Chapter 2: Molecular Biology Flashcards
Why is carbon a key element in molecular biology?
It forms four covalent bonds, enabling a variety of stable compounds.
What are the four groups of carbon compounds in living organisms?
Carbohydrates, lipids, proteins, nucleic acids.
What is metabolism?
The web of all enzyme-catalyzed reactions in a cell or organism.
Define anabolism.
The synthesis of complex molecules from simpler ones by condensation reactions.
Define catabolism.
The breakdown of complex molecules into simpler ones by hydrolysis.
What role do enzymes play in metabolism?
They increase the rate of reactions by providing an active site for reactants.
What are examples of metabolic reactions in cells?
DNA replication, RNA synthesis, protein synthesis, cell respiration, photosynthesis.
Why is water essential in biological systems?
It acts as a polar solvent due to hydrogen bonding.
What are the key properties of water due to hydrogen bonding?
Cohesion, adhesion, thermal stability, and solvent properties.
cohesion -> surface tension
adhesion -> transpiration
What determines whether a substance is hydrophilic or hydrophobic?
Its polarity.
How are polysaccharides formed?
By condensation reactions linking monosaccharides with glycosidic bonds.
What is the general formula for carbohydrates?
Cx(H2O)y.
Give examples of hexose and pentose monosaccharides.
Hexose: glucose, fructose, galactose;
Pentose: ribose, deoxyribose.
What are the two main roles of monosaccharides in cells?
Energy source in respiration and building blocks for larger molecules.
energy released through respiration because contains many C-H bonds
What is the storage polysaccharide in plants?
Starch.
What is the structural polysaccharide in plants?
Cellulose.
What is glycogen, and where is it stored in animals?
A storage polysaccharide stored in liver and muscle cells.
What is the function of cellulose?
Provides structural support in plant cell walls.
What are triglycerides made of?
Three fatty acids and one glycerol via condensation.
What is a phospholipid, and what is its structure?
A lipid with a hydrophilic head and hydrophobic tails.
What is the role of phospholipids in the cell?
Form membranes with hydrophobic barriers and hydrophilic surfaces.
What are nucleic acids made of?
Polymers of nucleotides.
What are the structural differences between DNA and RNA?
DNA: two strands; RNA: one strand; differ in base composition and pentose sugar.
What is the structure of DNA?
A double helix with antiparallel strands joined by hydrogen bonds.
What are proteins made of?
Polymers of amino acids linked by peptide bonds.
How many amino acids are there?
20 different amino acids.
What determines a protein’s three-dimensional structure?
The amino acid sequence and types of bonds.
What is the primary structure of a protein?
The linear sequence of amino acids.
What creates the secondary structure in proteins?
Hydrogen bonding between CO and NH groups.
What bonds stabilize a protein’s tertiary structure?
Hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic interactions.
disulfide bridge is the strongest
ionic bonds are broken when pH changes
What is the quaternary structure of proteins?
The assembly of multiple polypeptide chains.
What is protein denaturation?
The loss of native shape due to changes in pH, temperature, or salt concentration.
What happens to DNA when heated?
Hydrogen bonds break, separating the strands.
What bonds link monosaccharides in polysaccharides?
Glycosidic bonds.
What type of bonds join the two strands of DNA?
Hydrogen bonds.
Which lipid contains hydrophilic and hydrophobic regions?
Phospholipids.
What distinguishes glycogen from starch?
Glycogen is more branched, more compact and found in animals.
What is the structure of cellulose?
Unbranched parallel β-glucose polymers linked by β-1,4 bonds.
Water has cohesive and adhesive properties due to […].
hydrogen bonding.
Cellulose is a polymer of […]-glucose with structural roles in plants.
β
Why can carbon atoms form a diversity of stable compounds?
Because they can form four covalent bonds.
What are enzymes?
Protein molecules with specific active sites that increase the rate of reactions.
Why is water called the ‘solvent of life’?
Because of its polarity and hydrogen bonding ability.
What happens when a hydrophobic substance encounters water?
It does not dissolve because ‘like dissolves like’.
How are monosaccharides linked to form polysaccharides?
Through condensation reactions forming glycosidic bonds.
What are the three main groups of carbohydrates?
Monosaccharides, disaccharides, polysaccharides.
What is the general formula of carbohydrates?
Cx(H2O)y.
What are common examples of hexose monosaccharides?
Glucose, fructose, galactose.
What are examples of pentose monosaccharides?
Ribose and deoxyribose.
What is cellulose, and what is its function?
A polymer of β-glucose with a structural role in plant cell walls.
What are fatty acids?
Carboxylic acids with chains of 15-17 carbon atoms.
What is the role of phospholipids in cells?
Forming membranes with hydrophilic heads outward and hydrophobic tails inward.
What are DNA and RNA made of?
Polymers of nucleotides.
What is the structure of DNA?
A double helix with antiparallel strands linked by hydrogen bonds.
What is the secondary structure of a protein?
Folding into α-helices and β-pleated sheets due to hydrogen bonding.
What is the tertiary structure of a protein?
