Water, Carbs and Lipids

Question 1

What is the bonding in water? (2)

Answer 1

• Hydrogen bonding between molecules

- due to the slight -ve charge on the O and slight +ve on the H

Question 2

What properties does water have that are necessary in the blood? (3)

Answer 2

• A liquid
• Good transport medium due to cohesion and and adhesion (capillary action)
• Solvent so it can carry dissolved nutrients etc

Question 3

What properties does water have that make it good for aquatic environments? (4)

Answer 3

• High specific heat capacity so stable temperatures
• Ice floats and is less dense so forms an insulating layer. Aquatic life can live underneath it
• Good solvent for necessary gasses (oxygen, carbon dioxide)
• Surface tension allows for small animals to inhabit the surface of the water

Question 4

What properties does water have that are necessary for mitochondria? (3)

Answer 4

• Good transport medium
• Solvent so chemical reactions can take place in it
• High specific heat capacity so temperatures are stable and are always at best temperature for body enzymes (37ºC)

Question 5

Why does glucose need to be stored as starch? (2)

Answer 5

• Polar molecule

- Soluble

Question 6

What properties does water have that make it good for humans? (3)

Answer 6

• Coolant (for sweating) and keeping body temperatures stable
• Necessary for hydrolysis reactions
• Solvent for minerals and sugars

Question 7

What are carbohydrates?

Examples of monosaccharides and polysaccharides (3 for each)

Answer 7

• Molecules that contain only carbon, hydrogen and oxygen

Monosaccharides - glucose, fructose, ribose

Polysaccharides - Glycogen, cellulose and starch

Question 8

Difference between alpha and beta glucose?

Answer 8

OH group on carbon-1 is below on alpha and above on beta

Question 9

Condensation reaction between two alpha glucose particles? (3)

Answer 9

• Forms 1-4 glycosidic bond
• Forms Maltose
• Forms one water molecule

Question 10

How is sucrose and lactose formed?

Answer 10

• Sucrose: Glucose + Fructose - 1-4 glycosidic bonds

- Lactose: Galactose + Glucose - beta 1-4 glycosidic bonds

Question 11

How and where is starch stored? (2)

Answer 11

• Inter-cellular starch grains in organelles called plastids. - Includes chloroplasts and colourless amyloplast in potatoes

Question 12

Structure of amylose? (3)

Answer 12

• Alpha 1-4 glycosidic bonds between glucose
• Chain curves to form helix (hydrogen bonding)
• Unbranched

Question 13

Structure of amylopectin? (3)

Answer 13

• Alpha 1-6 glycosidic bonds between glucose
• Highly branched structure
• 1-4 glycosidic bonds

Question 14

Why is starch important for plants? (4)

Answer 14

• Has fewer branches so good for long term storage.
• Insoluble - Doesn’t affect water potential
• Compact so good storage molecule
• Easily hydrolysed to glucose when energy is needed

Question 15

Order glucose, fructose and galactose from most to least sweet.

Answer 15

Fructose, glucose, galactose.

Question 16

Where are sugars found in genetics?

Answer 16

Ribose - a pentose sugar. The sugar present in RNA and DNA nucleotides.

Question 17

What is the structure of cellulose for its function? (4)

Answer 17

• Used for cell wall
• Beta glucose
• 1-4 glycosidic bond
• Rope-like microfibrils

Question 18

How does cellulose rotation work?

Answer 18

Each glucose is flipped 180º and allows hydrogen bonds to form between hydroxyl groups on adjacent parallel chains. More structural ability

Question 19

What are lipids properties and functions? (6)

Answer 19

• Membrane/hormone formation
• Electrical/thermal insulation
• Cushioning
• Waterproof
• Buoyancy
• Non-polar

Question 20

What is the structure of triglycerides? (2)

Answer 20

• Glycerol bonded with 3 fatty acids (releases 3 H2O).

- Glycerol is hydrophilic while acids are hydrophobic.

Question 21

Which fats do plants contain?

Answer 21

Unsaturated triglycerides (oils) - healthier

Question 22

What are phospholipids used for as they replace the fatty acids with a polar phosphate ion (hydrophilic head)? (2)

Answer 22

• Allows it to be surfactant.

- Used in membranes as the heads react with the cytoplasm and H2O

Question 23

Saturated vs. unsaturated fats and their effects? (4)

Answer 23

• Saturated - only single bonds
• solid at room temperature
• Unsaturated - has at least one double bond
• liquid at room tempurature

Question 24

What is cholesterol? (3)

Answer 24

• A sterol.
• Stabalsies fluidity of membranes.
• Carried in lipoproteins

Question 25

What is meant by a reducing sugar?

Answer 25

A sugar that can donate electrons or reduce another molecule or chemical.

Question 26

How do you carry out a test for reducing sugars? (4)

Answer 26

1) Place the sample to be tested in a water boiling tube. If it isn’t a liquid grind it up or blend it in water
2) Add equal volume Benedict’s reagent
3) Heat the mixture gently in a boiling water bath for five minutes.
- If reducing sugars are present, it will go from blue to red

Question 27

What is the iodine test for starch? (2)

Answer 27

• A few drops of iodine dissolved in potassium iodide solution is mixed with a sample
• If starch is present, colour changes from yellow/brown to purple/black.

Question 28

How do you test for lipids?

Answer 28

Emulsion test:
Add ethanol and shake.
If white emulsion forms on top, there is lipid present.

Question 29

differenves betwwen cellulose and amylose

Answer 29

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