1
Q
When and how did Earth form?
A
– Earth formed 4.6 billion years ago
– Cooling of the universe resulted in conversion of energy into subatomic particles
◦ Combined to form atoms
◦ Hydrogen – the first element
◦ Elements react, fuse, collide to form large masses
2
Q
What common properties do all forms of life share?
A
- Order (ordered structures)
- Reproduction
- Growth and development
- Energy processing
- Response to the environment
- Regulation
- Evolutionary adaptation
3
Q
Is a virus alive (pros and cons to it)?
A
-- Pros ◦possess genes ◦evolve by natural selection ◦Reproduce -- Cons ◦no cellular structure ◦no metabolism ◦require a host cell to make new products
4
Q
What are cells?
A
– Cells are the structural and functional units of life
◦regulate internal environment and respond to external environment
◦take in and use energy
◦complex organization
◦Arise only from growth & division of pre-existing cells (reproduce)
5
Q
Where does the unity and diversity of life come from?
A
- The unity of life is based on DNA and the common genetic code
- The diversity of life arises from differences in the DNA sequences (diversity is the hallmark of life)
6
Q
What is evolution?
A
- Evolution is the central organizing principle of biology
- Species living today are descendants of ancestral species - “descent with modification.”
- Natural selection is a mechanism for evolution
7
Q
How was natural selection inferred?
A
inferred by connecting two observations
• Individuals in a population vary in their traits, many of which are passed on from parents to offspring
• A population can produce far more offspring than the environment can support
8
Q
What is a scientific theory?
A
- Well substantiated (supported by a large and usually growing body of evidence) explanation
- Incorporates facts, laws and tested hypotheses
- End point of science developed from extensive observation and experimentation
9
Q
What is an element and a compound?
A
- An element is a substance that cannot be broken down to other substances
- A compound is a substance consisting of two or more different elements combined in a fixed ratio (NaCl is a 1:1 ration while H2O is a 2:1 ratio)
10
Q
What four elements make up 96% of living organisms?
A
◦oxygen,
◦carbon,
◦hydrogen,
◦nitrogen
11
Q
What is an atom?
A
- An atom is the smallest unit of matter that still retains the properties of an element
- made up of positively charged protons, negatively charged electrons, and electrically neutral neutrons
- Protons and neutrons have a mass of 1 dalton (or atomic mass unit amu) but electrons’ mass is too small so it is ignored
12
Q
What makes an element unique?
A
– the number of protons (atomic number - written as a subscript to the left of the symbol)
13
Q
What is the mass number?
A
- number of neutrons plus number of protons = mass number
- - written as a superscript as to the of the symbol
14
Q
What are isotopes?
A
- atoms of the same element (same protons) that have different number of neutrons
- In nature, an element occurs as a mixture of its isotope
15
Q
What are radioactive isotopes?
A
- an isotope in which the nucleus decays spontaneously, giving off particles and energy
- when a radioactive decay leads to a change in the number of protons, it transforms the atom to an atom of a different element
16
Q
How do radioactive tracers work?
A
– Living cells cannot distinguish different isotopes of an element so they use them as normal but these isotopes decay and give off energy (subatomic particles) which can be detected by the scanner
17
Q
What is a half-life?
A
- the time it takes for 50% of the parent isotope to decay
- each radioactive isotope has a characteristic half-life that is not affected by temperature, pressure or any other environmental variable
18
Q
How does radiometric dating work?
A
– scientists measure the ratio of different isotopes and calculate how many half-lives (in years) have passed since an organism was fossilized or a rock was formed
– Ex. Otzi the Iceman
◦ For every gram of Carbon in a living thing, 14 atoms of Carbon-14 decay each minute
19
Q
What is energy and potential energy?*
A
- Energy is defined as the capacity to cause change, for instance, by doing work.
- Potential energy is the energy that matter possesses because of its location or structure (for example, water in a reservoir has potential energy because of its altitude and when the gates are opened and water runs downhill, the energy can be used to do work, such as moving the blades of the turbine)
- Matter has a natural tendency to move toward the lowest possible state of potential energy and work must be done to restore the potential energy (ex. work must be done to elevate the water against gravity)
20
Q
What are the energy levels of electrons?*
A
- the electrons of an atom have potential energy due to their distance from the nucleus
- because the negatively charged electrons are attracted to the positively charged nucleus, it takes work to move an electron further away from the nucleus
- therefore, the more distant an electron is from the nucleus, the greater its potential energy (determined by its energy level or shell)
21
Q
How can an electron move from one energy level (or shell) to another?*
A
- an electron can move from one shell to another only if the energy it gains or loses is exactly equal to the difference in potential energy between the energy levels of two shells
- when an electron absorbs energy, it moves to a shell further out from the nucleus
- when an electron loses energy, it falls back to a shell closer to the nucleus, and the lost energy is usually released to the environment as heat
22
Q
Where does the chemical behaviour of an atom depend on?
