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List the several risk factors for cancer, and indicate why they are risk factor based on what you learned about cell division.
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What type of cancers are you most at risk? What can you do now to reduce your risk?
Note: you are welcome to do this analysis on another person (real or fictional) if you would rather not reveal personal information about yourself in this discussion board
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
BIO120 Concepts of Biology
Unit 2 Lecture Part Two: Cell Division
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
The ultimate purpose of cell division is to transmit genetic material to the next generation of cells. The sum of all genes or genetic material of an organism is called the genome.
• In prokaryotes, the genome is single circular piece of DNA
• In eukaryote, the genome consists of multiple, linear chromosomes (23 pairs in humans)
Eukaryote cells can have more than one copy of each chromosome, a condition called diploidy. Haploid cells have one copy; diploid cells have two. For example, human gametes (sperm and eggs) are haploid with 23 chromosomes. The rest of the cells of the body (somatic cell) are diploid with 23 pairs of chromosomes. Each pair of matched chromosomes are homologous chromosomes (e.g. the chromosomes 1 from your dad and from you mom are homologous chromosomes). Different species have different number of chromosomes, which provides a reproductive barrier between species.
Genome
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Prokaryotes reproduce asexually in which the daughter cells are clones of the original cell. The most common form of asexual reproduction in prokaryotes is binary fission. During binary fission, DNA starts to replicate at a specific site on the DNA: the origin of replication. After DNA replication, the chromosome attach to opposite sides of the cell. A protein called Ftsz then forms a ring between the genomes. A septum (a partition) then forms between the cells causing them to pinch off from each other.
Prokaryotes: Binary Fission
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Eukaryote cells have two forms of cell division: mitosis and meiosis. Cells divide by mitosis to create two daughter cells that have same genetic material. Mitosis allows multicellular organisms to grow and differentiate. Cells divide by meiosis to produce gametes that have half the genetic material of the starting cells. In this unit, we focus on mitosis. We will return to meiosis in Unit 4.
Eukaryote Cell Division
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Cells grow and divide by progressing through a series of stages called the cell cycle. There are two phases in eukaryotes: interphase and mitotic phase. During interphase, cells grow and replicate their DNA. Interphase has three subdivisions:
• G1 (Gap 1) when cells are growing to prepare for DNA replication.
• S phase when cells are synthesizing and replicating DNA and also duplicate centrosomes
• G2 cells check that DNA reproduction occurred correctly and continue to grow and prepare for mitosis.
After G2, cells entire the mitotic phase. During mitosis, the chromosomes and centrosomes that were duplicated in the S phase are now separated into the daughter nuclei. The cell then usually divides the cytoplasm among the two daughter cells, a process called cytokinesis.
Cell Cycle
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Animal cell mitosis is divided into five stage:
• Prophase – chromosomes condense and nuclear membrane breaks down.
• Prometaphase – mitotic spindles from the centrosomes attach to chromosomes
• Metaphase – chromosomes line up in the middle of the cell from the metaphase plate.
• Anaphase – sister chromatids are separated into opposite ends.
• Telophase— the reformation of the nuclear envelope in the daughter cells.
• Cytokinesis – final separate of cells into two daughter cells.
Mitosis
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Animal and plants cells undergo cytokinesis differently. In animal cells (a), a cleavage furrow forms at the former metaphase plate in the animal cell. The plasma membrane is drawn in by a ring of actin fibers contracting just inside the membrane. The cleavage furrow deepens until the cells are pinched in two. In plants (b), Golgi vesicles coalesce at the former metaphase plate and then fuse to form the cell plate. The cell plate grows from the center toward the cell walls. New cell walls are made from the vesicle contents.
Cytokinesis
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Cells that no longer need to divide can exit the cell cycle and enter G
0 . In some cases, this is a temporary condition until
triggered to enter G1. In other cases, the cell will remain in G 0
permanently (e.g. neurons, muscle cells).
G-Zero (G 0
)
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
The cell cycle is controlled at three checkpoints. Integrity of the DNA is assessed at the G1 checkpoint. Proper chromosome duplication is assessed at the G2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint. Disruption of these cell cycle check points by say mutations, can lead to uncontrolled growth.
