A TOUR OF THE CELL

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CHAPTER 7

• A TOUR OF THE CELL

Fluorescent stain of cell
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Cell Biology1. The fundamental life processes of
plants and animals depend on a variety of
chemical reactions that occur in specialized
areas of the organisms cells. As a basis for
understanding this concept, Students know

• a. cells are enclosed within semipermeable
  membranes that regulate their interaction with
  their surroundings.
• b. enzymes are proteins that catalyze biochemical
  reactions without altering the reaction
  equilibrium and the activities of enzymes depend
  on the temperature, ionic conditions, and the pH
  of the surroundings.
• c. how prokaryotic cells, eukaryotic cells
  (including those from plants and animals), and
  viruses differ in complexity and general
  structure.
• d. the central dogma of molecular biology
  outlines the flow of information from
  transcription of ribonucleic acid (RNA) in the
  nucleus to translation of proteins on ribosomes
  in the cytoplasm.
• e. the role of the endoplasmic reticulum and
  Golgi apparatus in the secretion of proteins.
• f. usable energy is captured from sunlight by
  chloroplasts and is stored through the synthesis
  of sugar from carbon dioxide.
• g. the role of the mitochondria in making stored
  chemical-bond energy available to cells by
  completing the breakdown of glucose to carbon
  dioxide.
• h. Students know most macromolecules
  (polysaccharides, nucleic acids, proteins,
  lipids) in cells and organisms are synthesized
  from a small collection of simple precursors.
• i. how chemiosmotic gradients in the
  mitochondria and chloroplast store energy for ATP
  production.
• j Students know how eukaryotic cells are given
  shape and internal organization by a cytoskeleton
  or cell wall or both.

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Organisms must exchange matter with the
environment to grow, reproduce and maintain
organization. Growth, reproduction and
maintenance of the organization of living systems
require free energy and matter.

• Molecules and atoms from the environment are
  necessary to build new molecules.

• 1. Carbon moves from the environment to organisms
  where it is used to build carbohydrates,
  proteins, lipids or nucleic acids. Carbon is used
  in storage compounds and cell formation in all
  organisms.
• 2. Nitrogen moves from the environment to
  organisms where it is used in building proteins
  and nucleic acids.
• 3. Phosphorus moves from the environment to
  organisms where it is used in nucleic acids and
  certain lipids.

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why are cells microscopic in size?

• http//www.youtube.com/watch?vxuG4ZZ1GbzI

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Geometric relationships explain why most cells
are microscopic
The smaller the object, the greater Its ratio of
surface area to volume. Metabolic requirements
depend on passage of oxygen, nutrients and
Carbon dioxide other metabolic Waste through
the plasma membrane.
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why are cells microscopic in size?

• Cell size is limited by the surface to volume
  ratio.
• As cells get larger the volume increases at a
  greater rate compared to surface area.
• Large cells can not get enough materials inside
  to stay alive.

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b. Surface area-to-volume ratios affect a
biological systems ability to obtain necessary
resources or eliminate waste products.

• 1. As cells increase in volume, the relative
  surface area decreases and demand for material
  resources increases more cellular structures are
  necessary to adequately exchange materials and
  energy with the environment. These limitations
  restrict cell size.
• Ex. root hairs, cells of the alveoli, cells of
  the villi
• 2. The surface area of the plasma membrane
  must be large enough to adequately exchange
  materials smaller cells have a more favorable
  surface area-to-volume ratio for exchange of
  materials with the environment.

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• villi cells within the small intestine
• root hair cells of plants
• cells of the alveoli within lungs
• All shaped and arranged in ways that increase
  surface area to volume ratio and maximize
  diffusion.

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what types of microscopes are used to view cells?

• Light (2,000x)
• Transmission Electron TEM (2,000,000x)
• Scanning Electron
• SEM (3-D)

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Rabbit trachea (windpipe) cell
Transmission electron microscope
(SEM)
(TEM)
Scanning electron microscope creates 3-D image of
the surface of the same cell.
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• 1665 1st Microscope
• Robert Hooke discovered cells-cork
• 1950s Electron Microscope
• Revealed the geography of the cell
• ORGANELLES
• Subcellular structures specialized
• for various specific functions.
• tiny organ
• compartments or rooms
• each contains specific enzymes

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The plasma membrane
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What is the difference between prokaryotic and
eukaryotic cells?

