stream
- allows nutrients to be utilized
- active transport / passive diffusion
- fat soluble vitamins are absorbed along fat
- water soluble vitamins are absorbed by diffusion
- minerals: fully absorbed (eg. Na+) or partially aborbed (eg. Cu2+, Fe2+, Ca2+, Zn2+)
What is metabolism? What are the two types of metabolism? What are the energy sources of metabolsim?
- refers to all the chemical changes which take place in the body,
- anabolism: syntheiss of glycogen, fat and proteins
- catabolism: breakdown of substances
- energy sources: amino acids, fatty acids, monosaccharides
How are carbohydrated digested? Into what are they tranformed? Where are they absorbed?
DIGESTION TYPE:
ruminant- microbial
non ruminant- enzymes (herbivorous, omnivorous, carnivorous)
DIGESTION OUTCOME:
ruminant: Volatile Fatty Acids (in rumen)
non-ruminant: Glucose (in small intestine)
FINAL ABSORPTION:
ruminant: into blood circulation
non-ruminant: into blood circulation
What is the digestion of carbohydrates catalysed by?
glycoside hydrolases (glycosidases)
Explain the digestion of carbohydrates.
CARBOHYDRATES:
- plant = starch
- animal = glycogen
MOUTH:
- alpha amylase (starch and glycogen) –> hydrolyses alpha (1-4) bonds
PANCREASE:
- pancreatic amylase (remaining poly and ogliiosaccharides) –> hydrolyses alpha (1-4) bonds
- starch & glycogen –> maltose
SMALL INTESTINE:
- sucrase
- lactase
- maltase
What does alpha amylase not hydrolyse? Where is it present?
- alpha 1-6 bonds
- present in: amylopectin and glycogen
Summarise the digestion of carbohydrates in monogastrics.
- polysaccharides –> monosaccharides
- monosaccharides taken up by active transport/ facilitated diffusion
- monosaccharides to liver
- glucose to cells
Summarise the digestion of carbohydrates in ruminants. What do ruminants not have?
- microbes= fermentat fibre & starch –> energy for cells, VFA, CO2 & methane
- VFA absorbed by host –> supplies energy for glucose synthesis
- no salivary amylase
- pancretic amylase for starch
- cellulolytic bacteria (digest fiber)
- amylolytic bacteria (digest sugars and starch)
RUMEN:
- microbes attach to fibers and secrete enzymes
- produce VFA
- digest polysaccharides, cellulose, hemicellulose
SMALL INTESTINE:
- secrete digestive enzymes
- digest carbohydrates
- absorb H2O, minerals, amino acids, glucose, fatty acids
CECUM & LARGE INTESTINE:
- fermentation of unabsorbed products
- absorption of H2O, VFA
- feces formation
What are fatty acids? What are their 3 basic types?
glucose –> VFA’s
- short chain fatty acids
- produced by microbes
3 types:
- acetic acid
- propionic acid
- butyric acid
What does 1 glucose molecule yield (VFA)? Describe how they are formed.
1) 2 acetate + CO2 + CH4 + heat
- acetyl CoA / formate –> acetate
2) 2 propionate + water
- succinate decarboxylation pathway –> propionate
- acrylate pathway: lactate –> propionate
3) 1 bytyrate + CO2 + CH4
- acetyl CoA + acetyl CoA –(butyrate kinase/acetate CoA transferase)–> butyrate
What are the uses of the different types of VFA’s?
ACETATE:
- energy
- fatty acid synthesis
PROPIONATE:
- energy
- gluconeogenic-glucose synthesis
BUTYRATE:
- energy
- rumen epithelial cells –> ketone (beta hydroxybytyrate)
What does the proportion of VFA’s depend on?
diets
What are the major constituents of dietary fat?
Triglycerides (TG’s)
smaller amounts:
- cholecterol (CH)
- cholesterol esters (CEs)
- phospholipids (PLs)
- fat soluble vitamins
What hormones regulate lipolysis? How do they regulate it?
What are they secreted by? Where?
- cholestokinin (CCK) (activated the release of bile of the gall bladder)
- secretin (biliary and pancreatic cells secrete NaHCO3–> neutralization of acidic chyme)
endocrine cells of the duodenum
What is the main function of the gallbladder?
