1. Chapter 3 Cell Structure and Function

2. 3.1 Cell Theory
Almost all cells are too small to see with the naked eye. Cells are the smallest unit of living matter that can carry out all processes required for life.
In 1665, English scientist Robert Hooke identified and named cells after looking at a piece of cork through a three-lens compound microscope.

3. In 1674, Anton van Leeuwenhoek, a Dutch tradesman, was the first to describe living cells when he observed single celled organisms in pond water.
German Scientist Mathias Scheiden also used compound microscopes to study plant tissue. He proposed that plants were made from cells.

4. In 1839, Theodore Schwann proposed that animals were made of cells
In 1839, Theodore Schwann proposed that animals were made of cells. He published the first statement of cell theory.
In 1855, Rudolf Virchow, reported that all cells come from preexisting cells.

5. Cell theory states the following: All organisms are made of cells
Cell theory states the following: All organisms are made of cells. All existing cells are produced by other living cells, and the cell is the most basic unit of life.
Cells can be separated into two broad categories based on their internal structures.

6. Cytoplasm is a jellylike substance that contains dissolved molecular building blocks such as proteins, nucleic acids, minerals, and ions.
Organelles are specialized structures that perform specific functions within the cell.

7. Cell Types and Cell Structure

8. Prokaryotic vs. Eukaryotic
nucleus
membrane enclosed organelle
chromosomes in pairs
streaming in the cytoplasm
cell division by mitosis
complex flagella
larger ribosomes
complex cytoskeleton
cellulose in cell walls
DNA bound to histone proteins
no nucleus
no membrane enclosed organelles
single chromosome
no streaming in the cytoplasm
cell division without mitosis
simple flagella
smaller ribosomes
simple cytoskeleton
no cellulose in cell walls
no histone proteins

9. Prokaryotic vs. Eukaryotic
Examples:
Bacteria
Examples:
Plant cells
Animal cells
Fungi
Protists

10. Plasma Membrane Plasma membrane 1. Surrounds Cells
2. Protected by cellulose and protein cell wall in
plants
Plasma Membrane

11. Cytoplasm Cytoplasm 1. Fluid (Cytosol) and organelles that make up
the inside of the cell
Cytoplasm

12. Nucleus Nucleus 1. Membranous nuclear envelope
2. Chromosomes of DNA and protein (Histones)
Nucleus

13. Endoplasmic reticulum (ER)
1. Rough ER - Transport of proteins (roughness
is the attached ribosomes)
2. Smooth ER – Processing and transport of lipids
Endoplasmic reticulum (ER)

14. Ribosomes Ribosomes 1. Attached to Rough ER
2. Site of protein synthesis
Ribosomes

15. Golgi Apparatus Golgi Apparatus (Golgi body, Golgi complex)
1. Assembly and editing of proteins
Golgi Apparatus

16. Lysosomes Lysosomes 1. Contain enzymes that break down and help
recycle large proteins in animal cells
Lysosomes

17. Mitochondria
1. Powerhouse ‑ site of ATP synthesis
Mitochondria

18. Flagella and Cilia Flagella and Cilia
1. Cell surface projections for movement
Flagella and Cilia

19. Microtubules and Microfilaments
1. Structural components of the cell
(cytoskeleton) in eukaryotes
Microtubules and Microfilaments

20. Vacuoles
1. Large central vacuoles in plant cells contain enzymes and pigments in plant cells
Vacuoles

21. Chloroplasts Chloroplasts 1. Photosynthetic organelles in plant cells,
containing the chlorophyll pigments
Chloroplasts

22. Comparison: Plant cells Animal cells
Large, central vacuole
Chloroplasts
Rigid cell wall outside
of cell membrane
No large, central vacuole
No chloroplasts
No rigid cell wall

23. Chapter 3. 3 Cell Membrane
Cell membranes are composed of two phospholipid layers.
The cell membrane, or the plasma membrane, forms a boundary between a cell and the outside environment and controls the passage of materials into and out of a cell.
Phospholipid is a molecule composed of three basic parts: a charged phosphate group, glycerol molecule, and two fatty acid chains.

24. “The head” is composed of the glycerol molecule and phosphate group
“The head” is composed of the glycerol molecule and phosphate group. The head bears an electrical charge. It is polar, and so is water. The two can form hydrogen bonds with each other.
The fatty acid tails are nonpolar, and are attracted to each other and repelled by water.
Cell membranes touch the cytoplasm, and as a result, the properties of the polar heads and nonpolar tails cause the phospholipids to arrange themselves in layers.

25. Proteins, cholesterols, and carbohydrates embedded in the bilayer, can alter the characteristics of the cell membrane.
Fluid mosaic model describes the arrangement of the molecules that make up a cell membrane.

26. The cell membrane is flexible, not rigid.
The variety of molecules studding the membrane is similar to the arrangement of colorful tiles with different textures and patterns that make up a dynamic mosaic.
Selective Permeability means the cell allows some, but not all, materials to cross the membrane. This enables a cell to maintain homeostasis in spite of unpredictable, changing conditions outside the cell.

27. Molecules cross the membranes in several ways
Molecules cross the membranes in several ways. Some require the cell to expend energy; others do not. These methods are dependant on molecule size, polarity, and concentration. Small nonpolar molecules easily pass through the cell membrane, small polar molecules are transported via proteins and large molecules are moved in vesicles.

28. Chemical signals are also transmitted across the cell membrane.
A receptor is a protein that detects a signal molecule and performs an action in response. It recognizes and binds only certain molecules. This ensures that the right cells get the right molecules. A molecule a receptor binds to is called a ligand.
Two types of receptors are intracellular and membrane receptors.

29. 3.4 Diffusion and Osmosis
Passive transport is the movement of molecules across a cell membrane without energy input from the cell.
Diffusion is the movement of molecules in a fluid or gas from a region of high concentration to a region of lower concentration.
Concentration gradient is the difference in the concentration of a substance from one location to another.
Osmosis is the movement of water molecules across a semipermeable membrane from an area of high concentration to low concentration.

30. Solutions can be described as isotonic, hypertonic, and hypotonic relative to another solution.
A solution is isotonic to a cell if it has the same number of dissolved particles as the cell.
A hypertonic solution has a higher concentration of dissolved particles than a cell. This means the water concentration is higher in the cell. Water then flows out of the cell. This may cause the cell to shrivel or even die.

31. A hypotonic solution has a lower concentration of dissolved particles than a cell. Water molecule concentration is higher outside the cell, so water will diffuse into the cell. This may cause the cell to burst.

32. Some molecules diffuse through transport proteins.
Facilitated diffusion is the diffusion of molecules across a membrane through transport proteins
Transport proteins are needed, because some molecules do not easily diffuse across the cell membrane.