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IDENTIFY STRUCTURES AND
FUNCTIONS IN DIFFERENT
TYPES OF CELLS

Iba Ruma Mohammed
BIOLOGY Assignment 2

Iba Ruma Mohammed

A tissue is a group of cells that have a similar shape and function
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In humans, there are four basic types of tissue: epithelial,
connective, muscular, and nervous tissue
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EPITHELIAL TISSUE
Epithelial tissue covers the body surface
and forms the lining for most internal
cavities
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The skin is an
organ composed of epithelial tissue
which protects the body from dirt, dust,
bacteria and other microbes that may be
harmful
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Cells can be thin, flat to
cubic to elongated
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All materials entering or leaving the body must cross at least one layer of
epithelial tissue
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Different types of epithelium may be distinguished by their morphological appearance,
which in turn is dependent on the location of the tissue and the particular tasks it must
accomplish
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If an epithelium consists of only one layer of cells on a basement
membrane, it is called simple epithelium
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In addition, the cross-sectional shape of
epithelial cells can be used to further classify these tissues
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CONNECTIVE TISSUE
Connective tissue is the most abundant and the most widely distributed of the
tissues
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These tissues are found in the human body, ordinary loose connective tissue,
fat tissue, dense fibrous tissue, cartilage, bone, blood, and lymph, which are all considered
connective tissue
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Skeletal muscle
is a voluntary type of muscle tissue that is used
in the contraction of skeletal parts
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It is an involuntary
type
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As the name implies, these tissues perform
connective and supportive functions: giving
form to and anchoring the organs of the body
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The matrix consists of widely dispersed fibers
embedded in a ground substance, which may range in form from solid to liquid
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Nerve cells or
neurons are long and string-like
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Examples
include the mucous membrane which
lines body cavities
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An organ is a part of the
body which performs a definite function
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A system is a group of organs each of which contributes its share to the
function of the body as a whole
Nervous tissue carries a fundamental property of living tissue, irritability, to an extreme
degree, being highly specialized to receive and transmit internal as well as external stimuli
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Iba Ruma Mohammed

Neurons receive signals from either the external or internal environment, and transmit
them in the form of electrical impulses to other neurons, muscles or glands
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(See figure in text
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Motor neurons lie mostly outside the brain and spinal
cord, and relay signals from the central nervous system to effector organs (muscles or
glands)
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MUSCLE TISSUE
All movement in higher animals is dependent upon
the contractile capabilities of muscle
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The
three types of muscle found in vertebrates are:
smooth, skeletal, and cardiac
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The muscle cells are wrapped by fibroconnective
tissue which maintains the shape of the muscle, and carries the blood vessels and nerves to
the muscle tissue
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These contain the intracellular contractile elements, the myofilaments
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Skeletal muscle
Skeletal muscle is striated (that is, it has "stripes" when viewed under the microscope) and
is under the control of the somatic nervous system
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Skeletal muscle cells are very large,
and are actually a syncytium, a fusion of a number of cells
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The
nuclei are usually found at the periphery of the cells
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Cardiac muscle
Cardiac muscle makes up the heart
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Cardiac muscle is comprised of uninucleate branching cells connected
together by intercalated discs, visible in the mid and high magnification image (three are
labeled on the high magnification view)
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Do not confuse these with the striations produced by the highly ordered

Iba Ruma Mohammed

myofilaments
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In the high
magnification images you may note that the cells each have a single nucleus
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Note that the fibers are branched and that there are interconnections between
fibers
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Because the contractile myofilaments are not highly
organized, no banding pattern is apparent
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However, if the cells are preserved in a contractile
state their overall shape and the shape of the nucleus may be distorted
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Smooth muscle is usually arranged in two layers around the hollow tubes of the
body: circular and longitudinal
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They do this by making things appear bigger
(magnifying them) and at the same time increasing the amount of detail we can see
(increasing our ability to distinguish between two objects or ‘resolve’ them)
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Different kinds of microscopes can show us different amounts of detail (they have different
resolving power)
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Microscopes magnify and show more detail
When we talk about how microscopes work, we often say that they make things look bigger
– that is, they magnify them
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This helps us to make sense of what we’re seeing
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This is why all
micrographs published in scientific journals must indicate the extent of magnification
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If microscopes did nothing but make
what we can already see bigger, they wouldn’t be much use! Instead, microscopes increase
the amount of detail that we can see
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Iba Ruma Mohammed

