Title: Erwin Shrdinger, What is Life, 1944
1Erwin Shrödinger, What is Life, 1944
What is Life?
- What is the characteristic feature of life? When
is a piece of matter said to be alive? When it
goes on 'doing something', moving, exchanging
material with its environment, and so forth, and
that for a much longer period than we would
expect an inanimate piece of matter to 'keep
going' under similar circumstances.
2(No Transcript)
3Biology is Beautiful!
- Biology is full of amazing diversity
- At a conceptual level, biology uses amazingly
complex systems of biochemistry, structure, and
behavior - The way these complex systems function together
will keep us involved in fascinating discovery
for generations.
4Patterns of Life
Life builds from the bottom up Life assembles
itself into chains Life needs an inside and an
outside Life uses a few themes to generate many
variations Life organizes with information Life
encourages variety by reshuffling
information Life creates variety with
mistakes Life occurs in water Life runs on
sugar Life works in cycles Life recycles
everything it uses Life maintains itself by
turnover Life tends to optimize rather than
maximize Life is opportunistic Life competes
within a cooperative framework Life is
interconnected and interdependent
5- So how would you define Life?
- Can it be defined, or only described
- (inductive vs. deductive thinking)
6Definition of Life (Themes of Biology)
- Metabolism (energy utilization)
- Self-reproducing
- Responds to its environment
- Growth Development
- Homeostasis regulation
- Evolution
- Made up of cells with membrane and DNA
7A Thermodynamic Definition of Life
- The Second Law of Thermodynamics states that
Left to themselves, all systems will eventually
decay into uniform disorder, and all energy will
be dissipated as heat (maximum entropy). - Living things have found a loophole in this law
by creating order in one place by using energy
and increasing entropy elsewhere in the universe.
- The processes we associate with life occur far
from equilibrium -- life demands the active
maintenance of structures in defiance of entropy,
structures which if left to themselves, would
decay and disappear.
8Life is Metabolism
- Living things need to maintain their highly
organized structure against a hostile world
(entropy). - In order to do this, they consume high energy
molecules, derive useful energy from carefully
controlled chemical reactions, and release the
resulting waste products. - Therefore, we can very simply define life as
that which eats.
9Homeostasis
- Biological systems (cells, organisms, ecosystems)
maintain stable internal conditions despite
changes in the environment. - Homeostasis requires constant work
- obtain food, remove waste products
- counter changes from the environment
- a multiplicity of dynamic equilibria rigorously
controlled by interdependent regulation mechanisms
10Regulation
- Every cellular system must be regulated
- respond to environmental changes
- respond to changes in internal chemical
concentrations - developmental changes as the cell grows,
reproduces and/or specializes - Feedback regulation
- a metabolic product blocks the reactions that
produce that product - Communication between cells
- cell surface sensors trigger internal processes
- signaling pathways - pass the message from one
molecule to another
11Growth Development
- Living things grow
- Each organism has a distinct life cycle
- It changes in some fundamental ways from the
time it is born until the time it is ready to
reproduce - May respond to environmental changes by a complex
program of physical, metabolic and/or behavior
changes - Multicellular organisms have cellular
specialization. - May have different physical forms at different
stages of the life cycle - At some point, mammals are just a sperm an egg
12Evolution
- Evolution explains both the diversity and the
unity of life. - Evolution is the central organizing principle of
all biology. - Variation in many traits among the members of a
species (DNA mutations) - Competition between members of a species for
limited resources - Survival (and reproduction) of the fittest
13Life is Cells
- Everything alive is made up of cells.
- Every living thing is either a single-celled
creature, or a creature composed of many living
cells.
14Are Viruses Alive?
Adenovirus Coronavirus HIV
-Cells? -Metabolism? -Self-replicating?
15The Cell Theory of Life
- Omnis cellula e cellula or literally All
cells from cells - In more precise language
- All living things are made up of cells.
- All cells come from pre-existing cells.
- There is no spontaneous generation (under current
conditions)
16Properties of Cells
- Every cell is bounded by a membrane and contains
a full set of instructions necessary for its
operation and reproduction. - Every cell uses the same operating system
- instructions are stored in the DNA molecule
- DNA is transcribed into RNA
- RNA is translated into protein
- There are hundreds of thousands of different
proteins used by living things, but all of them
are made from the same twenty amino acids
17So What is a Cell?
- In its simplest description, a cell has 3
essential parts - a membrane that defines the boundary of the cell
- inner material called cytoplasm
- DNA that contains the information that the cell
requires to live and reproduce.
18Cell Membranes
- All cells have membranes which are made up of
phospholipid molecules - similar to fat
molecules. - Phospholipids are composed of two parts, a
phosphate ion, which forms a negatively charged,
water soluble head, and long fatty acid tails
which are non-polar and insoluable in water.
19(No Transcript)
20Phospholipids form membranes
- A small group of phospholipids in water will
self-assemble into a micelle - non-polar hydrocarbon tails on the inside and the
phosphate heads pointing out into the water.
21Liposomes
- A larger amount of phospholipids will form a
bi-layer membrane phosphates pointing out and
the fatty acids in the middle. - This bilayer membrane tends to form a liposome
with some water trapped inside.
22Cells are Liposomes
- A cell is a liposome
- The membrane creates and inside and an outside.
