5. Proteins Flashcards
Describe the structure and role of amino acids.
Contain nitrogen, carbon, hydrogen, and oxygen.
Typically supply 4 kcal per gram.
Functions: regulates and maintains body functions.
What are essential amino acids?
9 essential amino acids.
Not synthesized, must be consumed from diet.
Limiting amino acid: essential acid in lowest concentration in food or diet relative to body needs.
What are non essential amino acids?
11 non essential amino acids.
Can be synthesized by the body.
Why are adequate amounts of each of the essential amino acids required for protein synthesis?
DNA contains coded instructions.
Copies of codes transferred to cytoplasm via mRNA.
Amino acids added one at a time:
- with aid of tRNA
- the mRNA is fully read
- amino acids have been connected into the polypeptide
- polypeptide is released into the cytoplasm
- processed further to become a functioning cell protein
Required energy.
What are some food sources of protein?
- peach
- banana
- edamame
- kidney beans
- non-fat greek yogurt
- cheddar cheese
- quinoa (cooked)
- oatmeal
- chicken
- tuna
- peanuts
What are high-quality proteins?
Complete proteins.
Contain ample amounts of all nine essential amino acids.
What are low-quality proteins?
Incomplete proteins.
Low in or lack one or more essential amino acids.
All-or-none principle in protein synthesis.
Limiting amino acids and complementary proteins.
Describe the concept of complementary proteins.
Combining two food protein sources that make up for each others inadequate supply of specific essential amino acids.
Together they yield a sufficient amount of all 9 essential amino acids and provide high-quality protein for diet.
Ex. rice and beans; vegetables and nuts
How is protein digested, absorbed, and metabolized in the body?
Liver: amino acids are absorbed into the portal vein and transported to the liver. From there, they enter the general bloodstream.
Stomach: partial protein digestion by stomach acid and the enzyme pepsin.
Pancreas: pancreas releases enzymes (e.g., trypsin and chymotrypsin) that will further digest polypeptides in the small intestine.
Small intestine: once in the small intestine, the partially digested proteins (and fats) trigger the release of the hormone cholecystokinin (CCK) from the walls of the small intestine. CCK causes the pancreas to release protein-splitting enzymes, such as trypsin. Final digestion of peptides into single amino acids takes place mostly inside cells of the small intestine.
Large intestine/rectum: little dietary protein is present in feces.
What are the primary functions of proteins?
- produce body components
- maintain fluid balance
- contribute to acid-base balance
- form enzymes and hormones
- contribute to immune function
- glucose production
- provide energy and satiety
What is meant by positive protein balance?
A net gain of protein in the body.
What is meant by negative protein balance?
When more protein is used by the body than is taken in.
How can protein-calorie malnutrition lead to disease in the body?
Marasmus: starvation and insufficient protein and calories.
Kwashiorkor: marginal amount of calories and insufficient protein.
How are amino acids organized and used to form proteins?
Order of amino acids in a protein; determines the protein’s shape.
Protein’s final shape: determines its function in the body.
Proteins often form a coiled shape.
Shape is dictated by the order of the amino acids in the protein chain.
What are the current recommendations for protein intake?
Translates to about 10% of total calories: 0.8 grams protein per kg body weight per day
Food and nutrition board: upper range for protein intake - 35% of calores
