Life of the Cell

1
Life of the Cell

• Society on a micro-scale

2
Learning Objectives

1. What are the characteristics that distinguish
   prokaryotic and eukaryotic cells? Which type of
   cell is believed to be older (more primitive)?
2. Describe the four characteristics shared by all
   cells.
3. Describe the structure and function of the
   various eukaryotic cell organelles. What
   adaptive advantage(s) is/are associated with
   having organelles?
4. Describe the theories that describe the origin of
   membranous organelles in eukaryotic cells.

3
The Cell What do we know so far?

• Smallest unit of life
• Can survive on its own or has potential to do so
• Is highly organized for metabolism
• Senses and responds to environment
• Has potential to reproduce

p. 52
4
Cellular Diversity in the Human Body

• A huge population of 75-100 trillion cells in the
  adult body- _at_ 200 different types of cells
• What does cell shape tell you about its function?

5
Early Discoveries
p.54

• Mid 1600s - Robert Hooke observed and described
  cells in cork
• Late 1600s - Antony van Leeuwenhoek observed
  sperm, microorganisms
• 1820s - Robert Brown observed and named nucleus
  in plant cells

Visible light has wavelengths of light that are
400-750 nm. How does this limit our ability to
see objects with a light microscope?
6
An Introduction to Viruses
7
Why Are Cells So Small?

• Surface-to-volume ratio
• The bigger a cell is, the less surface area there
  is per unit volume
• Above a certain size, material cannot be moved in
  or out of cell fast enough

p. 53
8
Structure of Cells

• Common structures
• Plasma membrane
• DNA
• Ribosomes
• Cytosol

• Two types
• Prokaryotic
• Eukaryotic

Is this cell prokaryotic or eukaryotic? Could it
be an animal or a plant cell? Explain.
p. 52
9
Cell MembranesThe Phospholipid Bilayer

• Main component of all cell membranes
• Gives the membrane its fluid properties
• Two layers of phospholipids

p. 56

• The dense arrangement of phospholipids makes
  membranes selectively permeable
• What does this mean?

10
Fluid Mosaic Model
p. 56

• Membrane is a mosaic of
• Phospholipids
• Responsible for what characteristic of membranes?
• Glycolipids Glycoproteins
• What combination of molecules make up glycolipids
  and glycoproteins?
• Cholesterol
• Found in all cells?
• Proteins
• Most phospholipids and some proteins are fluid,
  and can move within the membrane

11

• Identify the 3 types of lipid molecules found in
  cell membranes glycolipids, cholesterol and
  phospholipids.
• Describe the function(s) of each.

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Membrane Proteins
See Figure 4.10
Integral vs. Peripheral Proteins
13
Overview of Membrane Proteins
14
Prokaryotic Cells

• Archaea and Eubacteria
• DNA is not enclosed in nucleus
• Generally the smallest, simplest cells
• No organelles

p. 58
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Sympathy for the life of bacteriaIf you were a
bacterium

• You live in a medium which has the viscosity
  similar to asphalt.
• You have a motor for swimming that only runs in
  two directions and you can never stop.
• While you can learn, you divide _at_ every 20
  minutes and have to restart your education.
• You can have sex. However, since you are going
  30mph (relative to your size), it is difficult to
  find each other.

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Prokaryotic Cell Structure
bacterial flagellum
Sex pilus
plasma membrane
bacterial flagellum
Most prokaryotic cells have a cell wall outside
the plasma membrane, and many have a thick,
jelly-like capsule around the wall.
cytosol, with ribosomes
Circular DNA in nucleoid region
Describe the difference(s) between a cell
membrane and a cell wall. Can you explain why a
cell wall is a necessary adaptation for
prokaryotes?
17
Eukaroytic Cells

• Functions of a Nucleus
• Keeps DNA molecules separated from (potentially
  damaging) metabolic machinery of cytoplasm
• Makes it easier to organize DNA and to copy it
  before parent cell divides into daughter cells

• What? Where? Who?
• Have a nucleus and other organelles
• Tend to be larger, but no more important than
  prokaryotes!
• Diverse environments
• Eukaryotic organisms
• Plants
• Animals
• Protistans
• Fungi

p. 60
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Nuclear Envelope
p. 61

• Two outer membranes (lipid bilayers)
• Pores span bilayer
• Why are there pores in the nuclear envelope?

one of two lipid bilayers (facing nucleoplasm)
NUCLEAR ENVELOPE
one of two lipid bilayers (facing cytoplasm)
nuclear pore (protein complex that spans both
lipid bilayers)
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Nucleus vs. Nucleolus

• Dense mass (one or more) inside nucleus
• Cluster of RNA and proteins
• Materials from which ribosomes are built
• What is the role of ribosomes?
• Subunits must pass through nuclear pores to reach
  cytoplasm
• Nucleolus disappears during cell division
• Why?

