1. Topic #1: Cell Biology

2. Introduction to cells
A. The cell theory
1. Living organisms are composed of cells
2. Cells share common features
a. Cells are surrounded by membranes
b. Cells contain genetic material
c. Chemical reactions occur and are catalyzed by enzymes
d. Cells have their own energy release systems
3. Cells are the smallest living structures – nothing smaller can survive
4. Three statements of the cell theory
a. Cells are the basic unit of life
b. Cells come only from pre-existing cells
c. All living things are made of cells

3. Introduction to cells

4. Introduction to cells
B. Unicellular organisms
1. Organisms consisting of only one cell carry out all functions of life in that cell
2. Seven functions of life
a. Nutrition – obtaining food or making it
b. Metabolism – chemical reactions inside the cell
c. Growth – an irreversible increase in size
d. Response – the ability to react to changes in the environment
e. Excretion – getting rid of the waste products of metabolism
f. Homeostasis – keeping conditions inside the organism within tolerable limits
g. Reproduction – production of offspring

5. Introduction to cells
C. Limitations on cell size
1. Surface area to volume ratio is important in the limitation of cell size
2. Rate of metabolism is proportional to the volume of the cell
3. The rate at which substances cross this membrane depends on its surface area
4. If the ratio of surface area to volume is too small, then substances will not enter the cell and waste will not leave the cell as quickly as they need to
5. Heat production and loss
a. Too small a ratio? Cells may overheat
b. Metabolism produces heat faster than it is lost over the cell’s surface

6. Introduction to cells
D. Multicellular organisms
1. Multicellular organisms have properties that emerge from the interaction of their cellular components
2. Organisms consisting of a single mass of cells, fused together are multicellular
3. Adult human have about 10,000,000 cells
4. Cells differentiate to perform specific functions
5. The characteristics of the organism as a whole are known as emergent properties
a. Arise from component parts of a complex structure
b. “the whole is greater than the sum of its parts”

7. Introduction to cells
E. Cell differentiation in multicellular organisms
1. Specialized tissues can develop by cell differentiation in multicellular organisms
2. Different cells perform different functions
a. Red blood cells – carry oxygen
b. Nerve cells – transmit impulses
3. A group of cells that specialize to perform the same function = tissue
4. By becoming specialized, cells in a tissue carry out their role more efficiently than if they were performing many different tasks
F. Gene expression and cell differentiation
1. Differentiation involves the expression of some genes and not others in a cell’s genome

8. Introduction to cells
2. There are 220 different cell types in the human body
3. They all have the same set of genes
4. They work the way they do because of the genes expressed
G. Stem cells
1. The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development.
2. It also makes stem cells suitable for therapeutic uses
3. Zygotic development – egg + sperm = zygote
a. The zygote divides
b. One cell becomes two, then four, then eight…

9. Introduction to cells
4. Stem cell properties
a. Unlimited mitotic division
i. Growth of tissues
ii. Replacement of lost tissue
b. Not fully differentiated – they can produce different cell types
c. Can be used to replace specific cell types
ex. Type 1 diabetes
d. Future
i. to grow replacement organs
ii. Stem cell meat!
e. Early stage embryonic stem cells are most versatile and can become the most different things
= pleuripotent

10. Introduction to cells
f. Where can stem cells be found?
a. Embryos
b. Bone marrow
c. Skin
d. Liver
Ultrastructure of cells
The resolution of electron microscopes
1. Electron microscopes have a much higher resolution than light microscopes
The unaided eye can see things with a size of 0.1mm as separate objects
Resolution – making the separate parts of an object distinguishable by eye

11. Ultrastructure of cells
4. light microscope – 0.2mm resolution (200 nm)
a. Limited by the wavelength of light
b. Never will be better than that
5. electron microscope – 0.001mm (1 nm)
a. Can use the speed of electrons
b. Can see within the cell – not just the cell
B. Prokaryotic cell structure
1. Prokaryotes have a simple cell structure without compartments
2. First organisms to evolve on earth
3. Made up of a cell membrane and a cell wall
- the cell wall is made up of peptidoglycan
4. No nucleus is present
5. Cell is filled with cytoplasm – no organelles

12. Ultrastructure of cells
6. Contains lots of enzymes for metabolism
7. Ribosomes are only 70S
8. DNA in a prokaryote is not associated with proteins
9. nucleoid – lighter area in the cell where the DNA is located, but NOT a nucleus
C. Cell division in prokaryotes
1. Prokaryotes divide by binary fission
2. Cell division – asexual reproduction
a. Single circular chromosome is replicated
b. Two copies of the chromosome move to opposite ends of the cell
c. Division occurs quickly
d. Daughter cells are exact copies

13. Ultrastructure of cells
Let’s draw a prokaryote!!!

14. Ultrastructure of cells
D. Eukaryotic cell structure
1. Eukaryotes have a compartmentalized cell structure
2. Nucleus
a. Has a membrane
b. Contains DNA associated with proteins
3. Advantages to compartmentalization
a. Enzymes and substrates for a particular process
can be concentrated in an organelle instead of being spread throughout the cytoplasm
b. Waste can be stored in an organelle instead of damaging the cell
c. Conditions like pH can be maintained
d. Organelles can be moved around inside the cell

