Life at the Cellular Level 2 -water

Question 1

What polarity is a water molecule?

Answer 1

Water is a polar molecule.
This means that the charge within the molecule is not evenly distributed, giving a slight positive charge at the H end and a slight negative charge at the O end

Question 2

Why can water molecules bond with other water molecules?

Answer 2

Because they are polarized, two adjacent water molecules can form a covalent bond known as hydrogen bond

Question 3

What is a hydrogen bond?

Answer 3

hydrogen bonds occur when a hydrogen atom is attracted to an electronegative atom, such as oxygen or nitrogen, in a different molecule

Question 4

Give examples of hydrophillic molecules?

Answer 4

Sugars
Alcohols
Aldehydes
Ketones
Compounds with N-H groups
Charged particles such as ions

Question 5

How do charged particles dissolve in water?

Answer 5

for e.g. when NaCl is dissolved in water, the chloride anion attracts the partially positive pole of water and the sodium cation attracts the partially negative pole of water.

Question 6

Protein interactions and water?

Answer 6

When a substrate interacts with an enzyme, ordered water molecules are displaced and this increase in disorder favours (energetically speaking) the formation of enzyme-substrate complex.

Question 7

Give examples of hydrophobic molecules?

Answer 7

Fat soluble vitamins (A, D, E, K)
Lipids
Steroid hormones
Oxygen

Question 8

What are amphipathic molecules?

Answer 8

Amphipathic molecules contain both hydrophobic and hydrophilic parts.
Many proteins are amphipathic.

Question 9

How are proteins amphipathic?

Answer 9

The hydrophobic regions of the protein chain are on the inside and hydrophilic regions on the outside.
This allows them to be water-soluble.

Question 9

What causes sickling of red blood cell?

Answer 9

Hydrophllicic amino acid ‘Glutamic acid’ is replaced by hydrophobic ‘valine’. Hydrophobic interactions between haemoglobin molecules are promoted and causes them to clump together and form rigid fibres.

Question 10

What is haemoglobin?

Answer 10

The protein in red blood cells that carries oxygen and carbon dioxide.

Question 11

Describe some amphipathic molecules?

Answer 11

Phospholipids (key components of cell membranes) are amphipathic. The phosphate head is hydrophilic and the fatty acid tail is hydrophobic.

Question 12

What are phospholipid bilayers?

Answer 12

again hydrophobic part orientated towards centre of the “sandwich”, away from the surrounding water

Question 13

What are phospholipid micelles?

Answer 13

sphere of phospholipid with hydrophobic part orientated to the centre, away from the water

Question 14

What are liposomes?

Answer 14

If you put lots of phospholipids with water, you get a sphere with a lipid bilayer outer shell and a hollow core

Question 15

How are lipids transported in the body?

Answer 15

Lipids are transported in the blood in a chylomicron

Question 16

Describe a chylomicron?

Answer 16

A chylomicron is a like a liposome with protein embedded in the shell, and lipid stored in the core.
The phospholipid heads and outer edges of the proteins form a hydrophilic outer shell.
The hydrophilic shell is essential to allow the chylomicron to be transported in the aqueous plasma of the blood