Biology: Proteins and Amino Acids

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Questions and Answers

What is the fundamental structural element that distinguishes proteins from other organic compounds, according to the text?

A carboxyl group.

A carbon chain.

A hydroxyl group

The presence of nitrogen. (correct)

Which of the following best explains the term 'essential amino acid'?

An amino acid the body can synthesize from other substrates.

An amino acid that only becomes important in times of stress.

An amino acid the body can only obtain from dietary sources. (correct)

An amino acid that is required for basic metabolic functioning.

What role do heat, alcohol, acids and salts of heavy metals play in protein structure?

They cause denaturation by disrupting the normal protein chain. (correct)

They help form peptide bonds.

They maintain the precise sequence of amino acids.

They participate in protein syntheses

During digestion, which enzyme initiates the breakdown of large polypeptides in the stomach?

Pepsin Signup and view all the answers

What is the primary function of the liver in protein metabolism according to the information?

The monitoring of protein synthesis and the distribution of amino acids Signup and view all the answers

Which of the following BEST describes the concept of 'complementary proteins'?

Combining different types of food that have imbalanced essential amino acids to create a complete protein. Signup and view all the answers

According to the provided data, which food has the highest NPU (Net Protein Utilization) value?

Eggs Signup and view all the answers

A lacto-ovo vegetarian's diet is MOST likely to include which of the following?

Dairy products and eggs, but not meat Signup and view all the answers

Which of the following is NOT typically a health benefit associated with vegetarianism, according to the provided information?

Increased cardiovascular disease risk Signup and view all the answers

Which of these is a potential concern specifically for vegan individuals, as compared to lacto-ovo vegetarians, according to the provided material?

Risk of B12 deficiency Signup and view all the answers

What percentage of resting energy expenditure (REE) is typically attributed to protein metabolism?

15-20% Signup and view all the answers

Which of the following is NOT a primary function of proteins in the human body?

Regulation of blood glucose levels Signup and view all the answers

In the context of immune response, what is the role of antibodies?

To detect and neutralize antigens Signup and view all the answers

How do proteins contribute to maintaining fluid balance within the body?

By attracting water inside cells and back into blood vessels Signup and view all the answers

What role do proteins play in maintaining acid-base balance in the blood?

They act as buffers, accepting or releasing hydrogen ions Signup and view all the answers

Which of the following best describes how transport proteins function in the body?

They bind to a specific compound or group of compounds and move them through or across cell membranes Signup and view all the answers

What is the function of ferritin within the body?

To store iron within bodily tissues Signup and view all the answers

Which protein is responsible for carrying oxygen in the bloodstream?

Hemoglobin Signup and view all the answers

What is the primary function of fibrin in blood clotting?

To form stringy protein fibers that plug leaks in blood vessels. Signup and view all the answers

During the process of deamination, what is the immediate fate of the stripped nitrogen?

It is transformed into urea in the liver for kidney excretion. Signup and view all the answers

Which of the following statements best describes the body's response to excess protein intake?

Excess protein is primarily converted into fat for storage. Signup and view all the answers

A sedentary adult requires a daily protein intake of 0.8 grams per kilogram of body weight. What would the approximate daily protein need for an 80kg individual?

64 grams per day Signup and view all the answers

An endurance athlete requires approximately 2 grams of protein per kilogram of body weight per day. Why does an endurance athlete require more protein than a sedentary adult?

To repair and rebuild muscle tissue after prolonged activity. Signup and view all the answers

Which of the following signs is NOT associated with Kwashiorkor?

Significant Weight Loss Signup and view all the answers

A patient presents with low adipose tissue, significant weight loss, and no edema. Which form of protein-calorie malnutrition is most likely?

Marasmus Signup and view all the answers

Which is the most appropriate nutritional course of action for an individual that presents with edema caused by Kwashiorkor?

Administer a diet low in fat and high in protein Signup and view all the answers

A patient has a nitrogen balance of -6.4 grams. Which of the following is the most accurate interpration of the result?

