1.1-1.4 Flashcards
What are monomers and polymers?
Monomers- smaller/repeating molecules from which larger molecules/polymers are made
Polymers- molecule made up of many identical/similar molecules/monomers
What is a condensation reactions?
2 molecules join together forming a chemical bond, releasing a water molecule
What is a hydrolysis reaction?
2 molecules separated, breaking a chemical bond using a water molecule
What are monosaccharides (give 3 examples) ?
Monomers from which larger carbohydrates are made
Glucose, fructose, galactose
Describe the difference between the structure of alpha and beta glucose:
OH is below carbon 1 in alpha but above carbon 1 in beta
What does it mean that alpha and beta glucose are isomers?
Same molecular formula but differently arranged atoms
What are disaccharides and how are they formed?
Two monosaccharides joined together with a glycosidic bons
Formed by a condensation reaction, releasing a water molecule
List 3 common disaccharides and their monosaccharides:
Maltose - 2 x gluose
Sucrose - glucose + fructose
Lactose - glucose + galactose
What are polysaccharides and how are they formed?
Many monosaccharides joined together with glycosidic bonds
Formed by many condensation reactions, releasing water molecules
Describe the basic function and structure of starch
Function: energy store in plant cells
Structure: polysaccharide of alpha glucose
Amylose- 1,4 glycosidic bonds, unbranched
Amylopectin- 1,4 and 1,6 glycosidic bonds, branched
Explain how the structure of starch relates to its function:
Helical- compact for storage in cell
Large, insoluble polysaccharide- can’t leave cell/cross cell membrane
Insoluble in water- water potential of cell not affected
Describe the basic function of structure of glycogen
Function: energy store in animal cells
Structure: Polysaccharide made of alpha glucose
1,4 and 1,6 glycosidic bonds, branched
Explain how the structure of glycogen relate to their functions:
Branched- compact and more ends for faster hydrolysis, to release glucose for respiration to make ATP for energy release
Large, insoluble polysaccharide- can’t leave cell/cross cell membrane
Insoluble in water- water potential of cell not affected
Describe the basic function and structure of cellulose:
Function: provides strength and structural support to plant/algal cell walls
Structure: polysaccharide of beta glucose
1,4 glycosidic bond- straight unbranched chains
Chains linked in parallel by hydrogen bonds forming microfibrils
Explain how the structure of cellulose relates to its function
Every other beta glucose molecule is inverted in a long straight unbranched chain
Many hydrogen bonds link parallel strands to form microfibrils
H bonds are strong in high numbers so provides strength to plant cell walls
Describe the test for reducing sugars
Add benedicts solution to sample
Heat in a boiling water bath
Positive result= green/yellow/orange/red ppt
Describe the test for non-reducing sugars:
Do benedicts test and stays blue/negative
Heat in a boiling water bath with acid (to hydrolyse into reducing sugars)
Neutralise with alkali
Heat in a boiling water bath with Benedicts
Positive result= green/yelloe/orange/red ppt
How can you measure quantity of sugar in a solution?
Carry out Benedict’s test as above then filter and dry ppt
Find mass weight
How can you measure quantity of sugar in solution using colorimeter?
Make sugar solution of known concentrations
Heat a set volume of each sample with set volume of Benedict’s solution for same time
Use colorimeter to measure absorbance
Plot calibration curve and draw line of best fit
Repeat Benedict’s test with unknown sample and measure absorbance
Read off calibration curve to find conc. of unknown sample
Describe the biochemical test for starch
Add iodine dissolved in potassium iodide and shake/stir
Positive result = blue/black
Name two groups of lipid
Triglycerides and phospholipids
Describe the structure of a fatty acid
Variable R group - hydrocarbon chain
-COOH = carboxyl group
Describe the difference between saturated and unsaturated fatty acids:
Saturated: no C=C double bonds in hydrocarbon chain, all carbons fully saturated with hydrogen
Unsaturated: one or more C=C double bond in hydrocarbon chain (creating bend/kink)
Describe how triglycerides form:
1 glycerol molecule and 3 fatty acids
Condensation reaction
Removing 3 water molecules
Forming 3 ester bonds
Explain how the properties of triglycerides are related to their structure:
Function= energy storage
High ration of C-H bonds to carbon atoms in hydrocarbon chain- so used in respiration to release more energy than same mass of carbohydrates
Hydrophobic/non polar fatty acids so insoluble in water- no effect on water potential of cell
Describe the difference between the structure of triglycerides and phospholipids
One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
What is the function of phospholipids?
