Chapter 1 - Biological Molecules Flashcards
(91 cards)
1
Q
Monomer
A
Smaller units which can create larger molecules
2
Q
Polymer
A
Made from lots of monomers bonded together
3
Q
Examples of monomers
A
Glucose, amino acid and nucleotides
4
Q
Examples of polymers
A
Starch, cellulose, glycogen, protein, DNA & RNA
5
Q
Condensation reaction
A
Joining two molecules creating a chemical bond and removing water
6
Q
Hydrolysis reaction
A
Breaks a chemical bond between two molecules and involves the use of water
7
Q
What do carbohydrates contain?
A
Carbon, hydrogen and oxygen
8
Q
Name three monosaccharides?
A
Glucose, fructose and galactose
9
Q
What is sucrose made of?
A
Fructose
10
Q
What is maltose made of?
A
Glucose
11
Q
What is lactose made of?
A
Galactose
12
Q
What are the three polysaccharides?
A
Starch, cellulose and glycogen
13
Q
Where is the OH for alpha glucose?
A
Both on the bottom
14
Q
Where is the OH on beta glucose?
A
Bottom and top
15
Q
What is the bond between two monosaccharides?
A
Glycosidic bond
16
Q
How do you join two monosaccharides?
A
Condensation reaction
17
Q
Where is starch found?
A
Plants
18
Q
Where is glycogen found?
A
Animals
19
Q
What is the structure and function of starch?
A
Branched (amylopectin vs amylose) - many ends for attack for rapid release of alpha glucose
Insoluble so doesn’t affect water potential and osmosis
Large and insoluble - doesn’t diffuse out of the cell
Coiled into helixes to make it compact
Hydrolysed in to alpha glucose which is useful for respiration
Function : store of glucose
20
Q
Structure and function of glycogen
A
Insoluble, coiled
More highly branched than starch - glucose is released/ hydrolysed more rapidly (advantageous for animals respiring)
Storage polysaccharide - stored in animals fat as an energy store
21
Q
Structure and function of cellulose
A
Beta glucose chains (using hydrogen bonds which form cross links between adjacent chains) form microfibrils form into parallel groups called fibres - major component of plant cell walls due to structural strength
Straight, unbranched, no coils
Large and insoluble - won’t affect water potential
22
Q
What do all polysaccharides have in common?
A
They are large and insoluble so won’t affect the water potential
23
Q
What is a triglyceride made of?
A
1 glycerol and 3 fatty acids
24
Q
What is a phospholipid made of?
A
1 glycerol, 2 fatty acid chains and a phosphate group
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How are triglycerides formed?
3 condensation reactions between glycerol and 3 fatty acids.
1 water molecule is lost between the fatty acid and the part of the glycerol is attaching to = 3 condensation reactions and 3 waters lost.
3 ester bonds formed
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What is the bond between glycerol and fatty acids?
Ester bonds
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What are the two types of fatty acids you can get?
Saturated - the hydrocarbon chain has only single bonds between carbons
Unsaturated - the hydrocarbon chain has 1 or more double bonds between carbon atoms
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Properties of triglycerides
- Low mass so a lot can be stored without increasing the mass and preventing movement.
- Insoluble - triglycerides do not affect water potential and osmosis. This is because they are large and hydrophobic, making them insoluble in water.
- Metabolic water source due to high ratio of hydrogen to oxygen atoms. Triglycerides release water if oxidised. This is essential of animals in the desert, such as camels.
- Energy storage - high ratio of energy storing carbon hydrogen bonds compared to the number of carbon atoms a lot of energy is stored in the molecule
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How are phospholipids made?
Two condensation reactions to make 2 ester bonds.
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What structure of phospholipid make them attract water and repel fats?
Hydrophilic head due to negative charge on phosphate group.
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Are the fatty acid tails hydrophobic or hydrophilic?
Hydrophobic
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Are the heads of phospholipids hydrophobic or hydrophilic?
Hydrophilic
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How do phospholipids make bilayers?