• THINGS IN COMMON

• DIFFERENCES

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Overview of a prokaryotic cell
Overview of a plant cell
Overview of an eukaryotic animal cell
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Prokaryotic Vs. Eukaryotic

• Both have
• Plasma membrane
• Cytosol- semifluid substance in which organelles
  are found.
• Chromosomes/genes
• Ribosomes (tiny organelles that make proteins
  according to instructions from the genes)

• Only eukaryotic cells
• Have chromosomes inside a membrane bound
  organelle- the nucleus.
• eu true
• karyon kernel
• Are large -10x bigger than bacteria.
• Have other membrane-bound organelles.

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FYI CELL FRACTIONATION Technique used to
determine the function of organelles. ORGANELLES
are sub cellular structures that perform specific
sets of chemical reactions for the cell within
Eukaryotic Cells.
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Eukaryotic cells maintain internal membranes that
partition the cell into specialized regions.

• a. Internal membranes facilitate cellular
  processes by minimizing competing interactions
  and by increasing surface area where reactions
  can occur.
• b. Membranes and membrane-bound organelles in
  eukaryotic cells localize (compartmentalize)
  intracellular metabolic processes and specific
  enzymatic reactions.
• For example Endoplasmic Reticulum
  Chloroplasts / Mitochondrion Golgi Nuclear
  envelope

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• CHARACTERISTICS
• OF THE NUCLEUS
• Contains most of the genes
• Most conspicuous (big)
• part of the cell
• STRUCTURES of
• THE NUCLEUS (out to in)
• Nuclear envelope (double
• membrane system- 2plbls)
• 2) Pores (protein tunnels)
• Lamina (protein fiber
• scaffolding- network)
• 4) Chromatin (DNA protein)
• 5) Nucleolus (makes ribosomes)

Chloroplasts and Mitochondria have their own DNA
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Chromosomes are thick coiled chromatin fibers
that condense when the cell is ready to divide.

• Nucleosome subunit of a chromosome
• DNA wrapped around 8 histone proteins.

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Nuclei and F-actin in BPAEC cells
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Big Idea 4 Biological systems interact, and
these systems and their interactions possess
complex properties.

• The structure and function of subcellular
  components, and their interactions, provide
  essential cellular processes.

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Figure 7.10 Ribosomes

• RIBOSOMES are small universal structures (proks
  euks)
• made of ribosomal RNA (rRNA) and protein
• carry out protein synthesis in 2 areas
• free- suspended in the cytosol
• bound- attached to the outside of the endoplasmic
• reticulum or nuclear envelope.
• Ex. PANCREAS CELLS have a few million ribosomes
• (synthesize pancreatic juices, insulin, glucagon)

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The Endoplasmic Reticulum

• within the cytoplasm little net
• Labyrinth of membrane tubes and sacs
• gt 1/2 the total membrane of the cell
• Connected to the nucleus
• FUNCTIONS
• Occurs in 2 forms rough smooth
• rough ER provides site-specific protein synthesis
  with membrane-bound ribosomes
• plays a role in intracellular transport
  endomembrane system.
• smooth ER synthesizes lipids.

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Smooth ER vs. Rough ER

• Smooth ER
• Lacks ribosomes
• Functions
• Synthesis of lipids
• sex hormones, oils, phospholipids
• 2) Metabolism of carbohydrates
• Detoxification of drugs/poisons
• LIVER CELLS
• MUSCLE CELLS (store Ca)

• Rough ER
• Ribosomes attached to the cytoplasmic surface
• Functions
• Protein synthesis on ribosomes, protein enters
  cisternal space to fold into native conformation.
• Secretory Glycoproteins
• Phospholipid membrane production (factory)

? Specific functions of smooth ER in specialized
cells are beyond the scope of the course and the
AP Exam.
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Golgi Complex AKA golgi apparatus, golgi bodies

• STRUCTURE membrane-bound, consists of a series of
  flattened membrane sacs (cisternae).
• Looks like a smaller version of the ER but
  totally separate from nucleus)
• FUNCTIONS include synthesis and packaging of
  materials (small molecules) for transport
  production of lysosomes.
• Receives ships via transport vesicles- bags of
  membrane.

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Golgi sorts, modifies, and exports
cis receiving
trans shipping
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The formation and functions of lysosomes

• Lysosomes are membrane-enclosed sacs that contain
  hydrolytic enzymes, which are important in
• intracellular digestion
• The recycling of a cells organic materials and
• programmed cell death (apoptosis)

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lysosomes

• Made by rough ER, finished in the Golgi
• Contain hydrolytic enzymes that function at low
  pH
• Pumps hydrogen ions from cytosol into lysosome to
  maintain acidic pH
• Targets of primary lysosomes are
• 1) food vacuoles (formed via phagocytosis)
• ex. Amoeba (protist)
  Macrophages (white blood cells)
• 2) organelles or cytosol (autophagy- recycle
  materials)
• 3) Apoptosis programmed destruction of cells
• ex. tadpole tail, human hand
  development- webbing
• EX. Tay-Sachs genetic disorder is caused by
  missing/inactive lipid digesting enzyme which
  results in lipid accumulation in brain cells.

