Protein PGHT

8/3/2019 Protein PGHT

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Protein: Amino Acids

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Protein and Amino Acids

Protein: a compound composed of C, H, O and

N atoms, arranged into amino acids linked in a

chain.

Amino acid: a building block of protein, a

compound containing amino group and anacid group attached to a central carbon atom.

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Structure of Amino Acids

Central C is connected to three compounds:

amino group (NH2), acid group (COOH), and

hydrogen (H).

Central C is also another atom or group of

atoms that varies one amino acid to another.

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Structure of Amino Acids

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20 Amino Acids

G Glycine Gly P Proline Pro

A Alanine Ala V Valine Val

L Leucine Leu I Isoleucine Ile

M Methionine Met C Cysteine Cys

F Phenylalanine Phe Y Tyrosine Tyr

W Tryptophan Trp H Histidine HisK Lysine Lys R Arginine Arg

Q Glutamine Gln N Asparagine Asn

E Glutamic Acid Glu D Aspartic Acid Asp

S Serine Ser T Threonine Thr

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Aromatic Amino Acids

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Amino Acid Sequence

Dipeptide: two amino acids bonded together

by peptide bond.

Tripeptide: three amino acids bonded

together by peptide bond.

Polypeptide: many (ten or more) amino acids

bonded together by peptide bond.

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Amino Acid Sequence

Oligopeptide: an intermediate string of

between four to ten amino acids bonded by

peptide bond.

Peptide bond: a bond between amine group

of one and carboxyl group of another aminoacid.

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Amino Acid Sequence

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1

31

61

91

121

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60

90

120

150


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Structure of Protein

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Structure of Protein

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Protein Synthesis

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Complete and Incomplete Proteins

Complete proteins, meaning that all

indispensable AAs are present.

Incomplete proteins, meaning that one or

more of the indispensable AAs was absent.

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Dispensable and Indispensable Amino

Acids

Dispensable alanine

glutamic acid

aspartic acid

Glycine

serine

proline

glutamine(a)

asparagine

cysteine (b)

tyrosine (b)

Indispensable Lysine

isoleucine (c)

leucine (c)

valine

Histidine

Threonine

Methionine

Phenylalanine

tryptophan

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Dispensable and Indispensable Amino

Acids

a. Conditionally indispensable under times of

severe bodily stress

b. Conditionally indispensable if methionine

and phenylalanine are not available

c. Leucine, isoleucine, and valine are called

branch chain amino acids (BCAAs) because

of their structure.

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Complex proteins

Lipoproteins contain lipid subunits in addition to the

amino acid.

Glycoproteins contain carbohydrate subunits.

Phosphoproteins contain phosphoric acid, and

nucleoproteins contain nucleic acids.

Some proteins have important smaller molecules,

known as prosthetic groups, attached to their

surfaces.

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Enzymes: A Function of Protein

Protein catalysts

Enzymes are protein molecules that regulate

the metabolism of proteins, carbohydrates

and fats.

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Roles of Protein

Fluid and acid-base balance,

Antibodies and hormones,

Nutrient transportation,

Blood clotting,

Muscle contraction,

Blood vessel expansion,

Contraction to maintain normal blood pressure,

Connective tissues,

Visual pigments

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Biologically Active Peptides

Peptides that are inactive in the sequence of

the parent protein, but can be released duringenzymatic digestion or food processing, and

have health benefits to the body.

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Biologically Active Peptides

Antihypertensive activity,

Antibacterial activity,

Mineral-binding activity,

Enhancement of intestinal activity

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Peptide Sequences Showing

Antihypertensive Effect

Milk protein (casein, sour milk, whey protein)

Poultry (chicken muscle, ovalbumin)

Several kinds of fish (sardine, bonito, salmon)

Porcine skeletal muscle protein (actin, myosin,troponin)

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Protein Quality

Essential amino acid: an amino acid that the

body cannot synthesize in amounts sufficientto meet physiological need.

Non essential amino acid: an amino acid that

can be synthesized in the body.

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Protein Quality

Complete protein: a protein containing all the

essential amino acids in human nutrition in

amounts of adequate for human use.

High-quality protein: an easily digestible

complete protein that amino acids fit theprotein needed by human body.

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Protein Quality

Limiting amino acid: the essential amino acid

found in the shortest supply relative to the

amounts needed for protein synthesis in the

body.

Digestibility: the measure of the amount of

amino acids absorbed from protein intake.

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Protein Digestibility

Food source Protein digestibility (%)

Egg 97

Milk and cheese 97

Mixed US diet 96

Peanut butter 95

Meat and fish 94

Whole wheat 86

Oatmeal 86

Soybeans 78

Rice 76

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Protein Quality

Reference protein: egg protein is used as a

standard against which to measure the quality

of other proteins.

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Protein Quality

Reference protein: egg protein is used as a

standard against which to measure the quality

of other proteins.

Nitrogen balance: the amount of nitrogen

consumed (N-in) as compared to the amount

of nitrogen excreted (N-out).

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Protein Quality

The average amino acid weight is about 6.25

times as much as the nitrogen it contains, sothe scientists can estimate the amount of

protein in a sample of food, body tissue, or

excrete by multiplying the weight of nitrogen

in by 6.25.

