Chapter 1: Light and Life
Light (electromagnetic radiation) is the visible region of the electromagnetic spectrum,
humans can detect with their eyes. Light is described according to its wavelength but it
behaves as particles called photons (small units of light energy).
Why no alternatives?
Shorter wavelengths than light contain enough energy to destroy the bonds that are in
living things. Longer wavelengths are energetically relatively weak and would not supply
enough energy to move an electron from ground state to an excited state, also absorbed by
Pigments: major class of molecules hat are efficient at absorbing photons. (chlorophyll a,
retinal (in vision), and indigo (dye jeans))
They all share a common feature critical to light absorption: conjugated system: a
region where carbon atoms are covalently bonded to each other with alternating
single and double bonds= delocalization of electrons. None of these electrons are
closely associated with a particular atom or involved in bonding and thus are
available to interact with a photon of light.
Indigo dye is blue in colour because it does not absorb photons that are blue in
colour instead these photons are reflected off the pigment or transmitted through
pigments to reach your eyes
Sir Isaac Newton- Using light entering his room he used prisms and viewed colour
change, prisms show colour that is present in the oncoming light. Light changes speed
from one medium to another, causes the light to refract or bend. Light of shorter
wavelength (blue) retracts more than longer wavelengths (red).
Photosynthesis: plants capture energy from the sun and store it in chemical bonds of
sugars and other food molecules
Products: nutrients and oxygen
Cellular Respiration: Plants animals and fungi release the energy stored in the chemical
bonds of food and molecules use as fuel.
Products: Carbon dioxide and energy
Photoreceptor: Light Sensor
Rhodopsin (pigment: retinal, protein: opsin) in dark is inactivated (retinal changes
shape) enzymes allow it to be inactive. Opsins are membrane proteins that span a
membrane multiple times to form a complex with the retinal molecule at the
protein part causes retinal confirmation change
Rhodopsin in light is activated due to light absorption
*Confirmation change important!
Chlamydonmonas (algae) Eyespot (contains photoreceptor, rhodopsin): sensing light, not
seeing it, swims towards it for photosynthesis. -eyespot: light sensitive structure 1Um in diameter found within the chloroplast of the
cell, in a region closely associated with the cell membrane. The eyespot is composed of
two layers of carotenoid-rich lipid globules.
Plants contain phytochrome- critical for photomorphogenesis, the normal developmental
processes activated when seedlings are exposed to light. Present in cytosol of all plant
cells, and when a seedling is exposed to wave lengths of red light, phytochrome becomes
active and initiates a signal transduction pathway that reaches the nucleus.
The eye: organ used to sense light, important for vision, vision requires the brain to
interpret signals sent to the brain from the eye.
-simplest eye “ocellus” which consists of a cup or pit lined with cup to 100 photoreceptor
-Compound eyes, which are common in arthropods are build of hundreds of individual
units called ommatidia.
-ommatidium to axon to photo receptors microvilli light blocking pigment, crystalline and
-Pax6 (eye growth control gene in animals) may have effected eye evolution
Animal Eye: Light reaches photoreceptors photo receptor cells (rods and cones). Light
stopped by pigment cup, nerve to cerebral ganglion.
-retina contains photoreceptors rhodopsin (rods and cones)
- light enters through cornea helps focus the light onto photoreceptors, aided by the lens
- connect to the optic nerve, connection to the brain
**light causes the rods and cones to send chemical changes that generate neural signals
which activate bipolar cells, horizontal cells and neighbouring ganglion cells. Axons of
ganglion cells converge like strands of rope to form the optic nerve.
*electrical signal passes through rods and cones to bipolar cells horizontal cells and then
the ganglion cells to the fibres of the optic nerve.
BLIND Spot: peiece on your retina where there are no photoreceptors, otherwise optic
nerve cannot pass through retina.
