Cell Signalling - Monday, May 6

Cell Signalling

Gland - Any structure that secretes a hormone.
Hormone - Any chemical secreted by one part of the body that has its effect/s somewhere else. Two basic Types:
      1. Steroid (Fat-based - non-polar - can diffuse through cell membranes)
      2. Peptide ("Protein" - polar - bond to a receptor protein on cell surface). Pheremones - chemicals excreted by one individual that cause a physiological change in another individual.
  
I. Gonads - Primary sexual structures
           A. Ovaries - produce estrogens & progesterone - responsible for female structure, menstral cycle & pregnancy.
           B. Testes - Testosterone. Responsible for male anatomy, sperm production. How is it regulated? By the hypothalmus (Part of the brain - made up of Neurons) Pituitary (true gland) Negative Feedback System (HPNFS)
      1. Hypothalamus - raises levels of GnRH (Gonadotropin Releasing Hormone)
      2. Pituitary - is signalled by higher levels of GnRH to release LH (a gonadotropin)
      3. Testes - are signalled by higher levels of LH to produce higher levels of Testosterone.
     

Colonies- permanent association of cells, but little or no integration of cell activities.
            Volvox- unicellular green alga, colony is a hollow ball of cells.
Kingdom Protista-
Protists are the most diverse eukaryotic kingdoms.
-There are 15 distinct Phyla of Protists.
     -These are grouped into five general groups based on shared characteristics
        1. Presence/absence of flagella/cilia
        2. Presence and kinds of pigments
        3. The type of mitosis
        4. the types of cristae in mitochondrea
        5. Ribosomes are the same
      -There are five major, subdivided groups.
        1. Ameaboids- Heterotrophs with no permanent locomotor apparatus
        2. Heterotrophs with flagella
        3. Heterotrophs with restricted mobility (slime-molds)
        4. Photosynthetic protists (algae)
        5. Nonmotile spore-formers

5/2/2013

5/2/2013

Based on carbon and energy sources, prokaryotes can be divided into 4 groups

1. Photoautrouphs

• Use energy of sunlight to build organic molecules
• Cyanobacteria

1. Chemoautotrouphs

•  Obtain energy by oxidizing inorganic substances

1. Photoheterotrouphs

• Rare

1. Chemoheterotrouphs

• use organic molecules as carbon and energy sources

Viruses

• Latin for poison
• Non-celklur particle with
• DNA or RNA
• 1 or 2 Protien coats (capsids)
• May have Viral Envelope - Phosholipids

• Do Not respire or grow
• ONLY function in a living cell
• Not given Latin names like living organisms
• 4 Charicteristics - Only have 1 (Genetic material
• Made of cells
• has metabolism
• reproduces on its own
• Genitic material

Virus have 2 different cycles
Lytic cycle

• 1- Virus absorption/ attachment
• 2 - Injection/ entry
• 3- Replication of viral parts
• 4- Assembly of the Virions
• 5- Release by lysis
• cause disease, cell gets taken over and produces more viruses that bust the cell

 Lysogenic Cycle

• Lays dormant in your body, doesn't destroy host cell

Temperate Viruses do both (HIV)

Wednesday May 1, 2013

Forming Life's Building Blocks

• Concerns have been raised about the "primordial soup" hypothesis
• No oxygen=> no protective ozone layer
• therefore, the UV light would have been destroyed and the essential ammonia and methane gases
• Louis Lerman, in 1986, proposed the bubble model
• When the experiment is done one of the things formed is urisil which is found in RNA 

The First Cells

• The first step may have been the formation of tiny bubble termed microspheres 

Structure of Prokaryote

• Prokaryotes are small, simpily organized, single cells that lack a nucleus
• Include bacteria and archaea
• have a cell wall
• composed of peptidoglycan 
• network of polysaccharides linked by peptide cross-links

• bacteria are separated into two groups based on membranes
• Peptidoglycan are in either a thick layer with no outer membrane that will stain (gram-positive) or in a thin layer with an outer membrane that won't stain (gram-negative)
• Hans Christian Gram developed a stain to differentiate between the two
• When cells are stressed they pass their plasmid DNA following cell-to-cell contact
• Based on carbon and energy sources, prokaryotes can be divided into four categories
• 1. Photoautotrophs: Photosynthesizes, or plants. 
• Cyanobacteria: when a lake suddenly has an algae bloom and turns pea soup green, it's not algae, its cyanobacteria

• 2. Chemoautotrophs: use inorganic fuels as their food. 
• For example: nitrogen-fixing bacteria, nitrifiers oxidize ammonia or nitrite

• 3. Photoheterotrophs: Use light as energy and pre-formed organic molecules as carbon sources
• Purple nonsulfur bacteria
• Very Rare

• 4. Chemoheterotrophs: Use organic molecules and energy sources 
• Decomposers and most other types of bacteria.