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Nitrogen Balance

Nitrogen equilibrium/zero nitrogen balance:

N-in = N-out

Positive nitrogen balance: N-in > N-out

Negative nitrogen balance: N-in < N-out

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Measures of Protein Quality

Chemical score: a rating of the quality of a test

protein arrived at by comparing its amino acid

pattern with that of a reference protein.

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Reference Pattern for Chemical Score of

Protein

Essential amino acids Whole egg

mg AA per g N

Histidine 148

Isoleucine 340

Leucine 540

Lysine 440

Methionine 355

Phenylalanine 580

Threonine 294

Tryptophan 106

Valine 410

Total 3,210

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Biological value (BV): the amount of protein

nitrogen that retained from a given amount of

protein that has been digested and absorbed.

BV = [Food N (Fecal N Metabolic N) (Urinary N

Endogenous N)] / [Food N (Fecal N Metabolic N)]

x 100

BV = N retained / N absorbed x 100

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Biological Value of Proteins

Protein Biological Value

Egg 100

Milk 93

Rice 86

Beef, fish 75

Corn 72

Peanut flour 56

Wheat gluten 44

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Net protein utilization (NPU): the amount of

protein nitrogen that is retained from a givenamount of protein nitrogen eaten.

NPU = [Food N (Fecal N Metabolic N) (UrinaryN Endogenous N)] / Food N x 100

NPU = N retained / N intake x 100

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Protein efficiency ratio (PER): the weight

gained from protein intake.

PER = Weight gain (g) / Protein intake (g)

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Protein-kCalorie Malnutrition

Kwashiorkor: a malnutrition caused by protein

deficiency in the presence of adequate

kcalories.

Marasmus: a malnutrition caused by

inadequate kcalories.

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Recommended Protein Intakes

RDA = 0.8 g/kg body weight.

Factors are considered in establishing

recommended protein intake:

Body weight

Lean body

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Protein Sources

Animal foods

Cereals

Vegetables

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Protein Digestion and Absorption

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Digestion

Process that breaks down food into molecules

small enough to absorb.

Break polymers into monomers that are easier

to absorb and that can be used to synthesize

new polymers required by the organism.

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Absorption

Cells that line tract take up nutrients

Nutrients move to cells where they are

Incorporated into the cells

Converted to energy which may be used

immediately or stored until needed

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Di dalam Mulut

Tidak terjadi digesti protein yang signifikan di dalam

mulut, hanya membasahi jaringan konektif (protein

kolagen).

Distimulasi dengan timbulnya bau, indra penglihatan

dan rasa, atau pemikiran mengenai makanan,

menyebabkan saliva tersekresi.

Saliva mengandung: mucin (a glycoprotein lubricant),

amylase (untuk memecah KH dan glikogen)

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Di dalam Lambung (Stomach)

Distimulasi dengan aliran makanan, menyebabkan neurotransmitters acetylcholine

dan histamine dihasilkan oleh sel-sel dalam lambung (stomach)

Distimulasi dengan adanya makanan di dalam lambung, mengakibatkan hormone

gastrin tersekresi.

Kombinasi acetylcholine, histamine dan gastrin menyebabkan cairan lambung(gastric juices) tersekresi.

mucin selalu disekresikan dalam stomach

HCl - pH 0.8-2.5 (disekresikan parietal cells)

pepsinogen (zymogen, disekresikan oleh chief cells)

gastric lipase (enzyme yang meemecah lemak, tetapi aktif di intestine)

Protein terdenaturasi akibat pH rendah

Nilai pH yang rendah berfungsi sebagai antiseptik, dan membunuh bakteri dan sel

asing.

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Digesti dalam lambung

Zymogen Pepsinogen (MW=40,000) yang dihasilkan

di dalam lambung diaktivasi oleh adanya enzim

pepsin dan asam lambung. Pepsinogen memiliki 42

potongan asam amino untuk menjadi enzim pepsin

(MW=33,000) dan fragmen peptida yang akan

terdegradasi. Pepsin akan mendigesti secara parsial dengan

memotong ikatan peptida pada ujung N asam amino

aromatis (Phe, Tyr, Trp)

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Digesti dalam Duodenum

Cairan lambung yang disebut Chyme masuk ke duodenum, pH

rendah memicu sekresi hormon secretin dalam darah. Asam amino

menstimulasi sekresi cholecystokinin.

Secretin menstimulasi pankreas untuk mensekresikan bicarbonat ke

dalam usus kecil (small intestine), (pH changes to about 7).

Cholecystokinin menstimulai sell exocrine pancreas untuk

mensekresikan trypsinogen, chymotrypsinogen dan

procarboxypeptidase ke dalam intestine. (Sel exocrine juga

mengandung protein trypsin inhibitor untuk melindungi diri dari

free trypsin).

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Sel-sel intestinal mensekresikan enzim yang disebut enteropeptidase yangbertugas pemotongan trypsinogen menjadi trypsin.

