1. Cell Organelles 1.4
Cohick

2. Cell Theory review Cells are the basic unit of life
All organisms are made of one or more cells
All cells arise from pre-existing cells.

3. The Organelles “Little organs” Organelle functions: Produce energy
Build essential cellular materials
Remove wastes
Transport materials
Plants have CHLOROPLASTS. They contain CHLOROPHYLL, which is essential for PHOTOSYNTHESIS.
The ORGANELLES are the workers of the city. They clean, repair, & build structures to help the city grow.

4. Cell Membrane (Plasma)
Holds the cell together: Protect and support the cell
Keeps all the organelles and cytoplasm inside the cell.
Controls the flow in and out of the cell.
Forms a barrier between the cytoplasm and the environment
Example: Like a big plastic bag with tiny holes in it.

5. How does the cell membrane work?
The layers are made up of molecules called PHOSPHOLIPIDS.
Each phospholipids has a HYDROPHOBIC and HYDRPHILIC end.
HYDRO = means water
PHOBIC = means afraid
PHILIC = means loving
Like a sandwich made of two pieces of bread with “stuffing” on the inside.

6. Cell Membrane : PHOSPHOLIPIDS
One end of the phospholipid is “afraid” of the water and one end “loves” being in the water.
Proteins are stuck inside the membrane.
These proteins make the “holes” that let ions and other molecules in and out of the cell.

7. Cytoplasm
Cytoplasm is everything inside the cell membrane (except the nucleus if there is one).
It includes the watery, gel-like cytosol.
It also includes other structures. The water in the cytoplasm makes up about two-thirds of the cell’s weight.
It gives the cell many of its properties.

8. Cytoskeleton
Crisscrossing the cytoplasm is a structure called the cytoskeleton. It consists of thread-like filaments and tubules.
The cytoskeleton is like a cellular “skeleton.” It helps the cell keep its shape. It also holds cell organelles in place within the cytoplasm.
Figure 1.20 shows several cells. In the figure, the filaments of their cytoskeletons are colored green. The tubules are
colored red. The blue dots are the cell nuclei.

9. Nucleus The “brain” of the cell.
Controls all of the cellular activities.
Most of the DNA is inside the nucleus.
Genetic code
Surrounded by the nuclear envelope with pores to allow substances to move in and out of the nucleus

10. Nucleus Chromosomes –are found inside the nucleus
Chromosomes carry the information that determines what traits a living organism will have.

11. Nucleolus Dark area located inside the nucleus
Like a tiny nucleus inside the real nucleus.
Ribosomes are made here.

12. Mitochondria Mito = Mighty / Power The POWER-HOUSE of the cell
Mitochondria break down food molecules so the cell has energy to live. (Adenosine triphosphate = ATP)
If a cell needs a lot of energy—It will have MORE mitochondria.
The inner membrane folds many times to increase the surface area where chemical reactions occur= more energy is made! ATP=Energy

13. Ribosomes
Ribosomes are small dot-like structures located on rough ER or free floating in the cytoplasm. They do not have a membrane-so they are not considered real organelles.
They are the site of Protein synthesis
It’s like a factory within the cell
They gather amino acids and join them together into proteins
Ribosomes are made by the nucleolus.

14. Endoplasmic Reticulum
Also called “ER”
ER is made up of membranes
Smooth ER
Main function is to collect, maintain and transport things for the cell.
Tubular shaped
Creates steroids
Store ions for the cell to maintain a nutrient balance (Homeostasis)
Rough ER
Covered in “dots” of ribosomes
This ER collects the proteins made by the ribosomes and creates a package around them.
ER makes this “vesicle” by pinching off part of its membrane so it can transport the proteins.

16. Golgi Apparatus
The Golgi apparatus is a large organelle that sends proteins and lipids where they need to go. It’s like a post office.
It receives molecules from the endoplasmic reticulum. It packages and labels the molecules. Then it sends them
where they are needed. Some molecules are sent to different parts of the cell. Others are sent to the cell membrane
for transport out of the cell.
Small bits of membrane pinch off the Golgi apparatus to enclose and transport the proteins and lipids.

