How Cells Are Put Together

1
How Cells Are Put Together

• Chapter 3

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Early Cells

• First cells appeared between 3.9 billion and 2.5
  billion years ago
• Earliest were prokaryotic and anaerobic
• Photosynthetic pathway arose later and added
  oxygen to atmosphere
• Over time cells became more complex with internal
  compartments and specialized structures

3
Cell Theory

• Every organism is composed of oneor more cells
• Cell is smallest unit having properties of life
• Continuity of life arises from growth and
  division of single cells

4
Cell

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

5
Structure of Cells

• All start out life with
• Plasma membrane
• Region where DNA is stored
• Cytoplasm

• Two types
• Prokaryotic
• Eukaryotic

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Most Cells Are Really 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

7
Microscopes

• Create detailed images of something that is
  otherwise too small to see
• Light microscopes
• Simple or compound
• Electron microscopes
• Transmission EM or Scanning EM

8
Structure of Cell Membranes

• Fluid mosaic model
• Mixed composition
• Phospholipid bilayer
• Glycolipids
• Sterols
• Proteins

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Membrane Proteins

• Adhesion proteins
• Communication proteins
• Receptor proteins
• Recognition proteins
• Passive transporters
• Active transporters

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Prokaryotic Cells

• Archaebacteria and eubacteria
• DNA is not enclosed in nucleus
• Generally the smallest, simplest cells

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Eukaryotic Cells

• Have a nucleus and other organelles
• Eukaryotic organisms
• Plants
• Animals
• Protistans
• Fungi

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Eukaryotic Cell Features

• Plasma membrane
• Nucleus
• Endoplasmic reticulum
• Golgi body
• Vesicles
• Mitochondria
• Ribosomes
• Cytoskeleton

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The Nucleus

• Keeps the DNA molecules separated from metabolic
  machinery of cytoplasm
• Makes it easier to organize DNA and to copy it
• Components
• Nuclear envelope Nucleoplasm
• Chromatin Nucleolus

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Endomembrane System

• Group of related organelles in which lipids are
  assembled and new polypeptide chains are modified
• Products are sorted and shipped to various
  destinations
• Consists of endoplasmic reticulum, Golgi bodies,
  vesicles

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Endoplasmic Reticulum

• Starts at nuclear membrane and extends throughout
  cytoplasm
• Rough ER ribosome covered,processes proteins
• Smooth ER no ribosomes, builds lipids

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Golgi Body

• Puts finishing touches on proteins and lipids
  that arrive from ER
• Packages finished material for shipment to final
  destinations
• Material arrives and leaves in vesicles

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Vesicles

• Membranous sacs that move through cytoplasm
• Lysosomes- digests, recycles materials
• Peroxisomes- digests fatty acids and
• amino acids

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Mitochondria

• ATP-producing powerhouses
• Membranes form two distinct compartments
• ATP-making machinery embedded in inner
  mitochondrial membrane

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Chloroplasts

• Convert sunlight energy to ATP through
  photosynthesis
• Occur in plants and some protistans

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Organelle Origins

• Nucleus and ER
• Infolding of membranes formed compartments
• Mitochondria and chloroplasts
• Endosymbiosis- theory one species lives its life
  inside another species

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Cytoskeleton

• Present in all eukaryotic cells
• Basis for cell shape and internal organization
• Allows organelle movement within cells and, in
  some cases, cell motility