15. Ultrastructure of cells
Let’s draw a eukaryote too!!!

16. Membrane structure
A. Phospholipid bilayers
1. Phospholipids form bilayers in water due to the amphipathic properties of phospholipids molecules
2. hydrophilic – substances are attracted to water
3. hydrophobic – substances are not attracted to water
4. amphipathic – a substance with both hydrophobic and hydrophilic properties ex. Phospholipids
5. phosphate group is hydrophilic
6. the two hydrocarbon chains are hydrophobic
7. hydrocarbon chains orient toward the center
8. phosphate head orients toward the water on the
inside and outside of the cell

17. Membrane structure
B. Membrane proteins
1. Membrane proteins are diverse in terms of structure, position in the membrane and function
2. Functions of membrane proteins
a. Hormone binding sites
b. Immobilized enzymes with the active site on the outside
c. Cell adhesion to form tight junctions between groups of cells in tissues and organs
d. Cell-to-cell communication – synaptic transmission
e. Channels for passive transport for facilitated diffusion
f. Pumps for active transport

18. Membrane structure
VIDEOS!!!
3. Membrane protein types
a. Integral proteins
i. hydrophobic on part of their surface
ii. Embedded in the hydrocarbon chains
iii. Many are transmembrane – extend across
b. Peripheral proteins
i. Hydrophilic on their surface
ii. Not embedded on the surface of the cell membrane
4. protein content for membranes is variable
a. Varies depending on the cell type
b. Different cells need different membrane proteins

19. Membrane structure
Let’s Draw the Fluid Mosaic Model of the Membrane!!

20. Membrane structure
C. Cholesterol in membranes
1. Cholesterol is a component of animal cell membranes
2. Animal cells also contain cholesterol
3. Cholesterol is a type of lipid, but not a fat or oil
4. Positioned between phospholipids in the membrane
5. Amount in cell membranes varies
Membrane Transport
A. Endocytosis
1. The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis

21. Membrane transport
2. Endocytosis - definition
a. Fluidity of the cell membrane allows for materials to enter the cell
b. Membrane decreases in size
c. Vesicle forms with substance inside it
d. Used for large molecules – usually proteins
Vesicle movement in cells
1. Vesicles move materials within cells
2. Usually found in cells that secrete proteins for use in other part of the body
3. Protein synthesized by ribosomes on the rER will cause the ER to “bud” off and travel out of the cell
4. The vesicle moves to the Golgi body for packaging
5. The vesicle moves the protein out of the cell

23. Membrane transport
Exocytosis
1. The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis
2. Exocytosis – definition
a. Movement of materials out of the cell
b. Cell membrane increases in size
c. Expels large molecules…waste, proteins, enzymes, hormones
Simple diffusion
1. Particles move across membranes by simple and facilitated diffusion, osmosis and active transport

24. Membrane transport
2. Simple diffusion
a. movement of particles from high to low concentration (with a concentration gradient)
b. Does not require a membrane
c. Does not require energy
d. Does not require membrane proteins
3. Facilitated diffusion
a. Movement of particles from high to low concentration
b. Does require a membrane
d. Does require membrane proteins
4. Osmosis
a. Movement of water ONLY (only water!)

25. Membrane transport
b. From an area of low solute concentration to an area of high solute concentration
c. Does not require membrane proteins
d. Does not require energy
5. Active transport
a. Movement of particles from an area of low concentration to an area of high concentration
b. Against the concentration gradient
c. Requires energy
d. Requires membrane proteins
Videos…so many videos…and LABS!!

26. The origin of cells
A. Cell division and the origin of cells
1. Cells can only be formed by division of pre-existing cells
2. Cells formed by cell division are genetically identical to their parent cells
3. Disproves spontaneous generation
4. The story of Pasteur and his swan-neck flasks
B. Origin of the first cells
1. The first cells must have arisen from non-living material
2. Unless cells arrived on earth from somewhere else in the universe, they must have arisen from non-living material
3. How?

27. The origin of cells
4. Production of carbon compounds such as sugars and amino acids
a. Miller and Urey
b. Passed steam through a mixture of methane, hydrogen and ammonia (CH4, H2, and NH4)
c. Electrical discharges were used to simulate lightning
d. Amino acids and other carbon compounds needed for life were produced
5. Assembly of carbon compounds into polymers
a. A possible site is around deep-sea vents
b. Inorganic compounds like iron sulfide provided energy to assemble existing carbon compounds into polymers

28. The origin of cells
6. Formation of membranes
a. Phospholipids would have assembled naturally into membranes if they were first.
b. Experiments have shown that these molecules will assemble as a membrane and make a small “cell”
c. Allows for different internal chemistry from that of the surroundings to develop
7. Development of a mechanism for inheritance
a. Living things have DNA and use enzymes as catalysts
b. To replicate DNA and pass it on to offspring, enzymes are needed
c. Maybe there was a time when RNA was the