- provide bile salts and lecithin
- emulsify fats
Explain the function of pancreatic lipase.
hydrolyses fatty acids: position 1 and 3
produces free fatty acids (FA) and 2 monoacylglycerols.
Explain the function of phospholipase.
Phospholipase (PLA2):
- releases FA from C’2
- generates phospholipids and 1 free FA
Explain the function of cholesterol esterase.
- releases FA from cholesterol ester
- forms CH and FFA
Explain lipid absorption in the small intestine.
Lipid digestion end products –(micelles)–> luminal cells of jejunal mucosa (diffuse through brush borders, leaving bile salts behind)
What happens to bile salts once they are left behind when micelles are dissociated?
- return to lumen
- incorporate highly lipophylic dietary materials and move them to the jejunal surface
How are short and MCFAs absorbed?
- high water solubility
- not dependent on micelles
How are lippoproteins classified?
density:
- HDL
- LDL
- VLDL (triglycerides and cholesterol)
- Chylomicron (triglycerides)
How are fats transported? With what? Where?
- transported by: Chylomicrons (CM) (together with free CH, and absorbed fat soluble vitamins)
- trasported to: lymphatic system
Explain monogastric protein digestion.
pepsinogen + HCL –> pepsin
pepsin:
- optimal pH -2pH
- breaks peptide bonds between ttyrosine and phenylalanine amino acids
- produces peptide fragments and amino acids
- location: stomach
What amino acid groups does pepsin digest?
- phenylalanine (Phe)
- tyrosine (Tyr)
- tryptophan (Trp)
What structures does pepsin digest?
- secondary
- tertiary
- quartenary
What are the major enzymes present in the small intestine for protein digestion?
- trypsin (activated by trypsinogen): splits proteins into smaller peptides and single amino acids (cleaves on carboxy of Lys and Arg)
- chymotrypsin (activated by chymotrypsinogen): splits proteins into smaller peptides and single amino acids (cleaves carboxy terminal Phe, Tyr, and Trp)
- carboxypeptidase: splits single amino acids from the carboxyl end of proteins (removes carboxy terminal residues)
- aminopeptidase: continues protein digestion (removes amino terminal residues)
How do proteins cross the small intestine wall?
single amino acids, dipeptides and tripeptides: absorbed
free amino acids: co-transported via secondary active transport (Na+)
What is the principal function of the plasma membrane?
- control the passage of substances (selectively permeable)
What are the main macromolecules of membranes?
- lipids
- proteins
- some carbohydrates
What is the model called created by the lipids in membranes which produce a unique physical environment?
fluid mosaic model
Esplain the structure of the fluid mosaic model.
- phospholipids form a bilayer
- non-polar regions (tails) point inwards
- polar regions (heads) point outwards
- embedded proteins
What are the three types of amphipatic lipid aggregated which form in water?
- micelle
- liposome
- phospholipid bilayer
What does amphipathic mean? What is it used to describe?
- membrane lipids
- ## one end of the molecule is hydrophillic, the other is hydrophobic
What is the most abundant membrane lipid?
phospholipid
What two groups are phospholipids divided into?
- glycerophospholipids
- shingolipids
State examples of glycerophospholipids.
- lecithin
- cephalin
What is a spingolipid? Explain its structure.
- polar group and 2 non-polar tails
- sphingosine (long chain alcohol & amino group) / its derivatives (long fatty acid chain) and a polar head
State an example of a sphingo lipids. State its composition.
sphingomyelin
- amide bond b/w a fatty acid and sphingosine (18C alcohol)
Where is sphingomyelin present?
- plasma membranes (animal cells)
- myelin (membranous sheath surrounding and insulating neuron axons)
What are glycosphingolipid?
monosaccharides bonded to the -OH of sphingosine
- glycosidic bond
eg. cerebroside + galactose (plasma membrane)
What are gangliosides?
2+ monosaccharides
sphingosine
fatty acid
similar to cerebrosides
State an example of a ganglioside
GM2
State the common structure of a steroid.
4 fused rings:
-3 cyclohexane rings
- 1 cyclopentane ring
State the structure of cholesterol.
