question of the day what does a positive test for a monosaccharide look like? what does a positive...
TRANSCRIPT
Question of the Day
• What does a positive test for a monosaccharide look like?
• What does a positive test for a polysaccharide look like?
• A positive test for a disaccharide? {see the NOTE sections in your last lab,
at the bottom of pages 1 and 2}
Question of the Day:
• A monosaccharide turns Benedict’s solution from blue to orange after heating.
• A polysaccharide turns iodine from amber/ yellow to dark blue/black without heating.
• A disaccharide responds to neither Benedict’s nor iodine.
Proteins are found in many foods. They make up muscle, skin, hair, nails, and control all
the chemical reactions in your body.
Some other examples of proteins are
Receptors and pores in the cell membranes
Antibodies in the immune system, and neurotransmitters in the brain
AMINO ACIDS
• Proteins contain carbon, hydrogen, oxygen, & nitrogen. Some also contain sulfur.
• Their building block units are called “Amino Acids” There are only 20 amino acids in nature.
Many amino acids joined together make a polypeptide or protein. The average length of a protein is about 600 amino
acids long.
Just like the 26 letters of the English alphabet can combine to make an almost infinite number of words
The 20 amino acids can combine to make an almost infinite number of proteins
• Hemoglobin, found in red blood cells, with a space in the middle to carry oxygen molcules
One kind of protein: Enzymes - large, complex proteins.•Every particular chemical reaction in living things is facilitated by one particular enzyme.•“Lock and Key” mechanism based on 3-D shape•The molecule that is changed by the enzyme is called the substrate•The place where the substrate attaches to the enzyme is called he active site•Enzymes are biological catalysts; they help reactions happen and speed them up•Enzymes are re-used over and over again• Name ends in –ASE (Lactase breakds down Lactose)
Example: Lactose Intolerance
• Lactose is a sugar found in most milk products
• Lactase is an enzyme that breaks down lactose
• People who are missing lactase (can no longer produce it) can’t eat lactose unless they get artificial lactase.
Enzymes can be denatured (destroyed) by heat because the shape changes. Changing the pH can have a similar effect.
• Egg white protein is denatured by heat,
Table 4-1 Results of Tests with Known Carbohydrates
Tube Number
Carbohydrate Type
Benedicts Color After Heating
Iodine Color
1 Monosaccharide
Orange Amber/ Yellow – no change
2 Disaccharide Blue – no change Amber/Yellow - no change
3 Polysaccharide
Blue – no change Blue/ Black
Table 4-2 Results of Tests with Unknown Carbohydrates
Carbohydrate
Hypothesis (Mono-, Di-, or Poly-)
Benedict’s Color After Heating
Iodine Color
Type of Carbohydrate
(after testing)
Honey Orange Amber/ Yellow
Mono – (fructose & glucose)
Oats Blue Blue/ Black
Poly- (starch)
Table Sugar
Blue Amber/ Yellow
Di- (sucrose)
Apple Juice Orange Amber/ Yellow
Mono- (fructose)
Powdered Sugar
Blue Amber/ Yellow
Di- (sucrose)
Maple Syrup
Yellow/ green
Amber/ Yellow
Mono- (fructose)some Di- (sucrose)
Today we will be looking at an enzyme in your saliva, called salivary amylase. It breaks down starch into
glucose molecules.
Investigation 4.5
• You’ll be using the same testing methods as in lab 4.4 however you’ll do the lab in 3 Parts
1. Part A: Properties of Starch
2. Part B: Properties of Salivary Amylase (enzyme present in saliva – yes someone will be spitting, discreetly into a test tube!)
3. Part C: Properties of Starch Mixed with Salivary Amylase
• At each Part you’ll test with both Benedict’s (and heat) and iodine (no heat) and record your data.
SAFETY!
• No eating or drinking during the lab!• Iodine and Benedict’s can stain and are
both toxic!• If you are the generous saliva donor,
you will be the only one to handle, and wash your test tubes!