55 Questions
Which monomers are used to build the nucleic acids DNA and RNA?
Nucleotides
Which nucleotide is present in RNA but not in DNA?
Uracil
What are the components of a nucleotide?
A base, a sugar, and a phosphate group
What forms the backbone of a nucleic acid chain?
Sugars and phosphates
What type of charge does each phosphate group carry at normal pH?
Negative
Which sugar is found in RNA nucleotides?
Ribose
Which of the following nucleotides serve as coenzymes?
ATP, GTP, UTP, and CTP
What is the primary role of nucleotides in respect to nucleic acids?
Component of nucleic acids
What is the main role of ribonucleotides?
RNA synthesis
Which molecule primarily serves as the source of free energy for all cellular activities?
ATP
Which of the following is NOT a role of RNA?
Synthesizing new proteins directly from DNA
What determines the sequence of proteins synthesized within the cell?
The sequence of bases (adenine, cytosine, guanine, and thymine) in DNA
Which nucleotide pairs with guanine (G) in nucleic acids?
Cytosine (C)
What type of bond holds the nucleotide pairs together in nucleic acids?
Hydrogen bond
Which component is not part of a nucleotide?
Hydrogen bond
What does thymine (T) pair with in nucleic acids?
Adenine (A)
Which of the following is an accurate pairing in nucleic acids?
Adenine (A) with Thymine (T)
Which statement accurately describes a characteristic of vitamins?
They serve as coenzymes for many metabolic enzymes.
Which of the following is NOT a cause of vitamin deficiency?
Excessive sunlight exposure
What role do vitamins play in cellular function?
They act as catalysts in chemical reactions.
Which vitamin characteristic ensures they must be supplied in the diet?
They are not synthesized by the human body with few exceptions.
During which conditions might there be an increased requirement for vitamins?
Pregnancy and lactation
What might a vitamin deficiency result in?
Various metabolic diseases
What symptom can be produced by the destruction of intestinal microorganisms by antibiotic therapy?
Vitamin K deficiency
Which of the following vitamins is NOT fat-soluble?
Vitamin C
Which of these vitamins is part of the vitamin B complex?
Vitamin B6
How are vitamins classified based on their solubility?
Fat-soluble and water-soluble
Which of these drugs can affect vitamin absorption or excretion by forming complexes with specific vitamins?
Antibiotics
Which function of vitamin E is specifically important for protecting RBCs?
Protection from hemolysis
Which statement accurately describes vitamin E in terms of human fertility?
It is not essential for human fertility
How does vitamin E contribute to reducing the risk of myocardial infarction?
By reducing oxidation of LDL
Which of the following is NOT a function of vitamin E?
Increasing calcium absorption
What effect does vitamin E have on the aging process?
It slows down the process of aging
Which of the following conditions must be met for fat soluble vitamins to be absorbed?
Presence of bile salts
In what form are fat soluble vitamins transported in the blood?
Bound to specific binding proteins
What happens to fat soluble vitamins when their stores are depleted?
Their deficiency manifestations occur
Why don't fat soluble vitamins get excreted in urine?
They are insoluble in water
What is a potential risk associated with the over dosage of vitamins A and D?
Hypervitaminosis
How is vitamin D (cholecalciferol) unique compared to other vitamins?
It is considered a hormone
What is required for the synthesis of vitamin D from 7-dehydrocholesterol?
Exposure to sunlight
Where is 7-dehydrocholesterol, the precursor of vitamin D, found in the body?
Subcutaneous fats
Which of the following statements about vitamin D is true?
Its activity is unaffected by storage and cooking.
Why is vitamin D not considered a typical vitamin?
It can be synthesized by the body.
Where does the conversion of 25-hydroxy-vitamin D primarily occur?
Kidneys
Which of the following is a rare group at risk of vitamin B12 deficiency?
Vegetarians
Vitamin B12 deficiency in elderly subjects is often due to malfunctioning of which cells?
Gastric parietal cells
What critical factor is reduced due to malfunctioning gastric parietal cells leading to vitamin B12 deficiency?
Intrinsic factor
Which condition can lead to vitamin B12 deficiency due to the body's inability to properly absorb nutrients?
Malabsorption
Apart from vegetarians, what is another group that might struggle with vitamin B12 deficiency?
Elderly with malfunctioning gastric parietal cells
Which of the following statements about water-soluble vitamins is TRUE?