Make a resource about Prokaryotic and Eukaryotic cells:

Prokaryotic: prokaryotic is a group of single celled organisms which do not contain a nucleus
a true nucleus
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The genetic material (DNA) is localized to an area called the nucleoid which has no
2
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4
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surrounding membrane
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At the outside edge of the cell is the plasma membrane and in the some prokaryotes the
plasma membrane folds in to form structures called mesosomes, the function of which is
not clearly understood
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Some bacteria have flagella which are used for locomotion or pili, which is used to pull two
cells in close contact and possibly to facilitate the transfer of genetic material
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What is a eukaryotic cell?

Eukaryotic cells are the type of living cells that form the
organisms of all of the life kingdoms except monera
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An example of eukaryotic cells includes plant cells and
animal cells, but do not include bacteria this is because bacteria are part of the prokaryotic
cells
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The nucleus houses the cell’s DNA and directs the synthesis of proteins and
ribosome
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Animal cells have a centrsome and liposome’s while Plant cells do not

How to identify the organelles found in typical eukaryotic cells

The organelles the are found in eukaryotic cells are:
1
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2
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3
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4
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5
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The naked eye can tell apart (resolve) two
objects (such as grains of sand) that are about a tenth of a millimetre apart – any closer than

Iba Ruma Mohammed

that, and we see the two as a single shape
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If we try to magnify further, we won’t be able to see
any more detail than this – just like the digital photo above, the microscope will have
reached the limit of its resolution
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Eukaryotic cells contain membranebound organelles, such as the nucleus, while prokaryotic cells do not
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Prokaryotes were the only form of life on Earth for millions of years until more complicated
eukaryotic cells came into being through the process of evolution
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Folded DNA is then
DNA wrapping on
around proteins called
organized into a variety of conformations that are
proteins
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supercoiled and wound around tetramers of the
HU protein
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Most are unicellular, but some prokaryotes are multicellular
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The most characteristic membrane bound structure is the
nucleus
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Iba Ruma Mohammed


The most fundamental difference is that eukaryotes do have "true" nuclei containing their
DNA, whereas the genetic material in prokaryotes is not membrane-bound
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In prokaryotes similar
processes occur across the cell membrane; endosymbionts are extremely rare
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

Prokaryotes are usually much smaller than eukaryotic cells
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Although some eukaryotes have satellite DNA
structures called plasmids, these are generally regarded as a prokaryote feature and many
important genes in prokaryotes are stored on plasmids
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

Genes
o

o

o
o

Prokaryotes also differ from eukaryotes in the structure, packing, density, and
arrangement of their genes on the chromosome
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Whereas nearly 95% of the human genome does not code for proteins or RNA or
includes a gene promoter, nearly all of the prokaryote genome codes or controls
something
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In a prokaryote cell, all genes in an operon(three in the case of the famous lac
operon) are transcribed on the same piece of RNA and then made into separate
proteins, whereas if these genes were native to eukaryotes, they each would have
their own promoter and be transcribed on their own strand of mRNA
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Making a slide of Onion Epidermis

Iba Ruma Mohammed

Plant cells can be seen using a light microscope
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Here is a typical method:
1
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3
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5
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For example,
blood vessels are lined by simple squamous
epithelium (which is more specifically called
endothelium when it lines a blood vessel)
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This slide is a whole mount of sheet of
mesothelium and does not contain other tissues

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