UNIT A: Cell Biology

Chapter 2: The Molecules of Cells

Chapter 3: Cell Structure and Function: Section 3.2

Chapter 4: DNA Structure and Gene Expression

Chapter 5: Metabolism: Energy and Enzymes

Chapter 6: Cellular Respiration

Chapter 7: Photosynthesis

In this chapter, you will learn about how cell structures have critical roles to play in the health of an organism.

UNIT A Chapter 3: Cell Structure and Function

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Chapter 3: Cell Structure and Function

What other cellular organelles have a similar function to the lysosome?

Why doesn’t the cell “clean up” the faulty lysosomes?

3.2 Eukaryotic Cells

Eukaryotic cells are structurally complex, distinguished by the presence of a nucleus, which contains the genetic material. They also contain organelles, which are sub-cellular structures with defined functions.•Structures include the plasma membrane, cytoplasm, cell wall, nucleus, ribosomes, endoplasmic reticulum, Golgi body, lysosomes, vesicles, mitochondria, chloroplasts, and cytoskeleton•Animals, plants, fungi, and protists are composed of eukaryotic cells

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE Figure 3.3 Animal cell anatomy.

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE Figure 3.4 Plant cell anatomy.

Plasma Membrane and Cytoplasm

All cells are surrounded by a plasma membrane (cell membrane) consisting of a phospholipid bilayer embedded with protein molecules. The cell membrane separates the living contents of the cell from the surrounding environment.

Inside the cell is a semi-fluid medium called the cytoplasm, composed of water, salts, and dissolved organic molecules.

The cell membrane regulates the entrance and exit of molecules into and out of the cytoplasm.

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE From Figure 3.3 Animal cell anatomy.

Cell Walls

Some eukaryotic cells have permeable but protective cell walls in addition to cell membranes. Many plant cells have primary and secondary cell walls.•primary cell walls contain cellulose•secondary cell walls contain lignin; some fungi have chitin

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE From Figure 3.4 Plant cell anatomy.

The Nucleus

The nucleus stores genetic information. •Chromatin contains DNA and proteins•Condensed chromatin forms chromosomes•The nuclear envelope separates the nucleus from the cytoplasm and contains nuclear pores

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE Figure 3.5 Anatomy of the nucleus.

Ribosomes

Ribosomes are responsible for protein synthesis.

• Composed of large and small subunits, as well as rRNA

• Associate with mRNA during protein synthesis• Can be found as polyribosomes (several associated with a

single mRNA)

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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From Figure 3.3 Animal cell anatomy.

The Endomembrane System

The endomembrane system is the transportation and processing centre of the cell. It consists of

•The nuclear envelope•The endoplasmic reticulum (ER): a system of membranous channels and sacs, where proteins are synthesized and processed (rough ER) and phospholipids are made (smooth ER)•The Golgi apparatus: the “shipping centre” of the cell•Lysosomes and vacuoles (larger storage units, more prominent in plant cells)

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Figure 3.6 Endoplasmic reticulum (ER). Ribosomes are present on rough ER, which consists of flattened sacs, but not on smooth ER, which is more tubular. Proteins are synthesized and modified by rough ER, whereas smooth ER is involved in lipid synthesis, detoxification reactions, and several other possible functions

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE From Figure 3.3 Animal cell anatomy. The Golgi Apparatus.

The Golgi Apparatus

• The Golgi apparatus: flattened sacs where collection, packaging, and distribution of proteins and lipids occurs

• Produces lysosomes, which contain hydrolytic digestive enzymes and act as the garbage disposal for the cell

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDE Figure 3.7 The Endomembrane System

Peroxisomes

Peroxisomes, similar to lysosomes, are membrane-bound vesicles that enclose enzymes. •Typically peroxisomes contain enzymes that produce hydrogen peroxide, which is a toxic molecule that is broken down by an enzyme to oxygen and water•Peroxisomes are most prevalent in cells that synthesize and break down fats, for example in the liver

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Figure 3.8 Peroxisomes. Peroxisomes contain one or more enzymes that can oxidize various organic substances. Peroxisomes also contain the enzyme catalase, which breaks down the hydrogen peroxide (H2O2) that builds up after organic substances are oxidized.

Energy-Related Organelles

Chloroplasts and mitochondria specialize in converting energy to a form the cell can use.•chloroplasts use solar energy to synthesize carbohydrates (photosynthesis)

•mitochondria break down carbohydrates to produce energy in the form of ATP (cellular respiration)

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Chloroplasts• Present in plant and algae cells• Bound by two membranes that enclose the fluid-filled

stroma • Within the stroma are thylakoids stacked as grana

(chlorophyll in the thylakoid used for photosynthesis)

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Figure 3.10 Chloroplast structure.

Mitochondria

• Present in all eukaryotic cells• Bound by two membranes that enclose the matrix, a fluid-

filled region that contains ribosomes and DNA• Inner membrane folds in on itself to form cristea

UNIT A Chapter 3: Cell Structure and Function Section 3.2

TO PREVIOUS SLIDEFigure 3.12 Mitochondrion structure

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Cont’d on next slide

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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UNIT A Chapter 3: Cell Structure and Function Section 3.2

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Check Your Progress

1. Explain the function of the cell wall in eukaryotes.

2. Explain the function of select organelles within the cell.

3. Describe the advantages that different compartments provide for the cell.

UNIT A Chapter 3: Cell Structure and Function Section 3.2

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UNIT A Chapter 3: Cell Structure and Function Section 3.2

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UNIT A Chapter 3: Cell Structure and Function Section 3.2

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