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

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.

A dipeptide is two amino acids joined together through the removal of water

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!

• FIRST: Set up Part C – 1st! (it needs to sit for 15 minutes minimum!)

• Choose the person who hasn’t eaten something sugar in the last hour.

• READ the background info to help you with the DQ and Analysis Questions

• Quiz on lab (open notes/open lab) Thursday!