elements, molecules and cells Flashcards
what does the matter surrounding us consist of?
- chemical elements
what is the smallest unit of an element? what does it contain?
- atom
- contains nucleus with protons (+ charge) and neutrons (no charge)
what do electrons do? why is this important
- orbit the nucleus, which is important for atoms combining to form large elements
what is the charge of electrons equal to?
- negative charge of equal absolute value to protons
- ensures that the atom itself is neutral if electron number = proton number
how is electron movement explained?
- sophisticated
- explained in terms of atomic orbitals
what is position of electrons depicted by?
- electron clouds which are denser where it is more likely to encounter electrons and thinner when less likely
how many elements are known to make up organisms? how many make up 97% of mass of biological substance?
- 26 elements
- around six form 97%
what are the abundant elements? what is an exception?
- hydrogen, carbon, nitrogen, oxygen, phosphorus and sulphur
- hydrogen is an exception due to single proton in nucleus
what is the atomic number?
- indicative of the number of protons in the nucleus
what is atomic mass? what is it calculated in?
- mass of one of the elements atoms
- calculated in dalton (1/12th of 12C atom)
why is the atomic mass useful?
- useful in calculating how much there is of a particular element within a substance
what is an isotope?
- two atoms of the same element differ in number of neutrons but same atomic number
how is molecular weight of diverse elements calculated?
- multiply number of atoms by their respective atomic mass and add them together
where do molecules frequently reside?
- in solution of water so its useful to understand their concentration
- express concentration in moles per litre
what is Avogadro’s number?
- mole of substance always equal to atomic mass in grams of the substance
- contains 6.023 x 10^23
what is molarity?
- refers to the number of moles of the substance in a given volume
- e.g., 1 molar glucose= 1 mole of glucose in 1 litre
what can atoms form bonds with?
- atoms with the same or different elements
what does bonding of atoms require?
- at least two electrons which in most cases are contributed mutually by atoms participating
what bond do atoms create?
- when two atoms share electrons it is known as a covalent bond
what is the number of bonds an atom can form determined by?
- distribution of electrons in its atomic orbitals
- known as electronic structure
what are molecules?
- atoms that are joint by covalent bond
what is a compound?
- if molecules of a substance exist of atoms belonging to two elements
what is the difference between organic and inorganic compounds?
-organic compounds contain carbon whereas inorganic don’t e.g. water
what is the difference in charges between molecules and compounds?
- molecules are electrically neutral
- compounds carry electrical charge in the form of ions
what does the little number demonstrate and why is this useful?
- little number shows the number of atoms
- useful in understanding how much there is of a certain compound in a substance
what is the molecular formula?
- gives a complete list of all the atoms in a molecule
- representation of a molecule that uses chemical symbols to indicate the types of atoms followed by subscripts
what is the structural formula?
- details the way in which atoms are connected in compounds via knowing number of bonds that each atom can form
what is an anion?
- carry electrical charge as some atoms are more stable with more electrons than protons
what is an cation?
- carry less electrons than protons so have a positive charge
what does radical mean?
- when a molecule or ion has an unpaired electron
what is polarity?
- what degree it is polar
- affects the physical property of miscibility
what is miscibility?
- its ability to mix with other substances
what are polar molecules?
- have one negative and one positive pole
- contains N, O or S connected to C or H
- nuclei of the two elements attract bonding electrons to a similar degree
what are non- polar molecules?
- charges evenly distributed within the molecules of a compound
- only contain C + H
- nuclei of the two elements attract bonding electrons to a similar degree
do polar and non- polar molecules readily mix?
- no; polar tend to mix with polar while nonpolar tend to mix with nonpolar
what is a solution?
- when the mixing of two or more substances results in a homogeneous mixture
- mixture has same composition all over its mass
what is a solvent?
- substance present in the highest proportion
what is a solute?
- consists of dissolved substances
what is the concentration of a solute defined as?
- amount of it that is contained in a certain amount of solution/ solvent
- common unit is mole per litre of solution
what does hydrophilic mean?
- mixes readily with other polar molecules e.g., sugar
what does hydrophobic mean?
- non polar compounds do not mix readily with water e.g., oil
what is a chemical reaction?
