L7 Macronutrients: Protein and Structure

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Questions and Answers

What is the primary function of proteins in the human body?

Providing energy as a primary source

Building and repairing tissues (correct)

Regulating the body's water balance

Serving as a storage form of energy

How are proteins different from carbohydrates and fats?

Proteins do not provide nitrogen to the body

Proteins contain amino acids instead of glucose (correct)

Proteins consist only of carbon and hydrogen

Proteins have a higher caloric value than fats

What is the composition of proteins primarily made of?

Fatty acids and glycerol

Amino acids linked together (correct)

Simple sugars and starches

Nucleotides and phosphates

Which classification of proteins refers to their structure and function?

Structural and functional proteins Signup and view all the answers

What term describes the balance of protein in the body, reflecting both intake and usage?

Protein balance Signup and view all the answers

Which of the following is a challenge faced by vegetarian diets regarding protein?

Lack of complete proteins from animal sources Signup and view all the answers

What is the approximate number of different amino acids commonly found in proteins?

20 Signup and view all the answers

What term describes the first level of protein structure, where amino acids form a linear chain?

Primary structure Signup and view all the answers

Which type of interaction leads to the formation of helices and pleated sheets in proteins?

Hydrogen bonds Signup and view all the answers

What is the role of the 'R' group in amino acids?

It determines the properties of the amino acid. Signup and view all the answers

How many common amino acids have been identified as vital to life and health?

20 Signup and view all the answers

Which of the following amino acids are classified as indispensable or essential?

Amino acids not synthesized in sufficient quantities by the body Signup and view all the answers

What does the tertiary structure of a protein entail?

The folding of helices and pleated sheets into a compact domain Signup and view all the answers

Which of the following amino acids is characterized by the presence of a sulfur group?

Methionine Signup and view all the answers

Where do humans primarily obtain their proteins?

From plants and animals that consume plants Signup and view all the answers

What links amino acids together to form proteins?

Peptide bonds Signup and view all the answers

Which type of amino acids must be consumed in the diet as they are not synthesized by adults?

Essential Amino Acids Signup and view all the answers

Which amino acids are classified as semi-essential?

Histidine and Arginine Signup and view all the answers

What happens to nitrogen when it is removed from amino acids during deamination?

It is converted into ammonia and excreted as urea Signup and view all the answers

What is the role of dispensable (nonessential) amino acids in the body?

They can be synthesized by the body as needed Signup and view all the answers

Which of the following amino acids is conditionally indispensable?

Cysteine Signup and view all the answers

Which process describes the removal of the nitrogen group from amino acids?

Deamination Signup and view all the answers

Why do adults not require histidine in their diet?

It can be fully synthesized in adults Signup and view all the answers

What is the primary purpose of maintaining nitrogen balance in the body?

To support tissue protein turnover Signup and view all the answers

Which amino acid is synthesized from methionine, but must be consumed if the diet is deficient?

Cysteine Signup and view all the answers

What are the five dispensable amino acids needed for a healthy life?

Alanine, Aspartic acid, Asparagine, Serine, Proline Signup and view all the answers

What are considered complete protein sources?

Soy products and animal protein Signup and view all the answers

What defines an incomplete protein?

Deficient in one or more indispensable amino acids Signup and view all the answers

What is the purpose of protein complementation?

To enhance the amino acid profile of a meal Signup and view all the answers

What is the recommended daily allowance (RDA) for protein for men?

56 grams Signup and view all the answers

What is the Acceptable Macronutrient Distribution Range (AMDR) for proteins?

10% - 35% of total calories Signup and view all the answers

What does nitrogen balance indicate in the body?

The efficiency of tissue maintenance Signup and view all the answers

Which condition is associated with positive nitrogen balance?

Pregnancy Signup and view all the answers

How much protein corresponds to 1 g of urinary nitrogen?

6.25 g Signup and view all the answers

What happens when there is a negative nitrogen balance?

Body breaks down more tissue than it builds Signup and view all the answers

What percentage of ingested protein is absorbed as amino acids in the small intestine?

99% Signup and view all the answers

What is the first step in the digestion of proteins?

Breaking down into amino acids Signup and view all the answers

What happens if an essential amino acid is missing during protein synthesis?

