From Cells to Organisms

1
9.2 Inside Cells
Organisms have many different kinds of cells
which exist in various shapes and sizes. However,
all cells share some common features.
human cheek cells
2
Animal Cells
cell membrane

• thin layer around the cell, allowing shape of
  cell to change
• partially permeable

cytoplasm

• jelly-like substance that fills the cell
• contains water and many other substances
• involves chemical reactions

nucleus
vacuoles

• controls cell activities
• contains chromosomes

• small spaces containing air, liquid or food
  particles
• numerous in animals

3
Plants Cells
chloroplasts
cell wall

• small disc-like structures found in the cells of
  green plants
• contain chlorophyll

• thick layer around the cell
• made up of tough substance (cellulose)
• supports the cell and gives it a regular shape

cell membrane

• thin layer around the cell, allowing shape of
  cell to change
• partially permeable

vacuole
cytoplasm

• single large space containing liquid (cell sap)
• cell sap contains water and dissolved substances
  (eg. sugar and salt)
• cell sap keeps the cell firm by taking in water

nucleus

• jelly-like substance that fills the cell
• contains water and many other substances
• involves chemical reactions

• controls cell activities
• contains chromosomes

4
Chromosomes, Genes and Heredity
What are Chromosomes???

• Definition
• They are the thread-like objects found in the
  nucleus in each cell. They carry information
  which controls
• how the cell works
• what the organism will look like

5
Chromosomes, Genes and Heredity
Different organisms contain different numbers of
chromosomes in their cells. In a human cell
there are 46 (or 23 pairs) of chromosomes.
nucleus
genes on a chromosome
chromosomes
each chromosome is made up of many genes each
gene contains instructions for a different
feature of an organism
6
Comparing between Animal and Plant Cells
7
Dead Cells
A living plant cell has a cell wall, a nucleus
and cytoplasm. When a cell dies, the nucleus and
cytoplasm become part of the cell wall. The
remainder of the cell becomes a large space
containing only air. Example cork
8
Cells - Two-dimensional or Three-dimensional
Are cells two-dimensional or three-dimensional?
Cells are actually three-dimensional,
not flat.