NAME: DOYE OGHENETEJIRI FAVOUR
DEPARTMENT: NURSING SCIENCE
LEVEL: 100
COURSE CODE: BIO 101
1)
What is a cell? Give the features a true cell should possess.
A cell is the simplest unit of a living organism. It is the basic unit of structure and function of
life.
ii) the basic features of a true cell are;
-
A set of genes
A limiting plasma membrane
A metabolic machinery
2) Differentiate between the prokaryotic and the eukaryotic cells.
PROKARYOTIC CELL
Cell wall is present in most
Absence of nucleus
Absence of nuclear membrane
Chromatin with histone is absent
Circular or linear double stranded DNA
Absence of nucleoli and mitotic apparatus
Plasmids are common
EUKARYOTIC CELL
Only plants and fungal have cell walls
Presence of nucleus
Presence of nuclear membrane
Chromatin with histone is present
Linear double stranded DNA
Presence of nucleoli and mitotic apparatus
Plasmids are rare
3) With the aid of well labelled diagrams illustrate the ultastructures of plant and animal cells.
The ultrastructure of a plant cell
4). Briefly describe the structures and functions of the following cellular organelles illustrating
with diagrams where necessary
a) NUCLEUS
Function of nucleus
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c) MITOCHONDRIA
Mitochondria are rod shaped structure found in both animal and plant cells. It is a double
membrane bound organelle. It has the outer membrane and the inner membrane. The membranes
are made up of phospholipids and proteins.
The functions of mitochondria
It depends on the cell type in which they are present.
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The most important function of the mitochondria is to produce energy. The simpler
molecules of nutrition are sent to the mitochondria to be processed and to produce charged
molecules. These charged molecules combine with oxygen and produce ATP molecules. This
process is known as oxidative phosphorylation.
Mitochondria help the cells to maintain proper concentration of calcium ions within the
compartments of the cell.
The mitochondria also help in building certain parts of blood and hormones like
testosterone and estrogen.
The liver cells mitochondria have enzymes that detoxify ammonia.
The mitochondria also play important role in the process of apoptosis or programmed cell
death. Abnormal death of cells due to the dysfunction of mitochondria can affect the
function of organ.
d) GOLGI APPARATUS
Structure of Golgi apparatus
Golgi Apparatus Function
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 determines the final destination of the protein
e) PLASMA MEMBRANE
Structure of plasma membrane
Function of Plasma Membrane
1) It separates the contents of the cell from its outside environment and it regulates what
enters and exits the cell.
2) 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.
3) 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.
4) 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.
5) The lipid bilayer is semi-permeable, which allows only selected molecules to diffuse across
the membrane
e) CILIA
Cilia are slender, microscopic, hair-like structures or organelles that extend from the surface of
nearly all mammalian cells (multiple or single).
Functions of cilia
Cilia use ‘kinesin’ which has an ATPase activity that produces energy to perform the movement.
Helps in locomotion, feeding circulation, aeration, etc.
5). How can you differentiate between cilia and flagella?
S.N.
Characteristics
1
Definition
2
Length
3
Occurrence
4
Beating
5
Motion
6
Found in
7
Energy Production
8
Functions
Cilia
Cilia are short, hair like
appendages extending from the
surface of a living cell.
Short and hair like organelle (510µ)
Occurs throughout the cell
surface.
Cilia beat in a coordinated
rhythm either simultaneously
(synchronous) or one after the
other (metachronic).
Flagella
Flagella are long, threadlike
appendages on the surface of a
living cell.
Long wipe like organelle (150µ)
Presence at one end or two ends
or all over the surface.
They beat independent of each
other.
Wave-like, undulating,
Rotational, like a motor, very fast
sinusoidal, slow movement
moving
compared to cilia
Eukaryotic cells
Eukaryotic and prokaryotic cells
Cilia use ‘kinesin’ which has an
Flagella are powered by the
ATPase activity that produces
proton-motive force by the
energy to perform the
plasma membrane.
movement.
Helps in locomotion, feeding
Help mainly in locomotion only.
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Examples
circulation, aeration, etc.
Cilia present in Paramecium
Flagella present in Salmonella
6). Explain symbiosis, commensalism and protocooperation as positive forms of biologiacal
interactions giving examples where necessary.
- Symbiosis (from Greek σύν "together" and βίωσις "living")[2] is close and often long-term
interaction between two different biological species. In 1877 Albert Bernhard Frank used the word
symbiosis (which previously had been used to depict people living together in community) to
describe the mutualistic relationship in lichens.[3] In 1879, the German mycologist Heinrich
ASymbiotic relationships include those associations in which one organism lives on another
(ectosymbiosis, such as mistletoe), or where one partner lives inside the other (endosymbiosis,
such as lactobacilli and other bacteria in humans or Symbiodinium in corals).[12][13] Symbiosis is also
classified by physical attachment of the organisms; symbiosis in which the organisms have bodily
union is called conjunctive symbiosis, and symbiosis in which they are not in union is called
disjunctive symbiosis.[14]
-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). Examples of metabiosis are
hermit crabs using gastropod shells to protect their bodies and spiders building their webs on
plants.
-Protocooperation: It 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; Flowers and insectsThe 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 and amensalism as negative forms of biological interactions
citing examples where necessary.
-Exploitation; this is a form of social parasite interaction whereby one species uses the other for
various advantages e.g egg parasitism in old world cuckous and brood parasitism in Indian koel and
crow, one species of ant snatches food from another and so on.
-Predation: This is a form of negative interaction whereby members of one species eat those
another specie
-Amensalism; this biotic interaction brings about the adverse effect of one of the competing
popution or species while the other remains stable the suppression of the growth through the
release of chemicals by higher plant is know as allelopathy e.g salvia leucophylla emits some
volatile oil which reach the surface of the soil and inhibit the germination of seeds of other species a
complete of partial inhibition or death of one organization e.g chlorella vulgaris produces substance
which inhibits the growth of diatoms
8). Define the term ecosystems. Classify ecosystems citing examples of each type.
Ecosystem is any unit that includes all the organisms in a given area which interacts among their
selves and with their physical environment so that a flow of energy leads to clearly defines trophic
structure, biotic diversity and material cycles within the systems.
It is classified into;
a) Natural ecosystem: These are ecosystem that are not built but occur naturally in nature.
Examples are;
i) Terrestrial ecosystem- e.g forest, grassland, deserts and so on
ii) Aquatic ecosystem- e.g lotic( running water as spring, streams and lentic (stagnant water as lake,
ponds, pools.
b) Artificial ecosystems; they are man made ecosystems e.g cropland and so on
9). What do you understand by these terms:
(a). Ecological pyramid
Ecological pyramid is the graphical representation of the trophic structure and function at
successive trophic levels where the first or producer level constitute the base of the
pyramids at successive levels, the last making up the apex,
b) Ecological niche
Ecological niche is the ultimate unit within which each species is held by it’s structural and
instinctive limitations.
c)Food web
It is a complex network whereby various food chains are linked together.
d)Food chain; is a linear feeding arrangement or organisms which energy flows from one level to
another in a unidirectional manner.
10). Differentiate between ordinary food chain and detritus food chain
Detritus food chain; this type of food chain where decomposed material is the first organiam in d
food chain then to organisms feeding on detritivores and their predators. E.g decomposed plant –
insect- frog – snake- eagle
While
An ordinary food chain the primary produces e.g plants are the first organisms in the food chain
then to consumers then decomposers e.g plant- grasshopper- frog and snake