1B - More Biological Molecules Flashcards
How much of a cell is water?
About 80%
What is a metabolic reaction?
A chemical reaction that happens in a living organism to keep it alive.
What is a metabolite?
A substance involved in a metabolic reaction.
Give some of the functions of water in living organisms.
- Metabolite
- Solvent
- Temperature control
- Water transport
Explain how water is used as a metabolite in living organisms.
It is involved in many metabolic reactions, including condensation and hydrolysis reactions.
Explain how water is used as a solvent in living organisms.
Most metabolic reactions happen in solution (in the cytoplasm of cells).
Explain how water helps with temperature control in living organisms.
It has a high latent heat of vaporisation and a high specific heat capacity so it can be used to regulate temperature.
Explain how water is used for water transport in living organisms.
Water molecules are very cohesive, which allows plants to transport water around the plant easily.
Describe the structure of a water molecule.
- One atom of oxygen joined to two atoms of hydrogen by shared electrons.
- The oxygen has a slight -ve charge and the hydrogen has a slight +ve charge.
Explain why water is a polar molecule.
- Shared electrons are pulled closer to the oxygen, giving it a negative charge while the hydrogens are left with a positive charge.
- Uneven distribution of charge makes the molecule polar.
What is the symbol for a slight positive charge?
Delta +
What is the symbol for a slight negative charge?
Delta -
What bonds are formed between water molecules?
Hydrogen bonds
What is the result of water being a polar molecule?
Hydrogen bonds form between molecules due to the positive and negative charges.
Why is water an important metabolite?
- Involved in condensation and hydrolysis reactions
* e.g. Energy from ATP is released through a hydrolysis reaction
Why does water have a high latent heat of vaporisation and how is this useful in living organisms?
- Takes a lot of energy to break hydrogen bonds between water molecules
- So a lot of energy is used up when evaporating water
- This allows organisms to cool down by evaporating water
What is latent heat of vaporisation?
The amount of energy required to turn a certain liquid into gas (per unit mass).
Give an example of an important condensation reaction in living organisms.
Amino acids joining to make a polypeptide.
Give an example of an important hydrolysis reaction in living organisms.
Energy is released from ATP by hydrolysis.
Why can water buffer changes in temperature and how is this useful in living organisms?
- Hydrogen bonds between molecules can absorb a lot of energy
- So water has a high specific heat capacity
- Water stays at a stable temperature, maintaining the internal temperature of organisms and the habitats they live in.
What is specific heat capacity?
The amount of energy required to heat a substance up (per degree per unit mass).
Why is water a good solvent and how is this useful in living organisms?
• The charged parts of water molecules are attracted to ions in ionic compounds.
• The ions are totally surrounded by the water molecules - this dissolves them.
• This is all due to water’s polarity.
• This allows reactions to happen in solution.
(See diagram pg 21)
Why is there cohesion between water molecules and how is this useful in living organisms?
- Water’s polarity makes it very cohesive.
- This allows it to flow, so it is useful for transport (e.g. up the xylem).
- This also creates surface tension, which allows certain insects to walk on the surface.
Name a way in which surface tension is important in living organisms.
Pond skaters and other insects can walk on water.
Name a way in which water’s cohesion is important in living organisms.
It allows water to flow up the xylem in plants.
What type of molecule are DNA and RNA?
Nucleic acids
What does DNA stand for?
Deoxyribonucleic acid
What does RNA stand for?
Ribonucleic acid
What is the function of DNA?
• Stores genetic information.
What is the function of RNA?
- Transfers genetic information from the DNA to the ribosomes
- Makes up some ribosomes (along with proteins)
What do ribosomes do and what molecules do they work with?
They read RNA to make polypeptides (proteins).
What is translation?
The process by which ribosomes read RNA to make polypeptides (proteins).
What are nucleic acids?
- Polymers of nucleotides
* Examples: DNA and RNA
What are nucleotides made from?
- Pentose sugar (with 5 carbon atoms)
- Nitrogen-containing organic base
- Phosphate group
What is the sugar in DNA called?
Deoxyribose
What is the sugar in RNA called?
Ribose
What two things can be different in a nucleotide?
- The sugar
* The base
Describe the structure of a DNA nucleotide.
- Deoxyribose
- Phosphate group
- A, T, C or G base
What are the 4 types of possible base in a DNA nucleotide?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
Describe the structure of an RNA nucleotide.
- Ribose
- Phosphate group
- A, U, C or G base
What are the 4 types of possible base in an RNA nucleotide?
- Adenine (A)
- Uracil (U)
- Cytosine (C)
- Guanine (G)
What is the difference in possible bases in a DNA and RNA nucleotide?
In RNA, uracil replaces thymine.
What do nucleotides join to form?
Polynucleotides
Through what type of reaction do nucleotides join?
Condensation reaction
What is the bond between two nucleotides called?
Phosphodiester bond
Between which parts of nucleotides are phosphodiester bonds formed in a polynucleotide?
The phosphate group of one nucleotide and the sugar of another.
Why is a phosphodiester bond called that?
It consists of a phosphate group with two ester bonds joining it to each sugar on either side.
(See diagram pg 17)
Remember to revise the structure of a phosphodiester bond.
Diagram pg 17
What is the full name of the A base?
Adenine
What is the full name of the C base?
Cytosine