Iodopsin- cones (colour or chromatic vision). : allow the light of different wavelength to
be interpreted as colour in the brain
- different proteins in the cone allow us to see red, green, blue (trichromatic vision)
all three rhodopsin proteins in the cones
- dichromatic vision: reduced ability to interpret colour (Colour blind) only two
present in cones
-noctornal animals large eyes to collect photons. Noctornal insects have compound eyes
that enhance their light gathering ability. Monkeys
Trichromatic: Old world
Dichromatic: New World
Eye evolves from simpler forms
a) Region of photosensitive cells EYE SPOT
b) Depressed/ forlded area allows for limited directional sensitivity EYE CUP
c) Pinhole eye allows for finer directional sensitive and limited imaging PINHOLE
(opened area can cause damage to photoreceptors)
d) Transparent humar develops in enclosed chamber (allows for protection)
e) Distinct lens develops PRIMITIVE LENS
f) Iris separate cornea develop
EVOLUTION OF EYES – closely related species
Limpet- simple layer of photosensitive sells
Slip shell snail- simple layer of cells
Squid- advanced camera eye
Nautilis- pinhole camera eye
LIGHT: Ecology and Behaviour
- Circadian rhythm
Many physiological and behavioural responses are geared to daily changes in light and
darkness and these daily changes controlled by (endogenous) internal organism-based
clock. Light influences, but it is not a direct response (conditioned response). Light hues
allow to set a biological rhythm (produces hormones and neurotransmitters) (possibly
encouraged by natural selection).
DNA synthesis happens at night, (light damages DNA could cause mutation).
Photosynthesis- proteins programmed to be made at night
***Clock found in the superchiasmatic nucleus of the brain
Retina absorbes light and it is transmitted to the Superchaismatic nucleus (SCN)- pineal
land melatonin release.
-day (photoperiod)- changes can cause change in fur and feathers, trigger migration,
hibernation and changes in sexual behaviour
When an animal fails to distinguish another from the background.
As a means of signalling, organisms can use scent, sound or colour
Many organisms use colour to: hide, attract and warn
But these signals are only useful if the organism is trying to attract or warn can see them
Example: Flower colour and pollination
Coevolution Simultaneous evolution of adaptions in two or more populations that interact
so closely that each is a strong selective force on the other
- Using light as colour signals The dark side of light- “PHOTO-OXIDATIVE DAMAGE”
-Light can damage biological molecules (including DNA).
*Thymine DIMER.- Two thymines on the same strand form covalent bonds. . The
absorption of excess light energy results in excited electrons reacting with O2
producing reactive oxygen species, (like hydrogen peroxide) damage to proteins and
death of a cell.
-Plants can repair photo-oxidative damage by removing damaged proteins and
replacing them with newly synthesized copies.
-UV light damage-> 400nm blue to 200nm x-ray are more damaging to biological
molecules. Ozone O3 is produce when photons of ultraviolet light interact with molecular
oxygen, O2 While short wavelengths of ultraviolet light are absorbed by ozone longer
wavelengths of ultraviolet light reach Earth’s surface.
(feathers and other natural protections)
Melanin: a pigment that is found in all branches of the tree of life. Major component of
ink released by cephalopods such as squid. Very efficient in absorbing UV light and
dissipates 99% of the energy harmlessly as heat.
Eumelanin- brown (lighter skin)
Pheomelanin- reddish brown (red hair)
-blonde includes both.
*Humans synthesize melanin in specialized cells call melanocytes: increases upon sun
exposure= tan. People who produce high melanin levels in areas that do not receive
abundant sunlight are susceptible to vitamin D deficiency. (African living in Winnipeg).
However condition is rare because foods usually fortified with the nutrient!
Spectrophotometer- by passing light of varying wavelengths through a solution of pure
pigment, it determines the wavelengths of light transmitted through sample and
determines which wavelengths are absorbed
-The data from the spectrophotometer can be used to produce an absorption spectrum.
Ecological light Pollution: The electricity light bulb causes rapid proliferation of artificial
lighting causing pollution, Disrupts orientation in nocturnal animals, hatchlings in beaches
become disoriented due to lighting, and could head inland and die, can cause birds
colliding with buildings and towers.
-cause higher rates of anxiety
– Bats and geckos benefit because light attracts insects
Bioluminescence: algae, bacteria, fish, fungi, insects and squid are able to make their
own light. Bioluminescence is like the reverse of the light absorption by pigment.
