Proteins are composed of amino acids and perform many essential functions in living organisms. There are 20 standard amino acids that make up proteins. Proteins are broken down into amino acids through digestion in the stomach and small intestine by enzymes like pepsin and trypsin. Amino acids are then absorbed into the bloodstream and transported to tissues. Insufficient protein intake can lead to protein-energy malnutrition conditions like marasmus and kwashiorkor. Alcohol is also broken down through metabolic pathways in the liver involving enzymes. Excessive alcohol consumption can cause serious health issues like liver disease and cancer.

1. Proteins and Amino Acids
By
Zahid gul
University of
peshawar

2. Protein
• Proteins are the most abundant and functionally
diverse molecules in living systems where they
constitute 50% or more of their dry mass.
• The word protein is derived from the Greek Protos,
which means the first or supreme.
• Proteins are nitrogenous macromolecules,composed
of aminoacids linked by peptide bond.

3. Amino acid
•monomers of protein.
•consists of carbon,hydrogen,oxygen,nitrogen
and some contain sulfur.
• our body protein are made up from 20 types
amino acids.

4. • Although more than 300 naturally
occurring amino acids are known but only
20 amino acids take part in the formation
of all types of proteins,plants as well as
animal in origin.
• These 20 amino acids are known as
Primary,Standard or normal amino acids.

5. General structure of an amino acid
Each amino acid (except proline) has a
carboxyl group, an amino group and a
distinctive side chain bonded to the alpha
carbon atom. At physiological pH the carboxyl
group is dissociated forming the negatively
charged carboxylate ion(-COO-
), and the amino
group is protonated(-NH3
+)
7/5/2012 5Biochemistry For Medics

8. • Semi-essential aminoacids.
Two amino acid cysteine and tyrosine can
be sythesiszed from essential amino
acid{thionine and phenyalanine} and can
also be consumed in diet.
• the process of amino acid formation from
other amino acid is called transamination

10. Classification of proteins regarding
nutrition
• HIGH QUALITY PROTEINS
Protein that contain all the nine essential
amino acid
• LOW QUALITY PROTEINS
Protein that lack one or more essential
amino acid

11. Protein for Our Body

12. Protein synthesis
• DNA contains coded instructions for protein
synthesis in the form of three nucleotide per
unit of instruction called codon, each codon
represent a specific amino acid.
• Protein synthesis consists of two main steps,
• Transcription and translation.

13. Transcription
• Formation of mRNA from DNA is called
transcription.
• Transcription occurs in three stages:
1.Initiation:
– RNA polymerase binds to DNA at a specific
sequence of nucleotides called the promoter.
– The promoter contains an initiation site where
transcription of the gene begins.

14. Transcription
– RNA polymerase than unwinds DNA at the
beginning of the gene.
• 2.Elongation:
– Only one of the unmound DNA strands acts as a
template for the RNA synthesis.
– RNA polymerase can only add nucleotides to the
3' end of the strand.
– Free nucleotides from the cytoplasm are paired
up with their complementary base on the
exposed DNA template.

15. Transcription
Termination:
RNA polymerase continues to elongate until it
reaches the terminator, a specific sequence of n
Transcription stops and mRNA polymerase and
the new mRNA transcript are released from DNA.
The DNA double helix reforms.
• And the mRNA enters into the cytoplasm.

16. translation
• Translation may be divided into three distinct
steps.

17. translation
• Inatiation,results in the formation of an initiation complex
in which the ribosome is bound to the specific initiation
(start) site on the mRNA while the initiator tRNA is
annealed to the initiator codon and bound to the ribosome.
• , elongation consists of joining amino acids to the growing
polypeptide chain according to the sequence specified by
the message. Incorporation of each amino acid occurs by
the same mechanism. Thus, the same steps are repeated
over and over again until the termination codon is reached
in the message. The termination codon gives the signal for
the third and last stage of protein synthesis, the
termination in which the ready-made protein is released
from the ribosome.

18.  Structural
 Movement
 Transport
 Storage
 Hormone
 Protection
 Enzymes
Collagen; bones, tendons, cartilage
Keratin; hair, skin, wool, nails, feathers
Myosin & Actin; muscle contractions
Hemoglobin; transports O2
Lipoproteins; transports lipids
Casein; in milk. Albumin; in eggs
Insulin; regulates blood glucose
Growth hormone; regulates growth
Immunoglobulins; stimulate immunity
Sucrase;
Pepsin;
Functions of Proteins

19. Protein Deficiency
• Protein-energy malnutrition (PEM)
World’s most widespread malnutrition problem
Includes both marasmus and kwashiorkor and states
of overlap
MARASMUS. { to waste away}
symptoms.
Muscle wasting, Impaired immunity ,Lethargy,
Vomiting, Delayed wound healing, Loss of fat
stores and muscles

20. Causes.
•due to diet containing less amount of protein and
energy.
•no breast feeding or stop breast feeding in early
month
•working mother feed their infants through bottle
which also can cause this condition.
• in hospitalized patient marasmus can be caused by
lack of proper diet.