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Review relationships among organelles of the
endomembrane system 
Endomembrane System Organelles that share
membrane Components with each other. Nuclear
Envelope, ER, Golgi, Lysosome, Vacuoles, and
Plasma Membrane How? Transport Vesicles-
little bag of Membrane.
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Endomembrane System

• Rough ER
• vesicle
• Golgi Apparatus
• vesicle
• Plasma Membrane

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The Golgi apparatus stack of pita bread insides
cisternae
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lysosome formation
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VACUOLES

• Larger than vesicles
• Food vacuoles (formed by phagocytosis)
• Contractile vacuoles- pump excess water out of
  the cell (freshwater protists)
• Central vacuole- large vacuole in mature plant
  cells (membrane tonoplast)
• - contains reserves of important compounds
• ie. pigments (petals), metabolic by-products
  (waste), poisons (repel predators), water,
  proteins and lipids (seeds)

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The plant cell vacuole 
Which cells have the larger vacuoles- animal or
plant?
plant cells
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Mitochondrion / mitochondria (pl)

• Energy conversion organelle
• Site of cellular respiration
• (x,y,z--gtATP)
• Mitochondrial membrane proteins made by free
  ribosomes in the cytosol
• Contain ribosomes and own DNA
• Double membrane system
• - outer membrane smooth
• - inner membrane convoluted (cristaefolds) w/
  proteins increases surface area for rxns.
• Two spaces
• 1) mitochondrial matrix
• (inner most area)
• 2) inter membrane space- between the two
  membranes.

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PLASTIDS

• Family of closely related plant organelles.
• Four kinds
• Chromoplasts- contain pigments that give fruits
  and vegetables their orange and yellow hues.
• Leukoplasts- store starch, protein, oil
• Amyloplasts- store starch (amylose) in roots and
  tubers.
• Chloroplasts- contain green pigment chlorophyll
  enzymes related to photosynthesis.

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CHLOROPLAST STRUCTURE

• Double membrane system
• Pancakes in a to-go box
• Thylakoids flattened sacs (inside called
  thylakoid space
• Grana stacks of thylakoids
• Stroma area outside thylakoids and outer
  membrane contains ribosomes, enzymes, and
  chloroplast DNA.

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The chloroplast, site of photosynthesis
note chloroplasts are larger than mitochondria.
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PEROXISOMES

• Specialized, one membrane, metabolic compartment
  that detoxifies substances.
• Transfers hydrogen from substrates to oxygen-
  makes H2O2
• ie. detoxify alcohol or
• use oxygen to break fatty acids into small
  molecules to be used as fuel for the
  mitochondria.
• Contains catalase to convert H2O2 to water and
  Oxygen.
• Liver cells have many.

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The process of evolution drives the diversity and
unity of life.

• Organisms are linked by lines of descent from
  common ancestry. Organisms share many conserved
  core processes and features that evolved and are
  widely distributed among organisms today.
• Structural evidence supports the relatedness of
  all eukaryotes.
• Cytoskeleton (a network of structural proteins
  that facilitate cell movement, morphological
  integrity and organelle transport)
• Membrane-bound organelles (mitochondria and/or
  chloroplasts)
• Linear chromosomes
• Endomembrane systems, including the nuclear
  envelope

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THE CYTOSKELETON
plays a major role in organizing the structures
and activities of the cell
made of 1.microtubules 2.microfilaments 3.interme
diate filaments
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Table 7.2 The structure and function of the
cytoskeleton
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microtubules

• structrure
• hollow fibers of tubulin protein that makes
  microtubules
• - 2 types alpha beta (tubulin)
• functions
• 1) shape support cell- compression resisting
• 2) tracks to move organelles
• equipped w/motor molecules.
• 3) assist in cell division
• (moving chromosomes)
• ex. Spindle fibers
• 4) motion for the cell-
• cilia/flagella

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Figure 7.21 Motor molecules and the cytoskeleton
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MICROTUBUELES grow out of a centrosome (plant
cells) 2 centrioles w/in the centrosome in
(animal cells) centriole structure 9
microtubule triplets in a ring
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cilia flagellaspecialized microtubular
structures

• basal bodies (same structure as centrioles)
  anchor cilia and flagella to the cell membrane
• flagella long tails (few) 10-200 micrometers
• cilia short hairs (many) 2-20 micrometers
  (10-6)
• structure of both nine pairs of tubules arranged
  around 2 central tubules (9 2 pattern in
  Euks)
• Dynein motor molecule (protein) attached to
  tubules, uses energy from ATP to move cilia.
• Dynein walking like a cat climbing a tree.

