TIPS FOR MASTERING KEY CONCEPTS

There are two general types of cells; prokaryotic and eukaryotic. Prokaryotic cells are smaller and less complex than eukaryotic cells. Eukaryotic cells contain a true nucleus and organelles (little organs) that allow specialization of cells and the separation of functions within the cell. This section of your text will introduce you to the major organelles and cell structures that allow eukaryotic cells to function. Remember, there are both single-celled and multi-cellular organisms that are eukaryotes.

Cytoplasm and Cytoskeleton

  • Cells contain a network of protein fibers, called the cytoskeleton that functions in cell structural support and motility.
  • The cytoskeleton is composed of three kinds of fibers.

–Microfilaments (actin filaments) support the cell’s shape and are involved in motility

–Intermediate filaments reinforce cell shape and anchor organelles

–Microtubules (made of tubulin) shape the cell and act as tracks for motor protein

The nucleus is the cell’s genetic control center

  • The nucleus controls the cell’s activities and is responsible for inheritance.
  • The nuclear envelope is a double membrane with pores that allow material to flow in and out of the nucleus.

The endoplasmic reticulum (ER) is like a factory

  • There are two kinds of endoplasmic reticulum—smooth and rough Smooth ER lacks attached ribosomes.
  • Rough ER lines the outer surface of membranes.
  • Smooth ER is involved in a variety of diverse metabolic processes.
  • For example, enzymes produced by the smooth ER are involved in the synthesis of lipids, oils, phospholipids, and steroids.
  • Rough ER makes additional membrane for itself and proteins destined for secretion.

Ribosomes make proteins

  • Ribosomes are involved in the cell’s protein synthesis.
  • Some ribosomes are free ribosomes; others are bound.
  • The ribosomes in the cytoplasm have the same function as those on the RER but toward a different end. Understand the difference.

The Golgi finishes, sorts, and ships cell products.

  • The Golgi apparatus functions in conjunction with the ER by modifying products of the ER.

Vacuoles function in the general maintenance of the cell

  • Vacuoles are membranous sacs that are found in a variety of cells and possess an assortment of functions.

Lysosomes are digestive compartments

  • A lysosome is a membranous sac containing digestive enzymes
  • One of the several functions of lysosomes is to remove or recycle damaged parts of a cell.

Centrioles

  • Formed by groups of microtubules.
  • Function during cell division.
  • Found in the cytoplasm of animal cells and most protists, usually near the nucleus.

Mitochondria harvest energy

  • Although the mitochondria, chloroplasts, and centrioles will be studied in more detail in later chapters, it is important to understand their basic structure and function at this time.
  • Cellular respiration is accomplished in the mitochondria of eukaryotic cells
  • Cellular respiration involves conversion of chemical energy in foods to chemical energy in ATP (adenosine triphosphate)
  • Mitochondria have two internal compartments; the intermembrane space, which encloses the mitochondrial matrix where materials necessary for ATP generation are found

Chloroplasts convert solar energy to chemical energy

  • Chloroplasts are the photosynthesizing organelles of plants
  • Chloroplasts are partitioned into compartments; The important parts of chloroplasts are the stroma, thylakoids, and grana.

Cell Wall

  • Found in plant cells.
  • Protects the cell and gives it support.
  • Made of a carbohydrate called cellulose.

Cilia and flagella move when microtubules bend.

  • Cell movement is not restricted to locomotion. There is also internal movement. Understand both processes.
  • A flagellum propels a cell by an undulating, whiplike motion
  • Cilia work like the oars of a crew boat
  • Flagella and cilia have a common structure and mechanism of movement
  • Cilia and flagella move by bending motor proteins.

Comparing Plant and Animal Cells

  • Plant cells contain chlorophyll
  • Animal cells do not usually contain vacuoles. If they do, they are small.
  • Animal cells do not have cell walls.

1.Skim Section 3. Write two questions that come to mind from reading the headings and the illustration captions.

a.______

______

b.______

______

2.Use your book or dictionary to define the word enzyme. ______

______

______

3.Explain how the cytoskeleton is related to the cytoplasm. ______

______

4.Write each term shown below under the heading that best describes it.

cell wallcentriolechloroplastcilium

cytoplasmcytoskeletonendoplasmic reticulumflagellum

Golgi apparatuslysosomemitochondrionnucleolus

ribosomevacuole

Cell Structure / Related to Genetic Material / Food, Storage and Waste / Energy

5.Compare and contrast each pair of terms by noting their similarities and their differences.

a.Chloroplast : Mitochondrion

Similarities ______

Differences ______

b.Vacuole : Centriole

Similarities ______

Differences ______

a.Cilium : Flagellum

Similarities ______

Differences ______

6.Explain how lysosomes might play a role in an organism’s immune system.

______

______

______

7.If a plant’s cell wall is rigid, how do materials such as water and nutrients enter the cell?

______

______

4.Identify the part of the cell that corresponds to each function described below.

Directs cell processes; contains the cell’s DNA
Double membrane that surrounds the nucleus
Helps manufacture proteins
Produces ribosomes inside the nucleus
Site of ribosome attachment; can be smooth or rough
Modifies, sorts, and packages proteins for transport outside the cell
Membrane-bound storage area within the cell
Vesicle that contains substances that digest or worn-out organelles
Structure near the nucleus that functions during cell division
Harvests energy from food (sugars)
Captures light energy and converts it to chemical energy
Gives support to plants.
Projections that allow the cell to move or to move substances along the surface of the cell

5.Compare and contrast the cell parts found in the following categories

Chapter 7, Section 7.3 Reading Guide1