- 3 cyclohexane rings
- 1 cyclopentane ring
- methyl groups
- OH attached to the steroid nucleus
State the main features of cholesterol.
- synthesised in the liver
- obtained from food
- needed for cell membranes, brain, nervous tissue, steroid hormones and vitamin D
Explain lipoproteins. Solubility?
- lipid + protein + phospholipid
- soluble in water
- classified into LDL, HDL, VLDV, Chylomicron
Explain the main parts of bile salts.
- synthesised in the liver
- synthesized from cholesterol
- stored in the gall bladder
- secreted into the small intestine
- have polar and non-polar regions
- emulsify fats
Explain the main parts of steroid hormones.
- chemical messengers
- produced from cholesterol
- eg. sex hormones, adrenal corticosteroids
What molecules are produced from cholesterol?
- bile salts
- steroid hormones
Explain the main parts of adrenal corticosteroids.
- steroid hormones
- produced in adrenal glands (top of kidney)
- eg. aldosterone (water+electrolyte balance); cortisone (blood sugar regulation)
Explain the main parts of anabolic steroids.
- derivatives of testosterone
- illegally increase muscle mass
- side effects: sleep disturbance, hair growth, liver damage etc.
Explain the main parts of prostaglandins.
- related to unsaturated fatty acids
- all tissues
- function: treatment of inflammatory diseases, blood pressure regulation, metabolism
What does aspirin do? What does that lead to?
- binds to cyclooxygenase
- inhibits production of prostaglandins
- reduction of inflammation and pain
What is conformation?
The spatial arrangement of atoms in a protein.
What are the functions of membrane proteins?
- transporters
- enzymes
- cell surface area
- cell surface identity markers
- cell-to-cell adhesion proteins
- attachment to the cytoskeleton
What determines most of the membranes specific functions?
proteins
What are the two types of membrane proteins?
- integral proteins (inserted into the membrane)
- peripheral proteins (top/bottom of membrane)
What part of the membrane is important for cell-to-cell adhesion?
membrane carbohydrates:
- sort cells into tissues and organs
- reject foreign cells by the immune system
- recognise markers
What compound usually makes cell markers?
carbohydrates:
- branched ogliosaccharides (< 15 monomers)
- covalently bonded to lipids (glycolipids)
- covalently bonded to proteins (glycoproteins)
Explain passive transport.
- movement of molecules through a membrane
- no energy is required
- concentration gradient
Explain diffusion.
- movement of molecules
- high to low concentration
What is selective permeability? What allows for it?
- integral membrane proteins allow the cell to be selective about what passes through the membrane
Explain channel proteins.
- polar interior (polar molecules pass through)
- ion channels: passage of ions
- gated channels: opened or closed (chemical/electrical stimulus)
What are carrier proteins?
- carry molecules through a membrane
- bind to specific molecules
What is facilitated diffusion?
- high –> low concentration
- specific
- passive
- saturates when all carriers are occupied
- carrier protein involved
What does glucose transport?
- erythrocytes
- mediates passive transport
What is the difference between the solvent and solute?
solvent- water
solute- dissolved substance
What is osmosis?
- water movement
- high to low concentration
- water moves to high solute concentration
In what two conformations does the glucose transporter exist as?
T1: glucose binding site exposed on the outer surface of the plasma
T2: glucose binding site exposed on the inner surface of the plasma
What is a hypertonic solution? Hypotonic?
hypertonic: high solute concentration
hypotonic: low solute concentration
How does osmosis move water? Toward what solution?
- through aquaporins
- towards the hypertonic solution
How do organisms maintain osmotic balance?
- extrusion (Water ejected through contractile vacuoles)
- isosmotic regulation (kepp cells in isotonic environment)
- turgor pressure (plants: push cell membrane agains cell wall)
What is active transport?
- requires ATP
- used directly/indirectly to fuel active transport
- low to high
- carrier proteins required
What are the types of carrier proteins used in active transport?
- uniporters (1 molecule at a time)
- symporters (2 molecules same direction)
- antiporters (2 molecules different direction)
What is the sodium potassium pump?
- active transport
- 3 Na+ out
- 2 K+ in
- ATP used to change conformation of the carrier protein
- affinity of the carrier protein changes allowing ions to be transferred across the membrane
