Bio 126- review Flashcards
This is the science of LIFE or LIVING THINGS.
Biology
LEVEL OF ORGANIZATION IN LIVING THINGS (9 LEVELS)
ATOM, MOLECULE, MACROMOLECULE, ORGANELLE, CELL, TISSUE, ORGAN, ORGAN-SYSTEM, ORGANISM.
Seven (7) characteristics of LIVING THINGS
- React to the outside environment
- Keep their insides constant
- Can store and use energy
- Are made of ONE or MORE cells
- Contain DNA in those cells – and use it to grow
- Have evolved (come) from other living things
- Are complex compared with non-living things
Subatomic Particles
Protons
Neutrons
Electrons
Many elements are commonly found in living organisms – particularly in the human body.
Protons (+)
number given by ATOMIC NUMBER – unique to each and every chemical element!
Neutrons (no charge)
included with protons in the mass number or atomic mass (weight) and are part of atom’s central core.
Electrons (-)
not solid but negatively-charged field moving around central atomic core. Move in rings or shells – and orbitals within those shells.
electrons fill the shells up as follows:
(Inner shell) 2 : 8 : 8: 18 (fourth shell)
moving electrons back and forth from shell to shell requires:
Moving to an upper (outer) level (shell) requires more energy and falling back to a lower one releases energy
how LEDs (light-emitting diodes) work:
The energy from the supplied electricity boosts electrons up to a higher shell within the substance of the diode but they then fall back, emitting their energy as light of a particular wavelength (colour).
In the case of water (H2O)
only two of the hybrid orbitals in the oxygen atom are shared with hydrogen atoms – resulting in a V-shaped molecule for water.
Atoms combine to form molecules in a process called
bonding
Strong bonds
are formed by the sharing of electrons – as in covalent bonding (either polar or non-polar).
Weaker bonds
are formed when electrons are actually transferred from one atom to another – as in ionic bonding – in the formation of ions (Na+ Cl-).
Even weaker bonds
are formed between oppositely charged parts of molecules – as in hydrogen bonds.
The weakest bonds
are formed from tint electrostatic charges and are called van der Waal’s bonds.
WATER
Water is a MOLECULE made of 3 ATOMS – with a V-shape (review slide 14).
H – O – H H2O H+ + OH-
If we mix a substance like SALT into WATER – it will make a mixture (SALTY WATER)
The salt actually dissociates due to the ions of water being attracted to the ions of the salt
Salty Water consists of:
SALT = SOLUTE WATER = SOLVENT MIXTURE = SOLUTION
Where the SOLVENT is WATER – we call the solution an
AQUEOUS SOLUTION (AQUA is Latin = water)
Since many things mix (dissolve in) water –
WATER is called the
UNIVERSAL SOLVENT
Something that mixes with water is called
HYDROPHILIC (water-loving)
Something that does NOT mix with water is called
HYDROPHOBIC (water-hating)
Special bonds between the H+ and the OH- parts of water – called
HYDROGEN BONDS – hold them together.
This is why water EXPANDS when it freezes - becoming ICE, which is lighter and so FLOATS on water.
When water freezes – hydrogen bonds become rigid and push the two parts slightly further apart.
Water has TWO(2) important properties:
- It is a HEAT STORE – holding heat well
2. It shows COHESION – due to hydrogen bonds
a “skin” that some insects can walk on.
Cohesion gives water surface tension
Although water is chemically H2O - it normally exists in a partly ionized form
It forms two ions:
H+ the Hydrogen ion (proton)
and the other ion - OH- the Hydroxide ion.
This gives rise to ACIDS and BASES
- The Hydrogen ion is said to be ACIDIC
- whereas the Hydroxide ion is BASIC (ALKALINE)
acids contain (and give out)
H+ ions (charged particles)
bases give out
OH- ions (or accept H+ ions)
Pure water itself contains both of these ions in equal amounts
10(to the power of)-7 MOLES (of each)
If we increase the number of H+ ions
we get more ACID
If we increase the number of OH- ions
we get more BASIC – or ALKALINE
We have a scale that is used to measure the POWER of HYDROGEN called the
pH scale
the pH of pure water
7
If we INCREASE the ACID (H ions) this decreases the minus number (-7) to (-6 or –5) and so the pH value gets
SMALLER
If we increase the BASIC (ALKALINE) part – we do what to the pH value:
INCREASE
Living tissues like to stay around what pH
7 – because this is safest – called NEUTRAL.
They often contain chemicals which will resist (stop) any change in pH AWAY from pH 7, This is called
BUFFERING
The CARBON atom is so important to the basis of life on Earth – that we have a whole branch of chemistry devoted to it – called
ORGANIC CHEMISTRY.
For a molecule to be ORGANIC
it MUST have Carbon (C) and Hydrogen (H) together in it – usually covalently bonded together.
Carbon has a valency of
4 - meaning that it can bond with four other atoms - as it does in many organic molecules
But when 2 carbons are linked - each carbon can only
hold THREE other atoms
When several carbon atoms are linked - those away from the ends can only
hold TWO other atoms
Because the carbon is in the centre of a tetrahedron - its four arms may not hold the same atoms and can therefore exist as
ISOMERS
ISOMERS - MIRROR IMAGE FORMS of each other called
Enantiomers or sterio-isomers.
isomeric change can
completely alter how a molecule acts in the living cell.
Enantiomers- The left-hand form - is called the
L form
Enantiomers- The right-hand form is called the
D form
Organic molecules can exist as Enantiomers - left handed or right handed, by how they
rotate polarized light.
ALL ORGANIC compounds contain
C and H!
Examples: CH4 , C2H5OH , C6H12O6 etc.
Carbon dioxide – CO2 is
is not organic [inorganic]
In living things there are FOUR(4) groups of complex organic molecules.
- CARBOHYDRATES
- LIPIDS
- PROTEINS
- NUCLEIC ACIDS
