Homeostasis/molecules of life: SHS 3.7.2, 3.1.2

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Homeostasis/molecules of life SHS 3.7.2, 3.1.2

• cell functions involve specific chemical
  reaction
• homeostasis is the dynamic regulation and
  balance of an organisms internal environment to
  maintain condistions suitable for survival

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Homeostasis

• The ability the body has in regulating its
  internal environment despite any changes in the
  external environment
• The body uses different systems to monitor and
  maintain homeostasis-the brain and its neurons
  (nervous system) and our glands and their
  hormones (endocrine system) are main examples

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Homeostatic example

• An example would be your body temperature
  staying at 98.6 despite it being 30 outside.
  This is due to the thermostat in your brain
  detecting whether you need to shiver or sweat to
  heat or cool your body

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Dogs and homeostasis

• Dogs pant to keep their bodies from overheating

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Reptiles and homeostasis

• Reptiles lay in the hot sun to increase their
  body temperature

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Cell transport and homeostasis

• Transport of substances across membranes is
  related to maintaining body homeostasis-red blood
  cells swell as water rushes in when placed in
  pure water. They shrink from water rushing out
  when placed in salt water (osmosis)

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Molecules of Life

• Most molecules of a cell are carbon based
• Its basic structure is the foundation of the wide
  range of lifes molecules

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Molecules of Life

• Monomers
• Small molecular unit that is the building block
  of a larger molecule

• Polymers
• Every living cell has thousands of polymers
• They are a chain of smaller molecular units
  (monomers)

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Examples of monomers making a polymer

• Polysaccharides are made from monosaccharides
• Proteins are made from amino acids
• Nucleic acids (DNA and RNA) are made from
  nucleotides

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Four main categories of large molecules

• 1. carbohydrates
• 2. Lipids
• 3. Proteins
• 4. Nucleic Acids

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Carbohydrates

• Organic compound made of sugar molecules
• Main fuel supply for cellular work

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Types of sugars

• Monosaccharide-simple sugars with only one sugar
  unit (glucose, fructose)
• Disaccharides-double sugar from two
  monosaccharides (sucrose)
• Polysaccharides-long chains of simple sugars
  monomers or complex carbohydrates (starch,
  glycogen, cellulose)

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Lipids

• Water avoiding compound-hydrophobic-
• Known as fats and store energy in your body
• Examples fats and steroids (cholesterol)

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Proteins

• Polymer constructed from a set of 20 kinds of
  monomers called amino acids
• Responsible for all functions of an organism

• Form hair, fur, muscles, nutrient storage, defend
  body from microorganisms, convey messages from
  cell to cell

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Enzymes

• Group of specialized proteins
• Cellular reactions depend upon catalysts to speed
  up chemical reactions
• Enzymes allow cells to perform reactions without
  raising their temperature to dangerous
  levels-enzymes lower the activation energy
  (energy to start a chemical reaction) for the
  reaction to take place

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Enzymes cont.

• Enzymes act upon only specific reactions
• Their shape determines which reactant they act
  upon-its structure and shape determines its
  function-this is sensitive to changes in the
  environment