A1 Unity and Diversity of Molecules (SL)

Why is water known as the medium of life?

The first cells originated in water, and water remains the medium in which most processes of life occur.

What is cohesion, and what role does it play in vascular plants?

When 2 polar molecules form weak bonds between them.

Plants must transport water obtained in the soil up to the leaves w/out force. Tubes that water travels in are called xylem, and they work like tiny straws. Water evaporating out of leaves creates tension. The cohesion between the molecules leaves the leaves as another is pulled up.

What is adhesion, and what role does it play in vascular plants?

An attraction between molecules of different substances.

Adhesion attractive forces between the polar cellulose of cell walls also helps to continually pull water up.

What is surface tension and how is it created in water?

Surface tension is created by the stronger hydrogen bonds at the surface of water, allowing some insects to walk on it.

What is the solvent properties of water?

hint:

link to it's role as a medium for metabolism and for transport in plants and animals

A wide variety of hydrophilic molecules dissolve in water, and most enzymes catalyse reactions in aqueous solutions.

The function of some molecules in cells depend on them being hydrohpobic and insoluble.

What are all the different properties of water and air?

1. Buoyancy

2. Viscosity

3. Thermal conductivity

4. Specific heat capacity

What is buoyancy?

The upward force when an object is placed on a medium

What is specific heat capacity?

How much heat is absorbed to raise the temperature by 1 degree Celsius

How does the buoyancy of water compare to air?

Water: There is a reasonably high buoyancy force. If objects have a lower density/mass, they could float.

Air: Almost no buoyancy force, so nothing can effectively 'float' on air

How does viscosity differ in water and air?

Water: Does have some viscosity due to H bonds (eg. swimming)

Air: No viscosity so objects move with little resistance

How does thermal conductivity differ in water and air?

Water: Has high thermal conductivity, which means organisms can lose heat in water - "cold-blooded" ectothermic

Air: Lower thermal conductivity - organisms better able to sustain temp - "warm-blooded" endothermic

How does specific heat capacity differ in water and air?

Water: High heat capacity - requires lots of heat/energy to raise temp. Stable temps for aquatic organisms.

Air: Lower heat capacity - air temp is highly variable.

Name two examples of water based adaptaion animals

1. Black Throated Loon

2. The Ringed Seal

State the full name of DNA

Deoxirbonucleic acid

RNA = ribonucleic acid

Describe the structure of a DNA

Double helix made of two antiparallel strands of nucleotides with two strands linked by hydrogen bonding between complementary base pairs.

Nucleotide: made up of a pentose sugar, a nitrogen base, and a phosphate group

Compare and contrast DNA and RNA (state the similarities and differences)

Similarities:

- Both are nucleic acids, and are made up of nucleotides

- Both form strong covalent bonds between nucleotides

- Both have 3 shared bases: Adenine, Cytosince + Guanine

Differences

- (DNA) contains deoxyribose sugar

- Adenine is complementary to Thymine

- Forms a double helix

- (RNA) contains ribose sugar

- Adenine is complementary to Uracil

- Generally exists in singled stranded form

List the different types of RNA and their function

Messenger RNA: a copy of a single gene of DNA, single-stranded, used for protein synthesis at the ribosome

Transfer RNA: a small loop of RNA that delivers amino acids based on mRNA

Ribosomal RNA: ribosomes are made up of RNA + proteins

What does it mean to say that the DNA code is universal?

In all living organisms, the same base sequences code for the same amino acid. *Evidence of evolution also has important implications for genetic technology