A
- depend on the number of electrons in its outermost shell (valence)
- Reactivity arises from the presence of unpaired electrons in one or more orbitals of the valence shell
- an atom with a complete valence shell is unreactive
23
Q
What are electronic orbitals?*
A
- three dimensional space where an electron spends 90% of its time
- each electron shell contains electrons at a particular energy level distributed among a specific number of orbitals of distinctive shapes and orientations
- an orbital is a component of an electron shell; the first electron shell has only one spherical s orbital that can hold a maximum of 2 electrons (1s2) but the second shell has four orbitals; one spherical s orbital that can hold a maximum of 2 electrons (2s2) and three dumbbell shaped p orbitals that can each hold 2 electrons (2px, 2py, 2pz = 2p6).
24
Q
What is the strongest type of bond?
A
– The strongest kind of chemical bond is a covalent bond in which two atoms share one or more outer-shell electrons, and ionic bonds in dry, ionic compounds
25
What is electronegativity?
- - The tendency of an atom to attract (pull) shared electrons
- - the more electronegative an element is, the more strongly it pulls electrons towards itself
26
What is a non polar covalent bond?
-- electrons that are shared between two atoms of equal electronegativities (usually same elements such as H2)
27
What is a polar covalent bond?
- - When an atom is bonded to a more electronegative atom, the electrons are not equally shared
- - such bonds vary in their polarity depending on their relative electronegativity (strength)
28
How do ionic bonds happen
- - when two atoms are so unequal in their electronegativities, the more electronegative atom strips an electron completely away from its partner resulting in two oppositely charged atoms (or molecules) called ions
- - because of their opposite charges, cations and anions attract each other forming an ionic bond (the transfer of electrons does not form the bond, it is the attraction of opposite charges that does)
- - environment affects the strength of ionic bonds (if a salt, or ionic compound, is dissolved in water, the bonds are much weaker because each ion is partially shielded by its interaction with water molecules)
29
What are hydrogen bonds?
- - Hydrogen, as part of a polar covalent bond, has a partial positive charge
- - The charged regions on molecules are electrically attracted to oppositely charged regions on neighbouring molecules
- - Because the positively charged region is always a hydrogen atom, the bond is called a hydrogen bond
30
What are Van der Waals attraction?*
- - even a molecule with a nonpolar covalent bond can have positively and negatively charged regions
- - electrons are not always evenly distributed; at any instant they may accumulate by chance in one part of a molecule or another and this results in ever-changing regions of positive and negative charge that enable atoms and molecules to stick to one another
- - these are called Van der Waals attraction and are individually weak and only occur when atoms and molecules are very close together but when they occur simultaneously, they can be powerful
31
What is the difference between thermal energy and temperature?*
- - thermal energy is the total kinetic energy (energy of motion) associated with the random movement of atoms or molecules (obtained by adding up the kinetic energy of all the molecules within it)
- - temperature represents the average kinetic energy of the molecules in a body of matter, regardless of volume
- - boiling water increases the average speed of the molecules, so the temperature increases (and so does the thermal energy). However a swimming pool contains more thermal energy because of its much greater volume
32
What is heat?*
- - when two objects of different temperatures are brought together, thermal energy passes from the warmer to the cooler object until the two are the same temperature (molecules in the cooler object because of the thermal energy of the warmer object like an ice cube cooling a drink not by giving coldness but by absorbing the thermal energy of the drink)
- - this transfer of thermal energy from one body of matter to another is defined as heat (measured in joules)
33
What is specific heat?*
- - the amount of heat (transfer of thermal energy) that must be absorbed or lost for 1g of that substance to change its temperature (average kinetic energy) by 1 degree celsius.