- when substances are mixed, they interact to form new chemical entities as part of chemical reactions
e.g., conversion of glucose to water and C02 via burning
how are chemical reactions not just physical processes?
- dissolving glucose in water means that glucose remains just in a different physical form
what are reactants?
- substances consumed during a chemical reaction
what are products?
- substance produced
what are reversible reactions dependent on?
- depending on factors associated with the surroundings
- can go the other way under certain conditions
what are irreversible reactions?
- certain reactions go almost completely in one direction under certain circumstances
what two laws are adhered to in order to understand chemical reactions?
- principle of mass conservation
- principle of charge conservation
what is the principle of mass conservation?
- atoms aren’t lost/ gained they are just simply rearranged
- two sides of chemical equation must have same number of atoms
- one may have to add numbers in front of some reactants/ products
what is the principle of charge conservation?
- ions adhere to this where there is no net increase/ decrease in charge
- one may have to add one or more H+ to one of the two sides
how does a balanced chemical equation comply with the two principles?
- shows which compounds react and what products result as well as proportions of molecules/ moles
what is equilibrium constant?
- if a reaction is left to proceed far enough it reaches a state in which no further change is detected in the concentration of any participating substance
what factor acts as a determinant of chemical reactions?
- pH describes concentration of protons or (H+ ) in a solution
- no relation to electrical charge
- ease in which protons are detached/ added to chemical compounds endows them with a role in chemical processes
what is the neutral pH number?
- 7
- pure water
what is the pH of an acid? what happens to H+ ?
- below 7
- H+ increases
what is the pH of an alkaline? what happens to H+ ?
- above 7
- H+ decreases
what is the pH of most biological fluids and what is it named?
- nearly neutral
- referred to as physiological
what does it mean if a compound in an aqueous solution can exchange protons with its surroundings?
- its form isn’t foxed but depends on the pH of the solution
- such a compound binds protons when pH decreases and loses protons when pH increases
what does changes in pH affect?
- affect the form of ionizable solutes which affect interactions among them, cells and multicellular organisms
what is a buffer system?
- expression of homeostasis
- organisms are protected against lethal instability
- maintain constancy of pH
what do living organisms contain?
- compounds of high buffer capacity
what is high buffer capacity?
- amount of strong acid/ strong base that needed to be added to one litre of a solution in order to change the pH by one unit
how do high buffer capacity compounds normally come?
- in pairs of conjugate acid and base which are interconverted upon absorbing/ releasing H+
when is buffer capacity maximal?
- when pH= pK
- concentrations of conjugate acid= base
what is pHa?
- log of conjugate base concentration divided by weak acid concentration
what is a monomer?
- smaller units that are identical to each other and act as building blocks
what are polymers?
- macromolecules result from joining monomers together
what are cells?
- building blocks of living organisms
what are eukaryotic cells described as and compromised as?
- complex
- compromise 4 kingdoms; protists, fungi, plants and animals
what are prokaryotic cells compromised of?
- two large group
- bacteria and archae
what are all cells enclosed in? and why?
- plasma membrane
- separates cell contents from extracellular space
- thick and consists of lipids and proteins that carbs may attach to
describe the cytoplasm
- interior of the cell
- main component is water
describe ribosomes
- involved in the production of proteins via protein synthesis
describe lysosomes
- involved in breakdown of proteins as they digest cell waste
describe what nucleolus contain and the importance
- contain genes for rRNA
- essential for transcription and translation
what does the nucleus contain and describe it
- contains DNA which carries instructions
- densest and largest part
describe the golgi apparatus
- membrane bound compartment in eukaryotic cells that modifies proteins and packages them into vesicles
describe the mitochondria
- powerhouse as it is the centre of respiratory ATP production
- essential in lipid metabolism
describe the endoplasmic reticulum
- large membrane bound network of tubules and flat compartments called cisternae
what is the endoplasmic reticulum continuous with and what does it do?
- continuous with the outer membrane of the nuclear envelope
- involved in protein+ lipid synthesis and storage
what is chromatin?
- DNA in eukaryotic cells found in a complex with proteins and RNA
- aid in tight packaging of DNA during cell division
what does the nuclear envelope do?
- separates contents of nucleus from cytoplasm