The patient is in a state of catabolism. Signup and view all the answers

Given a protein intake of 75 grams per day and a urinary urea nitrogen (UUN) output of 6 grams per day, what is the nitrogen balance of the patient?

+3 grams per day. Signup and view all the answers

Study Notes

Proteins

Proteins are organic compounds composed of acid and amino groups, with a variable side group.
Nitrogen is a key component of proteins.
Amino acids are the building blocks of proteins.

Amino Acid Structure

Amino acids have an amino group, an acid group, and a variable side group.
The side group differentiates the 20 different amino acids.

Amino Acid Examples

Glycine, Alanine, Aspartic acid, and Phenylalanine are examples of amino acids.
Diagrams of their structures were shown.

Amino Acids

The 20 amino acids are the basic building blocks of proteins.
9 are essential (indispensable); the body cannot produce them.
11 are non-essential (dispensable); the body can synthesize them.

Condensation

Amino acids link together via peptide bonds.
A peptide bond forms when water is removed.
This process builds dipeptides, tripeptides, oligopeptides, and polypeptides.

Amino Acids - Sequencing

The specific order of amino acids is crucial.
Errors in sequencing can cause genetic disorders like sickle cell disease.
In sickle cell disease, valine substitutes for glutamic acid at the 6th position.

Amino Acids - Denaturation

Denaturation is the process of altering the protein's structure.
It can be irreversible.
Heat, alcohol, acids, salts of heavy metals can denature proteins.

Digestion/Absorption

Protein digestion begins in the stomach with HCl and pepsin.
Pepsin breaks down polypeptides into smaller units.
In the small intestine, proteases and peptidases break down peptides into free amino acids.

Digestion - Small Intestine

Intestinal proteases and pancreatic proteases break down polypeptides into tripeptides, dipeptides, and oligopeptides.
Intestinal peptidases further break down these smaller peptides into amino acids.
Amino acids cross the intestinal villi and enter the bloodstream.

Transport of Amino Acids

Amino acids are transported by diffusion.
The liver monitors protein synthesis, releases free amino acids into the bloodstream, and controls catabolism.

Functions of Protein

Proteins are essential for growth, maintenance, enzymes, hormones, antibodies.
Proteins fulfill numerous roles like maintaining fluid and electrolyte balance, and acid-base balance in the body.

Growth, Maintenance

Proteins are crucial for cell manufacture, repair (e.g., collagen), and replacement.
Protein turnover is the continuous synthesis and degradation of proteins.

Enzymes - Catalysts

Enzymes are proteins that act as catalysts.
They facilitate reactions, by forming a complex with reactants.
The enzyme remains unchanged during the reaction.

Antibodies

Antibodies are proteins produced by the immune system to combat invaders.
Antigens are invaders like bacteria, toxins, viruses, and allergens.
Antibodies are made with amino acids.
Adequate protein promotes antibody production.

Fluid Balance

Proteins, transported as amino acids, are essential for maintaining fluid balance.
Proteins in blood draw water back into the bloodstream.
Insufficient protein can cause fluid build-up (edema) in tissues.

Fluid Balance - Details

Blood pressure forces fluid into tissue spaces.
Proteins draw water back into the bloodstream as pressure declines.
Without sufficient protein, fluid accumulates in tissues (edema).

Acid-base Balance

Proteins act as buffers, maintaining a healthy blood pH (7.35-7.45).
Acidosis (low pH) is when the body has too much acid.
Alkalosis (high pH) is when the body has too much base.
Proteins accept or release hydrogen ions (H+) to maintain equilibrium.

Transport Proteins

Proteins specifically carry compounds (e.g., vitamins, minerals, oxygen, lipids).
They maintain equilibrium of compounds in and out of cells.
Examples include ferritin (iron storage), transferrin (iron transport), hemoglobin (oxygen transport), and lipoproteins (lipid transport).

