Transcript Cell Structure and Function

BSC 2010 L

Cells are the basic unit of life

Cell Theory
 All living things are composed of cells and
 Cells come only from other cells

In this lab, we will look at a couple different
things:

Cell Structure

Plasma membranes
 Difference between prokaryotes and eukaryotes
 Eukaryotes – difference between plant and animal
cells
 Function of organelles
 Contents of the cell are bounded by plasma
membrane
 Regulates movement of molecules into and out of the
cytoplasm
 We will look at the how the passage of water into a
cell depends on the difference in concentration of
solutes between cytoplasm and the surrounding
medium

pH
 Well-being of cells also depends upon pH
surrounding them
 We will look at how a buffer can maintain pH within
a narrow range and how buffers within cells can
protect them from damaging pH changes
PROKARYOTIC CELL

Bacteria
EUKARYOTIC CELL

Protists, fungi, plants,
animals

Know the name and function of
organelles found in eukaryotic cells

Know differences between plant cells
and animal cells!

Looking at the Elodea Leaf

Human Cheek Cells


pH of a solution tells its
hydrogen ion concentration H+
Buffer – system of chemicals
that takes up excess H ions
or hydroxide ions

Maintaining pH is VERY
important in biological systems
 i.e. – human blood pH must be
maintained at 7.4

Exercise 4.5
 You will test the buffering
capacity of 3 solutions
 Water, inorganic solution,
simulated cytoplasm
 Which one do you think will be
able to hold its pH the longest
as drops of HCl are added?
Contents
pH before acid
pH after acid
Additional acid
~ 6.5
3.0
2.0
Inorganic Buffer
7.0
7.0
5.5
Cytoplasm
7.0
7.0
6.5
Distilled Water

Movement of molecules from a higher to a lower concentration until
equilibrium is achieved
 Dependent on temperature, size of molecules, and type of medium
(solid, semi-solid, liquid, air)




Air
Liquid
Semi-solid
Semi-permeable membrane

Dialysis tubing

Diffusion of methylene blue in agar (semisolid) versus water (liquid)

In which medium did the dye diffuse the fastest?


We will see what
happens with
animal cells -red
blood cells
And plant cells –
potato and elodea

Relative concentration of solute (particles)
or solvent (water) outside the cell compared
to inside

3 Types
 Isotonic
 Hypertonic
 Hypotonic

Check out tubes of prepared red blood cell
solutions

Isotonic

Hypertonic



In 10% NaCl solution
Water has left the cell across the plasma membrane
Notice how cell membrane has shrunk away from cell
wall and chloroplasts are all clustered in middle