BISC330L Lecture 24 Intro to Metabolism Chapter 15 Ac vated intermediates in metabolism Common theme carriers are kine cally stable in the absence of catalysts ATP and acetyl CoA are not readily hydrolyzed by water in the absence of a catalyst NADH NADPH and FADH2 react only slowly with O2 in the absence of catalyst these proper es enable enzymes to control the ow of free energy and reducing power Ac vated carriers in metabolism Many coenzymes are derived from B vitamins Which of the following statements about nico namide adenine dinucleo de NAD is correct a NAD is the ini al electron donor in many metabolic oxida on reac ons b NADH is the ini al electron acceptor in many metabolic oxida on reac ons c NAD is the ini al electron acceptor in many metabolic oxida on reac ons d NAD is a prosthe c group for several dehydrogenases Which of the following statements about avin adenine dinucleo de FAD is correct a FAD is a coenzyme for acetyl group transfers b FAD is derived from ribo avin a BXgroup vitamin vitamin B2 c FADH2 can accept two electrons ac ng as an electron carrier d FAD can also be an electron donor Not all vitamins are coenzymes Collagen brous protein Most plen ful protein in the body Each polypep de is a le Xhanded helical structure 3 le Xhanded helices join for a rightXhanded triple helix called tropocollagen CrossXlinks between lysine residues form between helices to form a collagen bril Hydroxyproline makes collagen tougher Vitamin C Other name ascorbic acid Chief functions in the body Collagen synthesis Strengthens blood vessel walls forms scar tissue provides matrix for bone growth Antioxidant Thyroxin synthesis Amino acid metabolism Strengthens resistance to infection Helps in absorption of iron Copyright 2005 Wadsworth Group a division of Thomson Learning Vitamin C and hydroxyproline Weakened collagen causes scurvy Deficiency disease scurvy Deficiency symptoms Anemia small cell type Atherosclerotic plaques Pinpoint hemorrhages under the skin bone fragility joint pain Poor wound healing frequent infections bleeding gums loosened teeth Muscle degeneration and pain hysteria depression rough skin blotchy bruises Vitamin C biosynthesis Ques on Why has evolu on selected for the inability to synthesize vitamin C Common mo fs in metabolism Limited number of ac vated intermediates The kinds of reac ons involved is small Regulatory mechanisms are highly conserved across all forms of life 6 common reac on types found in metabolism Redox reac ons Oxida on of carbon compounds produces reducing power through genera on of NADH and FADH2 Redox in CAC Redox from citric acid cycle feeds the reac ons of oxida ve phosphoryla on Liga on reac ons requiring ATP Free energy from ATP cleavage used to make carbonEcarbon bonds example from Citric Acid Cycle Which one of the following statements about ATP is correct a ATP can di use through cell membranes b ATP is considered a low energy phosphate compound c ATP is present at high concentra ons in the cell d Hydrolysis of ATP is a strongly exergonic reac on Isomeriza on reac ons Atomic rearrangement within the molecule example from Citric Acid Cycle Group transfer reac ons Mul purpose reac on in this case traps glucose in the cell rst step of Glycolysis Hydrolysis Used mostly for breakdown of complex molecules example shown is pep de bond hydrolysis Addi on or removal of func onal groups These reac ons involve addi on of func onal groups to double bonds OR group removal to form double bonds this is glycolysis reac on that creates a keto group Addi on or removal of func onal groups XX dehydra on This reac on allows forma on of PEP which has high phosphorylE transfer poten al and thus can make ATP from ADP one of last steps in glycolysis Common mo fs in metabolism Limited number of ac vated intermediates The kinds of reac ons involved is small Regulatory mechanisms are highly conserved across all forms of life Three major modes of regula on 1 Controlling the amount of enzymes how would this happen 2 Controlling the accessibility of substrates mostly via intracellular compartmen liza on 3 Controlling the cataly c ac vity of enzymes Reversible allosteric control eg feedback inhibi on Hormonal control Cellular energy charge overall energy levels in cell determine if energyEgenera ng pathway will proceed Energy charge Energy charge ATP ADP ATP ADP AMP Key concepts Introduc on to metabolism Coupled reac ons are a predominant feature of metabolic pathways The free energy change in a coupled reac on is Thermodynamically unfavorable reac ons can be addi ve made to go when coupled to favorable reac ons such as ATP hydrolysis ATP hydrolysis can shi the equilibrium of a coupled The structure of ATP provides three reasons for why it reac on by many orders of magnitude has high phosphorylXtransfer poten al ie large nega ve change in free energy upon hydrolysis Key concepts Introduc on to metabolism The oxida on of carbon fuels is an important source of cellular energy ATP synthesis is coupled to oxida on of carbon fuels both directly glycolysis and CAC and indirectly oxida ve phosphoryla on Three stages during the extrac on of energy from carbon fuels i e food Key concepts Introduc on to metabolism Common recurring mo fs in metabolism A small number of ac vated carriers do much of the work during metabolism ATP carries ac vated phosphoryl groups acetyl CoA carries ac vated acetyl groups NADH FADH2 carry highXpoten al electrons acquired during redox reac ons NADPH used during biosynthesis reac ons Metabolism involves a limited number of types of Metabolism is regulated by a small number of chemical reac ons regulatory mechanisms How do we get energy Step 1 on Friday Glycolysis 2 1 5 ATP 4 3 ATP