Biological Molecules Flashcards
What is a polymer?
A polymer is many monomers joined together
Describe a condensation reaction
A condensation reaction joins two molecules together with the formation of a chemical bond and involves the production of a molecule of water.
Describe a hydrolysis reaction
A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.
Define a monosaccharide. Name the three monosaccharides you need to know and give their formula.
Monosaccharides: a single carbohydrate unit which cannot be hydrolysed (broken down) to any simpler carbohydrate.
Glucose, galactose and fructose are examples – all have the formula C6H12O6
Draw the Structures of Alpha and Beta glucose
Check online to confirm (I can’t include images sorryyyy)
Describe the reaction which forms a disaccharide.
Formed when two monosaccharides join together. A condensation reaction occurs, a water molecule is removed and a glycosidic bond is formed between the two monosaccharides.
Draw the reaction which forms maltose from its monosaccharides and circle the bond formed.
Check online to confirm (I can’t include images sorryyyy)
For each of the disaccharides you need to know (there are 3), write the monosaccharides they are formed from and the chemical equation for each.
Lactose C12H22O11: made of glucose and galactose.
Sucrose C12H22O11: made of glucose and fructose
Maltose C12H22O11: 2 a-glucose molecules joined together
What is a polysaccharide?
Polysaccharides: are long chains of many monosaccharides joined together in condensation reactions with the formation of glycosidic bonds
Is starch found in animals or plants? What is it used for?
Found in plants used for storage
Is glycogen found in animals or plants? What is it used for?
Found in Animals used for storage
Is cellulose found in animals or plants? What is it used for?
Found in Plants - strength in cell walls
What monomers is starch made up of? Are they the same way up?
Made of alpha glucose
All the same way up
What monomers is glycogen made up of? Are they the same way up?
Made of alpha glucose
All the same way up
What monomers is cellulose made up of? Are they the same way up?
Made of beta glucose
Describe the structure of starch.
chains form a helical structure
Describe the structure of glycogen.
Helical with lots of branches
Describe the structure of cellulose.
Long straight chains
Are there hydrogen bonds in starch?
Yes – holding the starch in the helical shape
Are there hydrogen bonds in glycogen?
Yes – holding the glycogen in the coil
Are there hydrogen bonds in cellulose?
Yes – MANY H-bonds between the chains forming microfibrils and fibrils
Which bonds are present in starch?
1-4 glycosidic bonds and a few 1-6 glycosidic bonds.
Which bonds are present in glycogen?
1-4 glycosidic bonds are formed and lots of 1-6 glycosidic bonds
Which bonds are present in cellulose?
1-4 glycosidic bonds are formed
Describe the difference in structure between starch and cellulose
- Starch is made of alpha glucose and cellulose is made of beta glucose.
- Starch is made of 1-4 glycosidic bonds and some 1-6 glycosidic bonds. Cellulose contains only 1-4 glycosidic bonds.
- Starch glucose monomers are the same way up. -Cellulose glucose monomers are alternately inverted.
- Starch has a coiled structure whereas cellulose is made of long straight chains.
- Cellulose chains are held together by H-bonds forming microfibrils, but this doesn’t happen in starch
How is the structure of starch related to its function?
Compact storage molecule because of its helical structure
Doesn’t affect osmosis because it is insoluble
Cannot leave cells because it is a large molecule
How is the structure of glycogen related to its function?
Can be hydrolysed quickly because it has lots of branches so enzymes can act at the end of each branch
Doesn’t affect osmosis because it is insoluble
Is a compact storage molecule because it is tightly coiled
How does the structure of cellulose relate to its function?
Long straight chains are joined together by MANY hydrogen bonds forming microfibrils. This provides strength to the cell wall.
Describe the test for Reducing sugars
Heat with Benedict’s solution. An orange/ brick red precipitate shows the presence of a reducing sugar
Describe the test for non-reducing sugars
Heat with Benedict’s solution and stays blue/negative
Add HCl and heat
Add sodium hydrogen carbonate to neutralise the acid.