- - can be thought of as a measure of how well a substance resists changing its temperature when it absorbs or releases heat
34
Why does water have a relatively high specific heat?*
-- This is due to its hydrogen bonding; heat must be absorbed to break hydrogen bonds and heat is released when hydrogen bonds are formed
35
Why is waters high specific heat important to life?*
- - this high specific heat allows water to moderate temperatures in coastal areas by absorbing the heat while warming up only a few degrees and during winter the cooling of water can warm up the air
- - because organisms are made up of mostly water, they are better able to resist changes in their own temperature
36
What is heat of vaporization?*
- - the quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state
- - water has a relatively high heat of vaporization which allows it to moderate Earths climate
37
What is evaporative cooling?*
- - As a liquid cools down, the hottest molecules (the molecules with the greatest kinetic energy) are most likely to leave as gas so the rest of the liquid that has been left behind cools down (because the hottest molecules have left)
- - this allows for the stability of temperatures and lakes and ponds and prevents organisms from overheating
38
Why does ice float on water?*
- - Water is one of the few substances that is less dense as a solid than a liquid because of its hydrogen bonding
- - At temperatures above 4 degrees Celsius, water behaves like any other liquid, expanding as it warms and contracting as it cools. However, at temperatures between 4 and 0 degrees celsius, water begins to freeze because the molecules are moving to slowly to break the hydrogen bonds
- - water reaches its greatest density at 4 degrees celsius and becomes 10% less dense as a solid than liquid
- - the fact that ice floats is an important factor in the suitability of life on Earth because during the winter, only the upper few inches of water freezes and not the whole body of water. This allows the water underneath to be insulted for the aquatic life there.
39
What is a solvent, solute and solution?
- - a solution is a liquid that is a completely homogenous mixture of two or more substances
- - solvent is the dissolving agent (like water) and solute is the substance that is dissolved
40
How do ionic compounds dissolve in water?
- - the oxygen regions of water molecules are negatively charged and become attracted to the cations while the hydrogen regions are positively charged so they become attracted to the anions
- - As a result, water molecules surround the individual ions, separating and shielding them (called a hydration shell)
41
How do nonionic polar molecules dissolve in water?
-- water molecules surround them and form hydrogen bonds
42
What are hydrophilic and hydrophobic substances?*
- - hydrophilic: any substance that has an affinity (attraction) to water. Substances can be hydrophilic and not dissolve in water (molecules that are so large they can't dissolve but still form hydrogen bonds)
- - hydrophobic: substances that do not have an affinity for water. Substances that are nonionic and nonpolar can actually repel water (ex. vegetable oil)
43
What was the Miller-Urey experiment?
- - Stanley Miller set up a closed system to mimic conditions thought to have existed on the early Earth
- - A flask of water simulated the primeval sea. The water was heated so that some vaporized and moved into a second, higher flask containing the “atmosphere”—a mixture of gases. Sparks were discharged in the synthetic atmosphere to mimic lightning.
- - Miller identified a variety of organic molecules that are common in organisms
- - Miller concluded that organic molecules, a first step in the origin of life, may have been synthesized abiotically on the early Earth
44
What are hydrocarbons?
-- organic molecules consisting of only carbon and hydrogen
45
What is a carbon skeleton and how do they vary?
-- A carbon skeleton is a chain of carbon atoms bonded to hydrogen (covalent bond) that can vary in:
◦ Length
◦ Branching
◦ Bond position
◦ Presence of rings
-- A functional group can change a carbon skeletons function in a characteristic way
46
What are isomers and the three different types?
- - compounds that have the same numbers of atoms of the same elements but different structures and hence different properties
1) structural isomers: differ in the covalent arrangements of their atoms. The number of possible isomers increases tremendously as carbon skeletons increase in size
2) cis-trans isomers: carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements around a double bond. If a double bond is between two carbon atoms, and each C also has two different atoms (or groups of atoms) attached to it, then two distinct cis-trans isomers are possible (cis -groups are on same plane and trans- groups are on opposite planes)
3) enantiomers: isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon, one that is attached to four different atoms or groups of atoms. The four groups can be arranged in space around the asymmetric carbon in two different ways that are mirror images
47
What do organic compound functions depend on?
-- An organic compound has unique properties that depend upon
◦ size and shape of the compound
◦ functional groups attached to it.
48
What are functional groups?
-- chemical groups attached to organic compounds affect molecular shape which contributes to function
-- however, functional groups are chemical groups that are directly involved in chemical reaction and affect the biological molecules function in a characteristic way (Often impart charge/polarity, changing the bonding capacity
-- Compounds containing functional groups are hydrophilic
-- ex. Add –OH to hydrocarbon and you have an alcohol.
◦ Electronegativity of O results in polarity
49
What are the seven most important functional groups?
- - hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl groups
- - The first six groups can be chemically reactive; all of these, except the sulfhydryl group, are also hydrophilic and thus increase the solubility of organic compounds in water. The methyl group is not reactive
BIOL1103
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