Transcript Onion & Blood Cells Lab

Onion & Blood
Cells Lab
ONION CELLS
• The thick, juicy layers of the onion are separated from
each other by a protective skin. The onion skin is only
one cell in thickness. The cells can be seen very
easily through a microscope.
•
Around the cell is a protective cell wall. Just inside
the cell wall and very close to it is the cell membrane.
Inside the cell membrane is a liquid called cytoplasm.
The dark, round body floating in the cytoplasm is the
nucleus of the cell.
•
All the cells in the onion skin are alike. They are
shaped somewhat like bricks and fit neatly together to
make a protective wall. That is their job—to separate
the layers of the onion.
Draw what you see. Label the cell
wall, the cell membrane, the
cytoplasm, and the nucleus.
Complete the chart:
Structure of
onion cell
Function of structure
Cell wall
• Gelatin-like substance that flows inside the cell
membrane
• Important chemical reactions occur here
Cell membrane
• Directs all cell activities
• Contains hereditary material made of DNA.
Infer: why you don’t you see any
chloroplasts?
• Be aware that some
cells are SPECIALIZED
– this means that they
have a special job or
function. Think about
the location of the
actual onion in relation
to the ground. Would
the leaf have
chloroplasts?
BLOOD CELLS
•
The cells that are most numerous in an animal and
that look like doughnuts are red blood cells. They are
flat disks, thinner in the middle than at the edge.
Because of this, the red blood cells look light in the
middle and darker at the edge. A red blood cell has
no nucleus and never reproduces; rather, it is
produced in bone marrow.
•
Red blood cells contain a special chemical called
hemoglobin. This chemical makes it possible for the
red blood cells to do their most important job—to carry
oxygen from the lungs to other parts of the body.
White blood cells are larger than red cells, and have
nuclei. All white blood cells keep blood clean by
eating bacteria and other foreign particles. In a drop
of blood, there are approximately 5,000,000 red blood
cells and 7,500 white blood cells.
Draw what you see. Label the cell
membrane and the cytoplasm
Explain: why can’t a red blood cell
reproduce?
• Specialized cells (like the
onion cell seen previously)
don’t always have all the
structures you would see in
other cells.
• Red blood cells lack an
important organelle that
contains the genetic
material needed for
reproduction – if you can
figure this out, you’ll get the
answer!
Recall: What is the function of red
blood cells?
• Hint: reread the
paragraph
at the
beginning
of the lab
Compare: How
are white blood
cells like
lysosomes?
• Hint: Think about the FUNCTION of each
of these two things. What purpose do they
serve?
Why is it important for each cell
structure to have its own individual
function?
• This answer won’t be found
in the textbook or in your
notes… it’s in your head
already!
• This is your ticket out the
door!
Our Plant Cell Drawing
Our Animal Cell Drawing