CELL STRUCTURE

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CHAPTER 2

• CELL STRUCTURE
• AND
• CELL ORGANISATION

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Diagram of a typical animal cell. Organelles are
labelled as follows

• 1. Nucleolus
• 2. Nucleus
• 3. Ribosome
• 4. Vesicle
• 5. Rough endoplasmic reticulum
• 6. Golgi apparatus (or "Golgi body")
• 7. Cytoskeleton
• 8. Smooth endoplasmic reticulum
• 9. Mitochondrion
• 10. Vacuole
• 11. Cytoplasm
• 12. Lysosome
• 13. Centriole

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Organelle Main function Structure Organisms Notes
chloroplast (plastid) photosynthesis double-membrane compartment plants, protists has some genes
endoplasmic reticulum translation and folding of new proteins (rough endoplasmic reticulum), expression of lipids (smooth endoplasmic reticulum) single-membrane compartment all eukaryotes rough endoplasmic reticulum is covered with ribosomes, has folds that are flat sacs smooth endoplasmic reticulum has folds that are tubular
Golgi apparatus sorting and modification of proteins single-membrane compartment all eukaryotes cis-face (convex) nearest to rough endoplasmic reticulum trans-face (concave) farthest from rough endoplasmic reticulum
mitochondrion energy production double-membrane compartment most eukaryotes has some DNA
vacuole storage, homeostasis single-membrane compartment eukaryotes
nucleus DNA maintenance, RNA transcription double-membrane compartment all eukaryotes has bulk of genome
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Minor eukaryotic organelles and cell components Minor eukaryotic organelles and cell components Minor eukaryotic organelles and cell components Minor eukaryotic organelles and cell components
Organelle Main function Structure Organisms
centriole anchor for cytoskeleton Microtubule protein animals
cilium movement in or of external medium Microtubule protein animals, protists, few plants
lysosome breakdown of large molecules (e.g., proteins polysaccharides) single-membrane compartment most eukaryotes
myofibril muscular contraction bundled filaments animals
nucleolus ribosome production protein-DNA-RNA most eukaryotes
ribosome translation of RNA into proteins RNA-protein eukaryotes, prokaryotes
vesicle material transport single-membrane compartment all eukaryotes
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• Chloroplasts are larger than mitochondria, and
  are surrounded by two specialized membranes. In
  plants and some other eukaryotes, chloroplasts
  are the sites of photosynthesis, a process in
  which atmospheric carbon dioxide is "fixed" into
  organic compounds, and oxygen is released into
  the atmosphere

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• Mitochondria are small, oval shaped organelles
  surrounded by two highly specialized membranes.
  Mitochondria are the sites of aerobic
  respiration, and are generally the major energy
  production center in eukaryotes

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• Cell Organisation
• Organism can be categorised as unicellular or
  multicellular
• Unicellular organism are organism with just one
  cell, for example Amoeba sp. and Paramecium sp.
• Multicellular organisms are made up of more than
  one cell

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Amoeba proteus
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• The Amoeba sp. Exhibits various living
  processes as follows
• Feeding
• Locomotion
• Reproduction
• Feeding
• Amoeba sp. feeds on bacteria and algae much
  smaller than itself.
• When the amoeba sp comes in contact with its
  food, it puts its pseudopodia all around the food
  to enclose it in a drop of water, forming a food
  vacuole
• The cytoplasm secrete enzymes into the food
  vacuole to digest the food.
• The digested substances are absorbed into the
  cytoplasm while the undigested material are
  removed when the vacuole comes in contact with
  the plasma membrane and breaks

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• Locomotion
• The amoeba moves by putting out new pseudopodia
  in front withdrawing other behind.
• Movement by means of pseudopodia is known as
  amoeboid movement
• The shape of the amoeba changes as it move.

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• Reproduction
• The amoeba reproduce mainly by binary fission
• Binary fission is a method of asexual
  reproduction which does not involve the fusion of
  gametes.
• When food is abundant, the amoeba reproduces by
  binary fission. When the amoeba reaches a maximum
  size, the nucleus divides into two and the
  cytoplasm constrict, forming two new amoeba.
• The amoeba does not reproduce sexually.

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• Cell specialisation in multicellular organism
• Being multicellular not only enables organisms to
  be larger, it also enables their to become
  specialised.
• Each type of cell specialiseds in performing a
  particular function, for example the red blood
  cell in animal transports oxygen and the xylem
  vessel in plant transports water and mineral
  salt. This is known as division of labour.
• The division of labour permits greater efficiency
  and enables multicellular organisms to exploit
  environments that are denied to unicellular
  organisms. Foe example, only multicellular
  organisms can adapt to life in terrestrial
  environment.
• Multicellular organisms have a great potential
  for cell specialisation, leading to the
  development of tissues and organ

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• Cell organisation in the formation of tissues,
  organ and systems in the multicellular organism
• The study of cells is known as cytology

