Chapter%203:%20Cell%20Structure%20

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Chapter 3 Cell Structure Function

• The cell is the smallest structure capable of
  performing all of the functions of life.
• smallest living organisms made up of only 1
  cell (Ex. Bacteria)
• Multicellular composed of many cells
• (Ex. Humans)
• Can be prokaryotic or eukaryotic

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Discovery of the Cell

• Antonie van Leeuwenhoek
• made 1st microscope in late 1600s
• Robert Hooke
• Looked at thin slice of cork under microscope
• 1st to use the term cell

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The Cell Theory

• 1. All living organisms are made up of 1 or more
  cells.
• 2. Cells are the basic unit of life.
• 3. All cells come only from other cells.

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Common Features of Cells

• Most cells have these common features
• Plasma membrane boundary that separates cell
  from its environment
• Cytoplasm semifluid substance inside cell made
  up of water, salts, organic molecules
• Ribosomes where proteins are made
• DNA genetic material

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Cell Size

• ASurface area of a cell is important for carrying
  out the cells functions, such as acquiring
  adequate nutrients and oxygen
• A small cell has more surface area relative to
  its cell volume and is more efficientt larger
• Cells must be small to move substances quickly
  into or out of cell.
• creasesface area affecget material into and out
  of cell surface area faster exchange of
  nutrient wastes

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Prokaryotic Cells

• Lack membrane bound nucleus and organelles (cell
  parts)
• Bacterial cells
• Found in Bacteria and Archaea Domains
• DNA is shaped like rings stored in cytoplasm
• Some have cell walls sticky capsules

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Anatomy of a Prokaryotic Cell
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Eukaryotic Cells

• All living cells other than bacteria
• Ex. Plants, animals, fungi, protists
• DNA is found in the nucleus is enclosed by a
  nuclear membrane
• Can be multicellular or unicellular
• Contain tiny structures that perform specific
  functions called organelles (little organs)

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Eukaryotic Animal Cell
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Eukaryotic Plant Cell
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Nucleus

• Nuclear envelope
• Double membrane that separates nucleus from
  cytoplasm
• Has permanent nuclear pores where substances can
  leave nucleus
• Contains DNA
• Chromosomes DNA proteins coiled up
• Chromatin threadlike form of DNA proteins
• Contains nucleoplasm (like cytoplasm)
• Contains nucleolus (another organelle)
• Where rRNA is made

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Ribosomes

• Made up of two subunits that are composed of
  ribosomal RNA (rRNA) and proteins
• Large subunit
• Small subunit
• Proteins are made here
• May be attached to endoplasmic reticulum
• Found in the cytoplasm

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The Endomembrane System

• EThe membranes within a eukaryotic cell are
  physically connected and compose the endomembrane
  system
• The endomembrane system includes the nuclear
  envelope, endoplasmic reticulum (ER), Golgi
  apparatus, lysosomes, vacuoles, and the plasma
  membrane

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The Endomembrane System

• Some components of the endomembrane system are
  able to communicate with others with formation
  and transfer of small membrane segments called
  vesicles
• One important result of communication is the
  synthesis, storage, and export of molecules

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The Endoplasmic Reticulum

• There are two kinds of endoplasmic
  reticulumsmooth and rough
• Smooth ER lacks attached ribosomes
• Rough ER lines the outer surface of membranes
• They differ in structure and function
• However, they are connected

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Rough Endoplasmic Reticulum

• Some RER is continuous with the outer envelope of
  the nuclear membrane
• Once a growing protein is inside the RER, there
  are enzymes there which help to fold newly form
  proteins
• Some proteins also have carbohydrate segments
  added to them in the RER to make glycoproteins

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Smooth Endoplasmic Reticulum

• SER is also a series of membrane tubes without
  ribosomes attached, continuous with the RER at
  the periphery, with a number of very important
  functions.
• Functions
• In cells in testes produces testosterone
• Make phospholipids needed for all membranes in
  cell
• In liver cells, detoxifies some poisons
• Release free glucose from glycogen (liver)
• Assist in recycling of old, worn out cell parts

