To study biology.

1. BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 5
The Working Cell
Modules 5.10 – 5.21
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2. MEMBRANE STRUCTURE AND FUNCTION
5.10 Membranes organize the chemical activities of
cells
• Membranes organize the chemical reactions
making up metabolism
→
→
Cytoplasm
Figure 5.10
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3. • Membranes are selectively permeable
– They control the flow of substances into and out
of a cell
• Membranes can hold teams of enzymes that
function in metabolism
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4. 5.11 Membrane phospholipids form a bilayer
• Phospholipids are Head
the main
structural
components of
membranes
• They each have a
hydrophilic head Symbol
and two
hydrophobic tails
Tails
Figure 5.11A
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5. • In water, phospholipids form a stable bilayer
– The heads face outward and the tails face
inward
Water
Hydrophilic
heads
Hydrophobic
tails
Water
Figure 5.11B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. 5.12 The membrane is a fluid mosaic of
phospholipids and proteins
• Phospholipid molecules form a flexible bilayer
– Cholesterol and protein molecules are embedded
in it
– Carbohydrates act as cell identification tags
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7. • The plasma membrane of an animal cell
Glycoprotein Carbohydrate
(of
glycoprotein)
Fibers of the
extracellular
matrix
Glycolipid
Phospholipid
Cholesterol
Microfilaments Proteins
of the
cytoskeleton CYTOPLASM
Figure 5.12
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8. 5.13 Proteins make the membrane a mosaic of
function
• Some membrane proteins form cell junctions
• Others transport substances across the
membrane
Figure 5.13 Transport
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9. • Many membrane proteins are enzymes
• Some proteins function as receptors for
chemical messages from other cells
– The binding of a messenger to a receptor may
trigger signal transduction
Messenger molecule
Receptor
Activated
molecule
Figure 5.13 Enzyme activity Signal transduction
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. 5.14 Passive transport is diffusion across a
membrane
• In passive transport,
Molecule
substances diffuse of dye Membrane EQUILIBRIUM
through membranes
without work by the
cell
– They spread from
areas of high EQUILIBRIUM
concentration to
areas of lower
concentration
Figure 5.14A & B
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11. 5.15 Osmosis is the passive transport of water
Hypotonic Hypertonic
• In osmosis, water solution solution
travels from an
area of lower
solute
concentration to Selectively
permeable
Solute
molecule
membrane
an area of higher HYPOTONIC SOLUTION HYPERTONIC SOLUTION
solute Water
molecule
concentration
Selectively
permeable Solute molecule with
membrane cluster of water molecules
NET FLOW OF WATER Figure 5.15
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12. 5.16 Water balance between cells and their
surroundings is crucial to organisms
• Osmosis causes cells to shrink in a hypertonic
solution and swell in a hypotonic solution
– The control of water balance
(osmoregulation) is essential for organisms
ISOTONIC HYPOTONIC HYPERTONIC
SOLUTION SOLUTION SOLUTION
ANIMAL
CELL
(1) Normal (2) Lysing (3) Shriveled
Plasma
membrane
PLANT
CELL
Figure 5.16 (4) Flaccid (5) Turgid (6) Shriveled
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13. 5.17 Transport proteins facilitate diffusion across
membranes
• Small nonpolar molecules diffuse freely through
the phospholipid bilayer
• Many other kinds of molecules pass through
selective protein pores by facilitated diffusion
Solute
molecule
Transport
protein
Figure 5.17
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14. 5.18 Cells expend energy for active transport
• Transport proteins can move solutes across a
membrane against a concentration gradient
– This is called active transport
– Active transport requires ATP
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15. FLUID Phosphorylated
• Active OUTSIDE
CELL
Transport
protein
transport protein
transport in
two solutes
across a First
membrane solute
1 First solute, 2 ATP transfers 3 Protein releases
inside cell, phosphate to solute outside
binds to protein protein cell
Second
solute
4 Second solute 5 Phosphate 6 Protein releases
binds to protein detaches from second solute
Figure 5.18 protein into cell
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16. 5.19 Exocytosis and endocytosis transport large
molecules
• To move large molecules or particles through a
membrane
– a vesicle may fuse with the membrane and expel
its contents (exocytosis)
FLUID OUTSIDE CELL
CYTOPLASM
Figure 5.19A
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17. – or the membrane may fold inward, trapping
material from the outside (endocytosis)
Figure 5.19B
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18. • Three kinds of endocytosis
Pseudopod of Food being Plasma Material bound to
amoeba ingested membrane receptor proteins
PIT
Cytoplasm
Figure 5.19C
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19. 5.20 Connection: Faulty membranes can overload
the blood with cholesterol
• Harmful levels of cholesterol can accumulate in
the blood if membranes lack cholesterol
receptors
Phospholipid
LDL PARTICLE outer layer
Receptor protein
Protein
Cholesterol
Plasma membrane Vesicle
CYTOPLASM
Figure 5.20
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20. 5.21 Chloroplasts and mitochondria make energy
available for cellular work
• Enzymes and membranes are central to the
processes that make energy available to the cell
• Chloroplasts carry out photosynthesis, using
solar energy to produce glucose and oxygen
from carbon dioxide and water
• Mitochondria consume oxygen in cellular
respiration, using the energy stored in glucose
to make ATP
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

21. Sunlight energy
• Nearly all the chemical
energy that organisms
use comes ultimately Chloroplasts,
site of photosynthesis
from sunlight CO2 Glucose
+ +
H2O Mitochondria O2
• Chemicals recycle sites of cellular
respiration
among living organisms
and their environment
(for cellular work)
Figure 5.21 Heat energy
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings