4-Proteins

Question 1

Which are the protein sources for human’s body?

Answer 1

• Liver where protein production takes place

- Food which contains proteins

Question 2

How many different proteins are needed to carry out body’s activities?

Answer 2

Around 50,000

Question 3

Where are the half of the proteins been located?

Answer 3

In the muscles

Question 4

Which is the most abudant protein in human’s body and where is it found?

Answer 4

Collagen and is present in all connective tissues

Question 5

Name some protein functions

Answer 5

• Some proteins play primarily a structural role (muscles contain about half of the body’s protein)
• All hormones are proteins
• Transport proteins can shuttle chemical elements, such as oxygen(e.g haemogoblin) or store minerals, such as iron( e.g. ferritin)
• Proteins can also help maintain base-acid balance by acting as buffers to minimize changes in pH.
• Proteins contribute to a healthy immune system through the formation of antibodies
  Protein malnutrition might increase infection risk
• Proteins can also provide energy to the body (however the main role is for tissue building)

Question 6

What kind of molecules are hormones?

Answer 6

They are proteins.

Question 7

What is the function of enzymes?

Answer 7

Enzymes serve as chemical catalysts, speeding up chemical reactions

Question 8

Name a protein for each category:
Structural
Transport and binding
Enzymes
Regulation
Protection
pH regulation

Answer 8

Collagen
Haemogoblin, ferritin
Pepsin
Insulin
IgA antibodies
Silain

Question 9

From where is the word amino acid derived?

Answer 9

From the presence of both amino and acid group to the central group

Question 10

How proteins differ fromcarbohydrates and fats?

Answer 10

Due to the existence of the amino groups

Question 11

What do proteins contain?

Answer 11

Carbon
hydrogen
suplur
nitrogen

Question 12

What determines the properties / function of an amino acid?

Answer 12

ONLY the R-group

Question 13

Through which procedure do the petide bonds be formed?, are they strong?, how these bonds are destroyed?

Answer 13

They are formed by enzymatic reaction
They are very strong
They are destroyed through hydrolysis only by enzymes during digestion or these ones that are present in lysosomes.

Question 14

How can peptide chains be categorises by their lenght?

Answer 14

Dipeptides
Tripepeptides
Short- polypeptides(10-40aa)
Large polypeptides(proteins) (more than 40aa)
Large proteins (dystrophin=3648aa)

Question 15

How many amino acids are needed from our body in order to built all the proteins

Answer 15

20 amino acids

Question 16

How proteins differ each another?

Answer 16

number of amino acids
order/sequencing
types of amino acids (polar/non-polar)

Question 17

Where can proteins be synthesized in our body?

Answer 17

In the liver

Question 18

How can we say essential/ non-essential amino acids in other words?

Answer 18

indespensable/dispensable

Question 19

How many levels has protein 3D structure and which are the characteristics of each one?

Answer 19

4 levels

1) Primary- sequence of aa in peptide chain
2) Secondary-Folding/ coiling of peptide chain (usually to a-helix or b-pleated sheet)
3) Tertiary-peptide chain folds upon itself
4) Quaternary-folded peptide chains join together

Question 20

Can a protein be directly absorbed when eate?if not what procedures should happen?

Answer 20

 When a protein is eaten as part of the diet, it is not absorbed directly, but must first be broken down into its component amino acids

 Stage 1—Digestion in mouth

Digestion begins in the mouth with the moistening effect of saliva and the chewing by the teeth
Moistening the food creates a bolus, which can be more easily mix with acid and enzymes in the stomach.

2)Stage 2-Digestion in the Stomach

Hydrochloric acid (HCI) is secreted by parietal cells in the stomach lining in order to denature the protein and provide an appropriate environment for digestion

Chief cells in the stomach lining produce an inactive enzyme, pepsinogen

The acidic environment converts the pepsinogen to the active protease( protein-cleaving enzyme), pepsin.

Pepsin breaks the polypeptide chain at numerous sites, yielding:
 intermediate- length polypeptides
 small polypeptides
 and some amino acids

Stage 3- Digestion And Absorption in the Small Intestine

Further breakdown of the polypeptides takes place in the small intestine
It involves cleavage by proteases produces by both the pancreas and the small intestine

A variety of proteases (e.g. amylopeptidase , carboxylpeptidase etc.) is needed to cleave peptide bonds associated with the full range of proteins

Amino acids and short peptides are absorbed by the small intestine

Question 21

Can a protein be brokendownn to provide energy?

Answer 21

yes, but a samll percentage

Question 22

What is the destination of amino acids when are inserted in the bloodstream?

Answer 22

the liver

Question 23

What is protein turnover?

Answer 23

 Is the dynamic process whereby proteins are continually synthesized and degraded

Question 24

What is the average protein turnover in an adult?

Answer 24

 The average protein turnover in an adult is 300-400g per day

Question 25

Can amino acids released from protein degradation be re-incorporated into protein?

Answer 25

yes

Question 26

In which food categories do we find protein?

Answer 26

in all food categories(plant & animal)

Question 27

Why we need to recieve proteins?

Answer 27

• Tissue repair

- Replace the lost amino acids

Question 28

Should a well-fed individual have high-protein diet?

Answer 28

No, it is wasteful

Question 29

What happens if we recieve surplus amino acids in our body?

Answer 29

 Surplus amino acids are rapidly catabolised & the nitrogen is excreted as urea in the urine

Importance of protein is OFTEN overestimated!!

Question 30

What is the recommended protein intakefor adults?(UK recommendations) and what the current protein intakes males and females?

Answer 30

0.8g/kg body weight and no more than 1.5g/kg per day for adults
¬50-70g protein per day for adults

88g protein per day for men
64g protein per day for women

Question 31

How the protein’s quality is defined?

Answer 31

 Protein Quality is defined as the protein’s source ability to support growth

Question 32

When can a protein be characterised as complete?

Answer 32

 A complete protein has all the essential amino acids present in proper proportions to sustain growth

Question 33

Info: Proteins derived from animal sources(meat,fish) as well as soy protein are complete (high biological value)

Answer 33

.

Question 34

Info: Plant based proteins are incomplete proteins (low biological value)

Answer 34

.

Question 35

What are the effects of protein defficiency?

Answer 35

• People that are chronically ill, institutionalised and elderly are at high risk of protein malnutrition muscle loss (sarcopenia)
• Protein -energy malnutrition might be serious concern for children in developing countries.
• Malnutrition affects hundred of millions of young children and leads to growth failure (stunted growth)

Question 36

What are the effects of high protein intake?

Answer 36

• High-protein diets may have effects on calcium metabolism
• As protein increases in the diet, calcium excretion increases, which may be related to bone loss.
• Excessive intake ,may lead to deterioration of renal function in patients with chronic renal diseases (stages 1-4)