Biological Molecules
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110 Terms
What is a monomer?
Smaller units from which large molecules are made.
What is a polymer?
Molecules made from many monomers joined together.
Name examples of monomers.
Monosaccharides; amino acids; nucleotides.
What reaction joins monomers together?
A condensation reaction.
What happens in a condensation reaction?
Two monomers are bonded together, water is formed as a byproduct.
What reaction takes place when biological molecules are separated?
A hydrolysis reaction.
What happens in a hydrolysis reaction?
Two monomers are separated by breaking a bond; water is used up in this reaction.
Which monomers make up a polysaccharide?
Monosaccharides.
What are the common monosaccharides?
Glucose, galactose, and fructose.
What bond forms when monosaccharides join?
A glycosidic bond.
What is a disaccharide?
A molecule made from 2 monosaccharides.
How is a disaccharide formed?
A condensation reaction between 2 monosaccharides.
What is maltose and what is it formed from?
A disaccharide formed from the condensation reaction between 2 glucose molecules.
What is sucrose and what is it formed from?
A disaccharide formed from the condensation reaction between a glucose and a fructose molecule.
What is lactose and what is it formed from?
A disaccharide formed from the condensation reaction between glucose and a galactose molecule.
What is an isomer?
Molecules where the molecular formula stays the same, but the structural formula is different.
What are the isomers of glucose?
Alpha (α) and beta (β) glucose.
What is the difference between alpha and beta glucose?
The OH group on carbon 1 of α-glucose is below the ring, on β-glucose it is above.
What is a polysaccharide?
A complex carbohydrate formed from the condensation reactions of many monosaccharides.
What is glycogen and what is it made of?
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
What is starch and what is it formed from?
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
What is cellulose?
A complex carbohydrate, a polysaccharide made from multiple β-glucose molecules.
What is the purpose of glycogen?
It is an insoluble store of glucose in animals.
What is the purpose of starch?
It is an insoluble store of glucose in plants.
What is the purpose of cellulose?
It is an insoluble structural molecule for plants, found in plant cell walls.
What are the two molecules that together make up starch?
Amylose (a helical molecule) and amylopectin (a branched molecule).
What is the structure of glycogen?
Linked at 1-4 glycosidic bonds, branched with 1-6 glycosidic bonds.
How is glycogen's structure related to its function?
It is highly branched so many ends can be simultaneously hydrolyzed by enzymes to release glucose for respiration.
What is the structure of amylopectin?
Lightly branched polymer of α-glucose molecules.
How is starch's structure related to its function?
Compact due to helical structure so lots of glucose can be stored in small spaces.
What is the basic structure of cellulose?
Straight chains of β-glucose molecules bonded with 1,4 glycosidic bonds.
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down.
How is cellulose's structure related to its function?
Cellulose molecules form hydrogen bonds with each other to make microfibrils, providing strength and support to plant cells.
What are examples of reducing sugars?
All monosaccharides (glucose, galactose, fructose) and some disaccharides (e.g., lactose and maltose).
What is an example of a non-reducing sugar?
Sucrose.
What does the Benedict's test test for?
Reducing sugar.
What is the test for reducing sugars?
Add equal volumes of the sample and Benedict's reagent, then gently heat for 5 minutes. If reducing sugar is present, the color changes from blue to red/green/orange precipitate.
What is the test for non-reducing sugars?
Add equal volume of HCl, then slowly add sodium hydrogen carbonate to neutralize and re-test with Benedict's reagent.
How is the structure of triglycerides related to their properties?
High ratio of energy storing C-H bonds, large and non-polar so insoluble in water, and high ratio of H to O atoms releases water when oxidised.
What bond is formed when a fatty acid joins to glycerol?
An ester bond.
How can we test for starch?
Iodine solution turns from yellow/orange to blue/black if starch is present.
What is the role of lipids?
Source of energy, waterproofing, insulation, and protection.
What are the 2 main groups of lipids?
Triglycerides and phospholipids.
What are the components of a triglyceride?
1 glycerol molecule and 3 fatty acids bonded with a condensation reaction.
How can the fatty acids in a lipid vary?
They could be saturated or unsaturated.
What is the difference between saturated and unsaturated fatty acids?
Saturated means single bonds between carbon atoms; unsaturated means there are some double bonds.
Why do oils contain unsaturated triglycerides rather than saturated?
Structures containing unsaturated fatty acids are more fluid.
What does NH₂ represent in an amino acid?
The amine group.
What does COOH in an amino acid represent?
Carboxyl group.
What does the 'R' represent in an amino acid?
A variable group, mainly carbon and hydrogen, may also contain other groups.
What reaction causes two amino acids to bond together?
A condensation reaction.
What bond holds two amino acids together?
Peptide bond.
What is formed when two amino acids bond by a condensation reaction?
A dipeptide.
What is formed when many amino acids bond by condensation reaction?
A polypeptide.
What is a functional protein?
A protein which has a particular role, not involved in structure.
What is the primary structure of a protein?
Amino acid sequence in a polypeptide, joined by peptide bonds.
What is the secondary structure of a protein?
Alpha-helix and beta-pleated sheets, created by hydrogen bonding.
What is an alpha-helix?
A coiling of the polypeptide chain caused by hydrogen bonding.
What is the tertiary structure of a protein?
Folding of the polypeptide chain into a 3D shape held together by ionic bonds, hydrogen bonds, and disulphide bridges.
What is the quaternary structure of a protein?
A protein with two or more polypeptide chains joined together.
What are prosthetic groups?
Non-protein components in a protein, e.g., iron-containing haem group in haemoglobin.
What is the test for proteins and the positive result?
Add equal volumes of the sample and biuret reagent; if protein is present, a color change from blue to purple occurs.
What are the two main types of proteins?
Globular and fibrous.
What is the main role of fibrous proteins?
Structural.
What makes fibrous proteins stable?
Main parallel chains bonded with cross bridges.
What are the main roles of globular proteins?
Any role where a 3D shape is required, including enzymes, channel and carrier proteins, receptors, and cell recognition sites.
Where is DNA found in a eukaryotic cell?
In the nucleus in the form of chromatin.
Where is DNA found in a prokaryotic cell?
In the cytoplasm in the form of a loop of DNA.
What does monounsaturated mean?
There is one carbon-carbon double bond.
What does polyunsaturated mean?
There are many carbon-carbon double bonds.
What is the difference in structure between triglyceride and phospholipid?
Triglyceride: 3 fatty acid chains; Phospholipid: 2 fatty acid chains + 1 phosphate group.
What does hydrophobic mean?
Water fearing; will not dissolve, repels water.
What does hydrophilic mean?
Water loving; will dissolve in water.
How do triglycerides react to water?
They are hydrophobic and repel water.
Why is a phospholipid hydrophilic and hydrophobic?
It has a hydrophilic phosphate head and a hydrophobic fatty acid tail.
Describe the emulsion test and the positive result.
Mix sample with ethanol, then mix with water and shake; a white emulsion layer formed indicates lipid presence.
What are the monomers of proteins?
Amino acids.
What is the name of a polymer of amino acids?
Polypeptide.