1. Chapter 4 Cell Structure and Function

2. Section 1: The History of Cell Biology
All living things are made up of one or more cells
A cell is the smallest unit that can carry on all the processes of life

3. The Discovery of Cells Robert Hooke
Used light microscopy to observe cork and other plant material
He was observing the remains of cork cells and made some of the first sketches of cells, what he called “little boxes”

4. The Discovery of Cells Anton van Leeuwenhoek
First person to observe living cells
Made microscopes that had greater magnification than Hooke’s

5. The Cell Theory
The importance of Hooke and Leeuwenhoek’s observation was not realized until 150 years later
In the 1800’s it was determined that all plants and animals were composed of cells

6. The Cell Theory The cell theory has three essential parts:
All organisms are composed of one or more cells
Cells are the basic units of structure and function in an organism
Cells come only from the reproduction of existing cells

7. Section 2: Introduction to Cells
Cell Diversity
Cells of different organisms and even cells within the same organism are very diverse in terms of shape, size, and internal organization

8. Introduction to Cells Cell Shape
Cell shape reflects different cell functions
Each cell has evolved a shape that allows it to function effectively

10. Introduction to Cells Cell Size
The size of a cell is limited by the relationship of the cell’s outer surface area to its volume, or surface area-to-volume ratio
As a cell grows its volume grows much faster than its surface area
Materials must pass through the membrane (nutrients, wastes etc.)
If the cells were to become too large the volume would be much larger than the S.A. and materials entering and leaving the cell wouldn’t meet the cells needs quick enough

11. Surface Area to Volume Ratio

12. Surface Area to Volume Ratio

13. Basic Parts of the Cell
Three basic features are characteristic of all cell types
Plasma membrane: the cell’s outer boundary
Cytoplasm: the region of the cell that is within the plasma membrane that includes the fluid, cytoskeleton, organelles, and nucleus
Control Center: Cells carry information in the form of DNA; some cells its free floating, others have it located in a nucleus

14. Two Basic Types of Cells
Two major types of cells:
Prokaryotes
Eukaryotes
Prokaryotes: organisms that lack a membrane bound nucleus and membrane bound organelles
Eukaryotes: organisms made up of one or more cells that have a nucleus and membrane bound organelles

15. Prokaryotes and Eukaryotes

16. Comparing the Two

17. Two basic Types of Cells
Prokaryotes
Lack nucleus, but DNA is concentrated in a part of the cell called the nucleoid
Broken into two main domains
Bacteria
Similar to first cellular life forms
Archaea
Organisms that are more closely related to eukaryotes

18. Two Basic Types of Cells
Eukaryotes
Contain variety of substructures called organelles—well defined, intracellular bodies that perform specific functions in the cell
Organelles are like the organs in a human
Generally much larger than prokaryotic cells

19. Cellular Organization
Over time, cells began to form groups that functioned together
Colonial organism: collection of genetically identical cells that live together in a connected group
Not truly multicellular

20. Cellular Organization
True Multicellularity
Cells became more specialized and were unable to survive independently
Tissue: group of similar cells that carry out a specific function
Organs: groups of tissues that perform a particular job in an organism
Organ system: group of organs that accomplish related tasks
A collection of organ systems combine to form an organism

21. Organization

22. Organization

23. Section 3: Cell Organelles and Features
Plasma Membrane
aka the cell membrane
Semi permeable: only lets in certain things
Separates internal metabolic functions from the outside environment
Allows cell to excrete wastes and interact with the outside environment

24. Cell Organelles and Features
Membrane Lipids
Made primarily of phospholipids
Polar and non-polar ends
Two layers: bi-layer
Sterols: make membrane more firm and prevent freezing
Ex: Cholesterol

25. Cell Organelles and Features
Membrane Proteins
Integral proteins: embedded within the lipid bilayer, only on one side
Receptor/Transport proteins: exposed on both sides of the cell; able to detect environmental signals
Peripheral proteins: lie on only on one side, not embedded

