Lecture roadmap

1
Lecture roadmap

• Ch. 3 (cont.)
• Ch. 4 Cells
• Organelles of the endomembrane system
• Energy-converting organelles
• Cell skeleton and locomotion
• Cell surface and junctions
• Next time

2
Microscopes visualizing cells

• Light microscope (LM) light passes thru sample
• Magnification increase in the apparent size of
  object
• Resolution clarity of image (GOOD res. vs. POOR
  res.)
• Limited to 1000X magnification
• By the 1800s cell theory developed which states
  that all organisms are made of cells and cells
  come from other cells.

Euglena (1000X)
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High-powered microscopes

• Electron microscope (EM) uses a beam of e- and
  magnets to get higher resolution
• Transmission EM (TEM) view internal cell
  structure
• Scanning EM (SEM) view surface 3-D shapes
• Confocal microscopy (LM)
• Ability to watch living processes

Cancer cells w/flourescent dyes
1000X
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Why cells are so small

• Cells need to carry out basic functions to live.
• Exchange of nutrients, oxygen, water
• Disposing of waste
• Size is limited by logistics of carrying out cell
  functions
• Higher surface-to-volume ratio is better for cell
  functioning
• Allows for better exchange with environment and
  faster internal processes

10 um
30 um
27 smaller cells Higher surface-to- volume ratio
1 big cell Low-surface- to volume ratio
30 um
10 um
Surface area5400 um2
27 small cubes16,2000 um2
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Prokaryotic vs. eukaryotic cells
prokaryotic cell (0.1 mm 10 mm)
eukaryotic cell (10 mm 100 mm) 10 - 50x bigger!
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Common things to prokaryotes eukaryotes

• Plasma membrane boundary b/t outside and
  internal environment
• Ribosomes make proteins
• Nucleus (eu.) nucleoid (pro.)
• Contain DNA
• No membrane in nucleoid
• Cell wall rigid, protection
• Flagella long projections,
• movement (some eu.)

nucleus
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Prokaryotes
Capsule sticky outer coat
Pili short projections allow sticking to things
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Eukaryotic cells are partitioned

• Cytoplasm fluid-filled region b/t nucleus
  plasma membrane
• Organelles membrane-bound structures that
  perform specific cellular structures
• What are the benefits of having membrane-bound
  structures inside a cell?
• Different chemical activities can be in different
  compartments.
• - Ex. Endoplasmic Recticulum (ER) makes steroids
  right next to peroxisomes which break down toxic
  substances produce hydrogen peroxide (H2O2).
• 2) Increases total area of membranes in the cell
• Membranes are the surfaces where many important
  metabolic processes occur.

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Eukaryotes animal vs. plant cells
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Eukaryotic cells membranous organelles other
structures

• Non-membranous structures
• Ribosomes
• Cytoskeleton
• Microtubules
• Intermediate filaments
• Microfilaments
• Flagellum (animals only)
• Centriole (animals only)
• Cell wall (plants only)

• Membranous
• structures
• Plasma membrane
• Nucleus
• Mitochondrion
• Golgi apparatus
• Rough smooth E.R.
• Lysosome
• Peroxisome
• Vacuole (plants only)
• Chloroplast (plants only)

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Nucleus

• Functions
• Contains the DNA, which directs protein synthesis
• DNA gt messenger RNA leaves through nuclear pores
  synthesizes protein in cytoplasm
• Nucleolus building blocks of ribosomes are made
  (RNA protein), exit via nuclear pores
• Chromatin DNA bound to proteins, long fibers
• Chromosome one fiber of chromatin
• Duplicates DNA prior to cell division
• Enclosed by nuclear envelope
• Continuous with
• endoplasmic reticulum
• (ER)

nuclear pore
nucleolus
chromatin
ER
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Endomembrane System

• Collection of organelles in eukaryotes
• Vesicles sacs of membrane that transfer b/t
  organelles
• Move substances around cell
• Involved in export of materials
• Includes the following organelles/structures
• Plasma membrane Nucleus
• Rough ER Smooth ER
• Golgi apparatus Lysosomes
• Vacuole Vesicles

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Endoplasmic recticulum (ER)
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Smooth ER has many functions

• Functions
• Synthesizes lipids
• Ex. fatty acids, phospholipids, steroids
• Different cell types make different lipid types
  (ex. testes make testosterone).
• Detoxifies poisons
• Smooth ER in liver cells helps detoxify poisons,
  drugs, other potentially harmful substances.
• Ex. Alcohol is detoxified in liver cell smooth
  ER.
• Stores calcium
• In muscle cells, stores calcium ions (Ca2)
  important for muscle contraction

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Rough ER functions

• Called rough b/c of appearance in EM
  micrographsribosome-studded membranes.
• Functions
• 1. Synthesis, modification, and packaging of
  secretory proteins
• Synthesis of the protein occurs on ribosomes
  bound to rough ER ex. insulin secreted by cells
  in pancreas
• Glycoproteins ER links short sugar molecules
  tags molecule for identification tells where
  to go
• Transport vesicles export molecules from ER,
  takes to the golgi apparatus
• 2. Synthesis of membranes (vesicles) similar to
  plasma membrane

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Steps in ER processing
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The Golgi apparatus finishing shipping

• Flattened sacs stacked like pita bread
• Functions
• Receives vesicles from ER on receiving side (cis
  side)
• Modifies chemically marks and sorts for
  different destinations
• Could exit cell, delivered to another organelle,
  or fuse w/ the plasma membrane
• Moves to shipping side
• (trans) molecules
• packaged into
• vesicles and
• shipped out

cis
trans
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Lysosomes cell digestion

