TOPIC: METABOLISM & CELLULAR RESPIRATION

Outline:l. Metabolism: Description and Significancell. Sub types of Metabolism: Catabolism & {nabolismlll. Oxidation & ReductionlV. lmportant Metabolic Intermediate CompoundsV. CellularRespiration

A. GlycolysisB. Kreb's CycleC. Electron Transport Chain

l. Metabolism- comes from the greek word "metabolismos" meaning "change'lor'overthrow'.- biochemical modification of chemical compounds in living organisms and cells.- sum total of all chemical reactions involved in maintaining the living state of the cells and thus the

organism.- process that enables organisms to procesg nutrients into biochemical tools and structures they need to

maintain a living state (growth, reproduction, movement, homeostasis, respond to environment etc.)Brief History: In 1614, first controlled experiments in human metabolism weie published by Santorio in

his book Ars de statica rnedecina. He described how he weighed himself before and after eating,sleeping etc., and found out that most of the food he took in was lost through perspiration insen-sibilis"insensible perspiration

lll. Oxidation-Reduction (Redox Reactions)- paired reactions in which electrons are transferred from one compound to another- occur simultaneously in a chemical reaction, one cannot take place without the other.oxidation- involves the loss of electrons or removal of H atoms

when atom/ ion/ molecule losses one or more electrons, the molecule is oxidized- in redox reactions, electron acceptor is the oxidizing agent. lt is a substance that causes an increase in

the oxidation state/no. (no. of electrons losUgained oiunequally shared by an atom) of anothersubstance.

- electrons lost do not float, they reactively attach immediately to another molecule- biologicaloxidations are referred to as dehydrogenation reactions ( H and electrons are removed)Reduction- involves gaining of electrons or H atoms- when atom/ ion/ molecule gains one or more electrons, the molecule is reduced- in redox reactions, electron donor is the reducing agent. lt is a substance that causes a decrease in the

oxidation state of another substance.e-

--.------} @Oxidizin

ll. sub- of MetabolisnrBasis of Comparison Catabolism Anabolism

(1) Kind of Metabolism Destructive Metabolism Constructive Metabolism(2) Process lnvolved Breaking down of large or complex

molecules into smaller or simplermolecules

Building up of large or complexmolecules from precursor or smallmolecules

(3) Energy Requ ired/Reteased Energy Released/ Produced( Exe rgo n ic/Exoth e rrn ic)

Energy Required(Endergonic/Endotherm ic)(3) Example:

-Hydrolysis of complex molecules/macromolecules

-Glycolysis & Fermentation

C6H12O6 + Oz ) ATP + CO, + 11rgCoHrzOo )COz+C'HsOH

-Biosynthesis of macromolecules(nucleic acids, proteins, lipids,carbohydrates),-Photosynthesis in plants

tightCO. +l1rg ) C6H12O6 + Q,

chlorophyll

A (Reducing agent) B ( g agent)

tv. lmportant Metabolic Intermediate Compounds(1) Adenosine PhosphateNQeqos i ne & lts several forms : monoohosnhate, dirtfqsphate, triphosphate and cyclic monophosphate

Adenosine 5lo_cll)/o\

|t(I \-{o:l)-o otjI

o-

Aclcnosine 3.' -5'- cyclic monophosphate(*,clic r\r\{P; cAI\lp)

Adenqsllq4ipf osphare ({Dp)=- _

Adenosine triphosphate (ATIr)Adenosine Monophosphate (AMP)- structural component of RNAAdenosine Diphosphate (ADP)- a stable form; can be used as emergency source of energy by removal of

phosphate group producing AMpAdenosine Triphosphate (ATP)- a nucleotide triphosphate

-major energy storing/ carrying molecule in a cell.- main energy cunency of the cell- energy is stored in the bonds of ATP- its hydrolysis (breaking of high energy bond) yields energy and ADP (Adenosine

diphosphate) also a key compound in nnetabolic pathways

ATP + FI2O -------->n nP + I,l2c) _+

A nD -r qfiO l- + H - -L anpro\/I rrr v+AMP+HPO,: + H'-Pner('vI r rr vl

N.B. Other examples of nucleotide triphosphateUTP- Uridine Triphosphate

-involvedtparticipate in cHo metabolismGTP- Guanosine Triphosphate -CHON and CHO metabotismCTP- Cytidine Triphosphate - lipid metabotism

cAitP- function is associated with activity of epinephrine (hormone) which stimulates gAMP synthesis thathelp regulate release of glucose from glycogen.