The production of the required protein will not be met Signup and view all the answers

How are amino acids primarily absorbed into the bloodstream?

Active transport Signup and view all the answers

Which type of nitrogen balance is likely to occur during periods of illness?

Negative nitrogen balance Signup and view all the answers

What is the main role of proteins in the body?

Acting as enzymes and hormones Signup and view all the answers

Study Notes

Macronutrients: Protein

Protein is derived from the Greek word "proteos", meaning "holding first place" or "primary".
Proteins are large molecules composed of amino acids.
Amino acids are the building blocks of proteins.
Approximately 20 different amino acids are commonly found in plants and animals.
Proteins differ from carbohydrates (CHO) and fats due to nitrogen content, their amino acid structure differs from other molecules, unlike glucose molecules.
The sequence and number of amino acids determine protein's nature.

Protein Structure

Primary structure: Peptide bonds form a linear chain of amino acids.
Secondary structure: Attractions between R groups of amino acids create helices and pleated sheet structures.
Tertiary structure: The helices and pleated sheets fold into a compact domain.
Quaternary structure: Individual polypeptides form larger protein structures.

Amino Acids

All amino acids share a basic structure: an amino group (-NH2), an acid group (-COOH), a hydrogen group (-H), and a unique side chain (-R).
The -R group differentiates amino acids.
Some amino acids contain a sulfur group ("S").
Peptide bonds connect amino acids.

Types of Amino Acids

Essential amino acids: Nine amino acids that the body cannot produce enough of, and must be obtained from the diet.
Nonessential amino acids: Eleven amino acids that the body can synthesize from other compounds.
Conditionally essential amino acids: Six amino acids that the body typically produces, but may need to be consumed in the diet under specific circumstances or conditions.
Semi-essential amino acids: Two amino acids that are considered essential for children, but not for adults.
- Histidine
- Arginine

Protein Digestion and Absorption

Whole proteins are not readily absorbed.
Proteins are digested into amino acids, dipeptides, tripeptides, and polypeptides in the small intestine.
Most (99%) of ingested protein is absorbed as amino acids.
Amino acids are water-soluble and are absorbed directly into the bloodstream via active transport.
Cells combine amino acids to form the needed protein.
- Cells will produce nonessential amino acids if the essential amino acids are present.
The protein digestion process occurs in phases involving the mouth, stomach, pancreas, and small intestine.

Protein Functions

Growth and maintenance: Proteins are part of every cell and needed for building tissues (e.g., children's tissues, blood, hair, skin).
Energy source: When carbohydrate and fat stores are adequate, amino acids can be broken down for energy and are used to make proteins. When both are not adequate, proteins are broken down for energy resulting in protein deficiencies.
Regulatory role: Proteins play a vital role in numerous bodily functions, including chemical reactions (enzymes), chemical messengers (hormones), immunity (antibodies), fluid balance, and transporting nutrients.

Protein Food Sources

Animal sources: meat, fish, dairy products, eggs are complete proteins (contain all essential amino acids).
Plant sources: cereals, legumes, nuts, and seeds are incomplete proteins (lack some essential amino acids).
Complementary proteins are a diet that combines proteins that complement each other to provide a full amino acid profile.

Protein Recommendations and Factors Influencing Protein Needs

The recommended daily allowance (RDA) varies based on gender, pregnancy, and lactation.
Several factors, such as growth phases, illness, and dietary quality, influence protein requirements.

Clinical Implications of Low/High Protein Diets

Low protein intake can lead to severe protein-energy malnutrition (PEM).
Low protein intake during pregnancy may lead to low birth weight.
High protein intake from animal sources may increase saturated fat and reduce fiber, and could result in kidney problems.
Vegan diets necessitate paying particular attention to protein complementation for avoiding deficiencies.

Acceptable Macronutrient Distribution Range (AMDR)

The AMDR for protein is 10% to 35% of total calories.
Protein needs are typically met when 10% of your energy intake comes from protein, assuming adequate calorie intake.

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Description

Explore the fascinating world of proteins, their structures, and the essential amino acids they are made of. This quiz covers the importance of proteins, their classifications, and the unique properties that set them apart from other macromolecules. Test your knowledge and deepen your understanding of these critical biological components.