7.7 Metabolic Integration Flashcards
what happens to excess glucose in cells?
it can be stored in cells and then mobilized when necessary
what are the two major forms for glucose storage?
glycogen and starch
glycogen
the form in which glucose is stored in animals
starch
the form in which glucose is stored in plants
describe the structure of glycogen:
a large, branched chain of glucose molecules attached to a central protein.
describe the structure of starch:
a large, branched chain of glucose molecules found in plants,stored in granules inside cells
where can glycogen be stored?
the muscle (provides ATP for muscle contraction) or he liver (central glycogen storehouse)
glycogen provides a source of:
glucose-6-phosphate (cleaved as glucose 1-phosphate and then converted into glucose 6-phosphate which is an intermediate in glycolysis)
how many ATP molecules are produced from one glucose molecule cleaved from a glycogen chain?
3 (ATP consuming step 1 is bypassed)
how are disaccharides hydrolyzed?
they are converted into monosaccharides, generally glucose which directly enters glycolysis
how are monosaccharides other than glucose hydrolyzed?
they are converted into intermediates of glycolysis that come later in the pathway
in addition to carbohydrates, what is a good source of energy?
lipids (C-H bonds carry lots of chemical potential energy)
B-(beta)oxidation
the process of shortening fatty acids by a series of reactions that sequentially remove two carbon units from their ends
beta oxidation does not produce ATP, instead it…
releases a large number of NADH and FADH2 that provide electrons for the synthesis of ATP by oxidative phosphorylation
fatty acids are a useful and efficient source of energy but cannot:
be used by all tissues of the body (ex. brain and red blood cells depend on glucose for energy)
ATP is constantly being “turned over” in cells, what does this mean?
ATP is constantly being broken down to ADP and P and synthesized to ATP
the level of ATP inside a cell can indicate:
how much energy a cell has available
high levels of ATP indicate:
the cell has large amounts of free energy and is poised to carry out cellular processes; pathways that generate ATP are slowed or down-regulated
low levels of ATP indicate:
the cell activates or up-regulates pathways that lead to ATP synthesis
high NAD+ levels stimulate:
cellular respiration
high NADH levels:
inhibit cellular respiration
what is one of the cell’s mechanisms to control key steps of the pathway?
the regulation of enzymes
the 3rd reaction of glycolysis (fructose 6-phosphate converted to fructose 1,6-biphosphate -ATP is consumed) is:
highly endergonic and irreversible! IT IS CATALYZED BY PHOSPHOFRUCTOKINASE-1 (PFK-1)
PRK 1 can be thought of as a :
metabolic valve that regulates the rate of glycolysis-the 3rd step is viewed as a “committed” step to glycolysis and is subject to tight control
PRK-1 is an allosteric enzyme with:
many activators and inhibitors-changes its shape and activity in response to the binding of molecules at a site other than the active site
what are allosteric activators of PFK-1?
ADP and AMP-activates the enzyme and increases the rate of glycolysis and the synthesis of ATP
when ATP or citrate is in abundance, it can bind to the enzyme (PFK-1) and:
inhibits the enzyme’s catalytic activity, glycolysis and the rate of ATP production slows down
cellular respiration is inhibited by:
its products (ATP and NADH)
cellular respiration is activated by:
its substrates (ADP and NAD+)