Add Benedict’s solution and heat.
An orange/ brick red precipitate shows the presence of a reducing sugar
Describe the test for starch
Add iodine dissolved in potassium iodide.
It turns Blue/Black if starch is present
Describe how you would use colorimetry to identify the concentration of glucose in an unknown solution
- Carry out the Benedict’s test on samples of glucose with a known concentration of glucose
- Use a colorimeter to find the % light transmission of known samples of glucose
- Draw a graph with glucose concentration on the x-axis and % light transmission on the y-axis
- Plot the points on the graph and draw a calibration curve
- Carry out the Benedict’s test on the solution of glucose with an unknown concentration
- Find the % light transmission for this sample using the colorimeter
- Find this % of light transmission on the y-axis and draw a horizontal line until you reach the calibration curve. Then draw a vertical line down and read the conc. of glucose from the x-axis
what are the 4 most abundant elements present in biological molecules and how many bonds can they have
hydrogen- 1 oxygen- 2 nitrogen- 3 carbon- 4
Describe the structure of a triglyceride
One molecule of glycerol and three molecules of fatty acid
How is a triglyceride form?
A condensation reaction between glycerol and 3 fatty acids (RCOOH), with the elimination of 3 molecules of water and the formation of 3 ester bonds.
Draw a triglyceride – circle the ester
Check online (can’t put pics sorryyy)
Describe the structure and how it relates to the properties of a triglyceride
Non-polar structure (cannot form hydrogen bonds with water molecules) 🡪 Not water soluble (so doesn’t affect water potential) and waterproof.
High proportion of C-H bonds 🡪 Good store of energy
Describe the structure of a phospholipid
It is made of 1 glycerol molecule, 1 phosphate group and 2 fatty acid chains
In terms of structure, explain the difference between a phospholipid and a triglyceride
Phospholipids have a phosphate group which replaces 1 of the fatty acids
Draw a phospholipid and label the hydrophilic and hydrophobic parts
Check online (can’t put pics sorryyy)
Describe how Phospholipids can arrange themselves to form a cell membrane. Draw and label a diagram to show this.
The plasma membrane is a phospholipid bilayer. With hydrophilic phosphate heads on the outside of the bilayer and hydrophobic fatty acid tails on the inside of the bilayer.
What is the type of bond in unsaturated lipids?
At least one double bond between carbon atoms in the fatty acid chain
What is the type of bond in saturated lipids?
ONLY single bonds between carbon atoms in the fatty acid chain (no C=C bonds)
Are unsaturated lipids saturated with hydrogen atoms?
No
Are saturated lipids saturated with hydrogen atoms?
Yes
Describe the structure of the chains in unsaturated lipids.
The chains are rigid
The chains have bends (kinks) in in them (where the double bonds occur). This means that they can’t line up so closely next to each other
Describe the structure of the chains in saturated lipids.
The chains are flexible
The chains are straight, so they can line up closely next to each other
Describe the viscosity of unsaturated fats.
Low
Describe the viscosity of saturated fats.
High
Compare the density of saturated and unsaturated lipids.
Saturated lipids are denser.
Is the MP/BP higher for saturated or unsaturated lipids?
Higher for saturated lipids
For unsaturated lipids, how do the Intermolecular forces affect the melting point?
Less i.m.f. so less energy required to overcome them
For saturated lipids, how do the Intermolecular forces affect the melting point?
More of i.m.f – lots of energy needed to overcome them
What is unsaturated lipid’s state at room temperature?
Usually liquid
What is saturated lipid’s state at room temperature?
Usually solid
Describe the test for lipids
Crush/grind the food
Add ethanol
Then add water and shake/mix
If it forms a WHITE/ MILKY EMULSION this means that lipids are present
Draw the structure of an amino acid and label the amino, carboxyl and R group
Check online (can’t put pics sorryyy)
Describe the reaction which forms a dipeptide.
