Cells and Cell Specialization

Cells, Cell Division, and Cell Specialization

Fundamentally Different Types of Cell
Prokaryotic Cell- single celled: only DNA+ structure (“before nucleus”) E.g. zygote-complete DNA
Eukaryotic Cell-multi-celled (“after nucleus”) Prokaryotes Eukaryotes
DNA In “nucleoid” region Within membrane-bound nucleus
Chromosomes Single, circular Multiple, linear
Organelles None Membrane-bound organelles
Size Usually smaller Usually larger- 50 times
Organization Usually single-celled Often multicellular
Sexual Reproduction None Meiosis: Combination of DMA from 2 cells

3 postulates of cell theory
(Created by Schleiden, Schwann)
1. All living things are composed of cells
2. All cells from pre-existing cells (e.g. through cell division)
3. Cells are the basic functional units of living organisms

Functions of organelles
Organelle In business terms Functions
Cytoplasm Place to work -suspends organelles
-stores substances that are needed for later
-many chemical reactions take place
Cytoskeleton Place to work -transports vesicles and organelles
-determines cell shape
E.g. while blood cell: uses it to reach and swallow bacterium
Ribosome/ Enzymes Workers -makes proteins that enter the ER for modification
Nucleus The boss -protects DNA
-chromosome: large continuous piece of DNA, containing many genes
-gene: many sets of instructions on a chromosome, make functional products
-nucleolus: region of DNA that codes ribosomes
-nuclear pore: holes in a nuclear membrane
Endoplasmic Reticulum Internal transportation -transports materials throughout the cell with its branching tubes and pockets
-brain: assists with production, release of hormone
-muscles: involved with muscle contraction
Golgi Apparatus Exports transportation -collect and process materials to be removed from the cell
-make and secrete mucus
Cell Membrane Security/ export/import -support the cell
-allow some substances to enter while keeping others out (semi-permeable)
Chloroplasts Cash flow -absorb light energy for photosynthesis the process of converting carbon dioxide and water in glucose and oxygen using chlorophyll
Mitochondria Spender of cash -make energy available to the cell
-contains enzymes convert stored energy into a easily usable form ( cellular respiration)
Lysosomes Waste removal/ recycling -digestive system of cell break down waste from both inside and outside the cell
Vacuoles Storage -contain substance, removing unwanted maintaining internal turgor pressure within the cell

Differentiating between plant and animal organelles
Animals Plants
Lysosome: present in all animal cells but not all Cell Wall: provides structural support, prevents cells from rupturing, outside of cell membrane
Centrioles: involved in cell division Chloroplasts: absorb light energy for photosynthesis the process of converting carbon dioxide and water in glucose and oxygen using chlorophyll
Vacuole: a portion of the cell membrane may turn inside out to form a vacuole to digest the engulfed object Vacuole: controls turgor pressure, much larger

Reasons who cells must divide
1. Reproduction
-all cells use division to reproduce
-single celled organisms: split to form new organism (asexual reproduction)
-multi celled organisms: 2 parental cells combine to form new organism (sexual reproduction)
2. Growth
-transport of nutrients and waste across the cell limits cell size (diffusion: from highly concentrated areas to lower concentrated areas)
-movement of chemical occurs by diffusion cells get too large, chemical and water can’t move fast
-only way to get bigger and still function properly is to add more cells
3. Repair/Regeneration
-needed to stay alive
E.g. skin cells replaced daily, red blood cells replaced ever 120 days, breaking bones or cuts and blisters: new cells needed to fill the gaps
-replaces lost cells

Why do cells specialize?
Cells have exact same DNA in its nucleus location and chemical messages from other cells activate certain genes. As a result each cell has a unique function in which they must perform

Types of stem cells
“Undifferentiated”
Totipotent-“embryonic” stem cells
E.g. zygote
Completely undifferentiated E.g. cells from first few divisions after fertilization
 Can become any type
 Destroys the embryo when collected
Pluripotent- “adult” stem cells
E.g. trophoblast
 Already partially differentiated and located in specific body tissues E.g. bone marrow, umbilical cord
 Can become many types, but not all
Multipotent
 Can only differentiate into a limited range of cell types

Cancer- What and how it forms
What: When genes that control the duration of interphase get mutations (random changes in DNA code) that causes a cell to grow out of control. As a result it forms a tumor (lumps of cells) that doesn’t fully differentiate or function properly, using valuable resources
Tumor Types
1. Benign (non-cancerous): cells don’t interfere or invade other cells, but large masses can crowd nearby tissues
2. Malignant (cancerous): interferes or invades other cells, nearby tissues and potentially mestasize
Mestasize: process of cancer cells dividing and going to other places in the body by breaking away from an invasive primary tumor, forming additional secondary tumors
Causes of Cancer
1. Cellular: DNA is copied improperly during S phase of cell cycle
2. Environmental: mutations caused by carcinogens (E.g. chemicals, energy, some viruses)

Methods of Screening Cancer
-Pap smear (cervical cancer)
-Mammogram (breast cancer)
-Colonoscopy (colorectal cancer)
-PSA blood test (prostate cancer)
-Self-Examination
Biopsy: removal of body tissue for laboratory examination (E.g. taken with endoscope)

Methods of diagnosing cancer
-Endoscopy: Camera and tissue extractor
-X-ray: uses radiations to get images of tissues
-Ultrasound: uses sound waves to create images of soft tissues
-CT/Cat Scan: Computer Axial Tomography creates #.D images
MRI Scan: Magnetic Resonance Imaging creates #.D image using magnetic fields and radio waves and computer analysis

Different methods of treating cancer
-Surgery: physically removing
-Chemotherapy: treating with a series of drugs that target rapidly dividing cells
-Radiation: killing cancer cells with target radiation
Biophotonics: uses beams of light to detect and treat cancer

Different parts of the cell cycle- Description
Interphase:
-period before a cell divides
-longest part of the cycle (3/4 of its time)
-cell grows, performs daily functions and chromosomes are duplicated
S-Stage of Interphase
Strands of the SNA are copied but remain attacted to the original protein

Mitosis: process by which all cells divide (to divide up the DNA that has been copied and create 2 identical cells each with a complete set of chromosomes
Prophase:
-duplicated chromosomes shorten and thicken (chromatin begins to condense by supercoiling, wrapping around protein balls
-nuclear membrane starts to dissolve)
-spindle fibres (made of microtubles) form
-centrioles move to opposite ends (poles of the cell)
Metaphase:
-double stranded chromosomes line up along the equator (middle of the cell)
Anaphase:
-each double stranded chromosome splits and the single stranded chromosomes travel along the spindle fibres to opposite ends of the cell
-sister chromatids get pulled apart
Telophase:
-chromosomes reach the opposite poles of the cell and become longer and thinner
-new nuclear membrane forms around each set of chromosomes
-spindle fibres disappear
-supercoiled DNA begins to uncoil to form chromatin again
Cytokinesis:
-division of cytoplasm and cellular organelles (pinching off to form individual cells)
Plant cells: grow a new cell plate built with proteins to form a new membrane)

Result: mother cell splits in half to form 2 daughter cells

Drawing the cell cycle