• Functions
• Contains digestive enzymes
• (hydrolytic enzymes) that break
• things downs within acidic
• membranous sac
• Examples of uses
• Protists engulf food particles in food vacuoles
  fuse them with lysosomes to digest
• Our white blood cells ingest bacteria into
  vacuoles lysosomal enzymes released when
  lysosome fuse enzymes digest cell wall
• Damaged organelles recycled by being enclosed in
  vesicle that fuses with lysosomes

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Lysosomes
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Lysosomal storage diseases

• Problems when lysosomes are missing enzymes
• Lysosomes missing certain enzymes build up
  undigested substances interfere with cells
  function
• Ex. Pompes disease
• Harmful amounts of glycogen build up in muscle
  and liver cells
• Progressive muscle weakness death in childhood
• Ex. Tay-Sachs disease
• Lysosomes lack enzyme to break down lipid in
  nerve cells
• Nerve cells become damaged causes death in
  children and mental deterioration in adults

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Vacuoles general maintenance

• Vacuoles are membranous sacs, larger than
  lysosomes
• Central vacuole (plant vacuole)
• Can function as a large lysosome
• Helps plants grow by storing water helps
  maintain water pressure
• Can contain pigments, store chemicals
• Food vacuoles
• Formed by phagocytosis (eating food particles)
• Contractile vacuoles
• Pump excess water out of protists b/c take up too
  much water when living in water environments

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Energy-converting organelles

• Not a part of endomembrane system, have own DNA
  proteins, endosymbionts?
• Chloroplasts convert solar energy into chemical
  energy
• Organelles found in all photosynthetic eukaryotic
  cells (plant cells, algae, etc.)
• Contain the pigment chlorophyll (green color)

- Chloroplast structure in 3 compartments 1)
Intermembrane space 2) Stroma 3) Space inside
grana
Granum stack of membranous disks -
photosynthesis occurs here.
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Mitochondria

• Carry out cellular respiration (conversion of
  food to energy in the form of ATP)
• Found in both plants and animal cells
• Structure in 2 compartments
• 1. Intermembrane space
• - space b/t inner outer memb.
• - enyzmes that make ATP
• embedded in inner memb.
• - cristae folds in inner memb.
• that increase surface area
• and make rxns faster
• 2. Mitochondrial
• matrix rxns happen
• here

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Cytoskeleton cell support

• Network of protein fibers that organizes
• structures and activities in the cell
• Roles of the cytoskeleton
• Structural support
• Define cells shape
• Anchor organelles
• Motility
• Contraction (e.g. in muscle cells)
• Movement of organelles within the cell
• Movement of cilia flagella
• Regulation of cellular activities
• Transmit signals from cell surface to the
  interior.

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Types of cytoskeleton fibers
tubulin subunit
actin subunit
intermediate filament
microfilament
microtubule
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Cytoskeleton fibers

• Microtubules largest type
• Hollow cylindrical tubules composed of the
  globular protein tubulin
• Act as tracks for organelle movement inside the
  cell
• Guide the movement of chromosomes during cell
  division
• Main structural components of cilia and flagella
• flagella that move sperm cells
• Help maintain cell shape anchor some organelles
• Microfilaments thin
• Solid rods made of the the globular protein actin
• Cell contraction
• In muscle cells
• Allows movement like cell crawling of amoeba
• Help maintain cell shape along with microtubules
• Intermediate Filaments
• Ropelike structure, made of fibrous (not
  globular) proteins
• Reinforce cell shape, especially in cells that
  make hair, nails, claws
• Anchor for some organelles, particularly the
  nucleus

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Cilia flagella movement

• Contain specialized arrangements of microtubules
• Are locomotor appendages of some cells

flagellum of a sperm cell
cilia on a freshwater protozoan
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Cilia flagella have a common structure
Plasma membrane
Outer microtubule doublet
Dynein arms
Central microtubule
Microtubules
Radial spoke
Plasma membrane
Cross section of microtubule (9 2 pattern)
Basal body
Triplet
movement of the dynein arms allows
flagellum or cilium to bend
basal body acts as an anchoring structure
Cross section of basal body (triplet pattern)
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Plant cell surfaces junctions

• Plants have a cell wall in addition to the plasma
  membrane.
• 10-100 times thicker than plasma membrane
• Provides skeletal support to keep plants upright
  on land
• Made of cellulose, other polysaccharides, and
  proteins
• Helps protect
• Plasmodesmata are channels that link plant cells.
• Water other small molecules can pass from cell
  to cell

Central vacuole
Cell walls
Plasma membranes
Cytoplasm
Plasma membrane
Interior of cell
Cell walls
Interior of cell
Plasmodesmata
Plasmodesmata
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Animal cell surfaces

• Extracellular matrix (ECM) sticky layer of
  glycoproteins secreted by animal cells
• Outside of the plasma membrane.
• Glycoproteins (proteins w/polysaccharides
  attached) like cells ID tag
• Plays an important role in regulating cell
  behavior by interacting with cells in the plasma
  membrane
• Helps hold cells
• together
• Helps protect and
• support cells

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Animal cell junctions

• Animal cells are connected by 3 types of
  junctions
• 1) Tight junctions
• Bind cells very tightly together, forming seal
  around cells that prevents leakage of
  extracellular fluid
• Ex. in digestive tract, tight jxns form sheet of
  tissue
• 2) Anchoring junctions (also desmosomes)
• Intermediate filaments (keratins) tightly fasten
  cells together
• Ex. tissues that endure mechanical stress (skin,
  heart muscle)
• 3) Gap junctions
• Channels between animal cells that allow the
  passage of small molecules ions
• Ex. in embryos, where cells need to send
  chemical signals to one another to direct
  development

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Animal cell junctions
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Next time

• Ch. 5 The working cell