A condensation reaction between amine/NH2 and carboxyl/COOH produces a dipeptide linked by a peptide bond, and releases a molecule of water.
Draw a dipeptide and circle the peptide bond.
Check online (can’t put pics sorryyy)
Describe the formation of a polypeptide
A polypeptide is formed by the condensation of MANY amino acids.
Describe primary structure.
sequence of amino acids form a polypeptide chain
Describe secondary structure.
polypeptide chain is folded to form an alpha-helix or beta-pleated sheet
Describe tertiary structure.
Further folding of the secondary structure forms a unique 3-D structure (can be globular or fibrous)
Describe quaternary structure.
Two or more different polypeptide chains folded and twisted. (Can also contain non-protein (prosthetic) groups.)
What bonds are present in primary structure?
peptide bonds between the amine group and the carboxyl group of the adjacent (neighbouring) amino acid
What bonds are present in secondary structure?
Hydrogen bonding between NH of one amino acid and C=O of another amino acid
What bonds are present in tertiary structure?
disulphide bonds, hydrogen bonds and ionic bonds between different R groups
The primary structure is fundamental in the formation of the subsequent structures. Explain why.
A different sequence of amino acids means
There are different R-groups present
So there is different hydrogen, ionic, disulphide bonds in different places
which gives the tertiary structure a different shape
which can ultimately affect the function of the protein.
Describe the Biuret Test for Proteins
The Biuret Test
Add the NaOH
copper sulphate (too)
If it turns purple there’s a protein (for you)!
Describe the structure of globular proteins
Globular proteins form a spherical shape when folding into their tertiary structure because: their non-polar hydrophobic R groups are orientated towards the centre of the protein away from the aqueous surroundings and. their polar hydrophilic R groups orientate themselves on the outside of the protein.
State the functions associated with globular proteins
- Enzymes. All enzymes are globular proteins as their round shape can be altered appropriately to fit their target sites with high specificity. Examples include digestive enzymes such as amylase, pepsin, and lipase which break down starch, protein, and fats respectively.
- Transport proteins. Due to their soluble nature, globular proteins function well as transport proteins as they can cross cell membranes. An example is haemoglobin, which transports oxygen.
- Messengers proteins. Their solubility also makes globular proteins suitable as messenger proteins, otherwise known as hormones. They regulate the body’s metabolic processes. An example would be insulin, which regulates blood sugar levels.
State what a conjugated (globular) protein is
Globular protein with a prosthetic group. An example you need to know is haemoglobin
How do you calculate Rf value?
Rf= distance moved by the solute
distance moved by the solvent
Draw a molecules of water and indicate which parts are partially charged
Look online or summary sheet
Draw 6 water molecules and show how they interact with each other
Look online or summary sheet
What does it mean to say that water is a ‘metabolite’?
It means that water is either a reactant or a product of chemical reactions in living organisms
E.g. it is required for hydrolysis reactions to take place and it is produced in condensation reactions
What is a solvent? Why can water act as a solvent? How is this beneficial in terms of chemical reactions?
A solvent is a substance that other substance can dissolve into
Water is polar, so it can form hydrogen bonds
This means that polar and ionic substances are able to dissolve in water
(due to the attraction of opposite charges allowing them to be completely surrounded by the polar water molecules).
This is useful because many metabolic reactions occur when substances are dissolved in water.
Explain why there is surface tension in water
Because water molecules are polar, so can form H-bonds with other water molecules.
This causes cohesion between water molecules, holding them together.
(this allows pond skater to walk on water without falling in!)
Explain how the properties of water help water to move up the xylem vessel of a plant
Water is polar so it can form hydrogen bonds between molecules
Therefore there is COHESION between water molecules (due to H-bonds)
There is also ADHESION between the water molecules and the wall of the xylem
Therefore the column of water molecules in the xylem does not break
What does it mean that water has a high specific heat capacity?
