Cell: The Unit of LIfe Flashcards
what can unicellular organisms do? what are they
Organisms composed of a single cell is called Unicellular Organisms. Unicellular organisms are capable of (i) independent existence and
(ii) performing the essential functions of life. Anything less than a complete
structure of a cell does not ensure independent living. Hence, cell is the
fundamental structural and functional unit of all living organisms.
who found the first dead cell and live cell?
Robert Hooke observed dead cork cells. Anton von Leeuwenhoek first saw and described a live cell. Robert
Brown later discovered the nucleus. The invention of the microscope and
its improvement leading to the electron microscope revealed all the
structural details of the cell.
who were matthias schleiden and theodor schwann
In 1838, Matthias Schleiden, a German botanist, examined a large number
of plants and observed that all plants are composed of different kinds of
cells which form the tissues of the plant. At about the same time, Theodore Schwann (1839), a British Zoologist, studied different types of animal cells
and reported that cells had a thin outer layer which is today known as the
‘plasma membrane’. He also concluded, based on his studies on plant
tissues, that the presence of cell wall is a unique character of the plant
cells. On the basis of this, Schwann proposed the hypothesis that the bodies
of animals and plants are composed of cells and products of cells.
schleiden and schwann gave the cell theory but it did not explain one thing. who concluded the celll theory
Schleiden and Schwann together formulated the cell theory. This theory
however, did not explain as to how new cells were formed. Rudolf Virchow
(1855) first explained that cells divided and new cells are formed from
pre-existing cells (Omnis cellula-e cellula). He modified the hypothesis of
Schleiden and Schwann to give the cell theory a final shape.
what is the cell theory today
(i) all living organisms are composed of cells and products of cells.
(ii) all cells arise from pre-existing cells.
give an overview of a cell?
i)cell wall
ii)cell membrane
iii)nucleus
iv)cytoplasm
vorganelles
vi) ribosomes
vii)centrosome
i) plants have distinct cell walll within which they have cell membrance
ii)cell membrance is the delimiting structure in animal cells
iii) Inside each cell is a dense membrance bound structure called nucleus. Nucleus contains chromosome which in turn have genetic material, DNA. Prokaryotic cell do not have a welldefined membrane bound organelle, while eukarotic cell have one well defined.
iv) A semi-fluid matrix whcih occupies the volume of the cell. It is the main arena for all metabolic activities of the cell and all biochemical reactions. These reactions keep the cell in a living state
v) there are distinct membrane bound structure which perform certian functions in eukaryotes called organelle, like er, golgi apparatus, mitochondria, lysosome, microbodies and vacuoles.
vi) ribosomes are non membrance bound organelles in both eukaryotes and prokaryotes. theyre in cytoplasm also in chloroplast, mitochondria, rough er.
vii) Centrosome non membrance bound organelle for cell divison
how do cells differ in size?
Cells differ greatly in size, shape and activities.hey may be disc-like, polygonal, columnar, cuboid,
thread like, or even irregular. The shape of the cell may vary with the
function they perform.
what is the
i) smallest cell?
ii) largest isolated cell?
iii) longest cell?
iv) size of bacteria?
v) size of human rbc
vi) size of bacteria
i) mycoplasma 0.3-3 micrometre
ii) ostrich egg (15cm)
iii)nerve cell(0.1 micrometre-1m)
iv)3-5 micrometer
v) 7 micrometer in diia
vi)3-5 micrometer
The shape of the cell may vary with the
function they perform. give examples
WBC’s are amoeboid to facilitate phagocytosis which is for engulfing foreign material.
Nerve cells are branched and long since they have to continuously conduct nerve impulses
tracheids are elongated tube like with tapering ends to facilitate water transport
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