Topic 1: Biological molecules Flashcards
What is a condensation reaction
(3 marks)
- chemical reaction joining two molecules
- forming a chemical bond
- and releasing a water molecule
What is hydrolysis
(3 marks)
- chemical reaction separating two moelcules
- breaking a chemical bond
- using a water molecule
Name three monosaccharides
- glucose
- fructose
- galactose
Name three disaccharides
- maltose
- sucrose
- lactose
Name threee polysaccharides
- starch
- glycogen
- cellulose
Whar is the difference between alpha glucose and beta glucose
alpha glucose - OH on bottom
beta glucose - OH at top
How do you test for reducing sugars
Add benedicts to the solution, heat gently for 5 minutes, positive result changes to brick red
What is a disaccharide
Made of two monosaccharides, joined together by a glycosidic bond between the monomers
Name the components and products of the three disaccharides
Glucose + Glucose = Maltose + Water
Glucose + Fructose = Sucrose +Water
Glucose + Galactose = Lactose + Water
Explain how glycosidic bonds are formed
Formed by condensation reactions,
between the hydroxide groups (OH). One hydroxide group joins with one hydrogen to form water, and the monomers are held together by a single oxyen which becomes the glycosidic bond
Where is starch found, and what is its function
Found in plants,
Storage of glucose
Where is glycogen found and what is its function
Found in animals
Storage of glucose
Where is cellulose found and what is its function
Found in plants
To provide structural strength to the cell wall
What two polymers form starch
Amylose and amylopectin
both made from alpha glucose
Explain the structure of starch
The amylose is straight because of the 1,4 glycosidic bonds, making the starch helical.
The amylopectin can form 1,4 and 1,6 glycosidic bonds, making it branched.
Explain the strucure of glycogen
Highly branched polymer, yet still easily compactible
Where is starch and glycogen found
In animal and plants
starch - in grains in plant cells, e.g in chloroplasts
glycogen - in liver and muslce cells within the human body
How is glycogen adapted for its function
Glycogen is highly branched
Enzymes can only work on the glycosidic bond linking the outermost monomer.
By having many branches, glycoge increases the surface area for enzymes to act on, so it can easily be hydrolysed when necessary
Why is cellulose needed in the cell wall
It provides strength and supoort when the cell becomes turgid with water, preventing it from bursting
What is a fibril
When long chains of cellulose are held together by hyrogen bodning they form a fibril of cellulose. This fibril lays perpendicular to other fibrils to provide added strength.
Explain the importance of insolubility in glucose, starch, and cellulose
4 points
Insolubility means that they can be stored in cells without being dissolved.
This is important as the polysaccharides will not affect the water potential of the cell, and therefore will not cause osmosis to occur.
This allows for storage and structure.
What is food test for starch
Add iodine to the sample
positive result turns blue/black
What holds together (the reaction) the monomers bonds in lipids
Condensation reactions
What is the food test for reducing sugars
Benedicts
- Add benedicts to the liquid sample
- heat gently
- positive result turns brick red (orange brown)
What are two types of lipids
- phospholipids
- triglycerides
What do triglycerides consist of
- a glycerol
- 3 fatty acids
- ester bonds (from condensation reactions)
Where do you find saturated vs unsaturated fats
saturated - animal fats
unsaturated - plant fats
Why are unsaturated fats typically liquid at room temp
- contain double bond
- bends the shape, unable to pack together
- making them liquid
Adaptations of triglycerides related to their properties
- non-polar, insoluble in water meaningthey do not affect water potential
- large sa:v ratio, meaning they can store alot of eergy in a given volume
- high ratio of H :O, meaning they can release water for organisms in dry environments
What does a phospholipid consist of
- phosphate head
- 2 fatty acids
- glycerol
In a phospholipid, which bit is hydrophillic and which is hydrophobic
- head (phosphate) is hydrophillic
- tail is hydrophobic
How do you test for the presence of lipids
- emulsion test
- add ethanol and shake
- leave to settle
- cloudy-white if positive result
- do control with water
What three things does an amino acid consist of
- R group
- Carboxyl group (COOH)
- Amine group (NH2)
How many diff aminoa acids are there
20
What kind of bonds do amino acids form
Peptide bonds
What is the primary structure of a protein
- sequence of amino acids held together by peptide bonds
What is the secondary structure of a protein
- local motifs of alpha helices / beta pleated sheets
- held by hydrogen bonding
What is the tertiary structure of a protein
- 3D folding of the protein
- held by disulfide bridges, ionic bonds, hydrogen bonds
What is the quaternary structure of a protein
- diff polypeptides joined together by hydrogen bodning and van der waals
What are the two types of proteins
Globular, fibrous
How do you test for proteins
- biuret test
- add bieurts to the sample
- positive result gives purple colour from blue
How do enzymes work
Lower the activation energy and therefore increase rate of reaction
What type of structure are enzymes
globular proteins with tertiary structure
Describe the induced fit model
- active site is specific and complementary
- one type of substrate witll fit into the active site, forming an enzyme-substrate complex
- the structure of the enzyme is altered to fit around the substrate
State 5 things that affect rate of enzyme controlled reaction
- conc of enzyme
- conc of substrate
- temp
- pH
- any inhibitors
Explain how temp affects rate in enzyme controlled reactions
- as temp increases rate increases
- more energy more movement
- above the optimum rate, enzymes begin to denautre
- decreases rate
Explain how pH affects rate in enzyme controlled reactions
- pH affects the tertiary structure of the enzyme
- enzyme will work best at the optimum ph, and as the pH moves away from this
- rate will decrease
What consists of a nucleotide
- pentose sugar
- nitrogenous base
- phosphate
What bases can DNA have
- Adenine
- Thymine
- Cytosine
- Guanine
What bases can RNA have
- Adenine
- Uracil
- Cytosine
- Guanine
What bonds hold together nucleotides
phosphodiester bonds joined through the sugar-phosphate backbone
Why is DNA stable
- Phosphodiester backbone protects the reactive bases
- H bonds form bridges between bases
Describe semiconservative replication of DNA
- DNA helicase breaks the hydrogen bonds between bases
- One strand is used as a template to undergo base pairing between free nucleotides
- DNA polymerase rejoins the backbone by forming phosphodiester bonds.
Describe the structure of ATP
- Ribose
- Adenine
- 3 phosphates
What happens during hydrolysis of ATP
- hydrolysed to form ADP and Pi
- catalysed by ATP hydrolase
- energy released from the bonds
Why is hydrlysis of ATP good for the release of energy
- quick
- releases alot at once beacuse the bonds are very unstable
What can you do with the inorganic phosphate ion
use it to phosphorylate other things and make it reactive
Describe the properties of water
(6)
- Polar molecule, with uneven distribution of charge
- Metabolite, used in condensation reactions
- Solvent, readily diffuses gases and enzymez
- High specific heat capacity, it can absorb alot of energy without changing its state
- H-Bonds, keeps it together
- Cohesion, allows water to travel in the xylem