High specific heat capacity means that a lot of energy is required to raise the temperature of water
Why does water have a high specific heat capacity?
Because there are lots of Hydrogen bonds between water molecules and they can absorb lots of energy. OR water can gain / lose a lot of heat / energy without changing temperature;
How is water having a high specific heat capacity beneficial?
This makes it good at BUFFERING CHANGES OF TEMPERATURE.
How is water having a high specific heat capacity useful to a) aquatic organisms b) humans?
(a) it makes water a good habitat because the temperature underwater is likely to be more stable than on land (so the temperature changes are not as big)
(b) Water INSIDE organisms remains at a fairly stable temperature therefore helping to maintain a constant internal body temperature.
What does it mean when we say that ‘Water has a large latent heat of vaporization’?
This means a lot of energy is required to convert liquid water into water vapour
How is water having a large latent heat of vaporization useful to organisms living in hot countries?
It allows water to provide a cooling effect with little loss of water through evaporation.
This is because it takes a lot of energy to break the hydrogen bonds between the water molecules for evaporation to take place.
This is why organisms sweat or cover themselves in mud!
Describe the structure of a starch molecule and explain how starch is adapted for its function in cells. [6]
STRUCTURE
- a polysaccharide made from α-glucose;
- joined by condensation/removing molecule of water/glycosidic bond;
- Mainly 1 : 4 glycosidic bonds;
- Some 1-6 glycosidic bonds form branches;
HOW STRUCTURE IS ADAPTED TO FUNCTION
5. Chains are helical so they are compact;
6 starch is insoluble so it doesn’t affect osmotic pressure / water potential;
7. Starch is a large molecule so it cannot leave the cell
Describe the structure of a glycogen molecule and explain how glycogen is adapted for its function in cells. [6]
STRUCTURE
1. A polysaccharide made from α-glucose;
2. joined by condensation/removing molecule of water/glycosidic bond;
3. Mainly 1 : 4 glycosidic bonds;
4. Lots of 1-6 glycosidic bonds to form many branches;
5. Chains are coiled so they are compact;
6 glycogen is insoluble so it doesn’t affect osmotic pressure;
7 highly branched allows it to be hydrolysed to release glucose for respiration
Describe the structure of a cellulose molecule and explain how cellulose is adapted for its function in cells. [6]
STRUCTURE
- A polysaccharide made from β-glucose that forms long, straight chains;
- joined by condensation/removing molecule of water;
- Forms a 1 : 4 glycosidic bond;
- “flipping over” of alternate molecules;
- MANY hydrogen bonds link chains together forming fibrlis;
HOW STRUCTURE IS ADAPTED TO FUNCTION
- cellulose makes cell walls strong/cellulose fibres are strong;
- can resist turgor pressure/osmotic pressure/pulling forces;
- bond difficult to break;
- resists digestion/action of microorganisms/enzymes;
Describe how the structures of starch and cellulose molecules are related to their functions. [6]
Starch (max 3)
Helical/ spiral shape so compact;
Large (molecule)/insoluble so osmotically inactive;
Branched so glucose is (easily) released for respiration;
Large (molecule) so cannot leave cell/cross cell-surface membrane;
Cellulose (max 3) Long, straight/unbranched chains of β glucose; Joined by many hydrogen bonding; To form (micro/macro)fibrils; Provides rigidity/strength;
Describe the roles of iron ions, sodium ions, and phosphate ions in cells. [5]
Iron ions
1.Haemoglobin binds/associates with oxygen
OR
Haemoglobin transports/loads oxygen;
Sodium ions
2. Co-transport of glucose/amino acids (into cells);
3. (Because) sodium moved out by active transport/Na – K pump; 4. Creates a sodium concentration/diffusion gradient;
5. Affects osmosis/water potential;
Phosphate ions
6. Affects osmosis/water potential;
7. Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
9. Phosphorylates other compounds (usually) making them more reactive;
10. Hydrophilic/water soluble part of phospholipid bilayer/membrane;