Blood Clotting

Fibrin is a stringy protein made during tissue injury that forms a clot to plug leaks.
Vitamin K and calcium are needed for clotting.

Protein for Energy

When energy needs are high, proteins may be used as an energy source, after deamination to remove the nitrogen.
This process generates urea, and the carbon skeleton may be converted to glucose, for later energy use.

Protein Excess

Excess protein is stored as fat.
It can overload the kidneys and increase calorie intake.
It may lead to increased calcium excretion.

Protein Recommendations

Protein needs are 10-15% of total calories or 0.8-1.0 grams per kilogram of body weight daily, depending on the individual lifestyle.
Protein needs increase with illness, stress, and age.

Do Athletes Need More Protein???

Athletes requiring strength building may require more protein (1-1.2 grams/kg of body weight per day).
Increased protein intake alone will not necessarily increase muscle size.

Health Effects of Protein

PEM/PCM (Protein-energy malnutrition) is widespread, especially in children.
Acute malnutrition often leads to thinness (thin for height).
Chronic malnutrition means the person is short for their age.
Two common types are Kwashiorkor and Marasmus.

Kwashiorkor

Kwashiorkor typically results from inadequate protein intake, even if calorie intake is adequate.
Visible symptoms involve edema, changes in hair, growth failure, fatty liver, and more.

Marasmus

Marasmus results from inadequate calories and protein intake.
Characterized by severe weight loss, low adipose tissue, low muscle mass, and potentially compromised immune system.

Nutrition Therapy

Therapy for malnutrition includes fluid balance (electrolytes), protein repletion, and in some cases, increasing fat intake.

Malnutrition in Hospitalized Patients

Different types of malnutrition exist in hospitalized patients based on the patient's specific condition.
Appropriate nutrition therapy is key.

Evaluate for PCM

Measurements for protein-calorie malnutrition include skeletal muscle circumference, mid-arm muscle circumference, creatinine-height index, and serum proteins. (Albumin, Prealbumin, Total Protein)

Nitrogen Balance

Nitrogen balance refers to the difference between nitrogen intake and nitrogen excretion, using a simple calculation using protein intake and urine nitrogen output.
Positive nitrogen balance means intake exceeds excretion (growth or recovery).
Negative nitrogen balance means excretion exceeds intake (disease or starvation).

Protein Quality

Chemical scoring, biological value (BV), net protein utilization (NPU), and protein efficiency ratio are used to evaluate the quality of a protein.

Protein Quality - Important Distinctions

Complete proteins contain all essential amino acids.
Incomplete proteins lack one or more essential amino acids.
Complementary proteins combine incomplete proteins to provide all essential amino acids.
Digestibility is also a crucial aspect of protein quality.

Complete/Incomplete Proteins

Complete proteins (e.g., eggs, milk, meat) provide all essential amino acids.
Incomplete proteins (e.g., beans, rice) lack certain essential amino acids.
Combining incomplete proteins, via careful meal planning, can improve the overall quality of protein intake.

Protein Sources (Examples)

Various food sources provide protein including dairy products, meat, fish, and plant-based options.

Complementation

Combining food sources to complement limiting amino acid content of an incomplete protein to result in a complete protein, as shown in examples from the slides.

Vegetarian Diets

Vegans completely avoid animal products.
Semi-vegetarians avoid red meat.
Lacto-ovo vegetarians consume eggs and dairy.
Lacto vegetarians consume dairy products.

Benefits of Vegetarianism

Some potential health benefits are often observed with vegetarian diets (e.g. lowered blood cholesterol and lower risk of cancer).

Vegetarian Concerns

Vegetarians may need to increase their intake of certain nutrients because they are avoiding animal products (e.g. iron, vitamin B12, zinc).

Allergic Reactions

Foods can cause allergic reactions, and it's important to identify potential allergens.

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Description

This quiz covers the structure and function of proteins and amino acids. It includes key concepts such as the classification of amino acids, their essential and non-essential types, and the process of peptide bond formation. Test your understanding of the building blocks of life!