Attracting a mate, or prey, camouflage and communication
-- Chemical energy in the form of ATP is used to excite an electron in a substrate
molecule from ground state to a higher excited state, and when the electron returns to
the ground state the energy is released as a photon of light. The conversion of the
chemical energy in ATP into light is very efficient. Considering that up to 95% of
energy of a light bulb is lost as heat, it is remarkable that less than 5% of energy in
ATP is lost as heat. Chapter 3: Defining Life and Its Origins
5 Levels of ecological scale-biosphere (global sum of ecological systems), ecosystems
(living things and the environment they interact with), communities (group of two or
more populations of different species in the same area), populations (organisms that
belong to the same species, living in the same place and breathe with each other), and
organisms (animals, plants and bacteria. CRITERIA: grow and develop, reproduce,
respond to stimulus, maintain homeostasis (metabolism)
a) Display Order: arrangement, social or environmental
b) Harness and utilize energy
d) Respond to stimuli: organisms can make adjustments to their structure function
and behaviour to respond to changes in external environment. (plant regulate
stomata to regulate gas exchange)
e) Exhibit homeostasis: regulate internal environment so conditions remain relatively
constant. (Sweating to remove heat to maintain temperature)
f) Growth and development: Increase size by increasing number of cells
g) Evolve: Populations of organisms change over the course of generations to become
better adapted to their environment (Snowy owl is white)
Exemption: Viruses- small infectious agents, the characteristics of life that it displays are
based on its ability to infect cells. (Ex. although contain DNA and RNA they lack cellular
machinery and metabolism to produce genetic info to synthesize their own proteins. To
make proteins they infect and hijack their translational machinery and metabolism in order
* Fig 3.4- A termite cathedral: Sophisticated structure of a termite nest emerges from
the simple work of thousands of individual termites. In a similar way the complex
properties of life emerges from simpler molecular interactions
Biodiversity: life is everywhere, can reflect population, ecosystem and even the biosphere.
Depending on how diverse, more diverse, more healthy (because everyone can thrive).
Organisms typically survive better in tropical regions in comparison to arctic conditions.
-organisms blend in to their environment, visibility (easier with bigger organisms than
smaller organisms), immigration/emigration, differentiation between species
(Time goes up on phylogenetic trees).
Heterotrophs- possibly the earliest form of life, organisms that obtain carbon from organic
molecules. (humans are examples: extract energy from organic molecules, sugars, proteins
Since early atmosphere contained only traces of oxygen, anaerobic forms of
respiration and fermentative pathways where used to extract energy from organic
Autotrophs: obtain carbon from environment in an inorganic form (often carbon dioxide) -Plants and other photosynthetic organisms are the dominant autotrophs today. The
earliest type of photosynthesis was ANOXYGENIC PHOTOSYNTHESIS. (probably
developed after heterotrophy)
-Compounds such as hydrogen sulphide and ferrous iron are used as electron donors
for the light reactions of photosynthesis. ATP and NADPH are used to synthesis
organic molecules from CO2
How they obtain energy:
Photoautotroph: Use light as a source of energy for photosynthesis
CO2- Found in some photosynthetic bacteria, in some proteins and in plants
Organic Molecules- found in some photosynthetic bacteria
Chemoautotroph: Used reduced chemicals rich in electrons as an energy source. Oxidized
inorganic or organic material to produce energy.
CO2 – Found in bacteria and archeans
Organic molecules-- Found in some bacteria and archeans and proteins, fungi, animals and
E.Coli (preview of Bacteria)- DNA present in nucleoid (chromosomal region and
possibly plasmids (circular non-essential independent of the chromosome).
Domains: phylogenetic tree
Archea- similarities between eukarya (features of protein synthesis) and prokaryotes (no
membrane bound nucleus).
Banded iron were formed in sediments of lakes and oceans when dissolved oxygen
replaced the iron in the water, forming a red coloured precipitate, iron oxide rust which
ended up being incorporated into the resulting sedimentary rock formations
-Cyanobacteria uses water as an electron donor
-Because it releases oxygen photosynthesis relies on the oxidation of water as the
source of electrons “OXYGENIC PHOTOSYNTEHSIS”
3 domains: Archea, Bacteria, and Eukarya
-Archea and bacteria similar cell architecture = Prokaryotes.
(But they do not share a close evolutionary origin)
- Archea are more closely related to Eukarya.
All life forms have fundamental attributes
1) Cells made of lipid molecules forming a bilayer
2) Genetic system based on DNA
3) A system of info transfer- DNA to RNA to Protein
4) A system of protein assembly from a pool of amino acids by translation using
messenger RNA (mRNA and transfer RNA 9tRNA) using ribosomes
5) Reliance on proteins as the major structural and catalytic molecule
6) Use of ATP as a molecule of chemical energy 7) The breakdown of glucose by the metabolic pathways of glycolysis to generate
3.5- Eukaryotic cells compared to archea or bacteria
- separation of DNA and cytoplasm by a nuclear envelope
- the presence of the cytoplasm of membrane-bound compartments with specialized
metabolic and synthetic functions- mitochondria, chloroplasts, the endoplasmic
reticulum, and the Golgi complex, among others.