(2) Coenzymes- nonprotein organic molecule which can be frequently separated from the apoenzyme which is apolypeptide segment of the enzyme/ protein portion which is inactive by itself.

a) Flavin Adenine Dinucleotide (FADF required in numerous metabolic redox reactions

iFlfifrff- Riuitor'-two components: flavin and ribitol (reduced form of

ribose)constituting Vit B Riboflavin are attached to ADp-active portion: flavin subunit; Flavin is reduced converting FAD to

FADH2 (reduced form); FAD is oxidized form.

Hr-CHO

r r---oHH-_]-oH

I

r"r-J-oHct-iroH

r llihosc

CH,OHI-H-f-oHH--OIJu-]-ou

cHroFIr r'l{ i hitol

IiFAI)

(oxirlizcrl lirrnr)FADH,

(reduced form)

Adenosinc monophosplratc (AM Ir)

o

\-*d-^-H-l--J-\"

In metabolic pathrvays in r'vhich it is in-volved, flavin adenine dinucleotidc con-tinually changes back ancl forth betweenits oxidized and reduced fbrms.

2ll* +2e- + FAD :- I:ADH:

Hr'

H,C

]o0.",".,

o\ilI

lzffilfc-NH, I Nicotinamide\--cz t

NH.I

>'Axltl--\ul

)*,0"."

)o0."'".)

Nrl,

,zz'\Ax(: ll'l'xixz

vr./o

..o o'll,CH..-C- CH3_C_OIIAccryl group Acctic rcid

V. Cellular Respiration- a.k.a aerobic respiratian whichin the form of ATp.

M itochorrd rr5 :lllgr- from g reek m itos-th read ; chondriong ra n ute; a. k. a,reeK mrros-rnreao; cnondrionranule; a.k.a "power house of the cell"

- sausage shaped organelle that have central role in enerov oroducticcentral role in energy production- outermembrane: 50 % lipid and 50 % protein which is plrmeaote to small

moleculesinnermernbrane: 2oYo lipid and B0 o/o protein which is impermeable to mostsubstancesMatrix- inner or interior region: matrix

- ltefmeryblane space- re$ion between inner and outermembraneCristae- folds of the innermembrane Iprotruding in mdtrix- ATP synthase complex- spherical knobs at the cristae for energy productloh

$lx- Carbon Stage of Glycotysls (Steps i-3)- intermediates die all either glucose or fructose derivdtives in which phosphate grdLps arepresent.

Step 1 Formation of Glucose 6- phosphate- Glycolysis begins with phosphorylation of glucose to yield glucose 6- phosphate(phosphate group attached to the hydroryioxygen on coyl enost[at! jroup came fromATP.- Hexokinase which requires Mg t* ion cataryzes this reaction.- Require energy provided by breakdown of ATp.

H',1

H-O-C-FI

? /"-Thiocstcr hond

cu.-tjs-coAAccrYl CoA

refers to complete catabolism of glucose to produce energy

A. Glycolysis- from greek "glyco"- sweet and "rysis'- breakdown- ?.k,a gry.corytic pathway or Embden Meyerhof-parnas pdthway-1930's-.discovered by German biochemists Gustav Embden

"nO Otto Meyerhof

-occurs.in the cytoplasm ofboth prokaryotic and eukaryotic cell-anaerobib process but can take place in the presence or absence of 612 (oxygen doesn,tparticipate in this phase)-metabolic pathway (series of linked biochemical reactions that occur stepwise manner leading' from a starting materialto an end product) which involves breakdown of gtucose (6c) sugar intotwo molecules of pyruvate (3c). At the 91!_oj.nis process, 2 ATp's

"nJ I runou Lr'proiu"*0.

