Lecture 4 - The chemistry of life Flashcards
What is matter
Occupies physical space and has a mass
Generally seen, smelled and felt - physical presence
Moved around by energy
What 3 states does matter exist in
Solid
Liquid
Gas
Solid
Definite shape and volume
Bones,teeth ( not much water, a lot of salts )
Liquid
Definite volume, flows to fill space
Blood plasma
Gas
No defined shape nor volume
Air we breath in and out
What is energy
Ability to put matter into motion - capacity to do Work
- Tangible, no mass, does not take up space
- Form of movement
Kinetic energy
Is that which moves things. From the constant movement of tiny bits of matter; atoms. To the movement of a bouncy ball.
e.g. bike moving up hill
Potential energy
Stored energy. Inactive energy, that has potential to do work. When the energy is
released, it becomes kinetic energy.
e.g. stopped bike on top of hill
What are the 4 forms of energy
- Chemical energy
- Electrical energy
- Mechanical energy
- Radiant energy
What is chemical energy
Stored in chemical bonds between atoms in compound. Chemical reactions rearrange atoms. Energy in our bodies is stored as useful potential energy in ATP.
What is electrical energy
Movement of charged particles through, or along cell membranes.
Nervous system - action potential
What is mechanical energy
Energy directly involved in moving matter.
What is radiant energy
Energy that travels in waves.
Law of energy
Energy can neither be created nor destroyed
Energy conversions
- With few exceptions, energy is easily converted between the different forms of energy.
- Need energy transfer to create something new = reactions
How are energy conversions inefficient
Energy is always ‘lost’ to environment - this is heat ( from bond making )
It is only ‘lost’ from that system into another.
Elements
- All matter is composed of elements
Can elements be broken down into smaller substances
No
it is the smallest building block
How many elements are there
118……
92 in nature
26 - in particle accelerator - smash elements together and see what they create
What 4 elements make up most of our body weight
C , O , H , N
What is each element composed of
An atom
Size range of atoms
Smallest < 0.1nm
Largest ~0.5nm
Physical properties of elements
Detected with sense ie colour, taste
Measurable ie boiling point
Chemical properties of elements
How elements interact with
each other
Charge and mass of proton
positive
1
Charge and mass of neutron
neutral
1
Charge and mass of electron
Negative
1/1,840
What do electrons do and what does it allow
Orbit the nucleus
Spin on outside = allows it to interact with other things in environment
- Charge difference holds it together
What makes up nucleus
Protons and neutrons
Charge of nucleus
Positive
What are atoms charge
Electrically neutral = same number of protons and electrons
i.e. 1 e- added = 1 proton also added
How do elements differ from each other
By number of protons, neutrons and electrons
What do the number of protons, neutrons and e-‘s give rise to
Variation in chemical and physical properties of the elements.
What are isotopes
Structural variants of elements
Electrons and protons remain constant in number. Different number of neutrons
What are radioisotopes
Isotopes formed from radioactivity e.g. C14
What is radioactivity
Atomic decay - releases forms of energy - mini explosion - destroys cells - radiation bad -energy source
Process of radioactivity
- Heavier variants of elements are unstable. ( because more neutrons than protons/e’s
- Atoms will spontaneously decompose into stable forms.
- Process of atomic decay is radioactivity
What is the mini explosion and what is released
Atomic decay
- alpha particles (2p + 2n) - helium
- beta particles (electron-like particles)
- gamma rays (electromagnetic energy)
What happens to energy released during radioactive decay
Transformed into different element
What is molecule of element
When atoms of same element combine
What is molecule of compound
Different kinds of atom combine
How does neutrons affect atomic decay
More neutrons = more atomic weight
Do atoms exist in free state
Not usually
They are often chemically combined with other atoms
Why form compounds or elements
To become stable
Why are atoms not in a free state
Unstable
What are mixtures
2+ components physically intermixed
- Same matter, don’t particularly interact
Where is most matter found
In mixtures
What are the 3 types of mixtures
- Solutions
- Colloids
- Suspensions
Solutions
- Tiny solute particles
- Do not settle out or scatter
Example of solution
Mineral water
Colloids
- Larger solute particles than solution
- Scatter light
- Do not settle out
Example of colloid
Jelly
Suspension
- Very large solute particles
- Settle out
- May scatter light
Example of suspension
Blood
Mixtures vs compounds
There is NO chemical bonding between components of a mixture
atomic properties do not change in a mixture
Mixtures can be separated physically by straining, evaporating, filtering
Compounds need chemical binds to be broken to separate
Mixtures can be heterogeneous or homogenous. Compounds are always homogenous.