They have too charged regions because they are polar
In water they are positioned so that the heads are exposed to the water and the tails are not.
This forms a phospholipid biosphere membrane structure which makes up the plasma membrane around cells
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What are the roles of lipids?
Cell membranes around cell and organelles (phospholipids)
Waterproofing of plants: cuticles on leaves, animals: oils from sebaceous glands of the skin
Insulation of heat: layer of fat under the skin (blubber) and electricity: insulators in the myelin sheath around nerves.
Protection: around delicate organs like kidneys and the heart
Energy (more than twice as much as carbohydrates) when lipids oxidised (also release of water)
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Structure of phospholipids related to properties
Forms of phospholipid bilayer in cell membranes.
Creates a hydrophobic barrier between inside and outside of cell.
Phosphate heads maintain the structure of the membrane.
Phosphate heads can attach to carbohydrates forming glycolipids
Useful in cell signalling (antigens on the cell surface)
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What are the monomers in proteins?
Amino acids
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What is an amino acid composed of ?
Amino group - NH2
Variable group - RH
Carboxylate group - C=O, OH
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What do two amino acids make and how are they formed?
Dipeptides by condensation reaction
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What is the bond between amino acids?
Peptide bond
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What is the primary structure of proteins?
The order of amino acids in the polypeptide chain - a polymer
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What is the secondary structure of a protein?
The sequence of amino acids causes parts of a protein molecule to bend in to alpha helix shapes or fold into beta pleated sheets
Hydrogen bonds hold the secondary structure
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What is the tertiary structure of proteins?
The further folding of the secondary structure to form a unique 3D shape. This is held in place by ionic, hydrogen and disulphide bonds
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What is the quaternary structure of proteins?
A protein made up of more than one polypeptide chain.
This includes alpha helixes and beta pleated sheets with or without a prosthetic group
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Enzymes
Tertiary structure protein which lower activation energy of the reactions they catalyse
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Why is the active site of an enzyme a specific and unique shape?
Due to the specific folding and bonding in the tertiary structure of the protein, the location of the bonds is determined by the primary structure.
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What two models explain how enzymes work?
Lock and key and induced fit model
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What is the induced fit model?
When the enzyme active site is induced, or slightly changes, shape, to mould around the substrate.
When the enzyme substrate complex occurs, due to the enzyme moulding around the substrate, it puts a strain on the bonds, and therefore lowers the activation energy
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What are the 5 factors that affect enzymes?
Temperature, pH, substrate concentration, enzyme concentration, inhibitors p
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How does temperature affect enzymes?
- if the temperature is too low, there is not enough kinetic energy for successful collisions between the enzyme and substrate.
- if the temperature is too high, the enzymes denature, the active site changes shape and enzyme-substrate complexes cannot form.
50
How does pH affect enzymes?
Too high or too low a pH will interfere with the charges in the amino acids in the active site. This can break the bonds holding the tertiary structure in place and therefore the active site changes shape.
Therefore, the enzymes denature and fewer enzyme-substrate complexes form.
Different enzymes have a different optimal pH.
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How does substrate and enzyme concentration affect enzymes?
- if there is insufficient substrate, then the reaction will be slower as there will be fewer collisions between the enzyme and substrate.
- if there is insufficient enzymes, then the enzymes active sites will become saturated with substrate and unable to work any faster.
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Two types of enzyme inhibitor
Competitive and non-competitive
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What does a competitive inhibitor do?
- same shape as the substrate
- bind to the active site
- prevents enzyme-substrate complexes
If you add more substrate, it will flood/out compete the inhibitor, knocking them out of the active site.
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What does a non-competitive inhibitor do?
- bind to the allosteric site
- causes the active site to change shape
- no enzyme-substrate complexes
The substate can no longer bind, regardless of how much substrate is added.
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What is the test for starch?
