Transport of Molecules in a Cell

1
Transport of Molecules in a Cell
2
Terms to Know

• SOLUTE refers to the substance that is to be
  dissolved (Salt, Sugar)
• SOLVENT responsible for dissolving the solute
  (Water)
• SOLUTION Solvent and solute after combining
  together
• ECF Extracellular Fluid. Surrounds all living
  cells
• CONCENTRATION mass of solute dissolved in the
  solvent
• SEMI-PERMEABLE (SELECTIVELY-PERMEABLE) a
  membrane that allows only some substances in or
  out

3
Selectively Permeable Membrane
4
Transportation of Molecules

• Passive Transport
• Movement of molecules across a semi-permeable
  membrane with the gradient
• 3 types Osmosis,Diffusion
• Facilitated Diffusion
• Movement of molecules across a semi-permeable
  membrane with a protein
• NO ENERGY required

• Active Transport
• Movement of molecules across a semi-permeable
  membrane against a concentration gradient with a
  protein
• ENERGY required

5
Diffusion

• Solute molecules moving from an area of high
  concentration to an area of low concentration
• Random motion drives diffusion
• Movement is based on kinetic energy (speed),
  charge, and mass of molecules
• Equilibrium is reached when there is an even
  distribution of solute molecules

(water)
6
Equilibrium Reached
Low Concentration
High Concentration
7
Osmosis

• Diffusion of water through a semi-permeable
  membrane
• Permeable to solvents (WATER), but not to large
  molecules
• High water to low water
• concentration
• Dissolved molecules (i.e. glucose, starch) are
  called solutes
• REMEMBER
• Water solvent Glucose, Starch, Salt
  solutes

8
Effect of Water on Cells

• Hypertonic Environment
• High solute, low water
• Isotonic Environment
• water solute
• Hypotonic Environment
• High water, low solute

9
OsmosisSucrose will not move but water will
10
(No Transcript)
11
Dialysis Bag Experiment

• Dialysis Bag
• Semi-permeable membrane
• Water, glucose, starch
• What passes through the dialysis bag?
• Glucose (Benedicts Test)
• Starch (Iodine Solution)
• Time Course Experiment
• Every 10 minutes, measure the amount of glucose
  starch present in the beaker

12
Osmosis in Living Cells
Normal
plasmolyzed flaccid
turgid
13
RED BLOOD CELLS
14
Osmosis in Plant Cells
Plasmolysis

• Observe Elodea leaves via a wet mount of the
  sample
• 10 NaCl
• Distilled water

15
Recall the Cell Membrane
16
Proteins in the Plasma (cell) Membrane
17
Proteins are Specific to certain Solutes
18
Active Transport
19
ENDOCYTOSIS The general term for bringing bulk
chemicals into a cell is endocytosis (endo
inside) the general term for bringing bulk
chemicals out of a cell is exocytosis
(exooutside). Moving material into the cell by
endocytosis involves the pinching in of a portion
of the cell membrane around the material to be
transported into the cell. The pinched-in
portion eventually breaks free from the cell
membrane and forms a vesicle in the cytoplasm.

20
Homework

• Complete your Cheek Cell Elodea Cell mini-lab
• Study for your Microscope quiz
• Answer questions on p.25 Q.1-19
• ? Next topic Cell cycle cell division