leo physio report

8/4/2019 leo physio report

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Protein Digestion


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Yummy!


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INTRODUCTION


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What are Proteins?

Macromolecules that are polymers of amino acids

Amino acids are linked covalently by peptide bonds

Figure 1. Formation of Peptide bonds to form a tripeptide


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ALL proteins contain C,H,O,N

Built from 20 common building blocks

Sequence of amino acid is dictated by the codons in

mRNA from which polypeptide was translated

Codons of mRNA in turn are based on the codons ofthe DNA template, via transcription

Differences in R- groups identify amino acids


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Polypetide has two ends:

a. N- Terminal (Amino terminal)

b. C- Terminal (Carboxyl terminal)

Figure 2. Polypeptide showing the N and C Terminals


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Modular nature of protein synthesis and folding are

embodied in the orders of protein structure:

a. Primary Structure

b. Secondary Structure

c. Tertiary Structured. Quaternary Structure

e. Quintinary Structure

(see video)


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Typical protein contains 200-300 amino acids

Some have much smaller (smallest are often

called peptides

Largest to date is titin, found in the skeletal and

cardiac muscle, with 34,350 amino acid in a

single chain


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Are proteins important?

Every function in the living cell depends on proteins.a. Motions and locomotion of cells and

organisms

b. Structure of cells and EMc. Transport of materials in body fluids

d. Receptors and signaling molecules

e. Transcription factors that turn genes on and

off to guide the differentiation of the cell


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Building and repair of body tissues

Immune molecules


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PROCEDURE


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(4) 5ml Pepsin Solution + 1 drop Conc. HCl;

incubate at 00C for 1 hour

(1) 5ml Pepsin Solution; incubate at 370C for

1 hour

(2) 5ml Pepsin Solution + 1 drop Conc. HCl;


(3) 5ml Pepsin Solution + 1 drop 10N NaOH;



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Add thin slice of egg white from hard boiled egg to

each test tube (must have same size; 1cmx1cmx1cm)

Examine each egg size for evidence of digestion


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RESULTS


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Set-up Contents Eggwhite Digestion

Tube 1 5 mL pepsin; eggwhiteat 370C

Flat,smooth and

white -

Tube 2 5 mL pepsin; HCl;eggwhite at 370C

Thin scrapes on

the surface

+

Tube 3 5 mL pepsin; NaOH;eggwhite at 370C

Jelly like and

smooth with no

scrapes on the

surface

-

Tube 4 5 mL pepsin; HCl;eggwhite at 00C

Very thin

scrapesSlightly +


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Test Tube 1: 5ml Pepsin and incubated at 370C


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Test Tube 2: 5ml Pepsin+HCl and incubated at 370C


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Test Tube 3: 5ml Pepsin+NaOH and incubated at 370C


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Test Tube 4: 5ml Pepsin+HCL and incubated at 00C


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Theoretical action of Pepsin with protein


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DISCUSSION


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(+) result for this test is the appearance of thin

scrapes on the surface of egg white

Pepsin is the primary agent responsible for protein

digestion

Pepsin its optimum effects in acidic pH, hence

addition of HCl to the second tube greatly lowered

the pH inside the tube


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The pH level in tube 1 is not acidic enough to

activate the action of pepsin

Pepsin in alkaline and neutral medium is not as

effective as it is when it is in an acidic medium

Lower temperatures slow down the action of Pepsin,

too much heat on the other hand will denature it


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Thin scrapes on the surface of the eggwhite in the

test tubes 2 and 4 are indications that pepsin digested

the protein, albumin

Cloudy appearance of egg-white suspension is due

to solid particles of albumen suspended in water

Optimal temp range of Pepsin: 37-420C

45-500C denatures pepsin


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Pepsin denatures if pH is >5

Optimal pH: 1.6-3.2

discovered in 1836 by Theodore Schwann, also

coined its name from Greek Wordpepsis, meaning

digestion


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PROTEIN DIGESTION

IN HUMANS


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Mouth

big pieces of food are broken down into smaller onesby the chewing and grinding of the teeth

helps to expose more of the foods surface area to

chemical digestion

saliva in the mouth moistens the food so it will travel

more smoothly down the digestive tract


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STOMACH

Beginning of protein digestion

Digestive enzymes(proteases):

a. Endopeptidase-hydrolyze PB between specific

AA

- first enzyme to act

!Pepsin catalyzes hydrolysis of PB adjacent to aromaticand branched-chain AA and Methionine

!Trypsin-hydrolysis of Lysine and Arginine Esters

!Chymotrypsin- esters of aromatic AA

!Elastase- esters of small neutral aliphatic AA


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b. Exopeptidase- hydolysis of PB, one at a time,

from the ends of peptides

!Carboxypeptidase- release AA from carboxyl terminal

!Aminopeptidase- relase AA from the Amino terminal

!Dipeptidases and tripeptidases


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Trypsin (trypsinogen) Enteropeptidase

Chymotrypsin

(chymotrypsinogen)Trypsin

Elastase (proelastase) Trypsin

Carboxypeptidase A

(procarboxypeptidase A)Trypsin

Carboxypeptidase B

(procarboxypeptidase B)Trypsin

Enzyme Activator


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STOMACH

Main enzyme: Pepsin

Released from the chief cells of the stomach

Inactive precursor (proenzymes), and activated in the

GI tract.

Precursor: Pepsinogens, activated by the gastric acid


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APPLICATIONS


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Celiac Disease or Gluten Enteropathy

- immunological (allergic) reaction within the

inner lining of the small intestine

- proteins (gluten) that are present in wheat, rye,

barley and, in oats.

-destroys the lining of the small intestine. This

reduces the absorption of the dietary nutrientsand

-nutritional, vitamin, and mineral deficiencies.


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Kwashiorkor

replacement of mothers milk by high caloric andlow protein diets in a child

Thinning of limbs, stunted growth retarded mental

abilities; abdomen, feet and legs are swollen in

nature


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Child suffering from Kwashiorkor


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Marasmus

the mothers mil is replaced too early by other foods,which are poor in both proteins and energy food

Head of child is large, limbs look like stick, loss of

body weight, impaired growth and brain

development


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Child with Marasmus


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Biotechnology: Genetic Engineering

a. Production of Hormone Insulin, through theuse of bacterial cells, Insulin R

b. Medical Pharming- Human Growth Hormone

produced by Bananas

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