The three-dimensional folding stabilized by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.
What is the quaternary structure of a protein?
The association of multiple polypeptide chains, e.g., hemoglobin.
What happens to protein albumin in an egg when heated?
It denatures and coagulates.
What is the difference between α-1,4 and α-1,6 glycosidic bonds?
α-1,4 is linear; α-1,6 is branching.
What bonds stabilize the tertiary structure of proteins?
Hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic interactions.
Which polymer of glucose is unbranched in plants?
Amylose.
Which polysaccharide in animals forms granules in liver cells?
Glycogen.
What type of bonds link the two strands of DNA?
Hydrogen bonds.
What is water influx?
Movement of water into cell
influx refers to movement
Why is lipid not a polymer?
Lack repeating monomer units.
What phenomenon is caused by water cohesive and adhesive properties?
Surface tension and transpiration (capillary action)
water pulls itself up by adhering to xylem and cohering to itself
Why is carbohydrate a good supply of energy?
Molecule contains many bonds (C-H), which releases a lot of energy when broken
Why must animal convert glucose into glycogen?
- Glucose is very reactive and soluble in water, which disrupts homeostasis
- Glycogen is more compact, thus unreactive and insoluble
Why is glycogen mostly stored in muscle and liver cells?
Such cells have high energy demand => energy at use
Which stores more energy, lipids or carbs.?
Lipids
higher C-H proportion, smaller volume, hydrophobic so storage doesn’t require H2O in environment
What are the elements in carbohydrates?
C, H, O.
What are the elements in nucleic acid?
C, H, O, N, P.
What are the elements in protein?
C, H, O, N, P, S.
What are the elements in lipid?
C, H, O, P.
Solubility of monosaccharides?
Highly soluble in watter
How are disaccharides formed?
Condensation reaction of 2 monosaccharides
What are some disaccharides?
Saccharose, maltose, galactose
Galactose = β-galactose + β-glucose
What is the glycosidic bond?
Covalent bond (C-O-C) between 2 sugars.
What are polysaccharides? Some examples?
Long chain of many monosaccharides.
e.g. starch, glycogen, cellulose.
Are polysaccharides sugar?
No.
they’re non-sugars
Structural difference between amylose and amylopectin?
- Amylose: unbranched, compact helix of α-glucose. α-1,4-glycosidic bond.
- Amylopectin: branched chain of α-glucose. α-1,6-glycosidic bond.
amylose takes up around 25-30% in starch, rest is amylopectin
Difference between glycogen and amylopectin?
Glycogen is more branched and compact, also more soluble
because more compact => higher surface area => -OH groups more exposed
Key difference between starch and glycogen vs cellulose?
Cellulose is chain of β-glucose, not α-glucose.
How does cellulose’s parallel chains contribute to its stable structure?
Chains can cross-link with each other (hydrogen bonds) to form higher structural levels with increased stability
Chain -> Microfibils -> Fibers
Structure of triglyceride?
3 fatty acid chains attached to a glycerol.
What are fatty acids?
Long tails attached to carboxyl group.
Non-polar.
What is monounsaturated and polyunsaturated?
Have 1 or 1+ unsaturated bond
Why are unsaturated triglycerides liquid at room temperature?
Pi bonds cause kinks in fatty acid tail
=> Weaker LDF
Functions of triglycerides?
- Energy storage
- Insulator against heat loss (stored underneath skin and around kidneys)
- Metabolic source of H2O
Structure of phospholipid?
A phosphate group attached to glycerol instead of a fatty acid chain.
2 parts: hydrophobic tails and hydrophillic head
What is a nucleotide?
3 parts: phosphate group, pentose sugar, nitrogenous base
How many types of nitrogenous bases are there?
2: purines (A, G) and pyrimidines (C, T/U)
How many types of bonds are there in a DNA chain?
2
Phosphodiester between nucleotides
Hydrogen bonds between bases
Why must there be big bases (purines) and small bases (pyrimidines)?
Create a stable structure of antiparallel chains, where the big bases bond with the small bases to even the size
Which group is at the 3’ and 5’ end?
3’: hydroxyl
5’: phosphate
Why is DNA charged?
DNA is negatively charged because of the phosphate groups.
How many amino acids make up proteins in the body?
20 (9 essential and 11 non-essential)
What is a polypeptide chain?
Many amino acids linked together by peptide bond (-CO-NH-)
peptide bond = amide bond = covalend bond
How many structural stages of protein are there?
4
Name the 4 structural stages of protein
Primary, secondary, tertiary, quarternary
What is the haem group in haemoglobin?
an inorganic, prosthetic group containing Fe, use to store oxygen
What is the shape of protein’s primary structure?
Long polypeptide chain
What is the shape of protein’s secondar structure?
α-helix
β-pleated sheet
due to hydrogen bonding between amino acids within
What is the shape of protein’s tertiary structure?
Coiled secondary structure
What is the strongest bond in proteins?
Covalent bond (disulfide bridges)
What is the shape of protein’s quarternary structur of protein?
Multiple polypeptid chains
-> globular
-> fibrous