Theory: broad explanation based on many lines of evidence
-aids in generation of new hypothesis
-has withstood rigorous testing
Theory of Evolution by Natural Selection
-Characteristics of a population change over time
-Inviduals with certain heritable traits produce more offspring than those without those
=force or phenomenon affects the survival and reproduction of individuals. Survival
causes populations to evolve. Driven by circumstances of the environment, changing the
direction of the evolution
-mutation doesn’t just happen, it has these mutations already in order to survive.
Darwin’s Theory of Evolution: Factors of Evolution:
3) Offspring Production
5) Beneficial Traits compared to weaker traits
-Artificial selection 1) Parental Generation: breeding largest most compact flowering
stalks 2) Of the offspring select individuals with the largest and most compact flowering
and breed (etc..) until broccoli from Brassica oleracea
- Evolution DNA level and population (levels we look at evolution from)- extrapolation
due to similarities between species
Endosymbiosis: A hypothesis stating that prokaryotic ancestors of modern mitochondria
and chloroplasts were engulfed by larger prokaryotic cells thus forming a mutually
advantageous relationship called symbiosis.
Evidence of Symbiosis
1) Morphology- the form or shape of both mitochondria and chloroplast is similar to
that of bacteria and archaea
2) Reproduction- a cell cannot synthesize a mitochondrion or a chloroplast because
they both divide by binary fission, which is how bacteria and archea divide
3) Genetic info- if ancestors of mitochondria and chloroplasts were free, then these
organelles should contain their own DNA WHICH IS TRUE, they can code
4) Transcription and translation- both chloroplasts and mitochondria contain
complete transcriptional and translational machinery: genes encoded by organelle genomes are translated into mRnA and translated on the ribosomes, messenger
RNA (mRnA) and transfer RNA (tRNA) necessary used to synthesize the proteins
encoded by their DNA. The ribosomes and mitochondria and chloroplasts are very
similar to the type found in bacteria
5) Electron Transport- similar to free living prokaryotic cells, both mitochondria
and chloroplasts have ETCs used to generate chemical energy. (inner membrane
location in both mitochondria and chloroplasts similar to the plasma membranes
found in bacteria and archea)
6) Sequence analysis: sequencing of RNA that makes up ribosomes of chloroplasts
and mitochondria firmly establishes that they belong in Bacteria family.
Chloroplasts and Mitochondria (not part of the endomembrane system- nuclear envelope,
endoplasmic reticulum, golgi complex, lysosomes, vesicles and plasma membrane.
-Contain their own DNA
-Contain shorter nuclear DNA and is circular
-Contain own transcription and translational machinery
Multiply by binary fission, cells cannot make either
Mitochondria: developed from ingested prokaryotes
Chroloplasts developed from ingested cyanobacteria
Horizontal Gene transfer: intergration of gene into nuclear genome or gene lost. Between
Genome: complete complement of an organism’s genetic material.
Endomembrane system: a collection of internal membranes that divide the cell into
structural and functional regions. (nuclear envelope, the endoplasmic reticulum, and the
Eukaryokes (plants fungi and animals) requires increased energy due to complexity.
Mitochondria undergo aerobic respiration to produce lots of ATP from organic molecules.
-Support larger genome that codes for greater number of proteins, energy supports a
variety of genes that led to traits such as: cell cycle, sexual reproduction, phagocytosisis,
endomembrane trafficking the nucleus and multi-cellularity.
Chapter 2- The Cell: An Overview
The Cell Theory
-All organisms are composed of one or more cells
-The cell is the smallest unit that has the properties of life
-Cells arise only from the growth and division of pre-existing cells
EX-Eggs are the largest most expensive cells (size does not correlate with value) - Unicellular almost all bacteria, archea, some protists (amoeba) (mostly prokaryotes) and
some fungi (yeasts (eukaryotes)) - functionally independent organism capable of carrying
out all necessary activities for life.
