What are the risk factors for

cardiovascular disease?

Vitamin C

• connective tissue• bones• teeth• skin • internal endothelial surfaces

Arteriosclerosis

Which foods contain Vitamin C?

By the end of the lesson you should be able to:

• describe how to investigate the vitamin C content of food and drink. (D/E)

• calculate the % concentration of Vitamin C for various fruit based drinks. (B/C)

• explain why vitamin C is needed by humans with specific reference to CVD (A)

Determination of the concentration of vitamin C by using DCPIP test

Practical investigation

DCPIP =

Dichlorophenol-indophenol

Freshly squeezed

orange juice

Carton Orange Juice

Orange Squash

Lemon Juice

Blue

Juice titrates against DCPIP solutionDCPIP solution changes to pink colourDCPIP solution changes to colourless

PinkColourless

A few steps in titration

Precaution:

Drop sizeDrop size must be constant.Press the squeezing syringe gently.

During determination,the dropper must be held vertical and the fruit juice should not flow down the side of the test tube.

At least three experimental trials must be taken and the average number of drops calculated.

Question:

To decolourize the DCPIP solution

Which one gets more vitamin C in it ?Answer: juice A

15 drops of juice A is required

20 drops of juice B is required

How to work out the concentration of vitamin C in different juices?

Concentration of vitamin C in fruit juice

Volume of standard solutionVolume of fresh juice X

Concentration of standard solution

By the end of the lesson you should be able to:

• describe how to investigate the vitamin C content of food and drink. (D/E)

• calculate the % concentration of Vitamin C for various fruit based drinks. (B/C)

• explain why vitamin C is needed by humans with specific reference to CVD (A)

Homework

• You will need to write this experiment up at home.

• Use the QIS Biology department website:• qisbiology.edublogs.org

• Then email your report to me at:• strachanm@qis.org