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NAME: UDOH, ABASIFREKE EKONG
DEPARTMENT: MEDICAL LABORATORY SCIENCE
COURSE: BIO 101.
LEVEL: 100L.
DATE: 7th NOVEMBER, 2015.
ASSIGNMENT.
1). What is a cell? Give the features a true cell should possess.
Cells are the basic building blocks of living things. The human body is composed of trillions of cells, all
with their own specialised function.
Cells are the basic structures of all living organisms.
Cells provide structure for the body, take in nutrients from food and carry out important functions.
Cells group together to form tissues, which in turn group together to form organs, such as the heart and
brain.
FEATURES A TRUE CELL SHOULD POSSESS.
Eukaryotic cells (from the Greek eu, meaning "true" and karyon, meaning "kernel" or "nucleus") are
more complex than prokaryotic cells and are found in both unicellular organisms like the amoeba and
multicellular organisms like sunflowers, mushrooms, and humans. The following are the features a
eukaryotic (true) cell should possess:
A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow
for compartmentalization of functions
The structure of eukaryotic cells
Eukaryotic cells are larger than prokaryotic cells and have a "true" nucleus, membrane-bound organelles,
and rod-shaped chromosomes.
The nucleus houses the cell's DNA and directs the synthesis of proteins and ribosomes.
Mitochondria are responsible for ATP production; the endoplasmic reticulum modifies proteins and
synthesizes lipids; and the golgi apparatus is where the sorting of lipids and proteins takes place.
Perixisomes carry out oxidation reactions that break down fatty acids and amino acids and detoxify
poisons; vesicles and vacuoles function in storage and transport.
Animal cells have a centrosome and lysosomes while plant cells do not.
Plant cells have a cell wall, a large central vacuole, chloroplasts, and other specialized plastids, whereas
animal cells do not.
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photosynthesis
the process by which plants and other photoautotrophs generate carbohydrates and oxygen from
carbon dioxide, water, and light energy in chloroplasts
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organelle
A specialized structure found inside cells that carries out a specific life process (e.g. ribosomes, vacuoles).
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eukaryotic
Having complex cells in which the genetic material is organized into membrane-bound nuclei.
A eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes. However, unlike prokaryotic cells,
eukaryotic cells have:
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a membrane-bound nucleus
numerous membrane-bound organelles (including the endoplasmic reticulum, Golgi apparatus,
chloroplasts, and mitochondria)
several rod-shaped chromosomes
Because a eukaryotic cell's nucleus is surrounded by a membrane, it is often said to have a "true nucleus.
" Organelles (meaning "little organ") have specialized cellular roles, just as the organs of your body have
specialized roles. They allow different functions to be compartmentalized in different areas of the cell.
The Nucleus & Its Structures
Typically, the nucleus is the most prominent organelle in a cell. Eukaryotic cells have a true nucleus,
which means the cell's DNA is surrounded by a membrane. Therefore, the nucleus houses the cell's DNA
and directs the synthesis of proteins and ribosomes, the cellular organelles responsible for protein
synthesis. The nuclear envelope is a double-membrane structure that constitutes the outermost portion
of the nucleus. Both the inner and outer membranes of the nuclear envelope are phospholipid bilayers.
The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA
between the nucleoplasm and cytoplasm. The nucleoplasm is the semi-solid fluid inside the nucleus
where we find the chromatin and the nucleolus. Furthermore, chromosomes are structures within the
nucleus that are made up of DNA, the genetic material. In prokaryotes, DNA is organized into a single
circular chromosome. In eukaryotes, chromosomes are linear structures.
2). Differentiate between the prokaryotic and the eukaryotic cells.
Eukaryotic cells
prokaryotic cells
Nucleus
Present
Absent (nucleiod).
# of chromosomes
more than one.
