Biological Molecules Flashcards
What are monomers?
Monomers are small units which are the components of larger molecules
Give examples of monomers
- Amino acids
- Glucose
- Nucleotides
How are polymers formed?
From many monomers joining together via a condensation reaction
What are carbohydrates?
Molecules consisting of only carbon, hydrogen and oxygen
Common monosaccharides
- Glucose
- Fructose
- Galactose
Common disaccharides and how they are formed
- Maltose is a disaccharide formed by condensation of two glucose molecules.
- Sucrose is a disaccharide formed by condensation of glucose & fructose.
- Lactose is a disaccharide formed by condensation of glucose & galactose.
Name the polysaccharides and how they are formed
- Glycogen and starch which are both formed by the condensation of alpha glucose.
- Cellulose formed by the condensation of beta glucose
Why is Glycogen a good storage molecule?
- Very branched so energy can be released quickly
- Large but compact molecule maximising the amount of energy that can be stored
- It is insoluble so does not affect the water potential of the cell
How is glycogen formed
Many glucose molecules joined up by 1,4 and 1,6 glycosidic bonds
Why is starch a good storage molecule?
- Amylose is an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds. So it is coiled and very compact
- Amylopectin is branched and the glucose molecules are joined up by 1,4 and 1,6 glycosidic bonds. The side branches allow enzymes to work simultaneously to release energy
- Starch is insoluble so will not affect water potential
- Compact so a lot of energy can be stored
How is cellulose formed?
Via long, unbranched chains of beta glucose
What do cellulose chains form?
They form microfibrils that are parallel cellulose chains joined up by hydrogen bonds
Why is cellulose important?
It provides structural support for cells and maximises surface area for photosynthesis as it exerts inward pressure that stops the influx of water, keeping the cell rigid and turgid
How to test for a reducing sugar
- Add Benedict’s reagent to a sample and bring the solution to a boil
- If positive a precipitate should form, from blue to green/ yellow/ orange/ brick-red
How to test for a non reducing sugar
- Carry out the test for a reducing sugar
- Take a new sample
- Add dilute hydrochloric acid and sodium hydrogencarbonate and place in a boiling water bath
- Add Benedict’s reagent
- If positive a coloured precipitate will form
What is the test for starch?
- Iodine dissolved in potassium iodide
- If positive solution will turn from orange/brown to blue/black
What is the monomer for proteins
Amino acids
What is the structure of an amino acid?
An amino group and a carboxyl group
How are dipeptides formed?
Formed via a condensation reaction between 2 amino acids joined by a peptide bond and releasing a molecule of water.
What is the primary structure of an protein?
- Order and number of amino acids in a protein
- The initial sequence of amino acids which will therefore
determine the proteins function in the end.
What is the secondary structure of a protein?
- Weak hydrogen bonds form between the amino acids in the chain to either coil into an alpha helix or fold into a beta pleated sheet
What is the tertiary structure of a protein?
- The further coiling or folding of the amino acid chain
- More hydrogen bonds (easily broken)
- Ionic bonds between the carboxyl and amino group not involved in the peptide bonds (can break due to changes in pH)
- Disulfide bridges in cysteine (strong, not easily broken)
What is the quaternary structure of a protein?
- Made of several polypeptide chains put together
- The final 3D structure eg, haemoglobin
Example of globular proteins
Enzymes - they are compact
Example of fibrous proteins
Keratin are long so can fibres
Describe the test for proteins
- Add sodium hydroxide to the sample
- Then add copper sulfate
- If positive solution will turn from blue to purple
What are enzymes?
Proteins that increase the rate of reactions by lowering the activation energy by providing an alternative pathway without being used up
Factors that affect the rate of enzyme controlled reactions
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
- Concentration of competitive inhibitors
- Concentration of non competitive inhibitors
How does temperature affect the rate of enzyme controlled reactions?
- Rate increases until it reaches the optimum temp
- Above optimum, the enzymes become denatured as the hydrogen bonds in the tertiary structure break, so rate of reaction decreases
How does pH affect the rate of enzyme controlled reactions?
- It changes the ionic and hydrogen bonds in the tertiary structure changing the shape of the active site
How does enzyme concentration affect the rate of enzyme controlled reactions?
- Rate increases as the enzyme concentration increases as there are more active sites to form enzyme-substrate complexes
- If will level off when substrate becomes the limiting factor
How does substrate concentration affect the rate of enzyme controlled reactions?
- As substrate concentration increases, rate of reaction increases as more enzyme-substrate complexes are formed
- Eventually it will level off as enzyme concentration becomes the limiting factor
How does the concentration of competitive inhibitors affect the rate of enzyme controlled reactions?
- As the concentration of competitive inhibitors increases, the rate decreases
- As substrates cannot bind
How does the concentration of non competitive inhibitors affect the rate of enzyme controlled reactions?
- As concentration on noncompetitive reversible inhibitors increases, rate of reaction decreases
- As it changes the shape of the active site
What does a DNA nucleotide contain?
- Deoxyribose sugar
- Phosphate group
- Nitrogenous bases; adenine, cytosine, guanine or thymine
What does a RNA nucleotide contain?
- Ribose sugar
- Phosphate group
- Nitrogenous bases; adenine, cytosine, guanine or uracil.
What bond is found between nucleotides?
Phosphodiester bonds
Where is the phosphodiester bond formed?
Between the deoxyribose of one nucleotide and the phosphate group of another
The steps of semi-conservative replication
- DNA helicase breaks the hydrogen bonds between the complementary base pairs to leave to strands
- One strand acts as a template for free DNA nucloetides to line up against
- The nucleotides are joined together by phosphodiester bonds and hydrogen bonds form between the complementary base pairs
How is energy released from ATP?
Through hydrolysis of ATP forming ADP and an inorganic phosphate. Catalysed by ATP hydrolase
Where is the energy released from in ATP?
Stored as chemical energy in the phosphate bonds, it is released through the breaking of the bond catalysed by ATP hydrolase.
Why is ATP a good source of energy?
- It can be broken down easily due to the phosphate bonds being unstable, so quick energy release
- It is a small, soluble molecule so it can be transported around the cell
- It stores and releases small, manageable amounts of energy, so no energy is lost through heat
- It can be remade quickly
- Makes other molecules more reactive due to its phosphate groups
- Provides an immediate supply of energy
What can the inorganic phosphate be used for?
To phosphorylate other compounds making them more reactive
How is ATP produced?
Through the condensation of ADP and inorganic phosphate catalysed by ATP synthase forming ATP during photosynthesis and respiration.
Properties of ATP
- ATP is an immediate source of energy as it can be broken down in a single step to release a manageable quantity of energy.
- ATP is not stored in large quantities as it can easily be reformed from ADP in seconds.
- ATP is used in a variety of different ways, such as metabolic processes, movement, active transport, secretion and activation of molecules.
Function of hydrogen ions
Determines the pH of substances such as blood – the higher the concentration of hydrogen ions the lower the pH
Function of iron ions
Component of haemoglobin which is an oxygen carrying molecule in red blood cells
Function of sodium ions
Involved in co-transport of glucose and amino acids
Function of phosphate ions
- Component of DNA, RNA and ATP
- Allow nucleotides to join up
