Cellular Transport

Chapter 8

Figure 8.6 The detailed structure of an animal cell’s plasma membrane, in cross section

Figure 8.4 The fluidity of membranes

Figure 8.9 Some functions of membrane proteins

Cells move substances through the cell membrane by

a process called transport

• Two Types of Transport:

–Passive Transport

–Active Transport

What is Diffusion or Passive Transport?

• Requires no energy from cell.

• Molecules move from high concentration to low concentration.

• Molecules move with the concentration gradient.

Figure 8.10 The diffusion of solutes across membranes

How would diffusion happen in a cell?

Osmosis is a type of diffusion

Cell Membrane

Figure 8.11 Osmosis

HELP WANTED!Facilitated Diffusion

tranport proteins help substances (glucose) pass through the cell membrane. Still passive transport - no energy required.

I’m a Channel, I can help!

Figure 8.14 Two models for facilitated diffusion

Water balance of cells without walls:

100% Distilled Water

80% H2O

70% Water30% Dissolved

Substances

80% H2O

80% Water20% Dissolved

Substances

80% H2O

Which way did the water move?

100% Distilled Water

80% H2O

Why did the cell get so big?

Which way did the water move?

80% Water20% Dissolved

Substances

80% H2O

Why did the cell stay the same

size?

Which way did the water move?

70% Water30% Dissolved

Substances

80% H2O

Why did the cell get so small?

Figure 8.12 The water balance of living cells

Figure 8.13 The contractile vacuole of Paramecium: an evolutionary adaptation for osmoregulation

Figure 8.15 The sodium-potassium pump: a specific case of active transport

Figure 8.17 An electrogenic pump

Figure 8.18 Cotransport

How is Active Transport different?

1. Active transport requires energy.

2. Molecules move from low concentration to high concentration

3. Molecules move against concentration gradient.

Figure 8.16 Review: passive and active transport compared

Endocytosis• Cells bring large in particles using

cell membrane

– There are 2 types:• Phagocytosis

• Pinocytosis

Phagocytosis

• This is the ingestion of large particles.• Your white bloods cells also do this.

Amoeba

Pinocytosis

• Tiny pockets form along cell membrane, and pinch off into vacuoles inside the cell. Sometimes called “Cell Drinking”

Figure 8.19 The three types of endocytosis in animal cells

Exocytosis

• This is how the cell gets rid of waste.