One - but not a true
chromosome; Plasmids present
Cell Type
multicellular
unicellular
True membrane -bound nucleus
Present (Lysosomes, Golgicomplex, Endoplasmic
Reticulum, Mitochondria,
Chloroplasts)
Absent
Telomeres
Present (Linear DNA)
Circular DNA; does not need
telomeres
Genetic Recombination
Mitosis, fusion of gametes
Partial, un-directional transfer of
DNA
Lysosomes/Peoxisomes
present
absent
Microtubules
present
absent (rare)
Endoplasmic Reticulum
present
absent
Mitochondria
present
absent
Cytoskeleton
present
possibly absent
DNA Wrapping on proteins
Yes
no
Ribosomes
Larger (80S); 70S in organelles
Smaller (70S)
Vesicles
present
present
Golgi Apparatus
present
absent
Mitosis
yes
no; binary fission
Chloroplasts
Present in plants
Absent; chlorophyll is scattered
in the cytoplasm
Cell Size
10-100 µm
1-10 µm
Permeability of Nuclear
Membrane
Selective
not present in cell
Cell Wall
Present on Plant and Fungi cells
Present (peptidoglycan)
(chitin)
Vacuoles
Present
Present
Flagella
Present; for movement
Present; for propulsion
3). With the aid of well labelled diagrams
illustrate the ultrastructures of plant and animal
cells.
ULTRA STRUCTURE OF A PLANT CELL.
ULTRA STRUCTURE OF A TYPICAL ANIMAL CELL.
Organelles and Structures that can be seen with
electron microscopes
All of the above are seen and the organelles
below
ORGANELLES OR STRUCTURES,DESCRIPTION
AND FUNCTIONS
Nucleolus
STRUCTURE: Dense spherical area in the
nucleoplasm that contains some DNA and RNA.
FUNCTION: Produces the organelle called
ribosomes.
Ribosomes
STRUCTURE: Small round dense granules
FUNCTIONS: Performs the tasks that are coded in the DNA. Produces proteins which are needed for
functioning and structure.
Golgi Bodies
STRUCTURE: Curved shaped surface called forming face with vesicles coming off.
FUNCTION: They place different membranes around cell products sorting and packaging them.
Rough Endoplasmic Reticulum
STRUCTURE: System of membranes with ribosomes connecting the nucleus cell membrane.
FUNCTION: Transport system and is the site of protein production made by ribosomes.
Smooth Endoplasmic Reticulum
STRUCTURE: System of membranes connecting the nucleus cell membrane.
FUNCTION: Transport system and is the site of lipid production.
Lysosome
STRUCTURE: Small membrane bound round sac of fluid
FUNCTION: Breakdown of cell organelles that are no longer needed, so that they can be used to create
new ones.
Mitochondria
STRUCTURE: Bean shaped organelle with an
inner and outer membrane.
FUNCTION: Cellular respiration which
provides energy for cell functions.
Centrioles
STRUCTURE: A dense granular cylindrical
structure made of microtubules
FUNCTION: Produces spindles which separates the cell during cell division.
4). Briefly describe the structures and functions of the following cellular organelles illustrating with
diagrams where necessary:
(a). Nucleus:
DIAGRAM OF THE CELL NUCLEUS
STRUCTURE; The cell nucleus is bound by a double membrane called the nuclear envelope. This
membrane separates the contents
of the nucleus from the cytoplasm.
FUNCTION; The cell nucleus is a
membrane bound structure that
contains the cell's hereditary
information and controls the cell's
growth and reproduction. It is the
command center of a eukaryotic
cell and is commonly the most
prominent organelle in a cell.
(b). Endoplasmic reticulum:
DIAGRAM OF THE ENDOPLASMIC
RECTICULUM.
STRUCTURE; The endoplasmic
reticulum (ER) is a series of
interconnected membranous sacs
and tubules.It is the membrane of network tubules and flattened sacs, which serves a variety of
functions within the cell. The space, which is present in the endoplasmic reticulum, is called as the
lumen.
FUNCTION;
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collectively modifies proteins and synthesizes lipids.
It is mainly responsible for the transportation of proteins and other carbohydrates to another
organelle, which includes lysosomes, Golgi apparatus, plasma membrane, etc.
They play a vital role in the formation of the skeletal framework.