1. Add iodine
2. Positive test observation = orange -> blue/black
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Test for reducing sugars
1. Add Benedict’s reagent and heat
2. Positive test observation = solution turns from blue -> green -> yellow -> orange -> brick red (the more red, the higher the concentration of sugar)
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Test for non-reducing sugar
1. Following negative Benedict’s test, where the remains blue.
2. Add acid and boil (this acid is hydrolysis)
3. Cool the solution then add an alkali to neutralise.
4. Add Benedict’s reagent and heat.
5. Positive test observation = solution turns from blue to orange or brick red (sucrose will probably be the non-reducing sugar which is made of 2 x glucose)
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Test for proteins
1. Add biuret solution
2. Positive test observation = solution turns from blue to purple
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Test for lipids
1. Dissolve the sample in ethanol
2. Then, add distilled water
3. Positive test observation = a white emulsion is formed
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What is the lock and key model?
Enzyme= key
Active site = jagged part of key
Substrate = key hole
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What does DNA stand for?
Deoxyribonucleic acid
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What does DNA code for?
The sequence of amino acids in the primary structure of a protein, which in turn determines the final 3D structure and function of a protein
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What is the structure of DNA
Double helix
Monomer that makes DNA is called a nucleotide
It is made up of deoxyribose (a pentose sugar), a nitrogenous base and one phosphate group.
The nitrogenous base can either be guanine, cytosine, adenine, thymine
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What is the monomer that makes DNA?
Nucleotide
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What is the polymer of a nucleotide?
Polynucleotide
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How is a polynucleotide created?
Via condensation reaction between the deoxyribose sugar and the phosphate group, creating a phosphodiester bond.
The DNA polymer occurs in pairs joined by hydrogen bonds between bases. This creates a double helix.
Hydrogen bonds can only form between the complementary base pairs.
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How many hydrogen bonds are there between cytosine and guanine?
3
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How many hydrogen bonds are there between adenine and thymine?
2
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What is the structure of RNA?
RNA is a polymer of a nucleotide formed of ribose, a nitrogenous base and a phosphate group.
The nitrogenous bases in RNA are adenine, guanine, cytosine and uracil.
RNA has the base uracil instead of thymine. In comparison to the DNA polymer, the RNA polymer is a relatively short polynucleotide chain, and it is single stranded
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What is the function of RNA?
The transfer the genetic code from DNA in the nucleus to the ribosomes. Some RNA (rRNA) is also combined with proteins to create ribosomes.
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What type of replication is DNA replication?
Semi-conservative
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What must cells do before dividing?
DNA must replicate to provide a copy for the new cell.
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What does semi-conservative replication mean for DNA?
In the daughter DNA, one strand is from the parental DNA, and one strand is newly synthesised.
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What is the process of semi-conservative replication?
DNA helicase breaks the hydrogen bonds between the complementary base pairs between the two strands within a double helix.
This causes the DNA double helix to unwind.
Each of the separated parental DNA strands act as a template.
Free-floating DNA nucleotides within the nucleus are attracted to their complementary base pairs on the template strand of the parental DNA.
The adjacent nucleotides are joined together (to form phosphodiester bonds) by condensation reaction.
DNA polymerase catalyses the joining together of adjacent nucleotides.
The two sets of daughter DNA contains one strand of the parental DNA and one newly synthesised strand
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Who discovered the structure of DNA?
1953 - Watson and Crick were helped by Rosalind Franklin’s research on x-ray diffraction.
Meselon and Stahl conducted an experiment which proved DNA replication must be semi-conservative
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What does ATP stand for?
Adenine Tri Phosphate
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What do metabolic reactions in cells have a constant, steady supply of?
ATP
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What is the function of ATP?
Immediate source of energy
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When is ATP made?
Made during respiration from ADP + Pi by a condensation reaction and using the enzyme ATP synthase.
ATP can be hydrolysed into ADP + Pi using enzyme hydrolase. This releases a small amount of energy?
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What enzyme is needed to catalyse the condensation reaction of ADP + Pi
ATP synthase
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What enzyme is needed for the hydrolysis reaction of ATP?