What are chemical bonds
Energy relationships between electrons of the reacting atoms
What happens to chemical bonds
Made or broken quickly ( otherwise slow metabolism )
What are the types of covalent bonds
- Ionic
- Covalent
- Hydrogen
Where do electrons orbit
Electron shells ( from nucleus )
What does each shell represent
Different energy level
Each shell can only hold certain number of e-‘s
What type of energy do electrons have
Potential energy
Which electrons have most potential energy and why
Electrons furthest from +ve nucleus
Need more energy to position so far away from +ve field
What electrons take part in chemical bonding
Electrons in outermost energy level
What is outer shell called
Valence shell
Each element has different valence shell depending on number of electrons
What does chemical inert mean
When the outermost energy level is full Unreactive Stable Not react easily with other elements due to full outer shell Noble gases
What happens to atoms with less than 8 electrons in their 2nd shell
Tend to gain, lose or share electrons with other atoms to achieve stability = form chemical bonds
What happens to atoms with more than 8 electrons in their 2nd shell
Atoms interact and stabilize with 8 electrons in valence shell
Rule of 8
What do atoms without 8 electrons in their valence shell do
Interact to leave 8 in their valence shell and are then stable.
What are Ionic bonds
Electrons donated from one atom to another to make full outer shell = stable
What happens to electrons in ionic bonds
Lost or gained
What is electron donor
Cation
Positive
What is electron acceptor
Anion
Negative
What is formed from transfer of electrons
Ions
Lost or gained electrons
How does ionic bond form
Two oppositely charged ions attract
chemical bond
What is covalent bond
Electrons can be ‘shared’ between two atoms
How does atoms stabilise
If both atoms now have 8 electrons in valence shell
What are the types of covalent bonds
Single bonds - 2 e-‘s shared ( 1 bond )
Double bonds - 4 e-‘s shared ( 2 bonds )
Triple bonds - 6 e-‘s shared ( 3 bonds )
How is covalent bond formed
Electrons orbit both valence shells - e- clouds overlap - orbit both nuclei at same time = share
What are non - polar molecules
If the electrons are shared equally between both atoms
No charge difference = charge balanced
What doesnt allow equal share of electrons sometimes
3D shape of molecules or electron sharing ability = polar molecules - dipoles
Example of non - polar molecule
CO2 - liner and symmetrical
What are the electron sharing abilities of atoms
electronegativity
(6-7 valence shell electrons)
electro positivity
(1-2 valence shell electrons)
What are polar molecules
Unequal sharing of electrons, slight negative charge at one end, slight positive charge at other end of molecule
Example of polar molecule
Water
What is weakest bond
Hydrogen bond
When does hydrogen bond form
-H is already covalently bonded to an electronegative atom (N or O)
-Another electron hungry atom
attracts the H
-The gap is ‘bridged’
Where is hydrogen bonding common
Between dipoles
e.g. H20
What is hydrogen bond
Attraction between a H atom carrying partial +ve charge and an electronegative atom
2 molecules attracted to each other - not sharing e-‘s
What is strongest bond and why
Covalent
Electrons interact with each other = sharing electrons = neither of them want to give up electrons = tightly bound
When do chemical reactions occur
When electrons are gained or lost
Why is matter in constant motion
Due to kinetic energy
What happens in solid
vibrations ( slight movement between atoms )
What happens in liquids and gases
Dart around and can collide. This interaction can initiate a chemical reaction.