They provide the increased surface area for cellular reactions.
They help in the formation of nuclear membrane during cell division.
They play a vital role in the synthesis of proteins, lipids, glycogen and other steroids like
cholesterol, progesterone, testosterone, etc.
(c). Mitochondria:
DIAG
RAM
OF
THE
MIT
OCH
OND
RION.
STR
UCT
URE; A mitochondrion contains two main membranes composed of phosopholipid bilayers and proteins
The smooth outer membrane – This encloses the entire organelle and contains porin protein molecules
that serve as diffusion channels for minute protein molecules across the membrane. Larger molecules
can enter only if their signaling sequence can bind to a large translocase protein in the outer membrane.
The folded inner membrane – This contains about 1/5th of the mitochondrion protein, but has no porin
proteins, and includes several hundred polypeptides. The inner membrane is impermeable and ions and
molecules require special membrane transporters to pass through it. The inner membrane folds are
known as cristae.
The cristae – With their folds, the cristae increase the total surface area of the inner membrane. The
cristae create two sections in the mitochondrion The intermembrane space – This lies between the outer and inner membranes.
The matrix – This is the inner space enclosed by the inner member. The matrix contains about 2/3rd of
the total mitochondrion protein. It also contains several hundred enzymes, transfer RNA (tRNA) and
copies of the mitochondrial DNA genome.
FUNCTION; The enzymes in the matrix break down carbohydrates and sugars to produce adenosine
triphosphate (ATP). ATP molecules store the chemical energy required by the cell to carry out its
metabolic functions. It is for this reason that the mitochondria are called the power plants of the
cell.Other functions of the mitochondria include controlling the cell cycle - signaling, differentiation,
growth and death - and assisting with cellular aerobic respiration.
(d). Golgi apparatus:
DIAGRAM OF THE GOLGI APPARATUS
STRUCTURE;
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The Golgi apparatus is a major organelle in most of the eukarytoic cells.
They are membrane bound organelles, which are sac-like. They are found in the cytoplasm of
plant and animal cells.
The Golgi complex is composed of stacks of membrane-bound structures, these structures are
known as the cisternae. An individual stack of the cisternae is sometimes referred as dictyosome.
In a typical animal cell, there are about 40 to 100 stacks. In a stack there are about four to eight
cisternae.
Each cisternae is a disc enclosed in a membrane, it possess special enzymes of the Golgi which
help to modify and transport of the modified proteins to their destination.
The flat sacs of the cisternae are stacked and is bent and semicircular in shape.
Each group of stacks is membrane bound and its insides are separated from the cytoplasm of
the cell.
The interaction in the Golgi membrane in responsible for the unique shape of the apparatus.
The Golgi complex is polar in nature.
The membranes of one end of the stack is different in composition and thickness to the
membranes at the other end.
One end of the stack is known as the cis face, it is the 'receiving department" while the other
end is the trans face and is the "shipping department". The cis face of the Golgi apparatus is
closely associated with the endoplasmic reticulum.
FUNCTIONS;
1. The cell synthesize a huge amount of variety of macromolecules. The main function of the
Golgi apparatus is to modify, sort and package the macromolecules that are synthesized by
the cells for secretion purposes or for use within the cell.
2. It mainly modifies the proteins that are prepared by the rough endoplasmic reticulum.
3. They are also involved in the transport of lipid molecules around the cell.
4. They also create lysosomes.
5. The Golgi complex is thus referred as post office where the molecules are packaged, labelled
and sent to different parts of the cell.
6. The enzymes in the cisternae have the ability to modify proteins by the addition of
carbohydrates and phosphate by the process of glycosylation and phoshphorylation
respectively.
7. In order to modify the proteins
the golgi complex imports
substances like nucleotides from
the cytosol of the cell. The
modifications brought about by
the golgi
body
might
form a
signal
sequence.
This
determin
es the
final
destinatio
n of the
protein.
8. The Golgi
complex
also plays
an
importan
t role in
the
production of proteoglycans. The proteoglycans are molecules that are present in the
extracellular matrix of the animal cells.