ATP hydrolase
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What is phosphorylation?
The inorganic phosphate released during the hydrolysis of ATP can be bonded onto different compounds to make them more reactive. E.g. this happens to glucose at the start of respiration to make it more reactive.
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What is responsible for the five key properties of water?
Hydrogen bonds form between different water molecules between the oxygen and a hydrogen atom. The positive hydrogen and the negative oxygen make a dipolar molecule.
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What are the five key properties of water?
1. Metabolite - e.g. in condensation or hydrolysis
2. Solvent in reactions e.g. readily dissolves other substances like gases such as carbon dioxide and oxygen
3. High specific heat capacity - it buffers temperature e.g in aquatic environments
4. Large latent heat of vaporisation - provides cooling effect with loss of water through evaporation e.g. from our skin
5. Cohesion - strong between water molecules; this supports water columns and provides surface tension e.g in a xylem vessel in plants
85
Why is DNA a stable molecule?
The phosphodiester backbone, protect them or chemically reactive organic bases inside the double helix.
Hydrogen bonds link the organic base pairs, forming bridges between the phosphodiester upright. As there are three hydrogen bonds between cystine and guanine, the higher the proportion of C-G pairings, the more stable the DNA molecule.
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How is the DNA molecule adapted to carry out its function?
- it is a very stable structure which normally passes from generation to generation without change and rarely mutates.
- It is two separate strands are joined together with hydrogen bonds only, which allow them to separate during DNA replication and protein synthesis
- it is a large molecule so carries an extreme amount of genetic information.
- By having the base pairs within the helical cylinder, the genetic information is protected from being corrupted by outside, chemical and physical forces.
- Base pairing leads to DNA being able to replicate and transfer information as mRNA.
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Why are there two strands of DNA antiparallel?
One nucleotide runs in the 5’ to 3’ direction, lost, another nucleotides runs in the 3’ to 5’ direction.
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What did the Conservative model of DNA replication suggest?
The original DNA molecule remained intact, and that a separate daughter DNA copy was built up from new molecules of deoxyribose, phosphate, and organic bases. Of the two molecules produced, 1 will be made of an entirely new material was the other would be entirely original material.
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What was Meselsohn and Sathl’s experiment?
Play reasoned that bacteria grown on a medium containing 14N would have DNA that was lighter than bacteria growing on a medium containing 15N.
The labelled the original DNA of bacteria by growing them on a medium of 15N.
Then, they transfer bacteria to medium of 14N for a single generation to allow it to replicate once.
The mass of each new DNA molecule would depend upon which method of replication of taken place.
To separate different DNA types , the centrifuged the exact DNA in a special solution.
The lighter the DNA, the nearer the top of the centrifuge tube it collected and the heavier the DNA, the lower to the bottom of the centrifuge it collected.
They also analyse the DNA after two, than three generations.
By interpreting the results, they could determine which hypothesis was correct :
Bacteria grown in 14N - both strands light.
Bacteria grown in 15N - both strands heavy.
Bacteria transferred to 14N medium and samples removed at intervals -
1st gen = on heavy and light stand mixed giving a mixed DNA molecule
2nd gen = one light and one mixed DNA molecule
3rd gen = none
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Why are the bonds between the phosphate groups easily broken?
Unstable - have a low activation energy
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What energy required processes in cells is ATP used for?
- Metabolic processes - to build macromolecules from basic units e.g. making starch from glucose and polypeptides from amino acids.
- Movement - provides energy for muscle contraction ( provides energy for the filament of muscle to slide past one another, and therefore shorten the overall length of muscle fibre.)
- Active transport - provide energy to change the shape of carrier proteins in plasma membranes for ions to be moved against a concentration gradient.
- Secretion - needed to form the lysosomes necessary for the secretion of cell products
- Activation of molecules - the inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, thus, lowering the activation energy of enzyme catalysed reactions e.g. The addition of phosphate to glucose molecules at the start of glycolysis.
