Download Cell Structure and Function

4.1 What is a Cell?
ƒ Each cell has a plasma membrane, cytoplasm,
and a nucleus (in eukaryotic cells) or a nucleoid (in
prokaryotic cells)
Cell Structure and Function
Chapter 4
cytoplasm
DNA in
nucleus
cytoplasm
DNA
plasma
membrane
plasma
membrane
a Bacterial cell (prokaryotic)
b Plant cell (eukaryotic)
Fig. 4.3, p. 52
Fig. 4.3, p. 52
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Components of Cell Membranes
cytoplasm
ƒ Lipid bilayer
DNA in
nucleus
plasma
membrane
c Animal cell (eukaryotic)
Fig. 4.3, p. 52
Key Concepts:
Cell Size and Shape
WHAT ALL CELLS HAVE IN COMMON
ƒ Surface-to-volume ratio limits cell size
ƒ Each cell has a plasma membrane, a boundary
between its interior and the outside environment
ƒ The interior consists of cytoplasm and an
innermost region of DNA
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4.2 How Do We See Cells?
Relative Sizes
ƒ Three key points of the cell theory:
• All organisms consist of one or more cells
• The cell is the smallest unit that retains the
capacity for life
• A cell arises from the growth and division of
another cell
4.3 Membrane Structure and Function
Common Membrane Proteins
ƒ Each cell membrane is a boundary (lipid bilayer)
that controls the flow of substances across it
ƒ Fluid mosaic model
• Membrane is composed of phospholipids, sterols,
proteins, and other components
• Phospholipids drift within the bilayer
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4.4 Introducing Prokaryotic Cells
Prokaryote Structure
ƒ Cell wall
ƒ Bacteria and archaeans
• Surrounds plasma membrane
• The simplest cells
• The groups with greatest metabolic diversity
ƒ Flagella
• Used for motion
ƒ Biofilms
ƒ Pili
• Shared living arrangements of prokaryotes
• Protein filaments used for attachment
• “Sex” pilus transfers genetic material
4.6 Introducing Eukaryotic Cells
cytoplasm,
with ribosomes
Most prokaryotic cells have a cell
wall outside the plasma membrane,
and many have a thick, jellylike
capsule around the wall.
ƒ Start with a nucleus and other organelles
• Carry out specialized functions inside a cell
bacterial flagellum
DNA in
cell plasma
pilus capsule wall membrane nucleoid
Fig. 4.11, p. 58
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Components of Eukaryotic Cells
4.7 Components of The Nucleus
ƒ Nucleus separates DNA from cytoplasm
• Chromatin (all chromosomal DNA with proteins)
• Chromosomes (condensed)
ƒ Nucleolus assembles ribosome subunits
ƒ Nuclear envelope encloses nucleoplasm
• Pores, receptors, transport proteins
Nucleus and Nuclear Envelope
Nucleus and Nuclear Envelope
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Nucleus and Nuclear Envelope
4.8 The Endomembrane System
ƒ Endoplasmic reticulum (ER)
• An extension of the nuclear envelope
• RER modifies new polypeptide chains
• SER makes lipids; other metabolic functions
ƒ Golgi bodies
• Further modify polypeptides
• Assemble lipids
The Endomembrane System
Endomembrane System
ƒ Vesicles
• Endocytic and exocytic: Transport or store
polypeptides and lipids
• Peroxisomes: Digest fatty acids and amino acids;
break down toxins and metabolic by-products
• Lysosomes: Intracellular digestion (animals)
• Central vacuole: Storage; fluid pressure (plants)
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Endomembrane System
Endomembrane System
4.9 Mitochondria and Chloroplasts
Mitochondria and Chloroplasts
ƒ Mitochondria
• Break down organic compounds by aerobic
respiration (oxygen-requiring)
• Produce ATP
ƒ Chloroplasts
• Produce sugars by photosynthesis
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Plant Cuticle
free surface of
epithelial tissue
ƒ Protective surface secretion, limits water loss
different kinds of
tight junctions
gap junction
basement membrane
(extracellular matrix)
4.12 The Dynamic Cytoskeleton
adhering junction
Fig. 4.23, p. 67
Components of the Cytoskeleton
ƒ Components of the cytoskeleton
• Microtubules
• Microfilaments
• Intermediate filaments (in most)
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Cytoskeleton Function
Flagellum and Pseudopods
ƒ Organizes and moves cell parts
ƒ Reinforces cell shape
ƒ Interactions between motor proteins and
microtubules in cilia, flagella, and pseudopods
can move the whole cell
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