9. It is also a major site of synthesis of carbohydrates. These carbohydratres includes the
synthesis of glycoasaminoglycans, Golgi attaches to these polysaccharides which then
attaches to a protein produced in the endeoplasmic reticulum to form proteoglycans.
10. The Golgi involves in the sulfation process of certain molecules.
11. The process of phosphorylation of molecules by the Golgi requires the import of ATP into
the lumen of the Golgi.
(e). Plasma membrane:
DIAGRAM OF THE PLASMA MEMBRANE
STRUCTURE;
Like all other cellular membranes, the plasma membrane consists of both lipids and proteins. The
fundamental structure of the membrane is the phospholipid bilayer, which forms a stable barrier
between two aqueous compartments. In the case of the plasma membrane, these compartments are
the inside and the outside of the cell. Proteins embedded within the phospholipid bilayer carry out the
specific functions of the plasma membrane, including selective transport of molecules and cell-cell
recognition. The Plasma Membrane is a fluid mosaic model, semi-permeable (selectively permeable),
double layer of phospholipids with embedded proteins.
FUNCTIONS;
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Isolate the cytoplasm from the
external environment
 Regulate the exchange of substances
 Communicate with other cells
 Identification
 It separates the contents of the cell
from its outside environment and it
regulates what enters and exits the
cell.
 Plasma membrane plays a vital role in
protecting the integrity of the interior
of the cell by allowing only selected
substances into the cell and keeping
other substances out.
It also serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in
others. Thus the cell membrane supports the cell and helps in maintaining the shape of the cell.
The cell membrane is primarily composed of proteins and lipids. While lipids help to give
membranes their flexibility and proteins monitor and maintain the cell's chemical climate and
assist in the transfer of molecules across the membrane.
The lipid bilayer is semi-permeable, which allows only selected molecules to diffuse across the
membrane.
(f). Cilia and flagella.
DIAGRAM OF CILIA AND FLAGELLA.
These whiplike appendages extend from the surface of many types of eukaryotic cells.
If there are many of them, they are called cilia;
if only one, or a few, they are flagella. Flagella also tend to be longer than cilia but are otherwise similar
in construction.
STRUCTURE;
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Both cilia and flagella consist of:
a cylindrical array of 9 filaments consisting of:
a complete microtubule extending into the tip of the cilium;
a partial microtubule that doesn't extend as far into the tip.
cross-bridges of the motor protein dynein that extend from the complete microtubule of one
filament to the partial microtubule of the adjacent filament.
a pair of single microtubules running up through the center of the bundle, producing the "9+2"
arrangement.
The entire assembly is sheathed in a membrane that is an extension of the plasma membrane.
FUNCTION;
Cilia and flagella move liquid past the surface of the cell.
For single cells, such as sperm, this enables them to swim.
For cells anchored in a tissue, like the epithelial cells lining our air passages, this moves liquid
over the surface of the cell (e.g., driving particle-laden mucus toward the throat).
5). How can you differentiate between cilia and flagella?
Differences between cilia and flagella.
Cilia
Flagella
From Latin word for eyelash pronounced as ‘sillyah’, is the plural of cilium
Pronounced as ‘fla-gel-ah’, is the plural of
flagellum. From Latin word for whip.
Cilia are short, hair like appendages extending
from the surface of a living cell.
Flagella are long, threadlike appendages on the
surface of a living cell.
Nexin arm present
Nexim arm absent.
short
Longer than cilia, can vary
Rotational, like a motor, very fast moving
Wave-like, undulating, sinusoidal, slow movement
compared to cilia
Many (hundreds) per cell
Few (less than 10) per cell
Eukaryotic cells
Eukaryotic and prokaryotic cells
6). Explain symbiosis, commensalism and protocooperation as
interactions giving examples where necessary.
positive forms of biological
 SYMBIOSIS: the living together of two dissimilar organisms, as in mutualism, commensalism,
amensalism, or parasitism.Sometimes beneficial, sometimes harmful, these relationships are
essential to many organisms and ecosystems, and they provide a balance that can only be
achieved by working together.Symbiosis describes close interactions between two or more
different species. It is different from regular interactions between species, because in a
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symbiotic relationship, the two species in the relationship live together. Many organisms are
involved in symbiotic relationships because this interaction provides benefits to both species.
