The Cellular Level of Organization –Part B

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The Cellular Level of Organization Part B
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Cytoplasm

• Cytosol
• Semifluid, mostly water
• Protein, carbohydrates, lipids, and inorganic
  substances (ions)
• Many important metabolic reactions take place
  here
• Cytoplasm is the cytosol plus the organelles

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Organelles
little organs have characteristic appearance
and have specialized functions in cell growth,
maintenance, repair and control. Number and types
of organelle vary with cell. Two basic
types nonmembranous membranous
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Ribosomes

• Made of ribosomal RNA and protein
• Free and associated with the endoplasmic
  reticulum ( fixed ribosomes)
• Site of protein synthesis
• Nonmembranous, Temporary structures made of large
  and small subunits

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Proteasomes

• Hollow cylinders which contain protein- digesting
  enzymes ( proteases)
• Remove and recycle damaged or denatured proteins
• Also play a role in the immune response

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Endoplasmic reticulum (ER)
Endo within Plasm cytoplasm Reticulum -
network Can be rough or smooth Rough ER has
ribosomes, makes proteins for export outside of
cell
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Smooth Endoplasmic Reticulum

• Synthesis of phospholipids and cholesterol
• Synthesis of steroid hormones
• Synthesis and storage of triglycerides
• Synthesis and storage of glycogen
• Storage of ions ( e.g. Ca in muscle)
• Detoxification and inactivation of drugs

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Gogli apparatus (body, complex)
Made of flattened sacs called cisternae cis,
medial, trans -Process, sort and deliver proteins
and lipids to the plasma membrane-forms vesicles
and lysosomes.-forms new plasma membrane The
UPS of the cell
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Vesicles

• Membrane bound sacs
• Formed during endocytosis or by golgi apparatus
• Transport
• Renew membrane membrane flow

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Lysosomes
The cells stomach vesicles that contain
digestive enzymes. Primary lysosomes contain
inactive enzymes work at low pH Found in large
numbers in white blood cells Intracellular
digestion ( phagocytosis etc.)worn-out
organelles ( autophagy)digestion of cell
contents (autolysis) Tay-Sachs disease
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Peroxisomes

• Smaller than lysosomes
• Enzymes use molecular oxygen to oxidize
  substances
• Reactions produce Hydrogen Peroxide- H2O2
• Free radicals

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Mitochondria
Mitochondrion singular Two membranes inner
folds called cristae. Main function is the use
of oxygen to produce ATP cellular (aerobic)
respiration These are the power plants of the
cell. Have their own DNA and RNA
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Centrosomes and Centrioles
Centrioles are 2 cylinders of tubules arranged at
right angles.9 0 array Form the microtubules
of the mitotic spindle during cell division, and
also make up a part of cilia and flagella Heart
of the cytoskeleton
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Flagella and cilia

• Cilia eyelashes cilium
• 92 array
• Anchored to basal body

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Flagella
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Cytoskeleton
Microfilaments, intermediate filaments and
microtubules Give the cell shape, and allow it to
move the Musculoskeletal system of the
cell. Myofilaments are made of the protein
actin Myotubules are made of the protein tubulin
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Inclusions
Usually contain chemical substances produced by
the cell, these are temporary structures that are
not surrounded by a membrane. Melanin, glycogen,
triglycerides ribosomes
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Nucleus

• Double membrane called the nuclear envelope
• Nucleoplasm
• Chromatin granules unwound DNA
• Nucleoli puts RNA and protein together to make
  ribosomes
• Nucleus is essential for cell survival

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The Cell Cycle

• Nuclear division (mitosis or meiosis)
• Cytoplasmic division cytokinesis
• Mitosis is somatic (body) cell division
• Meiosis is reproductive cell division

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Mitosis
Homologous chromosomes Cell cycle from one cell
division to the next Interphase resting phase
G1 Gap1 growth phase S Synthesis
replication of DNA G2 Gap 2
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Nuclear division mitosis or karyokinesis
Prophase Metaphase Anaphase Telophase PMAT
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Cytokinesis

• Contractile ring of actin microfilament
• Cleavage furrow
• Two new daughter cells

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GPCR
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GPCR
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Steroid receptors
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Control of cell division

• How many times a cell divides depends on the type
  of cell
• Stem cells retain the ability to divide and
  differentiate
• Cell senescence
• Telomeres
• Levels of proteins called kinases and cyclins

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Control contd.

• Cell size
• External factors hormones and growth factors
• Contact inhibition

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Loss of control over division

• Neoplasm or tumor
• Benign tumors remain in a single location
• Malignant tumors (cancer) can spread or
  metastasize
• Oncogenes want these turned off
• Tumor suppressor genes want these turned on
• Apoptosis

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