- Cellular processes such as osmosis and active
transport cause the accumulation of very
different concentrations of molecules inside
vs. outside
23Membrane Proteins
- A cell membrane also contains many proteins
- some on the outer surface
- some on the inner surface
- some buried inside
- some passing all the way through
- Some of these proteins are assembled into complex
structures such as pores that selectively allow
specific materials to move through the membrane - Others are receptors that function as sensory
devices for molecules outside the cell and
transmit signals to other molecules on the
inside.
24(No Transcript)
25Prokaryote vs. Eukaryote
- There are two basic types of cells
- Prokaryotes (bacteria)
- Eukaryotes (everything else)
- Prokaryotes are smaller and simpler than
eukaryotic cells - no cell nucleus
- DNA is organized in a single circular chromosome
- plus some smaller circles called plasmids
- Prokaryotes have existed on earth for about 4
billion years, but eukaryotes first appeared
about 1.7 billion years ago.
26(No Transcript)
27Prokaryote Grow Faster
- Prokaryotes can multiply faster than eukaryotic
cells - They have shorter genetic instructions to be
replicated (less DNA) - The replication process goes about ten times as
fast - Prokaryotes don't combine and specialize to form
multicelled creatures.
28(No Transcript)
29Prokaryote Diversity
- Bacteria come in a wide variety of types
- blue-green algae,
- free living vs. pathogens,
- anaerobic vs. oxygen requiring,
- thermophilic, halophiles, etc.
- Prokaryote diversity is much greater than that of
eukaryotes, but it is difficult to define a
species of bacteria
30(No Transcript)
31Archaebacteria
- There are two vastly different types of
prokaryotes. - Archaebacteria live in extreme environments (deep
ocean volcanic vents, hot springs, etc). - At a molecular level, archaebacteria are actually
more different from eubacteria than bacteria are
different from eukaryotes - There is evidence that archaebacteria are the
oldest kind of life on earth. - Concept of 5 or 6 kingdoms of life
- Concept of 2 domains archaea and everything else
32Three Domains of Life
- Note that plants, animals and fungi radiate from
a common origin, but protists do not. - Archaea may be closer to eukaryotes than to
bacteria.
33Eukaryotes
- Eukaryotic cells are much more complicated than
prokaryotic cells, primarily due to the existence
of internal membrane compartments (organelles). - Eukaryotic cells keep their DNA on multiple
chromosomes in a nucleus enclosed by a nuclear
membrane. - usually have two whole copies of their genome
(diploid) that is two copies of each
chromosome.
34Organelles
- Mitochondria and chloroplasts are membrane bound
cellular sub-structures that have their own DNA. - These two organelles enable eukaryotic cells to
conduct respiration and photosynthesis,
respectively. - Mitochondria and chloroplasts have internal
memberanes - There is considerable evidence to suggest that
mitochondria and chloroplasts originated as
prokaryotic cells that were incorporated into
early eukaryotic cells.
35(No Transcript)
36(No Transcript)
37Sub-cellular Structures
- Other membrane structures exist in some
eukaryotic cells - endoplasmic reticulum (site of protein
processing) - lysosome (protein degradation)
- vacuole (storage in plant cells)
- There are also single celled eukaryotes -
protists
38(No Transcript)
39(No Transcript)
40(No Transcript)
41Protists
- Protists are an extremely diverse group of
eukaryotes - single celled organisms such as algae, amoeba,
paramecium, plasmodium, euglena - some colonial organisms Volvox, brown
algae-kelp, slime mold (no cellular
specialization) - Genetic evidence suggests that various groups of
protists may have evolved separately - they are more evolutionarily distant from plants
and animals and from each other, than animals are
from plants. - some have chloroplasts, some have a contractile
vacuole, some have cilia or flagella that are
used for movement or to create currents of moving
water
42paramecium
amoeba
diatoms
euglena
43volvox
stentor
44Plant vs. Animal cells
- Although they are both eukaryotes, there are some
fundamental differences between plant and animal
cells. - Plant cells have a cell wall, chloroplasts, and
vacuoles. - Photosynthesis!
- Animal cells are specialized into many more
different cell types, some of which are mobile
within the organism.
45(No Transcript)
46Multi-cellular
- Eukaryotic cells are able to combine and
specialize to create multicelled organisms such
as animals, plants and fungi - Cells specialize and cooperate
- Differentiation into specialized cell types
- create tissues and organs
- control of gene expression
- as a developmental process
47(No Transcript)
48(No Transcript)
49Plants
- Plants conduct photosynthesis
- transform light energy into sugars, starches,
proteins and fats - absorb carbon dioxide and produce oxygen
- Simple body structure
- Leaf, stem, root
- More complex reproductive structure flower
- Cells have chloroplasts and central vacuole
- Woody tissue has cellulose and lignin in cell
walls
50(No Transcript)
51(No Transcript)
52(No Transcript)
53(No Transcript)
54(No Transcript)
55(No Transcript)
56(No Transcript)
57Fungi
- At a cellular level, fungi resemble plants
- They have a cell wall, and only form a few
specialized cell types - Genetically, they are quite distinct, with a
number of unique life cycle adaptations
(multicellular haploid organisms with a diploid
reproductive stage). - Parasitic or saporophitic life style
- mushrooms
- yeast
- plant diseases
- fungal infections
58(No Transcript)
59Kingdoms of Life
60(No Transcript)
61Tree of Life
- Since all life has a common organization, it is
possible to group living things according to
their similar properties. - The most informative groupings reflect the
relationships among both currently living and
extinct organisms - shows the course of evolution that led from a
single common ancestor to the present diversity
of living things - This organization is known as a phylogenetic tree
- The best trees are based on comparisons of DNA
and protein sequences.