Protein Flashcards
(34 cards)
Energy content of protein
1 gram = 17 kJ
What is the primary structure of proteins?
Linear sequence of amino acids determined by DNA.
What is the secondary structure of proteins?
Folding of the chain into pleated sheets or alpha helices due to hydrogen bonds.
What is the tertiary structure of proteins?
3D functional protein structure formed by interactions between side chains.
What is the quaternary structure of proteins?
Combination of multiple polypeptide chains (e.g., haemoglobin).
What unique characteristics do proteins have?
Contain nitrogen in addition to carbon, hydrogen, and oxygen (unlike carbohydrates and lipids).
How are proteins managed in the body?
Proteins are constantly broken down and reassembled based on body requirements.
What determines a protein’s unique shape and function?
The amino acid sequence.
What happens to proteins in the stomach during digestion?
HCl denatures proteins and activates pepsinogen to pepsin, which hydrolyses proteins into smaller polypeptide chains.
What occurs in the small intestine during protein digestion?
Bicarbonate neutralizes stomach acid; pancreatic proteases continue breaking down polypeptides; intestinal proteases hydrolyse peptides into dipeptides and tripeptides.
What is the role of enterocyte enzymes?
Convert dipeptides and tripeptides into amino acids for absorption.
What is deamination?
Excess amino acids converted into glucose, fat, or used for energy.
When is protein demand increased?
During growth periods (childhood, adolescence), pregnancy and breastfeeding, disease, illness, and injury.
What is positive nitrogen balance?
Protein intake > protein excretion (e.g., growth, pregnancy).
What is negative nitrogen balance?
Protein excretion > intake (e.g., illness, malnutrition).
What happens with excess protein intake?
Leads to increased urea production and excretion.
What are purines formed from?
Amino acid catabolism.
What are purines used to synthesize?
DNA and RNA.
What are rich sources of purines?
Sardines, liver.
What are the risks of high purine intake?
Increased uric acid levels, gout (often linked with insulin resistance).
What is protein turnover?
The body builds proteins daily from dietary and recycled amino acids.
What is the formula for nitrogen balance?
Protein (nitrogen) intake - protein (nitrogen) loss = nitrogen balance.
What is transamination in the liver?
Transfer of the NH2 group from an amino acid to a keto acid, producing non-essential amino acids (requires Vitamin B6).
What are ketogenic amino acids?
Convert to acetyl CoA → used for fatty acid synthesis.