26. Cell Membrane

28. Cell Organelles and Features
Fluid Mosaic Model
Scientists describe the cell membrane as a fluid mosaic
Fluid mosaic model states that the phospholipid bilayer behaves like a fluid more than it behaves like a solid
Lipids and proteins can move within the membrane like a “boat in an ocean”

29. Cell Organelles and Features
Nucleus
Control center of the cell
Filled with nucleoplasm
Houses and protects genetic information
DNA in chromatin form; condensed it forms chromosomes
DNA is read to form RNA where it carries out functions in the cell

30. Cell Organelles and Features
Nucleus
Surrounded by the nuclear envelope, which is made up of two phospholipid bilayers
Nuclear Pores: tiny protein-lined holes in the nuclear envelope that provide passageways for RNA and other materials to enter and leave the nucleus

31. Cell Organelles and Features
Nucleus
Nucleolus: a dense area of concentrated DNA within the nucleus
The site where DNA produces ribosomal RNA
Ribosomes: organelles made of protein and RNA that direct protein synthesis in the cytoplasm

33. Cell Organelles and Features
Mitochondria
Organelles that transfer energy from organic molecules to ATP
Powerhouse of the cell
Highly active cells = lots of mitochondria; less active cells = less mitochondria

34. Cell Organelles and Features
Mitochondria
Have an inner and outer cell membrane
Outer: separates mitochondrion from cytosol
Inner: many folds, called cristae, which contain proteins that carry out energy harvesting chemical reactions
Large surface area
Think! Why would mitochondria need a large surface area
Has its own DNA

35. Cell Organelles and Features
Ribosomes
Responsible for building proteins
Made of protein and RNA molecules
Contain a large and small subunit
Some are free within the cytosol, some are studded on the rough endoplasmic reticulum

36. Cell Organelles and Features
Endoplasmic Reticulum (ER)
Intracellular Highway: particles move from one part of the cell to another
Two types of ER:
Rough ER: covered in ribosomes, produces phospholipids and proteins
Smooth ER: lacks ribosomes, builds lipids such as cholesterol
Abundant in liver and kidney cells where it helps detox drugs and poisons

37. Cell Organelles and Features

38. Cell Organelles and Features
Golgi Apparatus
UPS factory of the cell
Get vesicles (transport sacs) from the ER containing proteins or lipids, these get transported throughout the cell

39. Cell Organelles and Features
Vesicles
Small sacs that are classified by their contents
Lysosomes: contain digestive enzymes that break down large molecules; involved in cell death; From golgi apparatus
Peroxisomes: not from GA; break down fats

41. Cell Organelles and Features
Cytoskeleton
Thin tubes and filaments in the cytosol that give the cell its structure and shape
Tent poles in a tent

42. Cell Organelles and Features
Cilia and Flagella
Hair-like structures that extend from cell’s surface; assist with movement
Cilia: short; Flagella: long and less numerous
Centrioles
Two short cylinders of microtubules; in cytoplasm near nucleus
Animal cells only
Involved in cell division

43. Unique Features of Plant Cells
Plant cells have three structures animal cells do not
Cell wall
Large central vacuole
Plastids

44. Unique Features of Plant Cells
Cell Wall
Rigid layer that lies outside of the cell’s plasma membrane
Made of cellulose
Provides structure and support

45. Unique Features of Plant Cells
Central Vacuole
Reservoir that stores large amounts of water
Also stores enzymes, metabolic wastes, other materials
Fusion of smaller vacuoles
Make up to 90% of the plant cell’s volume

47. Unique Features of Plant Cells
Plastids
Like mitochondria, contain their own DNA
Chloroplasts:
Use light energy to make carbohydrates from CO2 and water
Contain thylakoids (pancake stacks) that contain chlorophyll, main molecule in converting light to energy
Endosymbiosis: chloroplasts and mitochondria were free living prokaryotic cells that were incorporated into larger cells

48. Unique Features of Plant Cells