However, there are types of symbiosis that are not beneficial and may in fact harm one or both
of the species.
EXAMPLES:
The relationship between cattle egrets and cattle.The cattle egret will eat insects that have been
disturbed when the cattle forage.
Cleaner wrasse Labroides cleaning ectoparasites from a sweetlips.
clownfish feeds on small invertebrates that otherwise have potential to harm the sea anemone,
and the fecal matter from the clownfish provides nutrients to the sea anemone.
The clownfish is additionally protected from predators by the anemone's stinging cells, to which
the clownfish is immune. The clownfish also emits a high pitched sound that deters butterfly fish,
which would otherwise eat the anemone.
 COMMENSALISM: Commensalism describes a relationship between two living organisms
where one benefits and the other is not significantly harmed or helped. It is derived from
the English word commensal used of human social interaction. The word derives from the
medieval Latin word, formed from com- and mensa, meaning "sharing a table".Commensal
relationships may involve one organism using another for transportation (phoresy) or for
housing (inquilinism), or it may also involve one organism using something another created,
after its death (metabiosis).
EXAMPLE;Phoretic mites on a fly .
 PROTOCOOPERATION: Protocooperation is where two species interact with each other
beneficially; they have no need to interact with each other - they interact purely for the
gain that they receive from doing this. It is not at all necessary for protocooperation to
occur; growth and survival is possible in the absence of the interaction. The interaction
that occurs can be between different kingdoms.
EXAMPLE; of protocooperation is the connection between ants and aphids. The ant
searches for food on trees and shrubs that are hosts to honeydew-secreting species
such as aphids, mealybugs, and some scales. The ant gathers the sugary substance and
takes it to its nest as food for its offspring. It has been known for the ant to stimulate
the aphid to secrete honeydew straight into its mouth. Some ant species even look after
the honeydew producers from natural predators. In areas where the ant inhabits the
same ecosystem as the plant the plants normally suffer from a higher presence of
aphids which is detrimental to the plant but not to the two species protocooperating.
Flowers and insects; The flowers of plants that are pollinated by insects and birds
benefit from protocooperation. The plants, particularly those with large bright colourful
flowers bearing nectar glands, experience cross pollination because of the insects
activities. This is beneficial to the insect that has got the food supply of pollen and
nectar required for its survival.
7). Explain exploitation, predation as negative forms of biological interactions citing
examples where necessary.
 EXPLOITATION: the strongest interactions between populations are those that
enhance fitness of individuals in one population (the predator, parasite, etc.) while
decreasing fitness of individuals in another population (the prey, host, etc.). As a
rule, such interactions occur between species at different trophic levels.Interaction
where one organism benefits and the other experiences a decrease in growth,
reproduction, or survivorship.Competition is a negative interaction that occurs
among organisms whenever two or more organisms require the same limited
resource. All organisms require resources to grow, reproduce, and survive.
EXAMPLE;
For example, animals require food (such as other organisms) and water, whereas plants
require soil nutrients (for example, nitrogen), light, and water. Organisms, however,
cannot acquire a resource when other organisms consume or defend that resource.
Therefore, competitors reduce each other's growth, reproduction, or survival.
 PREDATION: Predation is a biological interaction where a predator (an organism
that is hunting) feeds on its prey (the organism that is attacked).Predators may or
may not kill their prey prior to feeding on them, but the act of predation often
results in the death of its prey and the eventual absorption of the prey's tissue
through consumption. Predation is often, though not always, carnivory. Other
categories of consumption are herbivory (eating parts of plants), mycophagy (eating
parts of fungi) and detritivory, the consumption of dead organic material (detritus).