-Multicellular organisms including plants and animals have cellular activities that are
divided among varying numbers of specialized cells. However they are potentially capable
of surviving individually if placed in a chemical medium that can sustain them (if opened,
the property of life is lost: unable to grow, reproduce or respond.) -typically falls under
-Bacteria and archea (similar in structure and shape but archea are similar to eukaryotes on
a molecular level) were grouped recently into a single domain: Prokaryota- this domain is
no longer considered accurate as recent research has shown that bacteria and archea are
not evolutionarily related.
-Cells representing all three domains of life assume a wide variety of forms. Individual
cells range in size from tiny bacteria to an egg yolk, a single cell that can be several
centimetres diameter. Cells organized basically based on similar activities.
Both prokaryotic and eukaryotic cells have:
-Electron Transport Chain
-DNA: (double stranded) deoxyribonucleic acid produce protein (TRANSLATION) by
- DNA copied onto molecules of ribonucleic acid (single stranded) (TRANSCRIPTION)
-composed of: 1) Nitrogenous Base 2) Pentose Sugar 3) Phosphate group
-Lack of hydroxide group (which RNA has)
-Nucleotide sugars have 5’ and 3’ ends
-Phosphate backbone on the outside to hold DNA together (2 Nucleotides linked through
-Only adding new nucleotides on the 3’ end
- Nitrogenous bases on the inside-anti-parallel arrangement: refers to polarity of each
DNA strand, strands arranged in opposite directions
A-T (double bond) (able to separate it using less energy)
C-G (triple bond)
Complementary base pairing (percentage can be found, Shargas rule)
DNA helix- repeatable, predictable measurements (major and minor grooves)
-sugar phosphate backbone
Primary: complete sequence of amino acids in a protein (peptide bonds)
Secondary structure- regions of alpha helix= a cylinder or barrel, beta strand= side by side
arrangement like two ribbons or random coil in a polypeptide chain (neighbouring amino
acids). Folded into arrangements based on hydrogen bonds between atoms of the
backbone H & N and O to C. *Tertiary structure: overall three-dimensional folding of polypeptide chain. Information
about what the protein might do, want a drug to bind to a protein, binding site, shows you
how different components react with each other.
-hydrogen bonds, ionic bonds, hydrophobic interactions and disulphide bridges
-allows for confirmational changes in shape
Quarternary structure: arrangement of polypeptide chains in a protein that contains more
than one chain.
-Collagen: helical polypeptides major component of connective tissue (like a braid)
Molecular structure: primary (sequence), secondary (local folding), tertiary (long range
folding), quarternary (multimeric organization)
Oxidation-reduction (redox) reactions are chemical reactions where there is a transfer of
one or more electrons from one reactant (donor) to another recipient)
Metabolism: the biochemical reactions that allow a cell or organism to extract energy from
its surroundings and use the energy to maintain itself, grow and reproduce.
-Adenosine triphosphate (ATP) coupling agent that links energy-releasing reactions to
those requiring energy
-structure: three phosphate groups, sugar (ribose), nucleotide base (adenine)
-steps to produce ATP =energy efficient, minimizes energy loss.
End terminus: amino end (beginning)
C-Terminus: carboxyl end (end)
Microscopy: a technique for producing visible images of objects, biological or otherwise
that are too small to be seen with the human eye.
Light microscope: light to illuminate specimen
Electron microscopes: use electrons to illuminate the specimen
-Different types of microscopes give different magnification and resolution of the
-Magnification is the ratio of the object as viewed to its real size, usually given as
something like 1200:3. Resolution is the minimum distance by which two points in the
specimen can be separated and still be seen as two points. Resolution depends primarily
on the wavelength of light or electrons used to illuminate the specimen. Shorter in
wavelength-= better resolution
-Thus electron microscopes have higher resolution
Why are cells small?- change in surface area-to-volume ration of an object as size
increases. (ex. doubling the diameter of a cell multiplies its volume to eight but surface
area by only four. – volume of a cell determines the amount of chemical activity that can
take place within it, whereas the surface area determines the amount of substances that can
be exchange between the inside of the cell and the outside environment (nutrients enter
and wastes leave)
** But passed a certain point increasing the diameter of the cell gives a surface area that is
insufficient to maintain an adequate nutrient-waste exchange for its entire volume. -Some cells increase ability to exchange materials with their surroundings by flattening or
by developing surface folds or extensions that increase their surface area
-EX. Human instestinal cells have closely packed, finger-like extensions that increase
surface area, enhancing their ability to absorb digested food molecules
Plasma membrane: what cells are bounded by, a bilayer of lipids with embedded protein
molecules. The lipid bilayer is a hydrophobic barrier to the passage of water-soluble
substances but selected water soluble substances can penetrate cell membranes through
transport protein channels. (selectively permeable- allows maintenance of specialized
internal ionic and molecular environment required for cell life.)