17. Vesicles and Vacuoles
Both vesicles and vacuoles are sac-like organelles. They store and transport materials in the cell. They are like movable storage containers.
• Some vacuoles are used to isolate materials that are harmful to the cell. Other vacuoles are used to store needed substances such as water.
• Vesicles are much smaller than vacuoles and have a variety of functions. Some vesicles pinch off from the membranes of the endoplasmic reticulum and Golgi apparatus. These vesicles store and transport proteins and lipids.
Other vesicles are used as chambers for biochemical reactions.

18. Lysosomes A lysosome is an organelle that recycles unneeded molecules.
It uses enzymes to break down the molecules into their components. Then the components can be reused to make new molecules.
If a lysosomes breaks open within the cell—it DIGESTS the cells organelles
Lysosomes are like recycling centers.

19. Centrioles
Centrioles are organelles that are found only in animal cells.
They are located near the nucleus. (When viewed with an electron microscope-the cylinders show up as nine bundles of tiny microtubules arranged in a circle.)
They help organize the DNA in the nucleus before cell division takes place.
They ensure that the DNA divides correctly when the cell divides by forming the fibers that the chromosomes divide along.

20. Special Structures in Plant Cells
Every organelle, except the centrioles, we have discussed so far is also found in plant cells.
Plant cells have 3 organelles NOT found in animal cells.
Cell Wall
Large Central Vacuole
And organelles called plastids.
Chloroplasts

21. Cell Wall
The cell wall is a rigid layer that surrounds the cell membrane of a plant cell.
It’s made mainly of the complex
carbohydrate called cellulose.
The cell wall supports and protects the cell.
The cell wall isn’t solid like a brick wall.
It has tiny holes in it called pores.
The pores let water, nutrients, and other substances move into and out of the cell.

22. Large Central Vacuole Most plant cells have a large central vacuole.
It can make up as much as 90 percent of a plant cell’s total volume.
The central vacuole is like a large storage container.
It may store substances such as water, enzymes, and salts.
It may have other roles as well. For example, the central vacuole helps stems and leaves hold their shape.
It may also contain pigments that give flowers their colors.

23. Plastids Chloroplasts Green pigment called chlorophyll
Photosynthesis takes place here.
Captures sunlight and use its energy to make glucose.

24. Lysosome
Centriole
Nucleolus
Nucleus
Mitochondria
Ribosomes
vesicle
Rough endoplasmic reticulum
cytoplasm
Cytoskeleton
Golgi apparatus
Smooth endoplasmic reticulum

25. Lesson Summary
• The cell membrane consists of two layers of phospholipids. It encloses the cytoplasm and controls what enters
and leaves the cell.
• The cytoplasm consists of watery cytosol and cell structures. It has several functions. The cytoskeleton is the
“skeleton” of the cell. It helps the cell keep its shape.
• Eukaryotic cells contain a nucleus and other organelles. They include the mitochondrion, endoplasmic reticulum,
Golgi apparatus, vesicles, vacuoles, lysosomes, and—in animal cells—centrioles. Each type of organelle
has a special function.
• Plant cells have several structures not found in animal cells. They include a cell wall, large central vacuole,
and plastids such as chloroplasts.

26. Review Questions Recall
1. Describe the composition of the cytoplasm and list its functions.
2. What is the cytoskeleton? What does it do?
3. Identify three organelles in eukaryotic cells and state their roles.
Apply Concepts
4. Why is the nucleus like the control center of a cell?
Think Critically
5. Explain how the structure of the cell membrane controls what enters and leaves the cell.
6. Compare and contrast plant and animal cells.
Points to Consider
The cell theory states that all cells come from pre-existing cells. Based on what you have learned about the structure
of cells:
1. What cellular components will be passed from one cell to the next?
2. How do you think new cells are ’born?’