-involves oxidation process, coenzyme NAD* is the oxidizing agent" Ar gilu"or" is oxidized topyruvate in glycotysis, NAq is reduced to NADH' -a ten step process in whrch every stbp is enzyme oataryzed,,

-Two stdges: 6C stage (Steps 1_3) and 3C stige (Stepi 4_10).

ATP ADP\1

_:/>llcx c,kinase

The symbol @ is a shorthandnotation for a f'tCrr- unit.

OH

OFI "Step 2 Formation of Fructose 6-phosphate6" ?tv'cst - c"Tkcsyk'|..E3Luco+e

- Glucose 6- phosphate is isomerized to Fructose 6-phosphate by phosphogluco-isomerase.(lsomers- different compounds with same atoms bui oirer in spatial arrang6ment)- C1 of glucose is no longer part of the ring structure. Glucose an aldose forms a six

membered ring while fructose, a ketose forms a five membered ring. Both however contain6 C atoms.

@)-o\'phosphosrucoisomcrase. @- OU'Cra,-,-ulCH'OH1r,- \*i34"

,.lwt r,s,"(-' -\^a5PLe*c | -'- ,. .-lI ..t..org- 6' p\'a:PLe*c

oH. ' HO \vwc*o:v'6'g\-osgL-ic-

cH.o-{P)t-

I

iItoFructr:c 1.6-bisphosphatc

o-C C1l

'u-c-ou ,I- -oH

I

cll20HC I vccnr ldch vrlc

Ct'r,OHC I r ccratc

o. o-\/,C

I

I

CH:[)r ru r rrl c

Dih)-dro\) ircct()ncPll()\l)llirlc

CIlceraldchldc.1-ph{)\phxlcStep

Step 3 Formation of Fructose 1,O-bisphosphate- a phosphorylation reaction and requires energy.- Phosphofructokinase requires Mg " ion to catalyze this reaction- Fructose 1,6-biphosphate contains 2 phosphate groups

@-otr,

I

HO[:ruct(]sc 6-l)lr(]sIll.rlc

Three- Carbon Stage of Glycolysis (Steps 4-10)- intermediates are phosphorylated derivatives:

c -o'r cl-l'ol-l Alr \DPl.'t

-\\ ll\) / I'lrr'.t':,rrllrrrttrkitrl:c\*/ oFI

C,,OIII

a'-_i\ --\/

I

. ctjrouI)ihy(tio\yrcc(\)rc

Step 4 Fbrmation of Triose Phosphate- Reacting G5species (Fructose 1,6- bisphosphate) which is unsymmetrical is split into

two Gs (triose) species which are not identical.- Products: dihydroxyacetone phosphate and glyceraldehyde 3- phosphate- Enzyme:Aldolase 'ctlro-@ 'cti,o{ H .o

,l .I ^ \1'z/'c:o 'c:o cll.lHolc-H Ho--ic-H H-"c-oH-:*+- Aldoksc, I +

.lt t-oC-ori

-

II 'cH,tl.-?.lH-C-OH,.I''(lHro-{]l)

, llrttclrrsc l.(t-bisphosplrrtc5 lsomerization of I nose PhosphateDihydroxyacetone phosphate (ketose) is readily converted to glyceraldehyde 3- phospftatr:(aldose). Both are isomers.

- Enzyme: Triosephosphate isomerasecH2o--@

rri^.-^,...^!, c:H'o-I lno\(-ltiu\l)n.tt( | -O---C isorrrcrr.c )_

| ..'--------------.'.._ l1(J-\' --ilFro-c-H L| ,rL'.-HOHt''n;1,1;;li,::''"' "..,,:;::ll;li...

Step 6 Formation of 1, 3-bisphosphoglycerate- A phosphate group is added to glyceraldehyde 3- phosphate to produce 1, 3

bisphosphoglycerate- Enzyme: glyceratdehyde 3-phosphate dehydrogenase- The H of the aldehyde group becomes part of NADH.

HO