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Active and Passive Transport. Chapter 5. 1. Passive Transport . Movement of materials in and out of the cell Requires no energy to happen. Two Types of Passive Transport. Diffusion: When substance moves that is dissolved in water Osmosis: When water moves across the membrane.

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1 passive transport
1. Passive Transport
  • Movement of materials in and out of the cell
  • Requires no energy to happen
two types of passive transport
Two Types of Passive Transport
  • Diffusion: When substance moves that is dissolved in water
  • Osmosis: When water moves across the membrane
solutions are made of 2 parts
Solutions are made of 2 parts:
  • Solute: Substance that is dissolved in water
  • Solvent: Liquid it is dissolved in (usually water)
vocab
Vocab:
  • Hypertonic:More solutes than the other solution
  • Hypotonic: Lesssolutes than the other solution
  • Isotonic: Equal solutes as another solution
  • Now go back to the pictures above and label the cell and the environment around it as one of the vocab words
slide10

Molecules of dye

Membrane (cross section)

WATER

Equilibrium

Net diffusion

Net diffusion

Net diffusion

Equilibrium

Net diffusion

Osmosis

Net diffusion

Net diffusion

Equilibrium

(a)

(b)

slide11

Lower

concentration

of solute (sugar)

Higher

concentration

of sugar

Same concentration

of sugar

Selectively

permeable mem-

brane: sugar mole-

cules cannot pass

through pores, but

water molecules can

Water molecules

cluster around

sugar molecules

More free water

molecules (higher

concentration)

Fewer free water

molecules (lower

concentration)

Osmosis

Water moves from an area of higher

free water concentration to an area

of lower free water concentration

describing a solution
Describing a solution
  • Hypotonic: when a solution is less concentrated than another solution
  • Example: if around a cell is hypotonic, then water will move into the cell.
  • Can cause a cell to get so large it may burst (cytolysis)
slide13
Hypertonic: When a solution is more concentrated than another solution
  • If around a cell is hypertonic, water will move out of the cell
  • Can cause the cell to get very small (in plants will see plasmolysis: wilting)
slide14
Isotonic: when two solutions have the same concentration (are at equilibrium)
  • Causes water to move in and out equally
  • The cell maintains its shape
slide15

Hypertonic solution

Hypotonic solution

Isotonic solution

(a)

H2O

H2O

H2O

H2O

Normal

Shriveled

Lysed

H2O

H2O

H2O

(b)

H2O

Turgid (normal)

Flaccid

Plasmolyzed

slide16
Osmosis
  • Water moves trying to balance out concentrations
  • Goes from where there is more water to less water
what if
What if…..
  • Environment around a cell is hypotonic. What direction will the water move?
  • Salt?
what if1
What if…..
  • The environment around a cell is hypertonic.
  • What direction will the water move?
  • Salt?
2 active transport
2. Active Transport
  • Requires energy
  • Goes against the concentration gradient (from lower concentration to higher concentration)
figure 7 16 the sodium potassium pump a specific case of active transport
Figure 7.16 The sodium-potassium pump: a specific case of active transport

Cytoplasmic Na+ binds to

the sodium-potassium pump.

EXTRACELLULAR

FLUID

[Na+] high

[K+] low

Na+ binding stimulates phosphorylation by ATP.

Na+

Na+

Na+

Na+

Na+

[Na+] low

[K+] high

ATP

P

Na+

5

2

1

6

4

3

ADP

CYTOPLASM

Phosphorylation causes the

protein to change its conformation, expelling Na+ to the outside.

K+ is released and Na+

sites are receptive again;

The cycle repeats.

Na+

Na+

Na+

K+

P

K+

Loss of the phosphate

restores the protein’s

original conformation.

Extracellular K+ binds to the

protein, triggering release of the

Phosphate group.

K+

K+

K+

K+

P

P i

slide21
Sodium Potassium Pump
  • Cells usually have more sodium ions outside and more potassium ions inside
  • Pump increases number of ions where concentration is already high
slide22
When substances are too large to pass through the cell membrane, use endocytosis or exocytosis
  • Membrane folds around substances and release into cell or out of cell
figure 7 20 exploring endocytosis in animal cells

PHAGOCYTOSIS

EXTRACELLULAR

FLUID

1 µm

CYTOPLASM

Pseudopodium

Pseudopodium

of amoeba

“Food” or

other particle

Bacterium

Food

vacuole

Food vacuole

An amoeba engulfing a bacterium via

phagocytosis (TEM).

PINOCYTOSIS

0.5 µm

Plasma

membrane

Pinocytosis vesicles

forming (arrows) in

a cell lining a small

blood vessel (TEM).

Vesicle

Figure 7.20 Exploring Endocytosis in Animal Cells
slide24
Endocytosis
  • Material moved into cell
  • Forms vesicle
  • Pinocytosis: Liquids
  • Phagocytosis: Solids
slide25
Exocytosis
  • Material released to outside of cell
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