Transcript Slide 1

Cell Structure and Function
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Cell Structure and Function
Introduction
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The cell is the structural and functional unit of all living organisms.
All human cells originate from a single fertilized egg (zygote).
During development, cell division and specialization give rise to
trillions of cells with a wide variety of cell types, such as nerve,
muscle, bone, fat and blood cells.
Each cell type has important characteristics to perform a
particular function.
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Cell Structure and Function
How we learn about cells?
1. Because most cells are too
small to be seen with the
unaided eye, it is necessary to
use microscopes to study cells.
2. Light microscopes allow us to
visualize some general features
of cells.
3. Electron microscopes allow us
to study the fine structure of
cells.
4. Microscopic techniques only
allow us to study cell structure.
Therefore, other techniques
such as tissue culture must be
employed to study cell
function.
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Cell Structure and Function
Cells are enclosed by a plasma membrane
Each cell is surrounded by a thin plasma membrane, which isolates
the cell's contents from the external environment.
Functions of plasma membrane
1. Enclose and support the cell contents.
2. Control the movements of substances into and out of the cell.
Structure of plasma membrane
1. The plasma membrane is made up of lipid, protein and
carbohydrate components.
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Cell Structure and Function
Cytoplasm
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The cytoplasm is the cellular material inside the plasma
membrane and outside the nucleus.
The fluid portion of the cytoplasm contains various inorganic and
organic chemicals that are dissolved and/or suspended. This fluid
suspension is called the cytosol.
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Cell Structure and Function
Cytoplasm contains organelles
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Organelles are small structures within cells that are specialized
for particular functions.
Most organelles have membranes that are similar to the plasma
membrane.
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Cell Structure and Function
Ribosomes
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Ribosomes are the sites of protein synthesis.
Each ribosome is composed of a large subunit and a smaller one.
Ribosomes can be found free in the cytoplasm (free ribosomes)
or associated with membranes called the endoplasmic reticulum
(attached or bound ribosomes).
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Cell Structure and Function
Endoplasmic reticulum
The endoplasmic reticulum consists of broad,
flattened, interconnecting membrane-limited sacs
(cisternae) and tubules
Rough endoplasmic reticulum (RER)
1. Is endoplasmic reticulum with attached
ribosomes.
2. The cisternae of RER are arranged in parallel.
3. The function of RER is the synthesis of proteins.
Smooth endoplasmic reticulum
1. Is endoplasmic reticulum that lacks ribosomes.
2. Consists of membrane-limited vesicles and
branched tubules.
3. It manufactures lipids and carbohydrates.
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Cell Structure and Function
Endoplasmic reticulum
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Cell Structure and Function
Golgi apparatus
1. It is composed of slightly curved smooth-surfaced cisternae that
run in parallel.
2. The cisternae are slightly expanded at either ends.
3. Numerous small vesicles are associated with the ends of the
cisternae.
4. The Golgi apparatus modifies (adds sugars to proteins) and
packages proteins to form secretory vesicles which fuse with the
plasma membrane as secretion occurs. Thus, secretion is the
main role played by Golgi apparatus.
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Cell Structure and Function
Mitochondria
1. They are usually rod-shaped structures.
2. Each mitochondrion has inner and outer membranes separated by
intermembrane space.
3. The outer membrane is a smooth, but the inner membrane has
numerous folds called cristae.
4. They produce the energy in the form of ATP.
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Cell Structure and Function
Lysosomes
1. Lysosomes are membrane-bounded vesicles that pinch off from
Golgi apparatus.
2. Contain a great variety of hydrolytic enzymes that are used for
intracellular digestion.
3. Their hydrolytic enzymes are capable of digesting foreign
materials, such as bacteria.
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Cell Structure and Function
Centrioles
1. Animal cells contain two centrioles that are oriented
perpendicular to each other.
2. Each centriole is a small cylindrical organelle with a microtubular
structure.
3. Synthesize microtubules of cilia and flagella and spindle fibers
during cell division.
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Cell Structure and Function
Nucleus
1. It contains our genetic information.
2. It consists of three distinguishable parts:
• The nuclear envelope.
• Chromatin.
• Nucleolus.
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Cell Structure and Function
Nuclear Envelope
1. The nucleus is bounded by a nuclear envelope which separates
the nuclear material from the cytoplasm.
2. It consists of two parallel membranes, the outer nuclear
membrane and the inner nuclear membrane.
3. The nuclear envelope is interrupted at many sites by small
nuclear pores.
4. It controls the passage of materials.
Chromatin
1. The nucleus contains a granular-looking material called
chromatin.
2. Chromatin is a complex of DNA and proteins called histones.
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Cell Structure and Function
Nucleolus
1. It is a dense region within the nucleus.
2. Lacks a surrounded membrane.
3. It manufactures the subunits of ribosomes.
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