• Chromatin cells collection of DNA and
  associated proteins w/in the nucleus
• Chromosome one DNA molecule and its associated
  proteins
• Appearance of nucleus changes as cell divides

Figure from micro.magnet.fsu.edu/cells/nucleus/nu
cleolus.html
20
Endomembrane System
p. 62

• Group of related organelles in which membrane
  materials are assembled, modified, and shared
• Endoplasmic reticulum
• Golgi bodies
• Vesicles
• Products are sorted, labeled, and shipped to
  destination
• Export from cell
• Insertion into cell membranes

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Rough ER

• Arranged into flattened sacs
• Ribosomes on surface give it a rough appearance
• Some polypeptide chains enter rough ER and are
  modified
• Cells that specialize in secreting proteins have
  lots of rough ER

Where else do you find ribosomes?
22
Smooth ER

• A series of interconnected tubules
• No ribosomes on surface
• Lipids assembled inside tubules
• Smooth ER contains enzymes, and may store some
  cell chemicals.
• Smooth ER of liver inactivates wastes, drugs
• Sarcoplasmic reticulum of muscle is specialized
  to store Ca2

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Golgi Bodies

• Put finishing touches on proteins and lipids that
  arrive from ER
• Package finished material for shipment to final
  destinations
• Material arrives and leaves in vesicles
• Lysosomes
• digestive enzymes
• pumps in H ions for acidic internal pH
• Peroxisomes
• Enzymes breakdown hydrogen peroxide (H2O2)

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Central Vacuole

• Single membrane organelle
• As cell grows, expansion of vacuole as a result
  of hydrostatic pressure forces a weakened cell
  wall to expand
• In mature cell, central vacuole takes up 50-90
  percent of cell interior

• What happens if you dont water your plants?
• Stores amino acids, sugars, wastes
• (including alkaloids nicotine, cocaine,
  caffeine, ephedrine, morphine, heroin codeine,
  theobromine, quinine.)

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Mitochondria

• Double membrane organelle
• central cavity filled with matrix
• inner membrane folds cristae
• large surface area for chemical reactions of
  cellular respiration
• Function
• efficient generation of ATP
• powerhouse of cell
• Mitochondria self-replicate
• increase in when need for ATP increases
• circular DNA with 37 genes
• only inherited from mother (in egg)

p. 64
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Chloroplasts

• Convert sunlight energy to ATP through
  photosynthesis

• Notice the larger surface area created by
  thylakoid discs.
• What chemicals are found embedded in these
  membranes?
• The fluid-filled portion of the chloroplast is
  called stroma.

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Origin of Membranous Organelles?

• No fossil record recording the origin of
  eukaryotes, however
• Both mitochondria and chloroplasts resemble
  bacteria
• Similar in size
• Reproduce by binary fission
• Have own DNA, RNA, and ribosomes
• All eukaryotes share same characteristics
• Cytoskeleton made of microtubules (tubulin
  protein) and actin
• DNA in chromosomes
• Membrane-bound organelles

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Two Theories for theOrigin of Eukaryotes
p. 294
Endosymbiosis
Autogenous
The Autogenous theory may explain the origin of
____, and the Endosymbiotic theory may explain
the origin of ____.
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Mechanisms of Intracellular Movement
p. 66

• Length of microtubules or microfilaments can
  change
• Parallel rows of microtubules or microfilaments
  actively slide in a specific direction
• Microtubules or microfilaments can shunt
  organelles to different parts of cell (see video)

Which human cells change their shape dramatically
with conscious control?
30
Plant Cell Features
Compare and contrast plant and prokaryotic cell
walls. What other eukaryotic organisms produce a
cell wall?
p. 65
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Animal Cell Features
p. 65