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BSC Zoology - Nutrition and Digestion > Lecture 8- Protein > Flashcards

Lecture 8- Protein Flashcards

1
Q

What are the essential amino acids?

A
  • One that the body is unable to make or can only make in inadequate quantities
  • Need to be consumed from the diet
  • 8-10 essential amino acids
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2
Q

What are non-essential amino acids?

A
  • One that the body can make in large enough quantities
  • Made from essential amino acids
  • Not necessary to consume these in the diet
  • 10-12 non essential amino acids
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3
Q

What is a conditionally essential amino acid?

A

• One that can become essential in certain physiologic conditions

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4
Q

What is an example of an conditional essential amino acid?

A

• Example: tyrosine becomes essential in people with phenylketonuria (PKU)

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5
Q

What is PKU?

A
  • Most common inborn error in AA metabolism
  • 1/12-15,000 people (mainly white and Asian populations)
  • Body cannot utilize phenylalanine(EAA)
  • Phe then builds up in the body as it is not metabolised
  • High phe can cause neurologic damage
  • Irreversible CNS damage, mental & growth retardation, seizures, small head size etc.

Unusual compounds: phenylpyruvate; phenyllactate; phenylacetate

Brain toxicity: reduced uptake of other aromatic amino acids

Tyrosine deficiency may lead to hypopigmentation

Cofactor processing can also be defective

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6
Q

What is this

A

• Normal situation

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7
Q

What happens in PKU?

A
  • In PKU:
  • Phenylalanine builds up

Can cause mental retardation

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8
Q

What is PKU prevention and treatment?

A
  • Tyrosine must be supplied by diet • Becomes EAA for those with PKU
  • Phenylalanine intake must be carefully restricted – but the amino acid is however essential for growth and development
  • All infants are tested for PKU at birth
  • Low protein diets (that is how you treat it)
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9
Q

What are the properties of amino acids?

A
  • About 25 commonly found in dietary proteins
  • Chemically diverse but have common general formula
  • Mostly water soluble
  • Optically active (except glycine)
  • Amphoteric
  • Forms cations at acid pH, anions at basic pH
  • Naturally occur as L-isomers

(don’t have to memorise this so much)

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10
Q

What is the struture of amino acids?

A

• Different side chains make different amino acids

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11
Q

What are the essential amino acids in humans?

A

Essential (10)
• Phenylalanine

  • Valine
  • Threonine
  • Tryptophan • Isoleucine
  • Methionine • Histidine
  • Arginine
  • Leucine
  • Lysine

(remember couple of each)

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12
Q

What are the nonessential amino acids in humans? (remember one example and what it means to be nonessential)

A

• Alanine

  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutaminc acid • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine
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13
Q

What are conditionally essential amino acids in humans?

A
  • Cysteine
  • Glutamine
  • Tyrosine
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14
Q

What is the primary structure of a protein?

A

• It is the sequence of amino acids that makes each protein different from the next

Dipeptide = 2 amino acids

Tripeptide = 3 amino acids

Polypeptide = many amino acids

Most proteins have many 100 amino acids

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15
Q

What is the secondary structure of a protein?

A
  • Alignment of polypeptides as a right-hand alpha helix
  • Stabilized by hydrogen bonds between carboxyl (C=O) and imido (NH) groups
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16
Q

What is the tertiary structure of the protein?

A
  • Three dimensional folding and coiling of polypeptide into globular 3-D structure
  • Caused by additional chemical interactions among side chains • Disulfide bonds
17
Q

What is the quaternary structure of a protein?

A

• Interactive folding of several polypeptide chains together to form a “single” functional protein

  • Functional proteins also might incorporate minerals or other nonprotein components
  • Final shape and components determine function of protein
18
Q

What is the nutritional importance of proteins?

A
  • Nutritional value of dietary proteins is determined mainly by its primary structure (i.e., amino acid composition)
  • Tertiary structure can influence protein digestibility
  • Globular proteins are generally more easily digested than filamentous proteins such as collagen, elastin and keratin
19
Q

What is umami?

A
  • “fifth taste”
  • Salt, sour, sweet, bitter
  • Relatively new discovery (confirmation, ~ year 2000)
  • Cured meats, cheese, soy, miso, Worcestershire sauce, vegemite, kimchee
  • Attractive taste to humans
  • Monosodium glutamate MSG
  • Free glutamate
  • Marker of nutrient (protein) rich food?
20
Q

What do you need to synthesise protein?

A

• Protein synthesis cannot proceed without an adequate supply of all amino acids, which contribute to the primary structure of that protein

21
Q

What is the biological value of a protein?

A

• The ability of a specific dietary protein to supply amino acids in the relative amounts required for protein synthesis by body tissues is defined as biological value

  • Influenced mainly by essential amino acid composition
  • Is not fixed, but varies with the needs of different species, physiological and nutritional states
22
Q

What are the biological functions of proteins?

A

Principal organic chemical constituents of body organs and soft tissues

Enormous functional diversity

  • Cell membrane structure and function
  • Enzymes
  • Hormones and other chemical messengers

Immune factors (antibodies)

Fluid balance

Acid-base balance

Transport

Source of energy and glucose

23
Q

How is protein important mechanically and structurally?

A
  • Collagen
  • Bone and skin
  • Keratin
  • Hair and nails
  • Motor proteins
  • Make muscles work!
24
Q

How are proteins important as enzymes?

A
  • Proteins that catalyze (speed up) chemical reactions without being used up or destroyed in the process.
  • Anabolic (putting things together) and catabolic (breaking things down) functions.
  • Examples
  • Digestion
  • Salivary amylase
  • Trypsin
25
Q

How do proteins act as hormones?

A
  • Chemical messengers that are made in one part of the body but act on cells in other parts of the body.
  • Peptide hormones are synthesized in the same steps as normal protein manufacture.
  • Examples
  • Insulin
  • CCK
  • Some reproductive hormones
26
Q

How are proteins important in immune function?

A

• Antibodies are proteins that attack and inactivate bacteria and viruses that cause infection

27
Q

How are proteins important for fluid balance?

A
  • Proteins in the blood help maintain appropriate fluid levels in the vascular system.
  • Fluid is forced into tissue spaces by blood pressure generated by pumping action of the heart.
  • Fluid returns to blood because of “osmotic pressure.”
28
Q

How are proteins important as transport proteins?

A
  • Transport substances in the blood
  • Lipoproteins (transport lipids)
  • Hemoglobin (transports oxygen and carbon dioxide)

• Transport materials across cell membranes.

29
Q

How are proteins important as source of energy?

A
  • Proteins are the last to be used for energy!
  • Occurs in starvation and low carbohydrate diets
  • When excess protein occurs…
  • Some amino acids converted to glucose which is converted to fat.

BSC Zoology - Nutrition and Digestion (24 decks)

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