Topic 1:Biological molecules Flashcards
What are the monomers of carbohydrates?
Monosaccharides (e.g., glucose, fructose, galactose).
What is the difference between α-glucose and β-glucose?
In α-glucose, the hydroxyl (-OH) group on carbon 1 is below the ring; in β-glucose, it is above.
What reaction forms a disaccharide from two monosaccharides?
A condensation reaction, which forms a glycosidic bond and releases water
Name three common disaccharides and their component monosaccharides.
~Maltose = glucose + glucose
~Sucrose = glucose + fructose
~Lactose = glucose + galactose
What test is used for reducing sugars?
Benedict’s test – a brick-red precipitate indicates a positive result.
What are the two main types of lipids?
Triglycerides and phospholipids.
What are triglycerides made of?
One glycerol molecule and three fatty acids.
What is the difference between saturated and unsaturated fatty acids?
Saturated fatty acids have no double bonds, whereas unsaturated fatty acids have one or more double bonds.
What test is used to identify lipids?
The emulsion test – a milky-white emulsion indicates lipids are present.
What are the monomers of proteins?
Amino acids.
What type of bond forms between amino acids?
Peptide bonds.
What are the four levels of protein structure?
~Primary: Sequence of amino acids.
~Secondary: α-helices and β-pleated sheets (formed by hydrogen bonds).
~Tertiary: 3D structure (involves hydrogen, ionic, and disulfide bonds).
~Quaternary: Multiple polypeptide chains joined.
What test is used for proteins?
Biuret test – a purple color indicates the presence of protein.
How do enzymes speed up reactions?
They lower the activation energy required for a reaction to occur.
What is the difference between the “lock and key” and “induced fit” models?
~Lock and key: The enzyme’s active site is a perfect fit for the substrate.
~Induced fit: The enzyme changes shape slightly to fit the substrate more closely.
How does temperature affect enzyme activity?
Increases activity up to the optimum, but too high a temperature denatures the enzyme.
How does pH affect enzyme activity?
Enzymes have an optimum pH; extreme pH changes alter the active site shape and denature the enzyme.
How does substrate concentration affect enzyme activity?
increases the numbers of substrate molecules that can form enzyme-substrate (ES) complexes at any one time. This increases the initial rate of reaction but when all the enzyme molecules are engaged in ES complexes the rate cannot increase any further.
How do competitive and non-competitive inhibitors work?
~Competitive inhibitors bind to the active site, blocking the substrate.
~Non-competitive inhibitors bind elsewhere on the enzyme, changing its shape.
How can you measure the rate of an enzyme-controlled reaction?
Measuring the increase in products or decrease in reactants over time
What does a plateau in a reaction rate graph indicate?
The reaction rate has reached its maximum and no longer increases, even with further increases in the factor being measured
What is a monosaccharide?
The monomer of carbohydrates, e.g., glucose.
What is a glycosidic bond?
A bond formed between two monosaccharides via a condensation reaction.
What is a triglyceride?
A lipid consisting of one glycerol and three fatty acids.
What is a phospholipid?
A lipid with a hydrophilic phosphate head and two hydrophobic fatty acid tails.
What is a peptide bond?
A bond linking amino acids in a protein.
What is denaturation?
The loss of an enzyme’s active site shape, preventing it from functioning.
What is the active site?
The part of an enzyme where a substrate binds.
What is a substrate?
The chemical reactants that enzymes bind to are called substrates.
What is the activation energy?
The minimum energy required for a reaction to occur.
What is a nucleotide?
The monomer of nucleic acids, consisting of a phosphate, a pentose sugar, and nitrogenous base.
What is semi-conservative replication?
The production of two daughter DNA molecules from one
DNA molecule which both contain one original DNA strand and one newly synthesised strand.
What is DNA helicase?
The enzyme that unwinds and unzips DNA by breaking hydrogen bonds.
What is a phosphodiester bond?
The bond that links nucleotides together in a polynucleotide chain.
What are the monomers of nucleic acids?
Nucleotides.
What are the three components of a nucleotide?
A phosphate group, a pentose sugar, and a nitrogenous base.
What are the differences between DNA and RNA?
~DNA has deoxyribose sugar; RNA has ribose.
~DNA has thymine (T); RNA has uracil (U) instead.
~DNA is double-stranded; RNA is single-stranded.
What type of bond forms between nucleotides in a polynucleotide chain?
Phosphodiester bond.
What type of bond holds complementary base pairs together in DNA?
Hydrogen bonds.
What is complementary base pairing in DNA?
Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).
What is the process of DNA replication called?
Semi-conservative replication.
What enzyme unwinds and unzips the DNA double helix?
DNA helicase.
What enzyme joins new nucleotides together?
DNA polymerase.
Why is DNA replication called “semi-conservative”?
Each new DNA molecule consists of one original strand and one new strand.
What experiment provided evidence for semi-conservative replication?
The Meselson-Stahl experiment.
Why is water described as a polar molecule?
It has a partial negative charge on oxygen and partial positive charges on hydrogen.
What type of bonding occurs between water molecules?
Hydrogen bonding.
Name three properties of water that make it important for life.
~ High specific heat capacity (helps maintain stable temperatures).
~High latent heat of vaporization (useful for cooling via sweating).
~It is a good solvent (dissolves many substances).
How does water help with transport in organisms?
It is a solvent and has cohesion, allowing substances to move in solution and in columns (e.g., xylem in plants).
What are the components of ATP (Adenosine Triphosphate)?
Adenine, ribose sugar, and three phosphate groups.
What enzyme catalyzes the breakdown of ATP?
ATP hydrolase.
What is ATP hydrolysed into?
ADP (adenosine diphosphate) and Pi (inorganic phosphate).
What enzyme re synthesises ATP?
ATP synthase.
When does ATP synthesis occur in cells?
During respiration and photosynthesis.
Why is ATP called an “immediate energy source”?
It releases energy quickly and in small, manageable amounts.
What are inorganic ions?
Ions that do not contain carbon and are important for biological processes.
What is the role of iron (Fe²⁺) ions in the body?
They are found in haemoglobin and help transport oxygen.
What is the role of hydrogen (H⁺) ions in the body?
They determine pH levels and affect enzyme activity.
What is the role of sodium (Na⁺) ions in the body?
They help with co-transport of glucose and amino acids in the small intestine.
What is the role of phosphate (PO₄³⁻) ions in the body?
They are found in DNA, ATP, and cell membranes (phospholipids).
What is a saturation point?
The point where increasing a specific factor (like substrate concentration, light intensity, or oxygen partial pressure) no longer leads to a further increase in the rate of a process (like enzyme activity or photosynthesis).
What is latent heat?
The amount of energy needed for a substance to change state.
What is heat capacity?
The amount of energy needed to raise the temperature of a substance by a specific amount.