Trypsin merubah chymotrypsinogen menjadi chymotrypsin,procarboxypeptidase menjadi carboxypeptidase dan proelastase menjadielastase (belum diketahui asal-nya dari mana), dan trypsinogen menjaditrypsin.

Trypsin memotong peptida pada ujung karboksil asam amino Lys dan Arg.

Chymotrypsin memotong ujung karboksil asam amino aromatis Phe, Tyr

dan Trp.

Enzim yang membutuhkan Zn.

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Carboxypeptidase memotong semua asam amino pada fragmen

yang masih memiliki satu asam amino pada ujung karboksil (akan

memotong pada sisi ujung N dari ujung C asam amino).

Elastase memotong derivat asam amino, desmosine.

Aminopeptidase merupakan sekresi sel usus halus dan bertugas

memotong ujung N asam amino pada semua peptida.

Banyak protein terdigesti secara sempurna menjadi asam amino,diserap dan kemudian diangkut ke dalam darah menuju sel-sel

dalam tubuh.

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Keratin dan protein fibrosa lainnya sulit untuk

didigesti (hanya lewat).

Kebanyakan protein tanaman tertutup

selulosa dan tidak dapat didigesti.

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Component of Gastrointestinal

System

Mouth

Oral cavity

Tongue

Pharynx

Salivary Glands

Esophagus

Stomach

Liver

Gall Bladder

Pancreas

Small Intestine

Large Intestine

Rectum

Anus

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Oral Cavity

Food enters the mouth and is reduced in size

by teeth and tongue.

Salivary glands secrete saliva which

Lubricates

Buffers

Contains antimicrobial substances

Contains amylase to digest starch

10/24/2011 51
http://www.vh.org/Providers/Textbooks/motilitygastro/7.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/salivary.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/salivary.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/esophagus.htmlhttp://www.ee.ualberta.ca/~mintchev/stomach.htmlhttp://www.vh.org/Providers/Textbooks/LiverPathology/Text/AtlasLiverPathology.htmlhttp://www.cag-acg.org/patinfo/gall_bladder.htmhttp://www.fda.gov/fdac/features/896_panc.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/smallgut/index.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/largegut/index.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/largegut/index.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/smallgut/index.htmlhttp://www.fda.gov/fdac/features/896_panc.htmlhttp://www.cag-acg.org/patinfo/gall_bladder.htmhttp://www.vh.org/Providers/Textbooks/LiverPathology/Text/AtlasLiverPathology.htmlhttp://www.ee.ualberta.ca/~mintchev/stomach.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/esophagus.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/salivary.htmlhttp://www.vh.org/Providers/Textbooks/motilitygastro/7.html


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Swallowing

Food passes to pharynx which contains both

trachea and esophagus

Epiglottis prevents food from entering trachea

Food passes through esophagus into the

stomach

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Stomach

Stores and digests food

Contains pits leading to Gastric glands with

three types of cells:

Mucous cells - produce mucous which lubricates

and protects lining. Parietal cells - secrete hydrochloric acid

Chief cells - secrete pepsinogen

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Small Intestine

Receives food from stomach

Bile from liver via the Gall bladder (kantung

empedu)

Enzymes from pancreas

Site of most digestion

Site of most absorption

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Duodenum

First 25 cm of small intestine

Receives enzymes from pancreas

Neutralizes acid from stomach

Site of most chemical changes in food

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Enzymes

Fat + bile and lipase = Fatty acids + glycerol

Starch + Amylase = simple sugars

Maltose + maltase = glucose + glucose

Sucrose + sucrase = glucose + fructose

Lactose + lactase = glucose + galactose

Protein + protease = amino acids

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Pancreas

Releases critical enzymes for digestion

Neutralize acid by releasing bicarbonate

Insufficient pancreatic function can lead to

starvation

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Liver

Produces bile

No digestive enzymes, but contains bile salts

Emulsifies fats

Made from cholesterol

Stored in Gall Bladder

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Enzymatic Action - Carbohydrates

Starch broken down into the disaccharide , maltose, by

pancreatic amylases.

Disaccharides converted to monosaccharides

Maltose is hydrolyzed by Maltase to give Glucose + Glucose

Sucrose is hydrolyzed by Sucrase to give Glucose + Fructose

Lactose is hydrolyzed by Lactase to give Glucose + Galactose

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Absorption

Following enzymatic action in the duodenum,

food is absorbed in the remainder of the small

intestine

Has a very large surface area

Contains Villi and microvilli

Rich in capillaries and lymph vessels

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http://orion1.paisley.ac.uk/courses/stfunmac/glossary/bile.html


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Large Intestine

Material not be digested or absorbed passes

into the large intestine.

90% of the water is absorbed into blood

Some vitamins are produced by bacteria and

are absorbed

Residue is stored in rectum

Eliminated through the anus

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How are proteins absorbed?

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How are proteins absorbed?

The absorptive cells of the small intestine can only

absorb individual amino acids, dipeptides ortripeptides.

Once transported inside the cells all di/tripeptides are

broken down into individual amino acids by proteases

within the cells.

Like monosaccharides, the amino acids are transported

out of the absorptive cells and diffuse into the

capillaries to move into general circulation.

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THANK YOU

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Protein PGHT