Cell Cycle Regulation
Genome
Mitosis
Cytokinesis
G-Zero (G 0 )
Cell Cycle Regulation
Cancer
Eukaryote Cell Division
Cell Cycle
Prokaryotes: Binary Fission
Cancer can results from mutations in different genes. Most mutations either have no effect or cause enough damage to cause the cell to activate a controlled, self-destruct sequence (apoptosis). However, some mutations will disrupt regulation of the cell cycle leading to uncontrolled growth. One of the most commonly mutated genes is the p53 gene, which encodes a protein that monitors for DNA damage. If the DNA damage is repaired, the cell resumes division. If the p53 gene is mutated, then DNA damage accumulates undetected, which can result in additional loses of cell cycle regulation. Most cancers are believed to require at least two mutations before the cells take on characteristic of cancer cells. Even after the cancer grows into a tumor, some tumors are benign and do not pose a serious risk. However, some tumors can acquire additional mutations that allow cancer cells to travel in the blood to latch on to other organs, a process called metastasis. A cancer that has metastasized is very dangerous. Some treatments for cancer such as radiation therapy and chemotherapy infer with cell division. Because cancerous cells tend to divide faster than noncancerous cells, these treatments should be more damaging to cancerous cells than noncancerous cells. More recent therapies are aimed at better targeting treatments to only cancerous cells and reduce the side effects of other treatments.
Cancer
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BIO120 Concepts of Biology
Unit 2 Lecture Part One: Cell Biology
Microscopy
Cell Structure
Osmosis & Diffusion
In 1665, Robert Hooke was the first person to describe a cell, because no one ever had a lens powerful enough to see one. His first specimen was a piece of cork, the cells reminded him of little rooms (cella). Hence the name.
Discovering Cells
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
Although Hooke was the first person to see a cell, Leeuwenhoek described the most cells in about 1683. He was first to see bacteria and other microbes, because his lens was 10 times more powerful than Hooke’s.
Discovering Microbes
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
Most modern light microscopes can magnify objects up to 400 or 1,000 times the size of what you can see with the naked eye. Some light microscopes are dissecting microscopes, which have a lower magnification, but allow biologist to examine larger objects.
Modern Light Microscopes
Bright Field MicroscopeDissecting Microscope
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
This image shows uterine cervix cells, viewed through a light microscope. The cells were obtained from a Pap smear during a gynecological exam. The cells on the left are normal. The cells on the right are infected with human papillomavirus, which can cause cervical cancer. These potential cancerous cells are bigger and appear to be dividing. The cells are blue, because they have been stained to help see them better.
Cell Image
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
Even more powerful than a light microscope is an electron microscope. Electron microscope uses electrons instead of light to form images and can magnify images 100,000 x. The top images shows the amazing details on an ant head. The lower image shows Salmonella infecting human cells.
Electron Microscope
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
This image summarizes the sizes of cells and their components and what can be seen by the naked eye, light microscope, and electron microscope.
Size of Cells
Microscopy
Discovering Cells
Discovering Microbes
Modern Light Microscopes
Cell Image
Electron Microscope
Size of Cells
Cell Structure
Osmosis & Diffusion
Cells can be classified as either prokaryotes or eukaryotes depending on whether a nucleus is present or absent. Prokaryotes are cells that lack a nucleus. They are single- celled organisms such as the E.Coli bacteria that lives in your intestine. Eukaryotes are cells that contain a nucleus,
and are found in animals, plants, and fungi. Some single-cell organisms such as amoebas are eukaryotes. The membrane surrounding the nucleus is called the nuclear envelope.
Prokaryote vs Eukaryote
Prokaryote
Eukaryote
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
One key characteristic of cells is that they are surrounded by a plasma membrane, a phospholipid bilayer with embedded proteins. Membrane proteins help control which molecules pass into and out of cells. Membrane proteins also play a role in communication between cells and adhesion of cells to each other and the surface. In eukaryotes, membranes surround organelles, allowing different parts of the cell to have specialized functions.
Membranes
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Cells contain proteins that provide internal structural support similar to how we need our bones to stand up right and move.
In eukaryotes, there are three types of cytoskeletal molecules from largest to smallest:
• Microtubules
• Intermediate filaments
• Microfilaments (actin filaments)
Cytoskeleton
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Mitochondria are the powerhouses of the cells, because they synthesize large quantities of ATP, the main energy carrier in the cell.
