IB biology higher topic 1 molecules

What causes nerve impulses

The movement of Na+ into cells and k+ out of cells

What 4 key processes involve water?

Metabolism (cytoplasm is aqueous)

Growth (cell must absorb water to increase in size)

Reproduction (sperm swims to egg and foetus are supported by water in the uterus)

Response to stimuli

Are water molecules polar?

Yes

What is a polar molecule or polar covalent bond?

When electrons of a molecule are more attracted to a nucleus of one of the atoms compared to the other

What’s the result of a molecule being polar?

One atoms is slightly negative (delta negative) and the other slightly positive (delta positive)

In water are electrons more attracted to hydrogen or oxygen and what charges will they have?

Oxygen

Hydrogen will have a delta positive charge

Oxygen will have a delta negative charge

Why do water molecules stick together?

They are polar

The negative oxygen and positive hydrogen of different molecules interact and form intermolecular forces

Do you draw intermolecular bonds between molecules with solid or dotted lines?

Dotted

What is cohesion?

Water molecules sticking to eachother because they are polar

What is adhesion?

Water sticking to another substance

When does adhesion occur?

When the other substance is hydrophilic as intermolecular bonds can be made with water

What materials are often hydrophilic

Polar and charged molecules

Why do cellulose in plant cells remain saturated with water?

They are hydrophilic

How do polar molecules dissolve in water?

They form intermolecular bonds with water

Why are hydrophobic materials hydrophobic?

Water molecules are more attracted to each other than the substance

What’s an intermolecular force?

Attraction between molecules

What’s an intramolecular force?

A bond between atoms within a molecule

What’s hydrolysis?

A chemical reaction where a water molecule is added to break a chemical bond and split the substance into 2 parts

E.g Hydrolysis breaks down proteins into amino acids

What’s viscosity?

How resistant a fluid is to flow

More resistant and thicker= more viscous

Why can water make seals more susceptible to hypothermia?

Water can conduct heat quite well

What’s specific heat capacity?

How much heat/energy needed to raise the 1kg of material by 1 degree c