Higher Biology Cells Mr G Davidson Unicellular Organism

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Higher Biology

• Cells

Mr G Davidson
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Unicellular Organisms

• Unicellular organisms consist of only one cell
  and include animals and plants.
• In order to survive, these organisms must be able
  to carry out all the functions required for life,
  e.g. gas exchange, feeding, reproduction ,etc.
• Unicellular organisms include yeast, Amoeba,
  Paramecium, Euglena, Pleurococcus, etc.

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Unicellular Organisms
Pleurococcus
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Unicellular Organisms
Amoeba
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Unicellular Organisms
Paramecium
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Unicellular Organisms
Euglena
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Unicellular Organisms

• Amoeba have numerous pseudopodia which are blunt
  projections, and the organism can flow into one
  of these, moving like a leech.
• The amoeba feeds by surrounding food particles
  and engulfing them into food vacuoles where the
  food is broken down by enzymes.

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Unicellular Organisms

• Any undigested food remaining in the vacuole is
  left behind until the vacuole can break through
  the membrane and release it.
• This process is called phagocytosis.

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Phagocytosis
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Tissues

• Multicellular organisms have many cells which are
  organised into tissues to perform a particular
  function.
• Although tissues are adapted to carry out a
  particular function, the cells of the tissue
  often vary e.g. phloem tissue contains sieve
  tubes and companion cells.

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Tissues

• Epithelial tissues are lining tissues which cover
  both internal and external surfaces of organisms.

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Tissues

• A lining tissue often contains more than one type
  of cell e.g. the trachea epithelium contains
  ciliated and goblet cells.
• The tissue is usually called after the
  predominant cell type e.g. ciliated epithelia.

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Tissues

• In ciliated epithelium the free surface has cilia
  which beat rhythmically, enabling them to move
  particles along tubes as in the trachea.

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Ciliated Epithelium
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Tissues

• Columnar epithelium is a tissue with column
  shaped cells.
• This type of tissue is found in the stomach and
  small intestine linings.
• The microvilli (s. microvillus) greatly increase
  the surface area to allow for efficient
  absorption of soluble molecules.

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Columnar Epithelium
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Tissues

• Glandular epithelium is made up of cells which
  secrete substances e.g. enzymes, mucus and
  hormones.
• These cells are often clumped together to form
  the glands of the body.

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Glandular Epithelium
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Plant Tissues

• Xylem tissue is composed of
• xylem vessels which offer strength
• tracheids whose cells overlap at the ends and
  they transport water as well as provide support.
• Xylem tissue has lignin impregnated walls which
  provide support.

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Plant Tissues

• Phloem tissue is composed of
• sieve tubes which transport soluble
  carbohydrates
• companion cells which control the sieve tubes.

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Xylem Tissue
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Phloem Tissue
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Cell Ultrastructure
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Cell Ultrastructure

• The ultrastructure of a cell is made up of cell
  organelles which can be seen with the increased
  power of the electron microscope.

Plant Cell
Animal Cell
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Cell Ultrastructure
Organelle Function
Lysosome Contains powerful degradation enzymes for cell lysis
Cell (plasma) Membrane Controls entry and exit of materials
Golgi Body Packages materials for secretion
Endoplasmic reticulum (ER) Smooth endoplasmic reticulum provides channels for transport and rough endoplasmic reticulum provides large surface area for ribosomes
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Cell Ultrastructure
Organelle Function
Mitochondrion Site of respiration
Ribosomes Site of protein synthesis
Nucleus Controls activities of the cell
Centriole Organises spindles during mitosis
Cell wall Provides a rigid framework around plant cells
Vacuole Storage of materials within the plant cell
Chloroplast Site of photosynthesis