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Biology > II: Chemical Context of Life > Flashcards

II: Chemical Context of Life Flashcards

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1
Q

What are organisms composed of?

A

They are composed of matter, which is anything that takes up space and has mass

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2
Q

What is matter?

A

matter is made up of chemical elements, substances that cannot be broken down to other substances by chemical reactions

-> 118 elements which 94 exist in nature

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3
Q

What is a compound?

A

a substance consisting of two or more elements in a fixed ratio
- characteristics differ from its elements

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4
Q

What are the elements that make up 96% of living matter?

A

Oxygen 65% > carbon 18%> hydrogen 9% > nitrogen 3.3%

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5
Q

Which element is the most common element in the human body?

A

hydrogen

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6
Q

What are the elements that make up the rest 3.7% of the human body?

A
  • calcium
  • phosphorus
  • potassium
  • sulfur
  • sodium
  • chlorine
  • magnesium
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7
Q

What are trace elements?

A

= Spurenelemente
the elements required by an organism in only minute quantities
-> make up less than 0.01% of human body weight

eg iron, iodine, selenium

some are required by all forms of life (eg Fe), others are required only by certain species

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8
Q

What is the evolution of tolerance to toxic elements?

A

Some species can become adapted to environments containing toxic elements
- eg some plant communities are adapted to serpentine

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9
Q

What are the properties of an element?

A

properties depend on the structure of its atoms

  • each element consists of a unique atom that is different from those of other elements
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10
Q

what is an atom?

A

the smallest unit of matter that still retains the properties of an element

  • subatomic particles
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11
Q

what do the different subatomic particles determine?

A
  • protons determine the element
  • neutrons determine the isotope
  • electrons determine the chemical behaviour
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12
Q

What are the mass of the subatomic particles?

A
  • neutrons and protons are measured in daltons (=atomic mass unit)
    -> 1.7 x 10^-24 = 1 dalton
  • electrons are considered negligible
    -> 1/2000 dalton
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13
Q

what is the atomic number?

A
  • the number of proton in the nucleus
  • unique to each element
  • written as subscript
  • equal to number of electrons
  • determines the elements properties
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14
Q

What is the mass number?

A
  • same as atomic mass
  • protons + neutrons
  • approximation of atomic mass in dalton
  • written as superscript
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15
Q

What are isotopes?

A

two atoms of an element that differ in the number of neutrons in the nucleus, but have the same number of protons

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16
Q

What are radioactive isotopes?

A

spontaneously give off particles and energy

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17
Q

What are some applications in biological research for radioactive isotopes?

A
  • dating fossils
  • tracing atoms through metabolic processes
  • diagnosing medical disorders
  • used with sophisticated imaging instruments
  • used in PET scanners -> monitor metabolism of cancers
18
Q

What is energy?

A

the capacity to cause change

19
Q

What is potential energy?

A

the energy that matter possesses due to its location or structure
- the further away the electrons are from the nucleus, the more their potential energy

  • matter has a natural tendency to move toward the lowest possible state of potential energy
20
Q

What are electron shells?

A

the energy level of an electron associated with the average distance from the atomic nucleus

  • electrons are found in different electron shells
  • 1st shell has the lowest potential energy
21
Q

How can changes in electron potential energy occur?

A

an electron can change the shell by absorbing / losing an amount of energy equal to the difference in potential energy between its position in the old shell and that in the new shell

  • when e absorbs energy, it moves a shell higher
  • when e loses energy, the energy lost is usually released to the environment as heat
22
Q

What are valence electrons?

A

= outermost electrons

  • determine the chemical behaviour of an atom
  • involved in chemical bonds between atoms
  • elements with a full valence shell are chemically inert
23
Q

What are electron orbitals?

A
  • 3D space where an electron is found 90% of the time
  • each shell consists of a specific number of orbitals -> no more than 2 electrons can occupy a single orbital
  • atoms interact in a way that completes their valence shells and become stable
24
Q

What are Covalent bonds?

A

The sharing of a pair of valence electrons by two atoms

  • the shared electrons count as part of each atom’s valence shell
  • intra- and intermolecular
25
Q

What types of covalent bonds exist?

A

a molecule consists of two or more atoms held together by covalent bonds

  • single bond: sharing of one e pair
  • double bond: sharing of two e pairs
26
Q

What is a compound?

A

a combination of two or more different elements held together by covalent bonds

27
Q

What is the bonding capacity called?

A

atom’s valence

28
Q

What is electronegativity?

A

an atom’s attraction for the electron in a covalent bond

  • the more electronegative, the more strongly it pulls shared electrons toward itself
29
Q

What is a non-polar covalent bond?

A

when the atoms have similar electronegativities, they share the electrons equally

30
Q

What is polar covalent bond?

A

when the atoms have differing electronegativities and share the electrons unequally
-> causes partial positive / negative charge for each atom or molecule

31
Q

What kind of bonds do the H and O atoms have in water?

A

polar covalent bonds

  • shared electrons are pulled more toward oxygen ( more electronegative)
  • oxygen is partially negative, hydrogen is partially positive
32
Q

What are ionic bonds?

A

when the atoms strip electrons away from their bonding partners
- transfer of electrons between to atoms -> oppositely charged atoms = ions

  • an attraction between anions and cations
33
Q

What are ions?

A

atoms with more or fewer electrons than usual -> charged atoms

  • anion = negatively charged ion
  • cation = positively charged ion
34
Q

What are ionic compounds?

A

compounds formed by ionic bonds

  • Salts
  • often found in nature as crystals
  • most salts are quite stable when dry, but dissociate quite easily in water
35
Q

What are weak chemical bonds?

A
  • Hydrogen bonds, dipole-dipole bonds, van der waals force
  • many large biological molecules are held in their functional form by weak bonds -> considered very important for biological science
  • reversible
36
Q

What are hydrogen bonds?

A
  • weak bond
  • form when h atoms covalently bonded to electronegative atom is also attracted to another electronegative atom
  • in living cells, the electronegative partners are usually oxygen and nitrogen

eg hydrogen atom in water with nitrogen atom in ammonia

internet:
interaction involving a hydrogen atom located between a pair of other atoms having a high affinity for electrons

37
Q

What are van der Waals interactions?

A

if electrons are distributed asymmetrically in molecules or atoms, they can result in hot spots of positive or negative charge
- van der waals are individually weak attractions between molecules that are close together as a result of these charges

-> attractions between molecules that are very close together
- can be strong due to strength in numbers ( eg gecko’s toe hairs and wall surface)

38
Q

What is the molecular shape and its function?

A

a molecular shape is determined by the positions of its atom’s orbitals

  • specific molecular shaped could be created by the hybridisation of the s and p orbitals in a covalent bond
  • weak chemical bonds reinforce the shapes of the large molecules and help molecules adhere to each other
  • the precise size and shape is vital for the function in cells, eg shape of proteins
    -> molecular shape determines how biological molecules recognize and respond to one another in an environment
39
Q

What are chemical reactions?

A
  • the making and breaking of chemical bonds -> leads to changes in the composition of matter

reactants -> products

40
Q

What are reversible chemical reactions?

A

products of the forward reaction become reactants for the reverse reaction

41
Q

What is the chemical equilibrium?

A

is reached when the forward and reverse reaction rates are equal and occur at the same time

  • at equilibrium, the relative concentrations of reactants and products do not change
42
Q
A

Biology (6 decks)

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