Most membranes have specific proteins embedded in the phospholipid bilayer

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The Membrane is a Fluid Mosaic

• Most membranes have specific proteins embedded in
  the phospholipid bilayer

Hydrophilic region of protein
Phospholipid bilayer
Hydrophobic region of protein
(b) Fluid mosaic model of membrane
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Selective Permeability

• Membranes of the cell are selectively permeable

• They allow some substances to cross more easily
  than others
• They block passage of some substances altogether

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THE NUCLEUS AND RIBOSOMESGENETIC CONTROL OF THE
CELL

• The nucleus is the manager of the cell

• Genes in the nucleus store information necessary
  to produce proteins

• The nucleus is bordered by a double membrane
  called the nuclear envelope

• It contains chromatin
• It contains a nucleolus

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Nuclear envelope
Ribosomes
Chromatic
Nucleolus
Pore
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Ribosomes

• Ribosomes build all the cells proteins

nucleus

• they sit on a
• system of membranes
• Outside of the nucleus

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How DNA Controls the Cell
Nucleus
DNA

• DNA controls the cell by transferring its coded
  information into RNA

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mRNA

• The information in the RNA is used to make
  proteins

Cytoplasm
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mRNA
Ribosome
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Synthesis of protein in the cytoplasm
Protein
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THE INNERMEMBRANE SYSTEM OF THE CELL
MANUFACTURING AND DISTRIBUTING CELLULAR PRODUCTS

• Many of the membranous organelles in the cell
  belong to the endomembrane system

• Rough ER
• Smooth ER
• Golgi Apparatus
• Lysosomes
• Contractile Vacuoles

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The Endoplasmic Reticulum

• The endoplasmic reticulum (ER)

Nuclear envelope

• Produces an enormous variety of molecules
• Is composed of smooth and rough ER

Ribosomes
Rough ER
Smooth ER
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Rough ER

• The roughness of the rough ER is due to
  ribosomes that stud the outside of the ER membrane

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• The functions of the rough ER include

1. Producing proteins 2. Producing new membrane
Remember ribosomes protein synthesis!
How does this work.?
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• After the rough ER synthesizes a protein it
  packages the molecule into transport vesicles

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Transport vesicle buds off
Secretory protein inside transport vesicle
Ribosome
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Protein
1
Rough ER
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Polypeptide
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Smooth ER

• The smooth ER lacks the surface ribosomes of ER
  and produces lipids, including steroids
• The smooth ER works together with the
• Golgi Apparatus.

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The Golgi Apparatus

• Works in partnership with the ER
• Refines, stores, and distributes the products of
  cells (the distribution center!)

Transport vesicle from ER
Receiving side of Golgi apparatus
Golgi apparatus
New vesicle forming
Transport vesicle from the Golgi
Shipping side of Golgi apparatus
Plasma membrane
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Lysosomes

• A lysosome is a membrane-enclosed sac

• It contains digestive enzymes
• The enzymes break down macromolecules
• The cells stomach

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• Lysosomes have several types of digestive
  functions

Lysosome
Digestive enzymes
Plasma membrane
Digestion
Food
Food vacuole
(a) Lysosome digesting food
1. They fuse with food vacuoles to digest the food
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• 2. They break down damaged organelles

Lysosome
Digestion
Damaged organelle
(b) Lysosome breaking down damaged organelle
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Vacuoles

• Vacuoles are membranous sacs

• Two types are the contractile vacuoles of
  protists and the central vacuoles of plants

Central vacuole
Contractile vacuoles
(a) Contractile vacuoles in a protist
(b) Central vacuole in a plant cell
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Rough ER
Transport vesicle from ER
Golgi apparatus

• A review of the endomembrane system

Secretory vesicle from Golgi
Vacuole
Lysosome
Secretory protein
Plasma membrane
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CHLOROPLASTS AND MITOCHONDRIA ENERGY CONVERSION

• Cells require a constant energy supply to do all
  the work of life

Making proteins Making DNA Dividing
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CHLOROPLASTS
Inner and outer membranes of envelope

• Chloroplasts are the sites of photosynthesis, the
  conversion of light energy to chemical energy
• Plant and animal
• cells

Granum
Space between membranes
Stroma (fluid in chloroplast)
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Mitochondria

• Mitochondria are the sites of cellular
  respiration, which involves the production of ATP
  from food molecules

Outer membrane
Inner membrane
Cristae
Matrix
Space between membranes
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THE CYTOSKELETONCELL SHAPE AND MOVEMENT

• The cytoskeleton is an infrastructure of the cell
  consisting of a network of protein fibers

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Maintaining Cell Shape

• Provides mechanical support to the cell and
  maintain its shape

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• The cytoskeleton can change the shape of a cell

• This allows cells like amoebae to move

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Cilia and Flagella

• Cilia and flagella are motile appendages

• Cilia move in a coordinated back-and-forth motion

• Flagella propel the cell in a whiplike motion

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• Some cilia or flagella extend from nonmoving cells

• The human windpipe is lined with cilia

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• Most cells secrete materials that are external to
  the plasma membrane

• insulin
• hormones
• mucus
• digestive enzymes in saliva
• ear wax (!)
• sap

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CELL SURFACES
Protection Support Cell-Cell Interactions
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Plant Cell Walls and Cell Junctions

• Plant cells are encased by cell walls

Walls of two adjacent plant cells
Cellulose?
Cell junctions
Vacuole

• These provide support for the plant cells

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Animal Cell Surfaces and Cell Junctions

• Animal cells lack cell walls

• They secrete a sticky covering called the
  extracellular matrix
• This layer helps hold cells together

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• Animal cells connect by various types of junctions

(a) Tight junctions
(b) Anchoring junctions
(c) Communicating junctions
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junctions

• What holds cells together?
• Cell Junctions, three main types
• 1. Tight Junction seams
• 2. Gap Junctions communication
• 3. Adhesion Junctions sticky rivits

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• Functions of Cell Junctions
• Communication Junction
• Tight Junctions