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Figure 7.23 A comparison of the beating of
flagella and cilia
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cilia in action (paramecium)
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microfilaments

• threads of protein
• actin helix shape
• twisted double chain of actin subunits
• present in all Eukaryotic cells
• bear tension used for structure movement.
• myosin involved in movement when interacting
  with actin.
• MA! myosin pulls actin

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muscles use actin and myosin for
contractionmyosin pulls actinmyosin acts
as the motor molecule by extending armsthat
walk along actin.
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Cell division uses microfilaments to pull the
cell membrane apartcontracting band of
microfilaments cleavage furrow
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amoeboid movement via pseudopodia

• pseudopod false foot
• cytoplasmic extensions
• localized contraction of actin myosin move the
  cell membrane
• reversible actin subunit assembly
• squeezing toothpaste tube
• ex. Amoeba white blood cells

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cytoplasmic streaming

• in plant cells occurs similarly to the movement
  of pseudopods.

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microfilament recap
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intermediate filaments(named for intermediate
diameter)

• Built from a family of proteins called keratins
• Form permanent cellular lattice(framework)
• cell to cell junctions

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Figure 7.x4 Actin and keratin
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THE CELL WALL

• 1) of PLANT CELLS made of cellulose
• Primary wall 1st wall to form
• Middle lamella space between two plant cells
• pectin is a polysaccharide that fills the middle
  lamella. As fruit ripens, pectin dissolves, cells
  loosen and fruit ripens
• c) Secondary wall develops in woody plants
• lignin is a molecule that strengthens the
  secondary wall.
• 2) of FUNGI made of chitin
• 3) of BACTERIA made of organic molecules
  (polysaccharides protein)

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THE CELL WALL

• 1) of PLANT CELLS made of cellulose
• Primary wall 1st wall to form
• Middle lamella space between two plant cells
• pectin is a polysaccharide that fills the middle
  lamella.
• As fruit ripens, pectin dissolves, cells loosen
  and fruit ripens
• c) Secondary wall develops in woody plants
• lignin is a molecule that strengthens the
  secondary wall.
• 2) of FUNGI made of chitin
• 3) of BACTERIA made of organic molecules
  (polysaccharides protein)

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Figure 7.28 Plant cell walls
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CELL COATING

• Animal cell membranes have short chains of
  carbohydrates bound to
• proteins (glycoproteins/proteoglycans)
• ie. collagen, fibronectins, integrins
• or lipids (glycolipids)
• Called glycocalyx or extracellular matrix (ECM)
• FUNCTIONS OF THE glycocalyx / ECM
• recognition sites (cell to cell for tissue
  formation)
• identification markers (ie. A or B on blood cell)
• communication (hormone messenger receptors)

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cell coating/ extracellular matrix
Collagen Proteoglycan Polysaccharide microfilament
s
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how are cells connected?

1. Intercellular matrix
2. Cell junctions

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CELL TO CELL ADHESION

• 1) Intercellular matrix (ECMs of adjacent cells)
• a) Collagen- the most abundant glycoprotein,
  protein fibers that bind cells together
• b) Elastin- also protein fiber that binds cells
  together
• Cell junctions (permanent connections)
• a) desmosomes anchoring junctions (plaques
  fibers) rivets, fasten cells together in strong
  sheets (keratin- intermediate filament)
• b) tight junctions proteins that tie cells
  together, leaving no space between the cells-
  cells fused (ie. intestines)
• c) communication junctions (2 kinds) allow flow
  of salt ions, sugars, amino acids- cytoplasmic
  channels between adjacent cells. (ie. heart
  muscle cells, cells of embryo)
• gap junction (animal cells) membrane channels
  that allow passage of material between cells.
• Plasmodesmata (plant cells) openings in the cell
  wall where adjacent membranes contact each other.

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desmosome (anchoring junction)

• (plaques fibers) rivets
• fasten cells together in strong sheets.
• keratin- intermediate filament.

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tight junction

• tight junctions proteins that tie cells
  together, leaving no space between the cells-
  cells fused (ie. intestines)

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Gap (communicating junction)

• communication junctions
• (2 kinds)
• allow flow of salt ions, sugars, amino acids-
  cytoplasmic channels between adjacent cells.
• ie. heart muscle cells, cells of embryo
• gap junction (animal cells) membrane channels
  that allow passage of material between cells.
• Plasmodesmata (plant cells) openings in the cell
  wall where adjacent membranes contact each other.

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Figure 7.30 Intercellular junctions in animal
tissues
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The End