Chapter 7 - Protein

Question 1

Structure of proteins

Answer 1

• Amino Acids
  
  • Supplied by protein containing food
  • Body requires 20 different amino acids to function, 9 of which needed to be obtained through diets

Question 2

Non essential AA

Answer 2

amino acids our bodies make in sufficient amounts

Question 3

Essential AA

Answer 3

amino acids our bodies do not make in sufficient amounts and therefore must be obtained through diet

Question 4

Synthesis of Nonessential AA by Body:

Answer 4

transamination: transferring an amino group from 1 amino acid to a carbon skeleton to form a new amino acid

Question 5

Deamination

Answer 5

process of losing an amino acid without it being transferred to another carbon skeleton

- Lost amino acids are incorporated into urea in the liver which is excreted in urine

Question 6

Complete Proteins

Answer 6

protein sources containing all 9 essential amino acids
- All animal sources of protein are complete
- Also plant sources such as soy, buckwheat and quinoa

Question 7

Incomplete Proteins

Answer 7

protein sources that do not contain all 9 essential amino acids
- Most plant sources are low in at least 1 of the 9 aa

Question 8

Complementary Proteins

Answer 8

when 2 or more plant proteins are combined to compensate for their individual differences in essential amino acid contents

Question 9

Limiting Amino Acid

Answer 9

limits the amount of protein the body can synthesize due to it being the essential amino acid in smallest supply

- Body cells require a pool of essential aa for the synthesis of body proteins
- A single plant protein cannot support the synthesis of body protein if it’s the sole source, therefore proteins cannot be made and remaining aa are converted to carbs or fat

Question 10

Synthesis of Proteins

Answer 10

through transcription and translation amino acids are produced and linked by peptide bonds

Question 11

size of Protein Chains

Answer 11

• Dipeptides:
  
  • Tripeptides: joining of 3 amino acids
  • Oligopeptides: joining of 4-9 amino acids
    
    • Polypeptides: joining of 10 or more amino acids

Question 12

Sources of Protein

Answer 12

• high protein food sources
• recycling of amino acids by breakdown of body protein

Question 13

How the body recycles body protein

Answer 13

• Digestive tract constantly sheds off the lining, which is treated like food particles and it releases amino acids during digestion.
  
  • The amino acids that are picked up are then reabsorbed and added to the pool of aa
  • Adults make and degrade 250-300g of protein per day
  • Dietary protein is needed to replenish and maintain an adequate amount

Question 14

Biological Value

Answer 14

a measure of how efficiently the absorbed food protein is converted into body tissue protein
- Determined by comparing nitrogen retention with the nitrogen content of the food protein
- The higher the match, the greater the BV

Question 15

Protein Efficiency Ratio

Answer 15

assesses a foods protein quality by comparing the amount of weight gain by a growing lab animal consuming a specifc amount of the protein source

Question 16

Chemical Score

Answer 16

also known as the amino acid score which the amount of each essential aa in a gram of the food protein being tested is divided by the ideal amount of that aa in a gram of reference protein(egg)

Question 17

Protein Digestibility Corrected Amino Acid Score

Answer 17

multiplies a foods chemical score by its digestibility

Question 18

Nitrogen Balance

Answer 18

• Healthy people not in periods of growth or recovering from illness or injury or are athletes need to consume protein in an amount that replaces protein lost in urine, sweat, feces, skin cells and hair and nails

Question 19

Recommended Intakes of Protein

Answer 19

• 0.8g/kg of body weight
• AMDR is between 10-35%

Question 20

Protein Digestion

Answer 20

• Protein digestion begins during cooking as heat denatures proteins and softens the tough connective tissue in meat

Protein digestion:
- Begins in the stomach by HCI
- Pepsin unravels polypeptides
- Partially digested proteins move into the SI
- CCK released from SI which travels to the pancreases and forces the release of proteases
- These enzymes break down proteins into short amino acids which can be absorbed

Question 21

Protein Absorption

Answer 21

• Short chain AA are absorbed by villi which are completely broken down into single amino acids
• Portal vein takes them to the liver
• Either stored, combined to form needed proteins or converted to fat

Question 22

Function of Proteins

Answer 22

• support the development of body tissues and structures
• Albumin and globulin blood proteins are important in maintaining fluid balance
• • Proteins located in cell membranes pump chemical ions into and out of cells which help keep the blood slightly alkalinic
  • Proteins act as good buffers
• Amino acids are required for the synthesis of most hormones in the body
• transporters carrying them through the bloodstream to cells and across cell membranes
• Antibody proteins are key components in the immune system as they bind to foreign proteins that invade the body, preventing attacks
• Amino acids can also be turned into glucose as a back up energy system

Question 23

Protein Energy Malnutrition

Answer 23

protein deficiency rarely developing as an isolated condition but in combination with deficiencies in other nutrients

- Occurs in the disease form as: 
- Marasmus: severe energy deficiency  leading to extreme weight loss, muscle and fat loss Kwashiorkor: underlying infections or disease due to severe protein deficits

Question 24

Issue with High Protein Diets

Answer 24

• High protein diets can overburden people with impaired kidney functions, limiting their ability to excrete excessive nitrogen as ureaI

Question 25

Issue with High Animal Protein DIets

Answer 25

• If protein intake is high in animal proteins, likely to lead to low plant based foods therefore low in fiber and some vitamins and minerals
  
  • Therefore increases the risk of cardiovascular disease and cancers

Question 26

Issue with Excessive Intake of Protein supplementation in athletes

Answer 26

excess protein intake and amino acid supplementation can compete for absorption leading to amino acid imbalances and toxicity risks