Chapter 6 protein

• Proteins are formed by linking amino acid end-to-end in different sequences to make different proteins... Essential Amino Acids• Body cannot make it at all or body cannot make enoug

Proteins

• Proteins are chains of AA

• Proteins contain Nitrogen

• Made from 20 different AA

20 Amino Acids

• Proteins are formed by linking

amino acid end-to-end in

different sequences to make different proteins.

• Chemical reaction that links

two AA:

–Water is release by putting

together the two AA

AA + AA Dipeptide + H 2 O

AA Chains

• Dipeptide : 2 AA bonded together

• Tripeptide : 3 AA bonded together

• Oligopeptides: 4-9 AA

• Polypeptide : 10 or more AA

bonded together

Shapes of proteins

Hemoglobin

Amino Acid Structure

C

Side Group

H

H

H

H

O

C O H

H C H

H

H C H

Essential Amino Acids

• Body cannot make it at all or

body cannot make enough

Essential Amino Acids

Non Essential AA

• Body can make it from Essential

Amino Acids

Conditionally Essential

Amino Acids

• Non essential become essential

under specific conditions

• Tyrosine from phenylalanine

• If can not make it, Tyrosine

become essential

Functions of Proteins

1.- Growth, repair, and maintenance

of body tissues (most important) 2.- Regulation of body process

3.- Provide energy

1.- Growth, repair, and maintenance of body

tissues

• MOST IMPORTANT FUNCTION

• To build different types of cells

and tissues

• Muscle, tendons, hair,

fingernails

2.- Regulatory Functions of Proteins

• Fluid Balance

• Hormone, enzyme and antibody

formation

• pH maintenance

• Transport of nutrients through the

body and across cell membranes

• Messenger substance

• One organ makes the messenger

& it travels to another part of the body to cause a change

• Many are proteins

Hormones

glu leu gln tyr leu ser Cys

val ser

ala

Cys Cys

gln glu val ile gly

asn asn

val phe

asn

S S

S S

S

Disulfide Bridges

Two polypeptide chains (51 AA)

• A protein that enables a

chemical reaction

• Specific for:

– Substrate

– Temperature

– Environment - pH of the media.

Lactose Glucose + Galactose Lactase

Enzyme Action

ENZYME

Maintenance of pH

• Balance between acid & base in

the body

• Acid - excessive H + ions

• Blood proteins buffer the H + ions

& make pH more basic

3.-Provide Energy and

Glucose

• WHEN:

– During STARVATION!!!!!!!!!!!

• Losing lean tissue

• To maintain blood glucose levels

High Quality Protein

• Complete

• Provides those EAA in a pattern or

balance which “mimics” human need for EAA

• The closer the balance or proportion

of EAA is to the human need the

higher the quality

Complementary

Proteins

• Two or more proteins whose AA

complement each other in such way that EAA missing from one are provided by the other

– legumes and grains.

Complementary Proteins

– Milk (high quality)

– Cheese

• Plant Sources

• Incomplete

– Dry Beans – Dry Peas – Nuts

– Cereals – Bread

Protein Synthesis

The Cell

Mitochondria

Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum

Protein Synthesis

• Requires that all the needed

Essential Amino Acid be present

• Requires sources of the AMINO

group (NH3) to use in making

Non Essential AA (NEAA)

Protein Synthesis

• If EAA are missing, Protein

synthesis does not take place

• If the missing AA is NEAA, the

body will make that NEAA, and Protein synthesis continues.

Elements of Protein

Synthesis

• DNA: deoxiribonuclic acid

• mRNA : messenger ribonucleic acid

• tRNA : transfer ribonucleic acid

• Ribosome: organelle

• Normal Hemoglobin AA chain

Val His Leu Thr Pro Glu Glu

• Sickle cell disease AA chain

Val His Leu Thr Pro Val Glu

Genetic Error

Sickle Cell Disease

RDA for Protein

Health Problems Related to Protein

Protein-Energy

Malnutrition

• Deficiency of protein, energy or both

• Seen in hospitalized patients, elderly,

people in poverty, use of drugs and alcohol, children in developing

countries, people with anorexia

nervosa

Protein-Energy

Malnutrition

• Two Forms:

– Marasmus: chronic PEM,

inadequate energy and protein

intake

– Kwashiorkor: lack of protein intake

Marasmus

Kwashiorkor

Health Effects of Protein

Protein Supplements

• Balance diet provide the protein

that we need

• Protein supplementation do not

stimulate muscle growth

• Excess of protein may overload

the kidneys

• Made of 20 different AA

• 9 AA are essential

• Conditionally essential AA

Functions of Proteins

1.- Growth,

repair, and

maintenance

3.- Provide energy

– Milk (high quality)

– Cheese

• Plant Sources

• Incomplete

– Dry Beans – Dry Peas – Nuts

– Cereals – Bread