1. The Working Cell Figures 5.14 – 5.19
CHAPTER 5
The Working Cell
Figures 5.14 – 5.19

2. Water Balance in Plant Cells
Water balance in plant cells is different
They have rigid cell walls
They are at the mercy of the environment
Figure 5.14

3. Active Transport: the Pumping of Molecules Across Membranes
Active transport requires energy to move molecules across a membrane
Lower solute concentration
Solute
Higher solute concentration
Figure 5.15

4. Exocytosis and Endocytosis: Traffic of Large Molecules
Secretes substances outside of the cell
Outside cell
Plasma
membrane
Cytoplasm
(a) Exocytosis
Figure 5.16a

5. Endocytosis
Takes material into the cell
(b) Endocytosis
Figure 5.16b

6. In phagocytosis (“cellular eating”) a cell engulfs a particle and packages it within a food vacuole
In pinocytosis (“cellular drinking”) a cell “gulps” droplets of fluid by forming tiny vesicles
Pseudopod
of amoeba
Food being ingested
Figure 5.17

7. Receptor-mediated endocytosis
Is triggered by the binding of external molecules to membrane proteins

8. The Role of Membranes in Cell Signaling
LDL particle
Phospholipid coat
Protein
Receptor protein
Cholesterol
Plasma
membrane
Cholesterol
processed
Liver cell
Figure 5.18

9. Cellular communication
Begins with the reception of an extracellular signal
The signal transduction pathway
Consists of proteins and other molecules that relay the signal

10. Reception Transduction Response
Outside cell
Inside cell
Reception
Transduction
Response
Receptor
protein
Hydrolysis
of glycogen
releases
glucose for
energy
Signal transduction pathway
Epinephrine
(adrenaline)
from adrenal
glands
Plasma membrane
Figure 5.19

11. EVOLUTION CONNECTION: EVOLVING ENZYMES
Organisms use many different enzymes
Scientists compare enzymes from different organisms
Comparisons show similarities between organisms

12. The processes of natural selection and directed evolution
Both result in the production of new enzymes with new functions

13. SUMMARY OF KEY CONCEPTS
ATP and Cellular Work
Energy for cellular work
Adenosine
Adenosine
(Phosphate
transferred
to other
molecules)
Adenosine
triphosphate
Adenosine
diphosphate
Energy from
organic fuel
Visual Summary 5.1

14. Higher water concentration (hypotonic)
Passive Transport, Osmosis, and Active Transport
Requires no energy
Requires energy
Passive transport
Osmosis
Active transport
Higher solute
concentration
Higher water concentration (hypotonic)
Higher solute
concentration
Solute
Water
Solute
Solute
Lower water
concentration
(hypertonic)
Lower solute
concentration
Lower solute
concentration
Visual Summary 5.2

15. Exocytosis and Endocytosis: Traffic of Large Molecules
Visual Summary 5.3