What happens during chemical reaction
Chemical bonds are altered…
- formed ( break existing bonds )
- rearranged ( same molecule )
- broken ( need energy )
What are the types of chemical reactions
- Synthesis: react molecules together
- Decomposition: bonds broken from larger to smaller molecules
- Exchange/displacement: Bonds both made and broken
What type of reactions are oxidation - reduction reactions
Decomposition reaction and an exchange reaction
Ionic reaction or covalent bonding
Basis for all food fuel breakdown reactions
Oxidation
One reactant loses electrons - electron donor
Reduction
One reactant gains electrons - electron acceptor
How is a substance oxidised
Losing a H or gaining an O
Electrons that ‘belonged’ to the substance are lost
Example of oxidation - reduction reaction
Respiration
C6H2O6 + 6O2 -> 6CO2 + 6H2O + ATP
What are chemical bonds
Stored potential energy
What are types of chemical reactions
- Exergonic
- Endergonic
In cells exergonic and endergonic tend to go hand in hand.
ie we do not want to lose energy from the system as heat, so we harness it.
Exergonic
Release energy - catabolic or oxidative - break molecule
Endergonic
Absorb energy - anabolic or reduction - need energy to form chemical bonds
What are factors that influence chemical reaction rates
Temperature
Concentration
Particle size
Catalysts (enzymes
How does temp affect rate of chemical reaction
higher temp = more energy = more chance of energy occuring
How does concentration affect reaction rate
increase conc of molecules - increase collisons - more energy transferred from one molecule to another = increase chance of reaction occuring
How does particle size affect reaction rate
increase particle size = more likely to collide = larger atom = more potential energy = increase chance of reaction occurring
How does catalysts affect reaction rate
catalysts increase reaction rate
Bring 2 molecules together, create right conditions
Organic compounds
Contain carbon
Covalently bonded
Inorganic compounds
Doesnt contain carbon
Example of inorganic compounds
Water, salts, acids, bases
Which bonding in organic compounds
Covalent bonds
Water
- high heat capacity - store lots of heat between molecules
- high heat of vaproisation - turn into liquid
- ‘Universal’ solvent – due to being a dipole - polar solvent
- essential reactant in many reactions - condensation and hydrolysis
- water is compressible - cushioning for body cells
How much water in cells
60 - 80%
What are salts
Ionic compounds
Does not include those that have H+ or OH-
What happens when salts are dissolved in water
They dissociate into component ions = bonds broken
What are ions in solution
Electrolytes
Uses of salts
- Electrolyte properties of Na and K are essential in nerve impulse transmission
and muscle contraction
-Bones are calcified with calcium salts (calcium phophates)
Acids and bases
- These are also electrolytes
- Dissociate into ions in water and conduct electricity
What are acids
- Releases H+ (hydrogen ions) = Proton donors
- When dissolved in water the release hydrogen ions (protons), and anions.
- HCL H+ + Cl-
What are bases
- Bind H+ (hydrogen ions) = Proton acceptor
- Hydroxides
- These also dissociate in water = hydroxyl ions and cations
- NaOH Na+ + OH-
- The hydroxyl is then free to bind to free protons
- H+ + OH- H2O
- This means bases can reduce the acidity of a solution by reducing hydrogen ions.
What is acidity
Free H+ ions in solution
Buffers
-Living cells are sensitive to changes in pH
-Homeostasis of acid-base balance is maintained by the kidneys (urinary system) and lungs (respiratory system)
- And by chemicals – proteins or other molecules that act as buffers
- These bind or release
H ions quickly.
- Consist of weak acid
and weak base
`Example of buffer
Bicarbonate
What does universe consists of
Matter
What is the difference between all three states
Amount of energy put into system - heat
What has smallest unit of molecule of that compound
Compounds
Different properties of whole compound compared to the individual atoms they contain
e.g. NaCl = compound = salt = :)
BUT Na = individual atom = shiny white metal = cant eat = :(
Cl = individual atom - posionous green gas = :(
Which type of chemical reactions is anabolic
Synthesis
Which type of chemical reactions is catabolic
Decomposition
