Download 2-6 Cell Basics

Name ____________________________ Date ______________ Period ________
Biology
Unit 2 – Life Processes, Background Paper 2-6
Cell Basics
All living things are composed of one or more cells. This statement is the basis of 'Cell Theory'. To understand how all
living things cycle energy it is necessary to become acquainted with a few basic components of cells. You met the
nucleus in the first unit as the control center in neurons. This reading will feature two new cell components (components
of cells are called organelles); the mitochondria and the chloroplast.
Mitochondria1 are found in all living cells except bacteria (more on that
later). The function of the mitochondria is to provide a working space for a
series of enzyme reactions that release the energy stored in food mole cules
(primarily sugars and fats). The enzymes oxidize the food molecules
analogous to the way food oxidizes when it is burned. The obvious difference
is that the oxidation process is slow enough that we don't burn up like a
marshmallow left in the fire too long. Just like the marshmallow is fuel for the
fire the sugars can be fuel for our bodies. As the marshmallow burns in the fire
energy is released (it will burn you if you grab the flaming glob). When the
flame dies all that is left is the carbon. The hydrogen, oxygen, and some of the
carbon have escaped into the air in the form of H2O and CO2.
When we eat the same marshmallow the sugars are transported to the mitochondria in our cells Figure 1 Mitochondria
where protein enzymes release the energy slowly. The left over carbon, hydrogen, and oxygen
leaves our bodies as H2O, and CO2 when we breath out. Rather than being released as heat the energy is captured by a
molecule that serves as cellular battery storage - Adenosine Tri-Phosphate (ATP).
The specifics of this process will be the subject of a future reading.
Chloroplasts2 are found primarily in plants. A common misconception is that plants make food from sunlight. If you
think this through it is really pretty ridiculous. What does sunlight weigh? What does food
weigh? Can you make anything from just sunlight? What plants are really doing is capturing
sunlight energy using protein catalysts. The energy they capture is used to assemble
carbohydrates and fats from CO2 and H2O. The site where the energy capture occurs is in the
chloroplasts. The plant can now store the 'food' for later use - or we can eat the plant and use
the energy ourselves.
An important point to remember here is that both plants and animals have mitochondria. Plants
do not 'eat' sunlight. They 'eat' the same carbohydrates and fats that we do. The difference is
that they also produce the food in their chloroplasts. Animals can't do that (no chloroplasts) so
we have to rely on the plants to do it for us. Another important note is the cycling of
molecules. Note that animals (and plants) give off CO2 and H2O as the left-overs from food
Figure 2 Chloroplasts in plant cells
oxidation while plants use that same CO2 and H2O to assemble the energy carrying carbohydrates
and fats. Pretty good system really!
Visit; http://learn.genetics.utah.edu/content/begin/cells/organelles/
You will find a surprising fact about the origin of both mitochondria and chloroplasts. Where did they come from?
Answer this question at the bottom of the back of this reading . Draw a simple plant cell with nucleus, mitochondria and
chloroplasts in your concept map on the back. Have answer and drawing ready for the quiz. Include the labeled cell
drawing in you journal when the readings is returned.
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Mitochondria images NIH public domain
Chloroplast photo by permission Kristian Peters 2006
Background 2-6, CellBasics 2012
Text 2012
Greg Ballog
Page 1
Name ____________________________ Date ______________ Period ________
tomorrow. Title of Reading: 2-6 Cell Basics
Points Earned
1 2 3 4 5 6 7
Label the plant cell (3 points)
Plant Cell Drawing
Visit:
http://science.halleyhosting.com/sci/ibbio/cells/notes/ch5/plant.htm
1 Point
A&B
A) What one question do I have about this article?
B) Show or describe the reading to a parent or guardian (Name ___________________).
What comments or questions did they have concerning the reading?
(Biology Homework Time __________)
#
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Class Quiz – Answers (3 Points)
X/C
Where did Mitochondria Come From?
Where did Chloroplasts Come From?
What do Mitochondria do?
What do Chloroplasts do?
Background 2-6, CellBasics 2012
Text 2012
Greg Ballog
Page 2