Chemistry Lecture 5

Question 1

Phospholipids:

Answer 1

• Structural components of cellular membranes.
• Amphipathic, containing both hydrophilic (polar) and hydrophobic (non-polar) regions.
• Composed of glycerol, two fatty acids, and a phosphate group.
• Form lipid bilayers in aqueous environments, facilitating selective permeability.

Question 2

Steroids:

Answer 2

• Consist of four rings of carbon.
• Examples include cholesterol, estrogen, testosterone, and cortisol.
• Roles: structural integrity of cell membranes, hormone precursor, and regulation of metabolism.
• Insertion into plasma membranes alters fluidity and strengthens the membrane.

Question 3

Eicosanoids:

Answer 3

• Oxidized derivatives of 20-carbon polyunsaturated fatty acids, such as arachidonic acid.
• Include prostaglandins (PGs) and leukotrienes (LTs).
• Functions: regulation of inflammatory responses, blood clotting, and bronchiole dilation.
• Commonly targeted by medications like aspirin and ibuprofen.

Question 4

Other Lipids:

Answer 4

Carotenes: Precursors to vitamin A, found in vegetables like carrots.
Vitamin E: Tissue healing and antioxidant.
Vitamin K: Essential for blood clot formation.
Lipoproteins:Carriers of cholesterol and triglycerides in the bloodstream.

Question 5

Lipoproteins:

Answer 5

Composed of fats (lipids) and proteins.
Transport cholesterol and triglycerides in the blood.
Types: HDL, LDL, VLDL, IDL, and chylomicrons.
HDL: “Good cholesterol” that removes cholesterol from the bloodstream.
LDL: “Bad cholesterol” that can deposit in arteries, leading to atherosclerosis.
VLDL: Another type of “bad cholesterol” that carries triglycerides.
IDL: Intermediate between VLDL and LDL.
Chylomicrons: Large lipoproteins that transport dietary fats through the blood.

Question 6

Proteins:

Answer 6

Polymers made up of amino acid monomers.
Range from two to several thousand amino acids.
Essential for the structure, function, and regulation of cells and tissues.

Question 7

Structural Proteins:

Answer 7

Roles: Key role in the formation and framework of different cells and tissues.
Example: Keratin in skin, hair, and nails.

Question 8

Regulatory Proteins:

Answer 8

Roles: Function as key parts of the structure of hormones.
Examples: Insulin and glucagon.

Question 9

Contractile Proteins:

Answer 9

Roles: Form filaments in muscles and cellular components, allowing muscles and cells to contract.
Examples: Actin and myosin in muscle cells.

Question 10

Immunological Proteins:

Answer 10

Roles: Form key parts of immunological cells like white blood cells and antibodies.

Question 11

Transport Proteins

Answer 11

Roles: Form key components of red blood cells and membrane structures of certain cells.
Example: Hemoglobin in red blood cells carries oxygen and carbon dioxide.

Question 12

Catalytic Proteins (Enzymes

Answer 12

Roles: Lower activation energy and accelerate chemical reactions in the body.
Examples: Digestive enzymes like amylase, lipase, and protease.

Question 13

Peptide Bonds:

Answer 13

• Formed by two amino acids joining together through dehydration synthesis.
• Covalent bonds between the amino group of one amino acid and the carboxyl group of another.
• Can be broken via hydrolysis reactions.

Question 14

Primary Structure:

Answer 14

• Unique sequence of amino acids in a polypeptide chain.
• Determines the protein’s overall structure and function.

Question 15

Secondary Structure:

Answer 15

• Repeated twisting of neighboring amino acids.
• Can form alpha-helices or beta-pleated sheets.
• Stabilized by hydrogen bonds.

Question 16

Tertiary Structure

Answer 16

• 3D arrangement of the polypeptide chain.
• Results from interactions between R-groups (side chains).
• Stabilized by various forces including hydrogen bonds, ionic bonds, disulfide bonds, and hydrophobic interactions.

Question 17

Quaternary Structure

Answer 17

• Arrangement of multiple polypeptide chains.
• Forms a complex with distinct functions.
• Stabilized by the same forces as tertiary structure.

Question 18

Nucleic Acids:

Answer 18

• Biomolecules essential for storing and transmitting genetic information.
• Composed of nucleotide monomers.
• Include DNA and RNA.

Question 19

Pentose Sugar:

Answer 19

• 5-carbon sugar that forms the backbone of nucleic acids.
• Deoxyribose in DNA and ribose in RNA.

Question 20

Nitrogenous Bases

Answer 20

Heterocyclic bases that pair in DNA and RNA.
In DNA: Adenine, Thymine, Cytosine, Guanine.
In RNA: Adenine, Uracil, Cytosine, Guanine.
Base pairing: A-T (DNA), A-U (RNA), G-C (both).

Question 21

Deoxyribonucleic Acid (DNA)

Answer 21

• Double-stranded helical molecule.
• Genetic material found in nearly all living organisms.
• Comprises nucleotides of deoxyribose sugar, phosphate group, and nitrogenous bases.

Question 21

Ribonucleic Acid (RNA):

Answer 21

• Single-stranded molecule involved in various cellular processes.
• Comprises nucleotides of ribose sugar, phosphate group, and nitrogenous bases.
• Types: mRNA, tRNA, rRNA.

Question 21

Adenosine Triphosphate (ATP)

Answer 21

• Energy currency of the cell.
• Comprised of adenine, ribose sugar, and three phosphate groups.
• High-energy bonds between phosphates store energy.
• Hydrolysis of ATP releases energy for cellular work.