EXAMPLE; Some predation entails venom that subdues a prey creature before the
predator ingests the prey by killing, which the box jellyfish does, or disabling it, found in
the behavior of the cone shell. In some cases, the venom, as in rattlesnakes and some
spiders, contributes to the digestion of the prey item even before the predator begins
eating. In other cases, the prey organism may die in the mouth or digestive system of
the predator.
8). Define the term ecosystems.Classify ecosystems citing examples of each type.
An ecosystem is a community of living organisms in conjunction with the nonliving
components of their environment (things like air, water and mineral soil), interacting as
a system.An ecosystem is a community of living organisms in conjunction with the
nonliving components of their environment (things like air, water and mineral soil),
interacting as a system.
CLASSIFICATION OF ECOSYSTEMS.
Classifying ecosystems into ecologically homogeneous units is an important step
towards effective ecosystem management. A variety of systems exist, based on
vegetation cover, remote sensing, and bioclimatic classification systems.Due to the
Abiotic factors, different ecosystems develop in different ways. These factors and their
interaction between each other and with biotic components have resulted in formation
of different types of ecosystems as explained below.
Terrestrial Ecosystems:
Tropical Rain-Forests
Temperature Forests
Tropical Seasonal Forests
Temperate Deciduous Forest
Woodland and Shrub Land
Boreal Forest
Temperate Grassland
Tundra
Cultivated Land
Extreme desert, Rock, Sand and Ice
Desert/Semi-desert Shrub
Aquatic ecosystems:
Open Oceans
Lakes and Streams
Continental Shelf
Estuaries and Brackish Waters
Swamp and Marsh
Upwelling Zones
Algal beds and Reefs.
9). What do you understand by these terms:
a) Ecological pyramid: An ecological pyramid (also trophic pyramid, eltonian pyramid,
energy pyramid, or sometimes food pyramid) is a graphical representation designed
to show the biomass or bio productivity at each trophic level in a given ecosystem.
Biomass is the amount of living or organic matter present in an organism.Ecological
pyramids begin with producers on the bottom (such as plants) and proceed through
the various trophic levels (such as herbivores that eat plants, then carnivores that
eat herbivores, then carnivores that eat those carnivores, and so on). The highest
level is the top of the food chain.
b) Ecological niche: In ecology, a niche is a term describing the relational position of a
species or population in an ecosystem.More formally, the niche includes how a
population responds to the abundance of its resources and enemies (e. g., by
growing when resources are abundant, and predators, parasites and pathogens are
scarce) and how it affects those same factors (e. g., by reducing the abundance of
resources through consumption and contributing to the population growth of
enemies by falling prey to them).
c) Food web: A food web (or food cycle) is the natural interconnection of food chains
and generally a graphical representation (usually an image) of what-eats-what in an
ecological community. Another name for food web is a consumer-resource system.
A food web consists of all the food chains in a single ecosystem. Each living thing in
an ecosystem is part of multiple food chains. Each food chain is one possible path
that energy and nutrients may take as they move through the ecosystem. All of the
interconnected and overlapping food chains in an ecosystem make up a food web.
d) Food chain: The food chain describes who eats whom in the wild. Every living
thing—from one-celled algae to giant blue whales—needs food to survive. Each
food chain is a possible pathway that energy and nutrients can follow through the
ecosystem.For example, grass produces its own food from sunlight. A rabbit eats the
grass. A fox eats the rabbit. When the fox dies, bacteria break down its body,
returning it to the soil where it provides nutrients for plants like grass.
10.) Differentiate between ordinary food chain and detritus food chain.
Ordinary food chain
Detritus food chain
In this food chain, energy is derived from the Sun.
In this food chain, energy comes from organic
matter (or detritus) generated in trophic levels of
the ordinary food chain.
It begins with producers, present at the first
trophic level. The plant biomass is then eaten by
herbivores, which in turn are consumed by a
variety of carnivores.
It begins with detritus such as dead bodies of
animals or fallen leaves, which are then eaten by
decomposers or detritivores. These detritivores
are in turn consumed by their predators.
This food chain is usually large.
It is usually smaller as compared to the grazing
food chain.