Biological Molecules Flashcards
what are biological molecules
essential molecules: carbohydrates, proteins, lipids, and nucleic acids
what is a monomer
a building block, the part that make up substances
what is a polymer
molecules made from a large number of monomers joined together
chemical elements in carbohydrates
C H O
chemical elements in proteins
C H O N
(2 amino acids contain Sulfur)
chemical elements in lipids
C H O
what are reducing sugars in carbohydrates (include examples)
- reducing sugars are soluble
- they include monosaccharides (glucose, fructose, galactose) and disaccharides (maltose, lactose, sucrose)
what is maltose made of
two glucose monomers joined together
what is lactose made of
a glucose and a galactose joined together
what is sucrose made of
a glucose and a fructose joined together
examples of carbohydrate polymers
- starch
- glycogen
- cellulose
starch
- glucose polymer only found in plants
- acts as storage for carbohydrates
glycogen
- glucose polymer only found in animals
- acts as energy store for liver and muscle
cellulose
- makes up plant cell walls
- humans cannot digest cellulose as we do not have the enzymes to break it down
- cellulose forms dietary fibre
what are proteins
long chains of amino acids
what are enzymes made of
enzymes are made of proteins
what is a polypeptide chain
a short chain of amino acids
how many amino acids are there
20
function of proteins
- muscle building
- immune system health
- enzyme building
- gene building.
what are lipids (include examples)
fats and oils
(butter, oil, cholesterol)
what are the monomers of lipids
a triglyceride
(made of 1x glycerol and 3x fatty acids)
importance of lipids
- good insulators (keep us warm)
- good source of long-lasting energy
- can be good to store energy as well after carbohydrates are used up
- lipids make up cell membranes
- protect organs from damage
unsaturated vs saturated lipids
unsaturated = has a double bond in fatty acids
saturated = has no double bonds in fatty acids
structure of a cell membrane made of lipids
forms a phospholipid bilayer made of a hydrophobic tail (fatty acid) and hydrophilic head (glycerol and phosphate)
what happens to unused carbohydrates
- they are turned into fat
example of a bad lipid
cholesterol (it is linked to heart disease)
test for starch
- Add 2cm3 iodine solution to the food sample
- if starch is not present = yellow/orange
- if starch is present = blue/black
test for reducing sugars
- Add 2cm3 benedict’s solution to 2cm3 sample
- Place test-tube in hot water bath (90ºC) for 5 minutes until colours start to change
- If glucose is present = orange/red (depending on how much
- If glucose is not present = stays blue
test for proteins
- add 2cm3 biuret test to 2cm3 sample
- shake
- if protein is present = violet
- if protein is not present = blue
test for lipids
- 2cm3 of ethanol to 2cm3 of sample (emlusion test)
- Shake
- Add 2cm3 of distilled water
- If lipids are present = layer of fat at the top or droplets of fat (white-ish)
- If lipids not present = clear sample
what do enzymes do
act as biological catalysts by speeding up the rate of a specific reaction without being used up
example of enzymes as biological catalysts
in metabolic reactions (e.g. digestion) as they break down food into smaller products
how do enzymes function
they have an active site which is where the substrate binds and is broken down into products
how are enzymes affected by temperature
enzymes are sensitive to temperature. When above the optimum temperature, enzymes will denature causing it to change the shape of the active site so the substrate no longer fits
how are enzymes affected by pH
enzymes are sensitive to pH. when above the optimum pH, enzymes will denature, causing it to change shape of active site so the substrate no longer fits
what happens to enzymes near optimum temperature and pH
the rate of enzyme activity will increase as they get closer to their optimum temperature/pH
what happens to the enzyme if the temperature is too low
- enzymatic activity decreases in colder temperatures.
- if the temperature is too low, there will be no enzymatic activity
practical: investigating how enzyme activity can be affected by changes in pH
AIM:
investigate the effect of pH on amylase
(amylase is an enzyme that digests starch into maltose)
METHOD:
1. add a drop of iodine to each of the wells of a spotting tile
2. use a syringe to place 2cm3 of amylase into a test tube
3. use a syringe to add 1cm3 of buffer solution (pH 2) to the test tube
4. use another test-tube to add 2cm3 of starch solution to the amylase and buffer solution; start the stopwatch and mix with pippette
5. every 10 seconds, transfer a droplet of the solution to a new well of iodine solution (which should turn blue-black)
6. repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
7. record the time taken for the reaction to be completed
8. repeat the investigation with buffers at different pH (from ph3 to pH11)
RESULTS AND ANALYSIS:
* At the optimum pH, the iodine stopped turning blue-black and remained orange-brown within the shortest amount of time. This is because the enzyme is working at its fastest rate and has digested all the starch
- At higher or lower pH’s (above or below the optimum) the iodine took a longer time to stop turning blue-black or continued to turn blue-black for the entire investigation. This is because on either side of the optimum pH, the enzymes are starting to become denatured and as a result are unable to bind with the starch or break it down
practical: investigating how enzyme activity can be affected by changes in temperature
AIM:
investigate the effect of temperature on the activity of amylase (amylase is an enzyme that digests starch into maltose)
METHODS:
1. Add 5cm3 starch solution to a test tube and heat to a set temperature using beaker of water with a Bunsen burner
2. Add a drop of Iodine to each of the wells of a spotting tile
3. Use a syringe to add 2cm3 amylase to the starch solution and mix well
4. Every minute, transfer a droplet of solution to a new well of iodine solution (which should turn blue-black)
5. Repeat this transfer process until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
6. Record the time taken for the reaction to be completed
7. Repeat the investigation for a range of temperatures (from 20°C to 60°C)
RESULTS AND ANALYSIS:
* At the optimum temperature, the iodine stopped turning blue-black the fastest. This is because the enzyme is working at its fastest rate and has digested all the starch
- At colder temperatures (below optimum), the iodine took a longer time to stop turning blue-black. This is because the amylase enzyme is working slowly due to low kinetic energy and few collisions between the amylase and the starch.
- At hotter temperatures (above optimum) the iodine turned blue-black throughout the whole investigation. This is because the amylase enzyme has become denatured and so can no longer bind with the starch or break it down
