Chapter 2 - Molecules of Life Flashcards
What are the 5 bases? (for Bio)
Cytosine, Thymine, Uracil, Guanine, Adenine
What are the 3 pyrimidines?
Cytosine, Thymine, Uracil
What are the 2 purines?
Guanine, Adenine
What are the 4 bases in DNA?
Cytosine, Thymine, Guanine, Adenine
What are the 4 bases in RNA?
Cytosine, Uracil, Guanine, Adenine
What are the base pairings?
Cytosine pairs with Guanine, Thymine (or Uracil in RNA) pairs with Adenine
What are the parts of the atom?
a dense central nucleus made up of positively charge protons and neutral particles neutrons. negatively charged electrons move around the nucleus at some distance.
What is the number of protons called?
atomic number
What is the atomic mass determined by?
the number of protons and neutrons together
What is the mass of protons considered to be?
1
WHat is the mass of neutrons considered to be?
1
WHat is the mass of electrons considered to be?
negligible
What are Isotopes?
atoms of the same element that have different numbers of neutrons
What is the charge of most atoms?
neutral
What is an ion?
when the atom is charged (has lost or gained electrons)
Where do electrons occupy?
space called orbitals
What is an orbital?
where an electron is present most of the time - the exact location at any point is unpredictable
WHat is the maximum number of electrons in an orbital?
2 (most atoms have several orbitals)
WHat is the difference between electrons close to nucleus and further away from nucleus?
electrons close to the nucleus have less energy than electrons in orbitals further away
WHo developed the periodic table?
Dmitri Mendeleev
What is a horizontal row in the periodic table called?
period (first 3 rows have the same number of shells)
What is a vertical column in the periodic table called?
group (same number of electrons in outer shell)
What is a molecule?
2 or more atoms attached together that act as a single unit
What is a chemical bond?
a form of attraction between atoms that holds them together
What is a covalent bond?
when 2 atoms share electrons (1 from each orbital the orbitals merge and form 1 molecular orbital
What are electrons shared in a covalent bond from and called?
from the outermost orbitals called valance electrons
they are at the highest energy level of the atom
What is a covalent bond denoted by?
a single line
What is a double bond denoted by?
double parallel lines (when four orbitals merge to become 2)
When are molecules most stable?
when the outermost shell is full
What are the 2 types of covalent bond?
polar and non-polar
What is a polar covalent bond?
when the electrons in a bond are shared unequally. e.g. Water the Hydrogen has a slight positive charge and Oxygen a slight negative charge.
What is electronegativity?
is when electrons are shared unequally, there is a difference in the ability to attract electrons
What is a non-polar covalent bond?
when there is a nearly the same charge or the same charge between the atoms
When does an ionic bond form?
When an atom with very high electronegativity pairs with an atom of very low electronegativity the difference is so great that more electronegative atom ‘steals’ an electron. They form an ionic bond as opposites attract.
What does hydrophilic mean?
“water loving” - polar - dissolve readily in water (water is a good solvent) (sugar dissolves in water)
What does hydrophobic mean?
“water fearing” - non polar- orientate away from water (oil forms droplets to minimise water oil interference)
What are some of the processes driven by the hydrophobic effect?
folding of proteins and the formation of cell membranes
What is a hydrogen bond?
an interaction between a hydrogen atom and an electronegative atom - water has lots of hydrogen bonds as they can form between the slight electronegative atoms. They are weaker and usually represented by a dotted line
In what way do hydrogen bonds give water unique properties when it freezes?
the water molecules become bonded to 4 other water molecules = crystalline. This makes it less dense than water, enabling fish and aquatic plants to survive underneath
Hydrogen bonds also give cohesion what is cohesion?
the tendency for particles to stick together (allows for movement up plant stems)
Why is water more resistant to temperature change?
due to high number of hydrogen bonds, the bonds can break and it will still maintain its form
What is pH?
the measure of concentration of protons in a solution
What is the equation for pH?
pH = -log(H+)
What is the range of pH?
0 to 14 (0 acidic 7 neutral 14 alkaline)
What is the pH of water and most cells?
7
what makes molecules acidic?
it is a molecule that releases a proton
what makes molecules alkaline (basic)?
it is a molecule that receives a proton
What is the pH of blood?
7.4
Why are Freshwater lakes, ponds and rivers slightly acidic?
due to dissolved Carbon Dioxide
What % of the total dry mass do Carbon, Oxygen, and Hydrogen account for?
90%
What are carbon containing molecules called?
organic molecules
What is unique about CArbons covalent bonding?
They form 4 covalent bonds (4 separate orbitals with 1 electron)
What is an Isomer?
same molecular formula but different structures therefore different functions
What did Stanley Miller do?
1953 conducted experiment with water vapour, methane, ammonia, and hydrogen gas (all thought to be part of earths early atmosphere)
In a sealed container and passed a spark through (lightning maY HAVE SUPPLIED ENOUGH ENERGY FOR cHEMical reaction) a reddish material was produced which were amino acids - so possibility that the building blocks of life could be developed in early atmosphere
What are the 2 types of amino acids?
D amino acids and L amino acids
Where are L amino acids used?
most living things
WHere are D amino acids used?
only some bacteria
What are the polymers of proteins?
Polypeptides
What are the bonds in polypeptides?
peptide bonds
What is lost when a peptide bond is formed between molecules?
a water molecule
What breaks down proteins?
enzyme proteinases
What are monomers of carbohydrates called?
Monosaccharides
What are polymers of carbohydrates called?
Polysaccharides
What do we use carbohydrates for?
carbon source and energy source
What are the uses of lipids?
energy (less than carbs) act as a store of carbon, cholesterol and derivatives (steroids) endocrine system act as a messenger.
What is the difference between saturated fatty acids and unsaturated fatty acids?
unsaturated has a double carbon bond
How do the properties change if fatty acids are saturated?
they are more tightly packed together so have a higher melting point
How do the properties of fatty acids change as the chain length gets longer?
as chain gets longer the melting point increases
What is a triglyceride?
a glycerol group with 3 fatty acid tails
WHat is a phospholipid?
a phosphate group with 2 fatty acid tails
What are fatty acid tails in relation to water?
hydrophobic
WHat are phosphate heads in relation to water?
hydrophilic
What do phospholipids form when togteher?
a phospholipid bilayer which makes up the cell membrane
