Carbohydrate Metabolism Flashcards
Organisms need energy for 3 purposes
- Mechanical work
- Active Transport
- Synthesis of macromolecules
- energy is obtained for the ox. of carbon fuels
Metabolism
- many interconnecting pathways
- pathways are interdependent
- coordinated by allosteric enzymes
- catabolism and anabolism
Catabolism
the breaking down of energy rich molecules to yield useful energy (ATP)
Anabolism
synthesis of molecules from building blocks (require ATP)
Principle
- biosynthetic and degradative pathways often have rxns in common
- regulatory rxns are unique to each pathway
Coupled Rxns
For a rxn to occur spontaneously the change in free energy must be negative
What makes a pathway?
- comprised of ind. rxns that are specific (only one product is made from 1 substrate)
- product of first rxn is substrate for the next rxn
- entire set of rxns is thermodynamically favourable
What is ATP
- the currency of the cell
- ATP is a high energy phosphate compound (adenosine triphosphate)
- G= -30.5 kJ/mol for each of the two terminal phosphate groups
- energy released can be used to drive unfavourable rxns
Note about delta G
delta G not; standard free energy for a rxn
- free energy change under standard conditions
- formation of 1 mole of that substance from component elements at their standard states
Cellular energy is derived from ox. of carbon fuels
- ATP turnover is very high in the cell
- need constant regeneration of ATP
How do plants capture energy?
Capture energy from sun as chemical energy
How do animals get energy?
- Animals and other cells use chemical energy from carbon based fuels
- Glucose and fats are oxidized to CO2, releasing energy , energy then captured to form ATP
Oxidation
the loss of electrons
Redox Rxn
Oxidation and Reduction
Activated Carriers
- ATP is an activated carrier of phosphoryl groups
- Activated Carriers are involved in e- transfer and Carbon transfer
- aerobic organisms transfer e- to O2
- fuel molecules transfer e- to special carriers
- transport via ETC
- provide e- for anabolic rxns
Activated C Carrier
- Two C fragments (acyl groups) are transferred to CoA to form acetyl-CoA and activated C source
Regulation of Metabolism
- complex network of degradation and synthesis pathways that make up metabolism must be highly coordinated
- nutrient levels must always be monitored and pathways adjusted to homeostasis
- metabolism must be able to adjust to changes in the environment
Carbohydrates
- most abundant organic compounds found in nature
- hydrates of carbon
Functions of Carbs
- provide energy in diet
- provide storage form of energy (glycogen)
- components of mammalian cell membranes
- cell wall components in bacteria
- components of insect exoskeleton
- comprise cellulose of plants
Monosaccharides
- simplest sugars
- can be aldoses or ketoses
Aldoses
contain an aldehyde
Ketoses
Contain a ketone
Isomerization
different placement of atoms in molecules
Monosaccharides connected by glycosidic bonds to form larger molecules
- O-glycosidid bond: bond between sugar and another sugar
(bond between sugar and serine side chain)
Polysacchardies
Contain 10 + monosaccharides
Oglionucleotides
Contain 3-10 monosaccharides
Disaccharides
Contain two monosaccharides
What are glucose storage molecules?
- Glycogen
- Starch
- Glucose
What is starch
- plant storage molecules
- have alpha 1,4 glycosidic bonds
- has B-1,4 glycosidic bonds
What is glycogen
- mammalian storage molecules
- have alpha 1,4 glycosidic bonds
Complex Carbs
- carbs that are attached to non-carbohydrate structures by glycosidic bonds
- sugar participating in the bond is termed a glycosyl residue
Digestion of Carbs
- large carbs must be broken down into smaller molecules that can be absorbed by the body
- digestion begins in mouth w/ salivary a-amylase, then continued in the small intestine by pancreatic a-amylase
N- and O-glycosides
- If sugar binds to an amine group its called N-glycoside
- if sugar binds to an OH group called an O-glycoside
How are Disaccharides digested
By specific enzymes in the small intestine
