Biological molecules + movement of substances

Question 1

What are the chemical elements present in Carbohydrates

Answer 1

CHO - Carbon, hydrogen, oxygen

Question 2

Lipids

Answer 2

CHO - Carbon, hydrogen, oxygen

Question 3

Protein

Answer 3

CHON - Carbon, hydrogen, oxygen, nitrogen

Question 4

Structure of carbohydrates

Answer 4

Basic unit of carbs is simple sugars (glucose)

Question 5

How do you test for the presence of glucose

Answer 5

• Add Benedict’s solution to the sample solution in a test tube
• Heat in a boiling water bath for 5 minutes
• Take the test tube out of the water bath and observe the colour
• pos = brick red

Question 6

What is the positive result for glucose

Answer 6

Brick red

Question 7

How do you test for protein

Answer 7

• Add drops of Biuret solution to the food sample

Question 8

What is the positive result for protein

Answer 8

Violet

Question 9

How do you test for lipids?

Answer 9

• Mix the food sample with 4cm3 of ethanol and shake
• Allow time for the sample to dissolve in the ethanol
• Strain the ethanol solution into another test tube
• Add the ethanol solution to an equal volume of cold distilled water (4cm3)

Question 10

What is the positive result for lipids?

Answer 10

Cloudy

Question 11

What are enzymes

Answer 11

Enzymes are proteins and biological catalysts that speed up a chemical reaction.
- They do not get used up.
- They are made of amino acids

Question 12

Explain how an enzyme works

Answer 12

1. Enzymes and substrates randomly move
2. A specific enzyme and substrate collide, substrate binds into enzymes active site
3. The enzyme splits substrate and is released from the active site

Question 13

How does temperature affect enzyme function

Answer 13

• Enzymes work fastest at their optimum temp
• High temps will make the enzymes lose its shape and denature it
• Low temps cause enzymes to work slower

Question 14

• how to test temp and enzyme activity

Question 15

How does pH affect enzymes

Answer 15

• low and high pH level denatures enzyme
• if pH changes beyond enzymes optimum level (7) it denatures the enzyme

Question 16

Structure of proteins

Answer 16

• long chains of amino acid

Question 17

Structure of lipids

Answer 17

• fatty acids + glycerol

Question 18

What is diffusion

Answer 18

Diffusion is the net movement from high conc to low conc
- does not require energy (passive transport)
- molecules move randomly

Question 19

What is the difference in concentration called

Answer 19

conc gradient

Question 20

What is osmosis

Answer 20

Osmosis is the net movement of water from high water potential to low water potential through a partially permeable membrane

Question 21

What is active transport

Answer 21

Active transport is the movement of molecules against the conc gradient by using energy

Question 22

What are the 4 factors affecting the rate of movement of substances into and out of cells

Answer 22

temperature
- high temp = more kinetic energy, faster rate

surface area to volume ratio
- larger sa to vol ratio = increased rate of diffusion

distance
- shorter the distance, faster the rate of diffusion

concentration gradient
- Higher gradient = faster movement
- higher conc = more collisions against membrane

Question 23

Diffusion practical

Answer 23

1. Make up a dilution series of sugar solutions in the range of 0.2M – 1.0M
2. Cut six potato cylinders of approximately 4cm in length
3. Blot dry and find the mass of each to the nearest 0.1g
4. Place the cylinders in each concentration of sugar and leave for 40 minutes
5. Calculate the percentage change in mass.
6. Record all data in a suitable table
7. Plot a graph of the percentage change in mass against the concentration of the sugar solution

Question 24

Osmosis practical

Answer 24

1. Prepare a range of sucrose (sugar) solutions ranging from 0 Mol/dm3 (distilled water) to 1 mol/dm3
2. Set up 6 labelled test tubes with 10cm3 of each of the sucrose solutions
3. Using the knife, cork borer and ruler, cut 6 equally-sized cylinders of potato
4. Blot each one with a paper towel and weigh on the balance
5. Put 1 piece into each concentration of sucrose solution
6. After 4 hours, remove them, blot with paper towels and reweigh them