Level of organisation meaning
Cell The smallest unit of life capable of carrying out all the function of living things.
Tissue A group of cells of the same type that perform a specific function in an organism.
Organ Several type of tissue that carry out a particular function
Organ system Several organ working together to perform a function
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cell Function
Muscle cell Able to contract and relax and are involve in movement
White blood cell Involves in defence of the body against diseases
Sperm Fertilises the ovum
Red blood cell Transport oxygen
Nerve cell Receive and sends out nerve impulses
Some of the human cell and their functions
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cell Function
Parenchyma cell For support and storage
Xylem vessel element Transports water and mineral salt
Sieve tube element Transports organic product of photosynthesis
Companion cell Regulates the metabolic activity of sieve tube element
Epidermal cell For protection and covering of other cells beneath
Some of the human cell and their functions
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• The study of tissues is known as histology
• In human and animal, there are four basic types
  of tissuesc

Tissue Function Example
Epithelial tissue Forms thin sheets that line and cover body structure the function depends on its location in an organ Ciliated cells that line the respiratory tract
Connective tissue Holds the body together Bone, cartilage, blood, tendon, ligament
Muscular tissue Contract to produce movement Skeletal muscles, smooth muscle, cardiac muscle
Nervous tissue Conduct nerve impulses Densely packed nerve cells
Humans and animal tissues
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• There are three major plant tissues epidermis,
  ground tissue and vascular tissue

Tissue Function Example
Epidermis Covers and protects underlying tissues from drying out and form mechanical abrasions Epidermis of leaves, cork layer of stems and roots
Ground tissue Chief functions are to store food and to provide support Parenchyma at the cortex and pith
Vascular tissue Distribute water, mineral salts and photosynthetic products throughout the plant Xylem, phloem
Plant tissues
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• Organ consists of several types of tissues and it
  is specialised to perform a specific function
• Example of human organ include heart, stomach,
  kidney, liver and blood vessels
• Organ system consists of a group of organs which
  carryout major function such as respiratory,
  nutrition and other
• There are 12 organ system in human.

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• Circulatory system
• Function
• Transport material such as nutrient, gases,
  metabolic waste and heat around the body
• Organs and structure
• hear, blood vessels

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Function provides a means for gaseous
exchange, that is oxygen Organs and
structure hear, blood vessels
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Function Breaks down complex food into simple
substance for easy absorption by body
cells Organs and structure mouth, oesophagus,
stomach, intestine, rectum and anus
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Excretory system Function Discard toxic waste
product Organs and structure Liver, kidney,
urinary bladder
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• Intergumentary System
• Function
• Physically separates the body from the external
  environment
• Protects the body against mechanical injuries,
  microbial infection and dehydration
• Organs and structure
• Skin

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Skeletal System Function Provides bodily
support and protection to soft internal
organs Organs and structure skull, rib cage,
humerus, backbone, ulna, radius, femur, fibula
and tibia
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Muscular System Function help in movement of
the body Organs and structure all muscle..
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• Lymphatic System
• Function
• Defend the body against infection
• Return excess tissue fluid to the blood
• Organs and structure
• all muscle..

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Endocrine System Function produces hormone
that control the bodily activities Organs and
structure Pituitary gland, adrenal gland,
thyroid gland, pancreas, testes and ovaries.
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Female reproductive system
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• Cell organisation
• Plant tissue
• Meristematic tissue consist of small cells which
  have thin walls, large nuclei, dense cytoplasm
  and no vacuoles.
• Apical meristems are located at the tips of roots
  and the bud of shoots. The tissues undergo
  mitotic cell division to increase the number of
  cell division to increase the number of cell for
  plant growth.
• Lateral meristems or cambium are found in the
  peripheral areas of stem and roots. They are
  responsible for secondary growth which adds girth
  to the plants.

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• Permanent tissues
• Permanent tissues consist of more mature cells
  that are either undergoing differentiation or
  have already undergone differentiation.
• There are three types of permanent tissues
• Epidermal tissues
• forms a layer to cover the entire surface of the
  plants and protects the surface of plants
• Protect the underlying tissues from physical
  damage infection
• Reduce water loss
• b) Ground tissues
• Provide support and strengthens the plants
• c) Vascular tissues
• Transport water and food
• Provide support

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• The importance of maintaining an optimal
• internal environment in cells
• The self-regulation of the internal environment
  of organisms have or cells is called homeostasis
• Multicellular organisms have a series or organ
  and systems that functional in homeostasis
• For a multicellular organisms to function
  efficiently, other factors in the internal
  environment also have to be maintained within
  narrow limits. Examples of these factors include
  the volume of water, temperature, acidity and
  concentration of salts.
• Homeostasis is essential for the maintenance of
  health and its breakdown will inevitably result
  in disease

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• Appreciating the uniqueness of the cell
• Each cell is unique and its organelles are
  specialised to perform specific roles to carry
  out the cell mechanisms
• With the division of labour among the different
  types of cells, it ensures the efficient and
  smooth functioning of the life processes in the
  body and the survival of the organism.
• The function of intracellular organelles such as
  mitochondria, lysosomes and the endoplasmic
  reticulum also depend on the integrity of their
  cell membrane (explain the function of each
  organelles)
• Generally, any damage to the cell parts or
  organelles can effect the cells activities and
  this could be detrimental to the cell as it could
  lead to cell death.