Comprehensive Notes on Cell Structure and Function

Unit 3: Cell Biology

This unit covers muscle function, respiration, cell biology, cell structure and function (Chapter 7), cell processes (Chapter 8), and the microscopic world (Chapter 9).

Chapter 7: Cell Structure and Function

Key Questions:

1. What is a cell, and how do we know cells exist?
2. Are human, animal, and plant cells all the same?
3. What is inside a cell, and how is a cell like a cookie factory?

7.1 What Are Cells?

A cell is the basic unit of structure and function in a living thing. Your body comprises trillions of cells, including skin, muscle, nerve, and blood cells, each with unique structures and functions but sharing similarities.

Characteristics of All Cells:

• Respond to their environment (homeostasis).
• Grow.
• Reproduce.
• Use energy.

Discovery of Cells:

The invention of the microscope in the late 1500s was crucial. Robert Hooke (1635-1703) first recorded observations of cells in 1663 using a microscope he built, examining cork and naming the square structures "cells."

Anton van Leeuwenhoek (1632-1723), a Dutch craftsman, made lenses and built a simple microscope, discovering single-celled protists, blood cells, and bacteria.

In 1839, Matthias Schleiden and Theodore Schwann concluded that all plants and animals were made of cells.

Fluorescence Microscopy:

Scientists use fluorescent proteins to make cells glow, using filters to highlight specific cell structures against a dark background.

The Cell Theory:

The cell theory explains the relationship between cells and living things. In 1855, Rudolf Virchow (1821-1902) proposed that cells come from other cells.

Statements of the Cell Theory:

1. All living things are made of one or more cells.
2. Cells come only from existing cells.
3. All of an organism's life functions occur within cells.
4. Cells contain hereditary information for regulating cell functions and transmitting information to the next generation.

Similarities Among Cells:

Multicellular organisms have specialized cells (e.g., retina cells, skin cells). All cells share similar characteristics:

1. Cell Membrane: A barrier controlling the movement of materials in and out of the cell.
2. Organelles: Structures inside the cell that help perform its functions.
3. Cytoplasm: A fluid mixture containing organelles, water, salts, enzymes, and carbon compounds.
4. DNA: Contains instructions for making new cells and controls all cell functions.

Classifying Cells:

Cells are classified into two groups based on structure:

1. Prokaryotic Cells:

   • Do not have a nucleus.
   • The word prokaryotic means "before nucleus" in Greek.
   • Oldest fossils are estimated to be 3.5 billion years old.
   • DNA is bunched up in the center of the cell.
   • Organelles are not covered with a membrane.
   • Smaller than eukaryotic cells.
   • Example: Bacteria

2. Eukaryotic Cells:

   • Have a nucleus and membrane-covered organelles (except for red blood cells of mammals).
   • Eukaryotic means "true nucleus" in Greek.
   • Oldest fossils are about 2 billion years old.
   • More DNA, found in the nucleus.
   • Larger than prokaryotic cells (about ten times).
   • Examples: Animals, plants, fungi, protozoans

7.2 Cells: A Look Inside

Comparing a Cell to a Cookie Factory:

The cell is analogous to a cookie factory, with various parts performing specific functions.

Analogy Table:

Diagram of an Animal Cell:

• Cell Membrane: Separates the inside of the cell from the outside environment, regulates the passage of materials.
• Cytoplasm: A fluid mixture containing organelles and compounds needed by the cell.
• Nucleus: Controls cell activities and contains DNA.
• Nucleolus: Storage area within the nucleus.
• Mitochondria: Produce most of the cell's energy.
• Vacuole: Stores water, food, and wastes.
• Ribosomes: Protein factories of the cell.
• Endoplasmic Reticulum (ER): Transports materials from one part of the cell to another.
• Golgi Body: Receives materials from the ER, packages them, and sends them to other parts of the cell.
• Lysosome: Contains chemicals that break down food particles and worn-out cell parts.
• Cytoskeleton: Gives the cell its shape and provides strength.

The Cell Membrane and Nucleus:

Cell parts can be made visible under a microscope using stains like methylene blue.

• Cell Membrane: A thin layer separating the inside of the cell from its environment, made of lipids and proteins.
• Nucleus: The control center of the cell, containing DNA.
• Nucleolus: A storage area for materials within the nucleus.

Organelles and Their Functions:

• Mitochondria: (singular: mitochondrion) The "powerhouses" of the cell, producing energy. Active tissues like muscle and liver cells have many mitochondria.

• Vacuoles: Fluid-filled sacs that store water, food, and waste. Plant cells usually have one large vacuole.

• Endoplasmic Reticulum (ER): A series of tunnels throughout the cytoplasm that transport proteins.

• Ribosomes: Protein factories of the cell. They release proteins into the ER.

• Golgi Bodies: Receive proteins and other compounds from the ER, package them, and distribute them throughout the cell.

• Lysosomes: Contain enzymes that break down foreign invaders, food, and old organelles.

• Cytoskeleton: A series of protein fibers that provide structure and shape to the cell.

Diagram of a Plant Cell:

Plant cells differ from animal cells.

• Cell Membrane: Separates the inside of the cell from the outside environment, regulates the passage of materials.
• Cytoplasm: A fluid mixture containing organelles and compounds needed by the cell.
• Nucleus: Controls cell activities and contains DNA.
• Nucleolus: Storage area within the nucleus.
• Mitochondria: Produce most of the cell's energy.
• Ribosomes: Protein factories of the cell.
• Endoplasmic Reticulum (ER): Transports materials from one part of the cell to another.
• Golgi Body: Receives materials from the ER, packages them, and sends them to other parts of the cell.
• Cytoskeleton: Gives the cell its shape and provides strength.
• Chloroplasts: Capture energy from sunlight and store it in molecules (photosynthesis).
• Cell Wall: Surrounds the cell membrane and provides rigid structure, made of cellulose.
• Central Vacuole: Stores water, food, and wastes and provides support for the cell when full.

How Plant Cells Are Different From Animal Cells:

Chapter 7 Assessment

Vocabulary:

1. Bacteria are prokaryotic cells.
2. The cell membrane controls what enters and exits the cell.
3. A structure inside a cell that does a certain job is called an organelle.
4. The fluid mixture with organelles and other vital compounds in cells is the cytoplasm.
5. Eukaryotic cells all have a nucleus that contains DNA.
6. The endoplasmic reticulum is the organelle that transports materials like proteins around the cell.
7. Fibers inside the cell that give structure and shape are called the cytoskeleton.
8. Muscle cells have a lot of mitochondria to produce the large amounts of energy necessary to do their work.
9. A ribosome is a protein factory in the cell.
10. Enzymes found in a lysosome are used to break down old cell parts that are then recycled by the cell.
11. Proteins move from the ribosome to the golgi body for packaging before distribution around the cell.
12. Animal cells can change shape to move because they don't have a cell wall, which is what makes plant cells rigid.

Concepts:

1. The statement that is not part of the cell theory is: c. The two major types of cells are prokaryotic cells and eukaryotic cells.

2. Characteristics of prokaryotic (P) and eukaryotic (E) cells:

   • a. name means "before nucleus" in Greek (P)
   • b. DNA is contained in nucleus (E)
   • c. believed to have originated 2 billion years ago (E)
   • d. larger of the two types-10 times the size of the other (E)
   • e. I have organelles without membrane covers (P)

3. ER : highway

4. cell wall : nutshell

5. vacuole : warehouse

6. cell membrane : skin

7. nucleus : brain

8. The part of the cell that is like a recipe book is: b. DNA

9. The nucleus is the largest organelle in the cell.