Function- form a bilayer in cell membrane, allowing diffusion of lipid-soluble or very small substances and restricting movement of water-soluble or larger substances
Describe how the properties of phospholipids relate to their structure:
Phosphate heads are hydrophilic so attracted to water so point to water either side of membrane
Fatty acid tails are hydrophobic so repelled by water so point away from water/to interior of membrane
Describe the test for lipids:
Add ethanol, shake, then add water
Positive=milky white emulsion
How many amino acids are common in all organisms and how do they vary?
20 amino acids that are common in all organisms
Differ only in their side group (R)
Describe how amino acids join together:
Condensation reaction
Removing a water molecule
Between carboxyl group of one and amine group of another
Forming a peptide bond
What are dipeptides and polypeptides?
Dipeptide- 2 amino acids join together
Polypeptide- many amino acids joined together
Describe the primary structure of a protein:
Sequence of amino acids in a polypeptide chain, joined by peptide bonds
Describe the secondary structure of a protein:
Folding of polypeptide chain e.g alpha helix or beta pleated sheets
Due to hydrogen bonding between amino acids
Between NH and C=O
Describe the tertiary structure of a protein:
3D folding of polypeptide chain
Due to interactions between amino acids of R groups
Forming H bonds, ionic bonds, and disulfide bridges
Describe the quaternary structure of a protein
More than one polypeptide chain
Formed by interactions between polypeptides
Describe the test for proteins:
Add Biuret reagent (NaOH + CuSO4)
Positive result = purple/lilac color
How do enzymes act as biological catalysts?
Each enzyme lowers activation energy of reaction it catalyses
To speed up rate of reaction
Describe the induced-fit model of enzyme action:
Substrate binds to active site of enzyme
Causing active site to change shape so it is complementary to substrate
So enzyme substrate complex forms
Causing bonds in substrate to bend/distort, lowering activation energy
Describe how models of enzyme action have changed over time
Initially lock and key model
- active site a fixed shape, complementary to one substrate
Now induced fit model
Explain the specificity of enzymes:
Specific tertiary structure determines shape of active site - dependent on sequence of amino acids
Active site is complementary to a specific substrate
Only this substrate can bind to active site, inducing fit and forming an enzyme substrate complex
Describe and explain the effect of enzyme concentration of the enzyme-controlled reactions:
As enzyme conc increases rate of reaction increases
- enzyme conc= limiting factor
- more enzymes so more available active sites
- so more enzyme substrate complexes form
At certain point, rate of reaction stops increasing/levels off
- substrate conc.= limiting factor (all substrates in use)
Describe and explain the effect of substrate conc. on the rate of enzyme controlled reactions:
As substrate conc. increases, rate of reaction increases
- substrate conc. = limiting factor as too few substrate molecules to occupy all active site
-More E-S complexes form
At a certain point rate stops increasing/levels off
- enzyme conc.=limiting factor
- as all active sites saturated/occupied
Describe and explain the effect of temp on the rate of enzyme controlled-reactions
As temp. increases up to optimum, rate increases
- more kinetic energy
- so more E-S complexes
As temp. increases above optimum, rate decreases
- enzymes denature- tertiary structure and active site changes shape
- as H/ionic bonds break
- so active site no longer complementary
- so fewer E-S complexes form
Describe and explain the effect of pH on the rate of enzyme-controlled reactions:
As pH increases/decreases above/below optimum, rate decreases
- enzymes denature- tertiary and active site change shape
- as H/ionic bonds break
- so active site no longer complementary
- so fewer E-S complexes form
Describe and explain the effect of conc. of competitive inhibitors on the rate of enzyme-controlled reactions:
As conc. increases, rate decreases
- similar shape to substrate
- competes for/binds to/blocks active site
- so substrates can’t bind and fewer E-S complexes form
Increasing substrate conc. reduces effect of inhibitors
Describe and explain the effect of conc. of non competitive inhibitors on the rate of enzyme-controlled reactions:
As conc. of non competitive inhibitor increases, rate decreases
- binds to site other than active site
- changes enzyme tertiary structure/active site shape
- so active site no longer complementary to substrate
-so substrates can’t bind and fewer E-S complexes form
Increasing substrate conc. has no effect on rate of reaction as change to active site is permanent
