Download About Cells

Name ________________________________ Class Period ____________ Date _______________
All about Cells
Read the information and then complete the questions at the end.
The cell is the basic unit of life. There are two types of cells, prokaryotes and eukaryotes. Prokaryotes
are the simplest of all cells, they lack membrane bound organelles (like a nucleus or mitochondrion).
Prokaryotes are microorganisms that do everything from make cheese to cause strep throat.
Eukaryotes are structurally more complex, larger in size, and have a nucleus. Eukaryotes are separated
into plant and animal cells.
All cells are surrounded by a cell membrane. The cell membrane is semipermeable, allowing some
substances to pass into the cell and blocking others. It is composed of a double layer of phospholipids
and embedded proteins. Plant cells have an outermost structure called a cell wall. A cell wall is a rigid
structure that gives support to a cell. Plants and algae have cell walls made of a complex sugar. Fungi,
including yeasts and mushrooms, also have cell walls. Prokaryotic cells such as bacteria and archaea
also have cell walls, but those cell walls are different from those of plants or fungi. The cell wall is
made of nonliving material called cellulose (a complex sugar).
The centrioles are a small body located near the nucleus in animal cells. The centrioles are where
microtubules are made. During cell division (mitosis), the centrioles divide and the two parts move to
opposite sides of the dividing cell. Microtubules are shaped
like soda straws and give the nucleus and cell its shape.
The nucleus in the center of a eukaryotic cell is a spherical body containing the nucleolus that makes
ribosomes. The nucleus controls many of the functions of the cell (by controlling protein synthesis). It
also contains DNA assembled into chromosomes. The nucleus is surrounded by the nuclear membrane.
Materials can move from the nucleus to the cytoplasm through nuclear pores in the membrane around
the nucleus. Prokaryotes do not have a nucleus, but still contain DNA.
The Cytoplasm is the jellylike material outside the cell nucleus in which the organelles are located.
All cells, even prokaryotes contain small bodies called ribosomes. Proteins are made here by a process
called protein synthesis.
Rough endoplasmic reticulum (rough ER) is a vast system of interconnected, membranous,
folded sacks that are located in the eukaryotic cell's cytoplasm. The ER is continuous with the outer
nuclear membrane. Rough ER is covered with ribosomes that give it a rough appearance. Rough ER
transports materials through the cell and produces proteins which are sent to the Golgi body (also
called apparatus). The Golgi apparatus or Golgi complex is a flattened, layered, sac-like organelle that
looks like a stack of pancakes. The Golgi body modifies & packages proteins and carbohydrates into
vesicles (sacks) for "export" from the cell. Smooth ER does NOT have ribosomes on its surface. It
makes proteins and lipids that will be exported by the cell.
Chloroplasts are elongated or disc-shaped organelles containing chlorophyll that trap sunlight for
energy. Photosynthesis (in which energy from sunlight is converted into chemical energy - food) takes
place in the chloroplasts. Only plant cells, not animal cells, can make their own food.
Plant cells (figure on the left below) also contain one large fluid-filled sac called a vacuole. Animal
cells have a few tiny vacuoles (figure on the right below). The vacuole fills with food being digested
and waste material that is on its way out of the cell. In plant cells, a large central vacuole takes up
most of the space in the cell.
Mitochondria (singular: mitochondrion) are spherical to rod-shaped organelles with a double
membrane. The inner membrane is folded many times, forming a series of projections called cristae.
The mitochondrion converts the energy stored in glucose into ATP (adenosine triphosphate) for the
cell. Both plant and animal cells have double membranes and their own DNA. Cells also contain
spherical organelles called lysosomes that contain digestive enzymes. Nutrients are digested by the cell
here, as well as, old cell organelles that are going to be broken down and recycled.
Answer the questions below:
1. At what level of organization does life begin? ____________________________________
2. What are some differences in prokaryotes and eukaryotes? ___________________________________
______________________________________________________________________________________
3. What are the two major types of eukaryotes? _____________________________________________
4. What surrounds all cells? ________________________________________________________________
5. What is meant by semipermeable? _________________________________________________________
6. What 2 things make up the cell membrane? _____________________________________________
7. Centrioles are found in what type of cell? ______________________________________________
8. Where is DNA found inside a eukaryotic cell? ___________________________________
9. What cell process is controlled by the nucleus? ______________________________________________
10. DNA coils tightly in division and assembles into visible _C________________________________.
11. Where are organelles located? ____________________________________________________________
12. Where are proteins made in a cell? _______________________________________________________
13. Do all cells need ribosomes? __________________________________________________________
14. The process of making ribosomes is called ___________________ _______________________.
15. How does the rough ER differ from the smooth ER? _________________________________________
16. Proteins made by rough ER travel to the Golgi. The Golgi body________________ and
________________ proteins for export out of the cell.
17. What does the smooth ER do? ____________________________________________________________
18. What process takes place inside chloroplasts? __________________________________
19. In photosynthesis, energy from _______________________ is converted to _____________________.
20. What is the name of the pigment that traps the energy? _______________________________
21. Chloroplasts are found in what type of cell? _____________________________
22. Both chloroplasts and mitochondria are alike in that they both have ____________________
membranes and their own _________________.
23. Food, water, and wastes are stored inside _________________________.
24. Cell digestion takes place inside ______________________ containing ______________________.
25. The largest organelle in plants is the ______________________________.
26. What organelle breaks down and recycles worn out cells? _____________________________