elements, molecules and cells Flashcards
(82 cards)
1
Q
what does the matter surrounding us consist of?
A
- chemical elements
2
Q
what is the smallest unit of an element? what does it contain?
A
- atom
- contains nucleus with protons (+ charge) and neutrons (no charge)
3
Q
what do electrons do? why is this important
A
- orbit the nucleus, which is important for atoms combining to form large elements
4
Q
what is the charge of electrons equal to?
A
- negative charge of equal absolute value to protons
- ensures that the atom itself is neutral if electron number = proton number
5
Q
how is electron movement explained?
A
- sophisticated
- explained in terms of atomic orbitals
6
Q
what is position of electrons depicted by?
A
- electron clouds which are denser where it is more likely to encounter electrons and thinner when less likely
7
Q
how many elements are known to make up organisms? how many make up 97% of mass of biological substance?
A
- 26 elements
- around six form 97%
8
Q
what are the abundant elements? what is an exception?
A
- hydrogen, carbon, nitrogen, oxygen, phosphorus and sulphur
- hydrogen is an exception due to single proton in nucleus
9
Q
what is the atomic number?
A
- indicative of the number of protons in the nucleus
10
Q
what is atomic mass? what is it calculated in?
A
- mass of one of the elements atoms
- calculated in dalton (1/12th of 12C atom)
11
Q
why is the atomic mass useful?
A
- useful in calculating how much there is of a particular element within a substance
12
Q
what is an isotope?
A
- two atoms of the same element differ in number of neutrons but same atomic number
13
Q
how is molecular weight of diverse elements calculated?
A
- multiply number of atoms by their respective atomic mass and add them together
14
Q
where do molecules frequently reside?
A
- in solution of water so its useful to understand their concentration
- express concentration in moles per litre
15
Q
what is Avogadro’s number?
A
- mole of substance always equal to atomic mass in grams of the substance
- contains 6.023 x 10^23
16
Q
what is molarity?
A
- 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
17
Q
what can atoms form bonds with?
A
- atoms with the same or different elements
18
Q
what does bonding of atoms require?
A
- at least two electrons which in most cases are contributed mutually by atoms participating
19
Q
what bond do atoms create?
A
- when two atoms share electrons it is known as a covalent bond
20
Q
what is the number of bonds an atom can form determined by?
A
- distribution of electrons in its atomic orbitals
- known as electronic structure
21
Q
what are molecules?
A
- atoms that are joint by covalent bond
22
Q
what is a compound?
A
- if molecules of a substance exist of atoms belonging to two elements
23
Q
what is the difference between organic and inorganic compounds?
A
-organic compounds contain carbon whereas inorganic don’t e.g. water
24
Q
what is the difference in charges between molecules and compounds?
A
- molecules are electrically neutral
- compounds carry electrical charge in the form of ions
25
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
26
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
27
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
28
what is an anion?
- carry electrical charge as some atoms are more stable with more electrons than protons
29
what is an cation?
- carry less electrons than protons so have a positive charge
30
what does radical mean?
- when a molecule or ion has an unpaired electron
31
what is polarity?
- what degree it is polar
- affects the physical property of miscibility
32
what is miscibility?
- its ability to mix with other substances
33
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
34
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
35
do polar and non- polar molecules readily mix?
- no; polar tend to mix with polar while nonpolar tend to mix with nonpolar
36
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
37
what is a solvent?
- substance present in the highest proportion
38
what is a solute?
- consists of dissolved substances
39
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
40
what does hydrophilic mean?
- mixes readily with other polar molecules e.g., sugar
41
what does hydrophobic mean?
- non polar compounds do not mix readily with water e.g., oil
42
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
43
how are chemical reactions not just physical processes?
- dissolving glucose in water means that glucose remains just in a different physical form
44
what are reactants?
- substances consumed during a chemical reaction
45
what are products?
- substance produced
46
what are reversible reactions dependent on?
- depending on factors associated with the surroundings
- can go the other way under certain conditions
47
what are irreversible reactions?
- certain reactions go almost completely in one direction under certain circumstances
48
what two laws are adhered to in order to understand chemical reactions?
- principle of mass conservation
- principle of charge conservation
49
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
50
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
51
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
52
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
53
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
54
what is the neutral pH number?
- 7
- pure water
55
what is the pH of an acid? what happens to H+ ?
- below 7
- H+ increases
56
what is the pH of an alkaline? what happens to H+ ?
- above 7
- H+ decreases
57
what is the pH of most biological fluids and what is it named?
- nearly neutral
- referred to as physiological
58
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
59
what does changes in pH affect?
- affect the form of ionizable solutes which affect interactions among them, cells and multicellular organisms
60
what is a buffer system?
- expression of homeostasis
- organisms are protected against lethal instability
- maintain constancy of pH
61
what do living organisms contain?
- compounds of high buffer capacity
62
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
63
how do high buffer capacity compounds normally come?
- in pairs of conjugate acid and base which are interconverted upon absorbing/ releasing H+
64
when is buffer capacity maximal?
- when pH= pK
- concentrations of conjugate acid= base
65
what is pHa?
- log of conjugate base concentration divided by weak acid concentration
66
what is a monomer?
- smaller units that are identical to each other and act as building blocks
67
what are polymers?
- macromolecules result from joining monomers together
68
what are cells?
- building blocks of living organisms
69
what are eukaryotic cells described as and compromised as?
- complex
- compromise 4 kingdoms; protists, fungi, plants and animals
70
what are prokaryotic cells compromised of?
- two large group
- bacteria and archae
71
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
72
describe the cytoplasm
- interior of the cell
- main component is water
73
describe ribosomes
- involved in the production of proteins via protein synthesis
74
describe lysosomes
- involved in breakdown of proteins as they digest cell waste
75
describe what nucleolus contain and the importance
- contain genes for rRNA
- essential for transcription and translation
76
what does the nucleus contain and describe it
- contains DNA which carries instructions
- densest and largest part
77
describe the golgi apparatus
- membrane bound compartment in eukaryotic cells that modifies proteins and packages them into vesicles
78
describe the mitochondria
- powerhouse as it is the centre of respiratory ATP production
- essential in lipid metabolism
79
describe the endoplasmic reticulum
- large membrane bound network of tubules and flat compartments called cisternae
80
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
81
what is chromatin?
- DNA in eukaryotic cells found in a complex with proteins and RNA
- aid in tight packaging of DNA during cell division
82
what does the nuclear envelope do?
- separates contents of nucleus from cytoplasm