29. The origin of cells
genetic material
d. It can store info like DNA but can act as a catalyst on its own
Endosymbiosis and eukaryotic cells
The origin of eukaryotic cells can be explained by the endosymbiotic theory
Mitochondria were once free-living prokaryotic organisms – developed the process of aerobic cell respiration
Larger prokaryotes that could only respire anaerobically took them in by endocytosis
Instead of killing and digesting them, the larger prokaryotes allowed them to live inside
As long as the smaller prokaryotes divided as

30. The origin of cells
quickly as the larger ones, they could persist indefinitely
6. The larger prokaryotes and smaller aerobic ones lived in a symbiotic relationship in which they both benefited (mutualism)
7. Smaller cell – food from the bigger one; larger cell – energy from the smaller one
8. Natural selection favored the cells that developed this endosymbiotic relationship
9. Also explains the origin of chloroplasts
 ingestion of photosynthetic prokaryotes would have caused the same situation as mitochondria

31. Cell division
A. The role of mitosis
1. Mitosis is division of the nucleus into two genetically identical daughter nuclei
2. Nucleus of a eukaryotic cell can divide to form two genetically
3. Before mitosis can occur, all the DNA must be replicated
4. This happens during interphase of the cell cycle
5. Mitosis occurs when new cells are needed
a. Embryonic development
b. Growth
c. Tissue repair
d. Asexual reproduction
6. Continuous process – prophase, metaphase, anaphase and telophase

32. Cell division
B. Interphase
1. Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm
2. The cell cycle has two phases: interphase and cell division
3. During interphase, the numbers of mitochondria in the cytoplasm increase and chloroplasts do the same in plant cells
4. Three phases of interphase:
a. G1  cell contents duplicated
b. S  chromosomes are duplicated
c. G2  growth and prep for nuclear division
Video anyone?

33. Cell division
C. Supercoiling of chromosomes
1. Chromosomes condense by supercoiling during mitosis
2. Human nuclei are less than 5mm in diameter, but DNA is over 50,000mm
3. The DNA must be packaged into chromosomes
4. This process is known as condensation of chromosomes and happens during the first phase of mitosis
D. Phases of mitosis
1. prophase
a. Chromosomes become shorter and fatter
b. To become short enough, they must coil rapidly
c. Microtubules grow and form spindle fibers

34. Cell division
2. Metaphase
a. Microtubles continue to grow and attach to the centromeres on each chromatid
b. The chromatids align in the center of the cell
3. Anaphase
a. The centromeres divide allowing pairs of sister
chromatids to separate
b. The chromatids travel to opposite poles of the cell
c. They are pulled by the spindle fibers
4. Telophase
a. As they go to the poles of the cell – they are called chromosomes again

36. Cell division
E. Cytokinesis
1. Cytokinesis occurs after mitosis and is different in plant and animal cells
2. After the nucleus divides, the rest of the cell divides
3. Different in plants v animals
4. Animal cells produce a cleavage furrow
a. Uses contractile proteins within the plasma
membrane
b. The proteins are actin and myosin
5. Plant cells have vesicles that move toward the equator of the cell
a. The vesicles fuse together
b. Pectins are deposited by exocytosis between the new membranes

38. Cell division
c. forms the middle lamella that links the new cell walls
F. Cyclins and the control of the cell cycle
1. Cyclins are involved in the control of the cell cycle
2. Each of the phases of the cell cycle involves many important tasks
3. Cyclins bind to enzymes called cyclin-dependent kinases
4. The kinases then become active and attach phosphate groups to other proteins
5. Four types of cyclin
a. Cyclin D
triggers cells to move from G0 to G1 and from G1 to S (G0 is stagnant phase for a nondividing cell)

39. Cell division
b. Cyclin E
 prepares the cell for DNA replication in the S phase
c. Cyclin A
 activates DNA replication inside the nucleus in S phase
d. Cyclin B
 promotes assembly of the mitotic spindle and readies the cell for mitosis
G. Tumour formation and cancer
1. Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours
2. Tumour – an abnormal group of cells that can develop at any stage of life and in any body part

40. Cell division
3. diseases due to malignant tumours are called cancer
a. Chemicals and agents that cause cancer are called carcinogens
b. There are various types of carcinogens
i. Chemicals
ii. Viruses
iii. High energy radiation – X rays, UV light
4. Mutagens are random changes to the base sequence of genes
a. Most genes do not cause cancer if they mutate
b. Genes that can cause cancer are called oncogenes
c. Oncogenes control the cell cycle and put it out of whack

41. Cell division
5. Several mutations must occur in the same cell for it to become a tumour cell
a. The chance of this happening is small
b. Since there are so many cells in the body – it increases the chances for cancer
c. Metastasis is the movement of cells from a primary tumour to set up secondary tumours in other parts of the body