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Organelles - PowerPoint PPT Presentation

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Organelles. Biology 11 E. McIntyre. Cytoplasm (cytosol): a cell's inner space. Plasma membrane. Cytoskeleton cytosol.

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Biology 11

E. McIntyre

Cytoplasm cytosol a cell s inner space l.jpg
Cytoplasm (cytosol): a cell's inner space





Cytosol: large fluid-filled space (mostly water + proteins that control most of the cell metabolisms): glycolysis, transcription factors, intracellular receptors etc.

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Reminder! Membrane-bound organelles are only found in eukaryotes.

  • Nucleus

  • Protein production machine: the ribosomes

  • Mitochondria and Chloroplasts

  • Endoplasmic Reticulum and the Golgi apparatus

  • Lysosomes and Peroxisomes

  • Adapted and/or specialized for carrying out one or more vital functions

Nucleus a cell s center l.jpg
Nucleus: a cell's center

Function of the nucleus:

  • Stores the chromosomes (genetic material) Note: Two kinds of genetic material:

    • deoxyribonucleic acid (DNA)

    • ribonucleic acid (RNA)

  • Keeps the DNA molecules of separated from metabolic machinery of cytoplasm.

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...Nucleus: a cell's center

  • Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

  • DNA replication and synthesis of messenger RNA (mRNA)

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  • Dense mass of material in nucleus

  • Cluster of DNA and proteins

  • Subunits must pass through nuclear pores to reach cytoplasm

  • production of ribosomes in nucleolus

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Nuclear Membrane (Envelope)

  • One continuous membrane which spans the ER’s membrane as well. (lipid bilayers)

  • Pores span bilayerand controls what enters/leaves nucleus.

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  • Cell’s collection of DNA and associated proteins

  • A chromosome is one DNA molecule and its associated proteins

  • Appearance changes as cell divides

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  • assembles proteins (non cytosolic & cytosolic proteins)

  • some are free in cytoplasm (cytoplasmic ribosomes), others are attached to the ER (ER ribosomes)

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Endoplasmic Reticulum (ER)


  • ER is a continuation of the outer nuclear membrane.

  • Two types: Smooth and Rough. (Rough ER has ribosomes on it)

  • Network of membrane that connects nuclear envelope to the cell membrane

Endoplasmic reticulum er11 l.jpg
…Endoplasmic Reticulum (ER)


  • Smooth ER (no ribrosomes): responsible for lipid and membrane protein modifications)

  • Rough ER (has ribosomes on it) responsible for the synthesis of other proteins). The ribosomes assemble the proteins within the rough ER. Once assembled, the proteins pinch off the ER and are released in a vesicle.

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…Endoplasmic Reticulum (ER)

Endoplasmic Reticulum (ER)

Golgi body golgi apparatus l.jpg
Golgi Body (Golgi Apparatus)


  • processes, packages, and, secretes cell products (lipids & proteins)

  • Put finishing touches on proteins and lipids that arrive from ER

  • Package finished material for shipment to final destinations. (Exocytosis)

  • Material arrives

    and leaves in vesicles

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  • Double membrane. Inner membrane is folded for greater surface area. Folds are called cristae.

  • Interior is called the matrix.

  • Contain their own genome (distinct from nuclear genome)

  • Self-replicating


  • ‘burns’ food, i.e. glucose to release energy. Energy is used to make ATP. ATP is a high-energy molecule that can be directly used by the cell.

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The “powerhouse” of the cell

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  • Formed by Golgi bodies

  • Bound by a single membrane


  • Digests the food particles inside the cell with help of enzymes. These enzymes work at low pH.

  • Involved in autolysis (suicide of cell)

  • Digest foreign bacteria that invade a cell

  • Recycling of membrane components

  • Repair damage to plasma membrane

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  • Made by Golgi

  • Surrounded by a single bilipid membrane

  • Detoxification of poisonous substances

  • Many in the liver/ brain


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Cell Wall


  • maintains the shape of a plant cell

  • found in plants, some fungi, some protists

  • In plants, cell walls are made of a polysaccharide called cellulose.

  • Structural component that wraps around the plasma membrane

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  • Photosynthesis: converts sunlight, carbon dioxide, and water into sugar (makes food for plants)

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  • A large membrane bound sac


  • storage area for proteins and


  • Maintain structure in plant cells by means of turgor pressure

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Cytoskeleton: a cell's scaffold

  • very complex and dynamic cell component!

  • organizes and maintains the cell's shape (e.g. epithelial cells of the gut)

  • Allows organelles to remain in place or to move throughout cell

  • helps during the uptake of external material (endocytosis)

  • involvement in cell movement

  • growth

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intermediate filaments





keratin family

All help maintain cell shape

Nuclear lamina

Anchorage of nucleus and some other organelles

Cilia, flagella

Chromosome movement

Organelle movement

Cytoplasmic streaming


Cell division

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Molecular motors

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Macrophage attacks bacteria

Microfilaments (actin) allow formation of pseudopods

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Striated Muscle

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Centrosome:Made up of centriole pairs

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