Lecture 1: The organization of life – From atoms to the biosphere
Learning goals of this lecture
To understand:
- how 'life' is defined
- the organization of:
• the building blocks of life: atoms and molecules
• the molecules of life (overview)
• the functional units of life: cells
• multicellular life: tissues and organs
• populations, communities & ecosystems
• biomes & the biosphere
Part 1 – The definition of life
The 7 main characteristics of life (all groups: plants, animals, bacteries,..)
Atoms team up and
become molecules.
Molecules form cells
and cells can form
tissues and organs.
Organs/tissues form
systems and out of
those a human is
created. Humans are a
part of ecosystems
(biotic and abiotic life)
,Part 2 – The building blocks of molecules: atoms
Atom
= a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of
electrons
Matter = everything we see + feel around us
The structure of an atom (Helium in this case)
Helium
- 2 protons (+)
- 2 neutrons (0)
- 2 electrons (-) -> amu is basically zero/weighs nothing
➔ Neutral atom because 2 + and 2 - → no charge at all
- Atoms differ in the number of protons, neutrons and
electrons
- Neutral atoms have the same number of protons (+) as
electrons (-)
➔ So if it has 2 protons it has 2 electrons; 10 protons 10
electrons etc.
- Depending on the number of electrons of an atom, it can
have multiple orbitals
- Each orbital can carry a different maximum number of electrons
-
,Orbitals have different electron capacities
- Orbital 1 can hold 2 electrons
- Orbital 2 can hold 8 electrons
- Orbital 3 can hold 8 electrons
Classification of elements
- The chemical elements are classified/distinguished based on the number of
protons they carry
- This is the atomic number (Z)
➔ In a neutral atom, the atomic number equals the number of electrons
- The number of protons (Z) plus neutrons (N) equals the mass number (A) of
an atom
➔ A=Z+N
The periodic table (Mendeleev, 1834-1907)
The table contains all elements, with increasing atomic number (Z) (and, thus, the number
of electrons) from left to right, top to bottom
, Valency and the periodic table
- The chemical behaviour of an atom depends mostly on the number of electrons
in its outermost shell, called the valence shell
➔ the electrons in this shell are the valence electrons
- An atom with a full valence shell is unreactive: it will not interact readily with
other atoms => noble gasses
- All other atoms interact in such a way that they complete (= either fill or empty)
their valence shells with electrons
Chemical bonding: sharing or transferring valence electrons
- Atoms with incomplete valence shells can interact with other atoms in such a way that
each partner atom completes its valence shell: these atoms either share or transfer
valence electrons
Atoms bond to make molecules or ionic compounds.
Learning goals of this lecture
To understand:
- how 'life' is defined
- the organization of:
• the building blocks of life: atoms and molecules
• the molecules of life (overview)
• the functional units of life: cells
• multicellular life: tissues and organs
• populations, communities & ecosystems
• biomes & the biosphere
Part 1 – The definition of life
The 7 main characteristics of life (all groups: plants, animals, bacteries,..)
Atoms team up and
become molecules.
Molecules form cells
and cells can form
tissues and organs.
Organs/tissues form
systems and out of
those a human is
created. Humans are a
part of ecosystems
(biotic and abiotic life)
,Part 2 – The building blocks of molecules: atoms
Atom
= a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of
electrons
Matter = everything we see + feel around us
The structure of an atom (Helium in this case)
Helium
- 2 protons (+)
- 2 neutrons (0)
- 2 electrons (-) -> amu is basically zero/weighs nothing
➔ Neutral atom because 2 + and 2 - → no charge at all
- Atoms differ in the number of protons, neutrons and
electrons
- Neutral atoms have the same number of protons (+) as
electrons (-)
➔ So if it has 2 protons it has 2 electrons; 10 protons 10
electrons etc.
- Depending on the number of electrons of an atom, it can
have multiple orbitals
- Each orbital can carry a different maximum number of electrons
-
,Orbitals have different electron capacities
- Orbital 1 can hold 2 electrons
- Orbital 2 can hold 8 electrons
- Orbital 3 can hold 8 electrons
Classification of elements
- The chemical elements are classified/distinguished based on the number of
protons they carry
- This is the atomic number (Z)
➔ In a neutral atom, the atomic number equals the number of electrons
- The number of protons (Z) plus neutrons (N) equals the mass number (A) of
an atom
➔ A=Z+N
The periodic table (Mendeleev, 1834-1907)
The table contains all elements, with increasing atomic number (Z) (and, thus, the number
of electrons) from left to right, top to bottom
, Valency and the periodic table
- The chemical behaviour of an atom depends mostly on the number of electrons
in its outermost shell, called the valence shell
➔ the electrons in this shell are the valence electrons
- An atom with a full valence shell is unreactive: it will not interact readily with
other atoms => noble gasses
- All other atoms interact in such a way that they complete (= either fill or empty)
their valence shells with electrons
Chemical bonding: sharing or transferring valence electrons
- Atoms with incomplete valence shells can interact with other atoms in such a way that
each partner atom completes its valence shell: these atoms either share or transfer
valence electrons
Atoms bond to make molecules or ionic compounds.
