Biological molecules

• Proteins consist of the elements: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur
• The primary structure is the sequence of amino acids that make up a protein.
• Amino acid residues are joined together by peptide bonds to form polypeptides.
• Secondary structures include alpha helix (coiled) and beta pleated sheet (flat).
• Tertiary structure refers to how secondary structures fold into 3D shapes.
• Lipids consist of the elements: Carbon, Hydrogen, Oxygen, and phosphorus in phospholipids
• Carbohydrates consist of the elements: Carbon, Hydrogen, Oxygen
• OH- ions can:

  • catalyse reactions
  • determine blood pH
  • neutralise stomach acid
  • determine shapes of proteins
• pyrimidines are Cytosine and Thymine and they are single ringed
• purines are Adenine and Guanine and they have 2 rings
• The fluid mosaic model describes plasma membranes as a phospholipid bilayer with a hydrophobic core where the hydrophobic tails face inwards away from the environment and hydrophilic heads facing outwards towards the environment. Also that the phospholipids are fluid and are able to move and that proteins are scattered across the membrane.
• Some molecules are able to freely pass through membranes through transport proteins with no energy due to facillitated diffusion where the molecule has its own kinetic energy and diffuses through the membrane down the concentration gradient.
• An immediate source of energy for active transport is ATP
• Compartmentalisation is separating substances and controlling the entry of substances to possibly create a space with different conditions for a process to occur
• What is the purpose of the membrane of the RER?

  • compartmentalisation
  • site where ribosomes are attached
  • packaging newly synthesised proteins into transport vesicles
• Roles of membranes within cells?

  • Compartmentalisation
  • forming vesicles for transportation of substances or organelles
  • Site of chemical reactions
  • provide attachment sites for enzymes and proteins like ATP synthase for oxidative phosphorylation in the membranes of mitochondria
  • allow for the formation of concentration gradients
• Molecules that have the following property can diffuse across the cell membrane:

  • hydrophobic (will not be repelled by the hydrophobic core)
  • non-polar (will not be repelled by the charged phosphate heads of of the phospholipids)
  • small

  note that they do not need all of these properties but have one at minimum and none of the opposing traits
• molecules that have the following property cannot simply diffuse through membranes:

  • large
  • hydrophilic (will be repelled by the hydrophobic core of the membrane)
  • polar - like ions
• How does the properties of phospholipids allow for the formation of plasma membranes?

  phosphate (on head), is hydrophilic and bonds with water (molecules), (two) fatty acid tails are hydrophobic ✓ heads orientate towards water / tails orientate towards other fatty acids / tails orientate away from water , (so a bilayer forms)✓
• What is the structure of a phospholipid?

  A phosphate and 2 fatty acids attached to a glycerol
• Structure of the RER?

  membrane is continuous with the nuclear envelope, has a network of membranes called cisternae, membrane is covered ribosomes
• difference between alpha and beta glucose is that alpha glucose has hydrogen above the ring whilst beta has it below
• An enzyme is a biological catalysts that increases the rate of reactions without being used up
• functions of triglycerides:

  • thermal and electrical insulation
  • storage energy molecule
  • source of energy
• A saturated triglyceride is one in which all three fatty acid tails are fully saturated with hydrocarbon chains
• properties of triglycerides:

  • large
  • non-polar
  • hydrophobic
• The bond the connects fatty acids and glycerol is called an ester bond
• What is a glycolipid?

  A lipid with a carbohydrate molecule attached.
• What is a glycoprotein?

  A protein with a carbohydrate molecule attached.
• Explain the orientation of phospholipids within the bilayer

  Hydrophilic phosphate heads are orientated outwards (towards water); hydrophobic fatty acid tails are orientated inwards (away from water)
• Give 3 examples of intrinsic proteins

  Channel proteins, carrier proteins, glycoproteins
• Channel proteins and carrier proteins have what main role within the membrane?

  Transport
• Define the term diffusion.

  The net movement of a substance from an area of high concentration to an area of low concentration. It is passive, does NOT require ATP.
• What is a carrier protein?

  A protein which changes shape to allow larger molecules to pass through the membrane. In facilitated diffusion this requires no energy, in active transport it requires ATP.
• Describe the effects of temperature on membrane structure

  As temperature increases, phospholipids will have more KE, so move faster and more, making the bilayer more fluid and it begins to lose its structure. This loss of structure allows molecules to cross it more easily. Carrier and channel proteins may become denatured, affecting membrane transport.
• Describe the effects of ethanol on membrane structure

  Non-polar ethanol molecules can insert themselves into the bilayer disrupting the structure by dissolving the fatty acids, meaning the bilayer becomes more fluid and permeable
• State 5 factors that affect the rate of simple diffusion

  Temperature, surface area, diffusion distance, size of molecule, concentration gradient
• Define the term active transport

  Movement of molecules, against their concentration gradient (using energy liberated from ATP hydrolysis) using specific protein channels or carriers
• Describe how carrier proteins are used in active transport

  Molecule binds to specific site in carrier protein; ATP binds to separate binding site; carrier protein changes shape (conformational change) and transports molecule across membrane
• What is the main difference between active transport and facilitated diffusion?

  Active transport requires ATP; facillitated diffusion is passive

  
  

  ATP involves carrier proteins, whilst faciliated diffusion uses both carrier and channel proteins whilst relying on the molecules kinetic energy for carrier proteins to alter its structure