biological molecules Flashcards
List out the elements that make up proteins.
C, H, O, N, S
Explain the polar nature of water.
- O is more electronegative than H / unequal share of e- / e- spend more time orbiting around O than H
- give regions of slight positive and negative
What allows water molecules to have cohesive and adhesive properties?
Hydrogen bond
Describe the structure of amylose, including the bonds involved and the shape.
All 1,4-glycosidic bonds, straight helix
Describe the structure of amylopectin, including the bonds involved and the shape.
1,4 and 1,6 glycosidic bonds, branched
State the two structures that make up starch.
Amylose + Amylopectin
State the reaction that breaks down maltose.
Hydrolysis
What is the reaction to join monosaccharides together?
Condensation
What are the 3 types of polysaccharides that α-glucose can form?
- Amylose
- Amylopectin
- Glycogen
What are the two monosaccharides that join up to make sucrose?
Glucose + Fructose
1,6 glycosidic bonds are found on ……..
Amylopectin / Glycogen
β-glucose can only be found in ……..
Cellulose
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down
Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.
- cellulose molecules form hydrogen bonds with each other to make microfibrils
- microfibrils join to make macrofibrils
- macrofibrils join to make fibres
- fibres are insoluble and tough
What does the Benedict’s test test for?
Reducing sugar
Explain how a positive result is formed in Benedict’s test.
Reducing sugar reacts with blue Cu2+ –> to make brick-red Cu+
How can we test for starch?
Iodine solution
How can we use a colorimeter to do a quantitative Benedict’s test?
- Colorimeter measure the absorbance or transmission of light by a coloured solution
- More concentrated solution more light absorbed / less light transmitted
- Compare to data table (known concentrations vs. abs/trans value)
What are the two parts that make up a carboxylic acid?
Carboxyl group + Hydrocarbon chain
How many water molecule(s) is/are needed when breaking down a triglyceride?
3
What is another term for the condensation reaction that makes lipids?
Esterification
What is the difference in structure between saturated and unsaturated lipids?
- Saturated: all single C-C bonds in fatty acid chain
- Unsaturated: 1 or more double C=C bonds in fatty acid chain
Why do oils contain unsaturated triglycerides rather than saturated?
- Unsaturated fatty acids cause the molecule to kink/bend
- cannot pack closely together (ie. Cannot form more H bonds)
What is the difference in structure between triglyceride and phospholipid?
- phospholipid: 2 fatty acid chains + 1 phosphate group
- Triglyceride: 3 fatty acid chains
Describe the phospholipid bilayer arrangement.
- Hydrophilic heads point outwards
- Hydrophobic tails point inwards (shielded from aqueous environment)
Describe 2 similarities and 1 difference between phospholipids and sterols.
- Similarities: both have dual hydrophilic/hydrophobic characteristics / both make up the plasma membrane
- Difference: sterols are complex alcohol molecules; phospholipids are lipids
Describe the steps in identifying lipids and state the positive result.
- mix sample with ethanol
- mix solution with water and shake
- white emulsion layer formed lipid present
State the monomer of a protein.
amino acids
What are the components that make up an amino acid?
Central carbon + H atom + Amine group + Carboxyl group
Name the bond formed between two amino acids.
Peptide bond
What is the primary structure of a protein?
Amino acid sequence
What is the secondary structure of a protein?
alpha-helix + beta-pleated sheets
What is the tertiary structure of a protein?
Folding into a 3D shape
What is the quaternary structure of a protein?
Binding with other subunits
State the bond involved in the primary structure of a protein.
peptide bond
Stat the bond involved in the secondary structure of a protein.
hydrogen bond
State the bond involved in the tertiary structure of a protein.
ionic, covalent, hydrogen, hydrophobic interactions, disulphide bridges
State the bond involved in the quaternary structure of a protein.
ionic, covalent, hydrogen, hydrophobic interactions, disulphide bridges
Name the reaction that breaks down proteins.
hydrolysis
What is the solution used to test for the presence of proteins?
Biuret solution
Describe a positive result for proteins.
Using Biuret solution: Blue to purple
What is thin layer chromatography?
a technique to separate individual components of a mixture (eg. Amino acids)
Based on what principles are the amino acids separated in TLC?
- depends on interactions (H bonds) aa form with silica in the stationary phase
- depends on solubility in the mobile phase
Why should the chromatography plate be only handled by the edges?
prevent contamination with proteins on hands
What are the three types of proteins?
Globular, conjugated, fibrous
Explain why insulin is soluble in blood.
Hydrophilic amino acids are folded on the protein surface
What are prosthetic groups?
non-protein component in a conjugated protein
Give an example of a conjugated protein.
Haemoglobin/Catalase
Compare the haem groups in haemoglobin and catalase.
- Hb: Fe2+ bond reversibly with O2 in blood
- Catalase: Fe2+ allows catalase to interact with H2O2 to speed up its breakdown
How many haem groups do a haemoglobin contain?
4
Explain why keratin is relatively strong, inflexible and insoluble.
Many strong disulfide bridges
Briefly describe the structure of collagen.
3 polypeptides wound together in a long, strong rope-like structure