-The central region contains DNA- stores hereditary information that is organized in the
form of genes (segments of DNA that codes for individual proteins). Also contains
proteins that help maintain DNA structure and enzymes that duplicate DNA and copy its
information into RNA.
-Cytoplasm: contains the organelles, the cytosol and cytoskeleton.
Organelles- small structures important for cell function
Cytosol- aqueous water solution containing ions and various organic molecules
Cytoskeleton: protein-based framework of filamentous structures that, among other
things, helps maintain proper cell shape and plays key roles in cell division and
chromosome segregation form cell generation to cell generation. Exists in eukaryotes and
recent research proves prokaryotes as well (that have functional equivalent cytoskeletal
Animal cell- microtubules, intermediate filaments and microfilaments
Plant- microtubules and microfilaments
Prokaryotic cell (no longer domain that includes bacteria and archea)- used as it refers not
to a single group of organisms but rather to a particular cell structure- NO NUCLEUS.
-the nucleoid- DNA-containing central region of the cell- has no membrane boundary
separating it from the cytoplasm. (some have internal membranes, but a number of both
species archea and bacteria contain extensive internal membranes)
-use a variety of substances as energy and carbon sources and to synthesize almost all
required organic molecules
-vastly outnumber all other types of organism
-live successfully in almost all regions of the earth’s surface, from Antarctic to hot springs
- no membrane bound organelles
-cell wall (bacteria)
Gram positive bacteria: single, relatively thick petidoglycan layer
Gram negative bacteria: relatively thin peptidoglycan sheath surrounded by outer-
-Determined by different staining dyes (stain with both but remains one colour) (purple
(positive) vs. pink (negative)) -capsule: some bacteria have extra layer of polysaccharides surrounding cell wall and
protects bacteria from extreme temperatures, desiccation, antibiotics, viruses and
Eukaryotes: make up the domain of Eukarya and have cells where DNA is contained
within a membrane-bound compartment called the nucleus.
-cytoplasm typically contains extensive membrane systems that form organelles with their
own distinct environments and specialized functions.
3 shapes: shape-spherical, rod-like, and spiral
Escherichia coli (E. coli)- normal inhabitant of the mammalian intestine that has been
studied extensively as a model organism genetics, molecular biology and genomics
research is rod-like in shape- basic features of prokaryotic cell structure.
Nucleoid: contains a highly folded mass of DNA. For most species the DNA is a single
circular molecule that unfolds when released form the cell. The DNA molecule is the
-individual genes in DNA molecule encode the info required to make proteins. This info is
copied into a type of RNA molecule called messenger RNA-Small, roughly spherical
particles in the cytoplasm. The ribosomes use the information in the mRNA to assemble
amino acids into proteins.
-A prokaryotic ribosome consists of a large and a small subunit, each formed from a
combination of ribosomal RNA (rRNA) and protein molecules. Each prokaryotic
ribosome contains three times of rRNA molecules which are also copied from the DNA
and more than 50 proteins.
-plasma membrane is surrounded by a rigid external layer of material the cell wall .
-transporting materials in and out of cells
-contains molecular systems that metabolize food molecules into the chemical energy
-cell wall: provides rigidity to prokaryotic cells and with the capsule, protects the cell
from physical damage.
-Composed of sugars and amino acids= PEPTIDOGLYCAN
-cell wall coated externally with polysaccharides called: Glycocalyx (a sugar coating).
When the glycocalyx is diffuse and loosely associated with cells, it is a slime layer, when
it is gelatinous and more firmly attached to cells it is a capsule.
- the glycocalyx helps protect prokaryotic cells from physical damage and desiccation and
may enable a cell to attach to a surface, such as other prokaryotic cells (as in form a
colony), certain eukaryotic cells, or non-living substrate.
-destruction of the cell wall can result in lysis of the cell
-Prokaryotic cytoskeletons play important roles in creating and maintaining the proper