Mitochondria
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Chloroplasts are found in plant cell and other cells that perform photosynthesis: the synthesis of sugar from light, water, and carbon dioxide. Chlorophyll is the pigment inside chloroplasts that absorb light and give these organelles their green appearance.
Chloroplasts
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
The endomembrane system is an interconnected system of membranes from several organelles: nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, plasma membrane, lysomes, and vacuoles.
The rough endoplasmic reticulum (RER) synthesizes membrane proteins & secreted proteins that are then modified by the Golgi apparatus and sorted to their final destination.
Endomembrane System
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Exocytosis is the process in which cells secrete molecules such as hormones, neurotransmitters, and growth factors by fusing a vesicle with the plasma membrane
Exocytosis
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Endocytosis is the process in which cells internalize molecules. There are three forms:
• Phagocytosis: plasma membrane surrounds the particle (which can be the size of bacteria) and pinches it off to form an intracellular vacuole.
• Pinocytosis: the cell membrane surrounds a small volume of fluid and pinches off to form a vesicle.
• Receptor-mediated endocytosis: molecules bind to specific receptors on the membrane that pinch off and internalize the molecule. (credit: modification of work by Mariana Ruiz Villarreal)
Endocytosis
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
After endocytosis, the vesicles are sorted to different parts of the cells. For example, macrophages are a type of white blood cells that destroy bacteria. During phagocytosis of a bacterium, the vesicle fuses with a lysosome that contains enzymes that will breakdown the bacterium.
Phagocytosis
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Cells also secrete molecules that surround the cell, forming the extracellular matrix that play several roles include protecting the cells.
Extracelluar Matrix
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Cells form four types of connections with other cells:
a. Plasmodesmata is a channel between the cell walls of two adjacent plant cells.
b. Tight junctions form water-tight seal between adjacent animal cells.
c. Desmosomes join two animal cells together. They form strong connections but are not as water-tight as tight junctions.
d. Gap junctions act as channels between animal cells. Both gap junctions and plasmodesmata connect the cytoplasm between adjacent cells allow the tissue to act together.
Intercellular Connections
Microscopy
Osmosis & Diffusion
Cell Structure
Prokaryote vs. Eukaryote
Membranes
Cytoskeleton
Mitochondria
Chloroplasts
Endomembrane System
Exocytosis
Endocytosis
Phagocytosis
Extracelluar Matrix
Intercellular Connections
Diffusion is the process of molecules moving from an area of high concentration to a low concentration (concentration gradient). Some nonpolar molecules can diffuse through membranes. Polar and charged molecules require transport proteins to cross the membrane.
Diffusion
Microscopy
Cell Structure
Osmosis & Diffusion
Diffusion
Osmosis
Tonicity
Electrochemical Gradient
Na/K Pump
Osmosis is the diffusion of water through a semi-permeable that allows water but not large molecules to move across. Water flows from higher to lower amount of water until the concentration of solutes is equivalent on both sides of the membrane.
Osmosis
Microscopy
Cell Structure
Osmosis & Diffusion
Diffusion
Osmosis
Tonicity
Electrochemical Gradient
Na/K Pump
Tonicity is the concentration of salt and other solutes.
Hypertonic solution have high salt concentration that draws water out of the cells and shrink them.
Isotonic solution are balanced with the cytoplasm resulting in no net change in water or shape.
Hyptonic soltions are low salt concentrations, forcing water into the cell and expanding them or causing them to lyse (break apart).
In plant cells, the cell wall resists this change in cell shape, creating an opposing pressure called turgor pressure
Tonicity
Microscopy
Cell Structure
Osmosis & Diffusion
Diffusion
Osmosis
Tonicity
Electrochemical Gradient
Na/K Pump
The movement of charge molecules is dependent upon two forces:
• The diffusion from high to low concentration (concentration gradient).
• The diffusion towards the opposite electrical charge (electrical gradient).
The end result is a electrical potential across the membrane of about – 60 mV
Electrochemical Gradient
Microscopy
Cell Structure
Osmosis & Diffusion
Diffusion
Osmosis
Tonicity
Electrochemical Gradient
Na/K Pump
The sodium-potassium pump uses energy from ATP to moves potassium and sodium ions across the plasma membrane in order to main and regulate the electrochemical potential across the membrane.
Na/K Pump
Microscopy
Cell Structure
Osmosis & Diffusion
Diffusion
Osmosis
Tonicity
Electrochemical Gradient
Na/K Pump
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