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Golgi

• Golgi is a series of flattened membrane sacs,
  like a stack of malformed pancakes, curling
  slightly toward the nucleus and toward the plasma
  membrane.
• Functions of Golgi
• Modify proteins
• Add carbohydrate portions (glycoproteins)
• Add lipid portions (lipoproteins)
• And/or cut into smaller piecesce of cell because
  it collects, sorts, packages, and distributes
  materials like proteins lipids

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Vesicles and Vacuoles

• These are membrane sacs containing material being
  stored or transported.
• May be formed from the Golgi, lysosomes, the ER
  or by endocytosis.
• Vacuoles are usually larger than vesicles
• Vacuoles are used for storage
• Water, sugar, salt, pigments, toxic substances
• Vesicles are used more for transporting
  substances either into or out of cell.

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Lysosomes

• Lysosomes are membrane bound sacs of hydrolytic
  enzymes
• Enzymes were made by ribosomes
• The integral membrane proteins of lysosomes pump
  H into the sac, making the inside of a lysosome
  have a very low pH, when compared to the
  cytoplasm.
• The enzymes are in their most active at low pH,
  so if a lysosome breaks, the enzymes will do
  little damage to the cells parts because they
  dont work at high pH
• Functions
• Recycle old, worn out cell parts
• Digest materials brought into cell by endocytosis

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Peroxisomes

• Peroxisomes are membrane sacs, similar to
  lysosomes.
• Most abundant in liver and kidney cells.
• Functions
• Breakdown of hydrogen peroxide (a powerful
  oxidant damaging to cells ) into water oxygen
• In liver, break down fats produce bile salts
• Detoxify ethyl alcohol in liver
• In plant leaves, they use up oxygen release CO2
  

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Mitochondria

• An endosymbiont, with its own DNA, ribosomes and
  internal membrane network.
• Double membrane
• Outer membrane surrounds organelle
• inner membrane is called the cristae
• Inner membrane is bacteria-like
• Site of cellular respiration
• Found in plant animal cells
• Outer compartment is the space between outer and
  inner membrane
• Matrix, fluid inside inner membrane

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Chloroplasts

• Use energy from sun to make carbohydrates by the
  process of photosynthesis
• Solar energy carbon dioxide H2O ? glucose
  oxygen
• Found in plants and algae
• Plastid
• Amyloplasts found in roots store starch
• Chromoplasts found in leaves contain red
  orange pigments
• Chloroplasts contains green pigment chlorophyll

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Chloroplast cont.

• Bound by 2 membranes
• Stroma fluid-filled space
• Contains DNA, ribosomes, enzymes
• Thylakoids interconnected flattened sacs of
  membrane
• Grana stacks of thylakoids that contain pigment
  chlorophyll used in photosynthesis

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Cytoskeleton

• The cytoskeleton is a series of proteins that
  give the cell its shape, much of its function,
  and mobility in cells that move.
• 3 basic types
• Microfilaments smallest in diameter, often
  contractile. Responsible for movement of
  cytoplasm and of some cell components.
• Examples actin and myosin
• Intermediate filaments permanent. Responsible
  for holding cell contents, especially the
  nucleus, in place.
• Microtubules largest diameter. Responsible for
  transport within the cell and, as part of
  cilia/flagella, along the outside of cells, too.

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MtOCsMicrotubule Organizing Centers

• Microtubules are small hollow cylinders that make
  up the cytoskeleton, cilia, flagella,
  centrioles
• Centrosome main area where microtubules are
  assembled found near nucleus
• No surrounding membrane
• Centrioles produce the spindle fibers that move
  chromosomes around during nuclear division
  (mitosis meiosis)

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Cilia and Flagella

• Hair-like structures on the surface of cells,
  growing out of the plasma membrane
• Movement is the function of both
• Cilia are short, there are usually many on the
  surface of one cell, and in humans, are found on
  surfaces where they move materials along the
  cells surface.
• Found in respiratory tract and female
  reproductive tract.
• A flagellum is a longer version, and there is
  usually only one or a few per cell. It moves the
  cell of which it is a part.
• Only one flagellate cell type in humans sperm