21. Kwashiorkor
• symptoms :
• change in skin and hair color (reddish-orange color)
• fatigue
• diarrhea
• loss of muscle mass
• failure to grow or gain weight
• damaged immune system, which can lead to more frequent
and severe infections
• irritability
• rash
• large belly that sticks out

22. Causes
• Kwashiorkor is a world from ghana that means
“ the disease that the first child gets when
the new child comes”
• When the breast feeding is no longer
possible for the first child the child diet
changes and can not fulfill the energy and
protein requirement of he child,
• The child also has infections and parasites,

23. Protein Digestion
and
absorbtion

24. Protein Digestion
• is the degradation of proteins by cellular enzymes
enzymes in a process called hydrolysis.
• Protein digestion takes place in two different
phases:
– In the stomach
– In the small intestine
• Both of these phases of digestion are based on
several types of enzymes that are called
proteinases and proteases.

25. In the Stomach : start of protein
Digestion
Gastrin
-stimulates Parietal cells to secrete HCL; Chief
cells of the gastric glands to secrete pepsinogen
Hydrochloric acid
-Denatures protein structure
-Activates pepsinogen (zymogen) to pepsin
Pepsin
-hydrolyzes proteins to smaller polypeptides and
some free amino acids.

26. In the intestine
. The remainder of protein digestion occurs in
the small intestine as the result of the action
of enzymes
such as trypsin (secreted by the pancreas) and
peptidases (located in the cells that line the
small intestine).

27. In the Small Intestine : enzymes
Secretin
- stimulates the pancreas to secrete bicarbonate
into the small intestine to neutralize the gastric HCl
Cholecystokinin
-stimulates secretion of several pancreatic enzyme
with activity optima pH 7 to 8.

28. In the Small Intestine
Trypsin
- activates chymotrypsinogen chymotrypsin
procarboxypeptidasescarboxypeptidases
proelastaseelastase
-further hydrolyze the peptides that were produced by
pepsin in the stomach specifically the peptide bonds next
to lysine and arginine
Chymotrypsin
-cleaves peptide bonds

29. Carboxypeptidase A & B
-cleave amino acids from the acid (carboxyl) ends of
polypeptides
Elastase and collagenase
-cleave polypeptides into smaller polypeptides and
tripeptides

30. Intestinal tripeptidases
-Cleave tripeptides to dipeptides and amino acids
Intestinal dipeptidases
-cleave dipeptides to amino acids
Intestinal aminopeptidases
-cleave amino acids from the amino ends of small
polypeptides (oligopeptides)

31. Amino acids absorbed
Free amino acid  small
intestine(villi)Liverblood circulation

32. Metabolism of -amino acids

33. Alcohol
• Alcohol are chemically called ethanol.
• Alcohol are classed as depressant because it
slows down vital function resulting in slurred
speech, unsteady movement, disturbed
perception and inability to react quickly,
• Alcohol overdose can causes coma and death
also.
• Besides these and many other effects alcohol
is a good source of energy

34. Alcohol metabolism
• Metabolism of alcohol is dependent on many
factors like gender, race, size and physical
condition.
• Alcohol is metabolized by three pathways.
• Alcohol dehydrogenase pathway.
• Microsomal ethanol oxidizing system.
• Catalase pathway.

35. Alcohol dehydrogenase pathway
Ethanol
NAD+ NADH+H
Acetaldehyde
NAD+ NADH+H
acetyl-CoA

36. Microsomal ethanol oxidizing pathway
• Excessive amount of ethanol is metabolized by
the liver through MEOS.
• Liver uses the MEOS to metabolized drugs and
other foreign substances.
• In MEOS NADPH+H are used in the first step,
• Whereas NADH+H are produced during
alcohol dehydrogenase pathway.

37. Microsomal ethanol oxidizing pathway
Ethanol
o2 NADPH+H NADP
Acetaldehyde
acetyl-coA

38. Catalase pathway
• Minor path for metabolizing alcohol,
• It is located in the peroxisomes,
Ethanol
H2O2 H2O
Acetaldehyde

39. Health problem and alcohol
• Alcohol is the third leading cause of preventable
death in north America
• Causes of alcohol are heart failure, cancer, liver
cirrhosis, motor vehicle accidents, hypertension,
hemorrhagic stroke, osteoporosis, brain damage,
suppression of immune system.
• Liver cirrhosis affects about 2 million people in
USA, AND IS the second leading cause of the liver
transplants.

40. Health problem and alcohol
• In 2011 about 35,000 American died of liver
cirrhosis.
• Increase heart muscle damage, blood clotting
and blood pressure.
• Reduce insulin sensitivity and damage to
pancreas,
• Damage skeletal muscle,