They must be provided continuously in the diet except for vitamin B12.
What is the main reason that toxicities from water-soluble vitamins are rare?
They can be excreted in urine once concentrations exceed the renal threshold.
What role do most water-soluble vitamins play in the body?
They serve as coenzymes or cofactors in enzymatic reactions.
Which water-soluble vitamin is stored in the liver?
Vitamin B12
Which property of water-soluble vitamins necessitates a regular dietary supply?
Their deficiency manifestation occurs rapidly due to no storage in the body.
What is a characteristic of the structure of vitamin C (ascorbic acid)?
It is formed of 6-carbon atoms and resembles monosaccharides.
Study Notes
Nucleic Acids
- Nucleic acids are polymers composed of monomers called nucleotides.
- Nucleotides are referred to by single letter abbreviations: A, C, G, T, and U.
- DNA contains A, C, G, and T, while RNA contains A, C, G, and U.
Chemical Structure of Nucleic Acids
- Nucleic acids are linear chains composed of nucleotides.
- Each nucleotide consists of a base, a sugar, and a phosphate.
- Sugars and phosphates form the backbone, while bases are attached as side chains to the sugars.
Phosphate Group
- Phosphate groups carry a negative charge at normal pH.
Sugars
- Ribose
- Deoxyribose
Nucleic Acids
- ATP, GTP, UTP, and CTP are essential ribonucleotides functioning as coenzymes.
- Nucleotides are components of nucleic acids.
- Ribonucleotides are important for DNA replication and repair, and RNA synthesis.
- ATP serves as a source of free energy for all cellular activities.
Deoxyribonucleic Acid (DNA)
- DNA consists of two long strings of nucleotides twisted around each other to form a spiral structure.
- The sequence of bases within the backbone of DNA determines which proteins are being synthesized and in what order.
Vitamins
- Vitamins are organic compounds occurring in natural foods, required in minute amounts for normal growth, nutrition, and reproduction.
- Vitamins are characterized by:
- Being essential factors that must be supplied in the diet.
- Being needed in small quantities for normal growth and maintenance.
- Being required for proper utilization of carbohydrates, lipids, and proteins.
- Not being oxidized to produce energy.
- Deficiencies resulting in various metabolic diseases.
- Being used in many chemical reactions inside the body, acting as catalysts.
Causes of Vitamins Deficiencies
- Inadequate dietary intake
- Malabsorption
- Increased requirements
- Increased excretion
- Treatment with some drugs
Classification of Vitamins
- Fat-soluble vitamins: A, D, E, and K
- Water-soluble vitamins: C and B complex
Fat Soluble Vitamins
- Absorbed as lipid, requiring bile salts for absorption
- Transported in the blood by carrier proteins
- Stored in the liver for varying periods of time
- Not excreted in urine, tending to accumulate in tissue
- Deficiency manifestation occurs only when stores are depleted
- Toxicity can occur with excessive intake
Vitamins A "Retinoid"
- Chemical structural: retinoid
- 7-dehydrocholesterol is the precursor of vitamin D
- Vitamin D is synthesized by the body upon exposure to sunlight
Vitamin D
- Stable in food, unaffected by storage and cooking
- Milk is a poor source of vitamin D3
- Daily requirements: 25-hydroxy-vitamin D
Vitamin E
- Antioxidant function:
- Protection of RBCs from hemolysis
- Enhancement of the immune response
- Reduction of the risk of myocardial infarction
- Protection against hepatic necrosis and damage of lung tissues
- Slowing down the process of aging
- Essential for fertility in animals, but not in humans
Water Soluble Vitamins
- Include vitamin C and vitamin B complex
- Polar hydrophilic molecules, soluble in water
- No stable storage form inside the body, requiring continuous dietary supply
- Excreted in urine once concentrations exceed the renal threshold
- Rare toxicities
- Serve as coenzymes or cofactors in enzymatic reactions
- Deficiency manifestation occurs rapidly
Vitamin C "L-Ascorbic acid"
- Structure resembles that of monosaccharides, with 6-carbon atoms
- Present as L and D forms, with only L-ascorbic acid being active
Deficiency of Vitamin B12
- Extremely rare, but can occur in:
- Vegetarians
- Malabsorption
- Elderly subjects with malfunctioning gastric parietal cells
Learn about the building blocks of nucleic acids, including DNA and RNA. Understand the composition of nucleotides and their differences in DNA and RNA.
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