Bio review :(

Water

  • Polar 

  • Made up of 1 Oxygen atom and 2 Hydrogen atom (Oxygen is more electronegative of the atoms)

  • Partial polar charges 

  • Some molecules can form H-bonds (hydrophilic) has partial charges (polar)

  • Some molecules can’t form H-bonds ( hydrophobic) lacks partial charges (non-polar)

  • Exception to the rule is carbon dioxide its non-polar and hydrophobic 



Hydrogen bond 

  • Weak attraction compared to covalent bonds

  • H bonds are the dotted line formed from attraction between electrical charges  

  • H bonds are easy to break 

  • Hydrogen partial positive charge and negative partial charge 



Macromolecules 

Carbohydrates : monosaccharides 

Protein: amino acids 

Nucleic acids: nucleotides 



Acids

  • release H+ protons 

  • Lowers the pH

Bases

  • accepts H+ protons 

  • Increases the pH



Cell Membrane Structures

  • All living cells are surrounded by cell membrane 

  • Protect and contain organelles 

Scientist define life by:

  • Take in resources and process them (metabolism)

  • Produce offspring with those resource (reproduction)




Basic Structure 

Phospholipid bilayer: 

  • Phoso group is the head and the tail is the lipid 

  • 2 layers of phospholipid bilayer facing outwards and its tails facing inwards like a sandwich 

  • They are amphipathic molecules: both hydrophilic and hydrophobic parts

  • The tails of the bilayer are lipids and hydrophobic (non polar) 

  • The heads of the bilayer are phosphate groups and hydrophilic and interact with the water molecules (polar)

  • The cell membrane is fluid move laterally changing shape of membrane depending on its environment  

  • Selectively permeable 

  • Unsaturated tail: are less ridged and more fluid 

  • Saturated tails: are more ridged making it less fluid

Carbohydrates: 

  • Carbohydrates called (Oligosaccharides) project from the bilayer and act as “street addresses” to identify individual cells 

Proteins: 

  • Membrane proteins are found on 3 different parts of the cell membrane on the exterior bilayer, in the middle of the bilayer tails, and interior of the of the cell on the bilayer 

  • Proteins that are inside or outside the bilayer are called peripheral molecules proteins

  • Proteins that are in the middle of the bilayer are called transmembrane proteins 



Diffusion and Osmosis 



Diffusion: spontaneous movement of atoms, ions and molecules from areas of high concentration to low

  • The difference in concentration is called the concentration gradient 

  • Particles moves because of the random motion of substances; without an input of energy passive process 

  • Diffusion is faster at higher temperatures 

  • Entropy: measure of disorder or randomness (high entropy is very random) (low entropy is more organized) 

  • Ex: food coloring in water pigment molecule slowly spread out until the coloration is even throughout solution

Passive transport: any movement of molecules that doesn’t require input of energy 

  • Occurs down a concentration gradient (high to low)

  • Increase entropy (happens at random)

Facilitated diffusion:  substance is too large or polar passive transport occurs through a membrane protein 

  • Channels transport of ions and small molecules (fast)

  • Carriers transport of large polar molecules (slow)

    • Protein changes shape to fit molecules 

    • This process is still passive but is facilitated by the protein

 Active transport: energy added to substance to move from one side of the membrane to the other 

  • Energy (ATP) is needed because particles are going from low to high concentration 

  • Protein pump is usually used to pump particle through the gradient

  • Entropy decreases 

Osmosis: water flows through a semi permeable membrane from low solute to high solute 

  • Water molecules also move from areas of high concentration to low based on random movements and increases in entropy under 3 conditions 

    1. Two solutions separated by a lipid bilayer 

    2. The solutions have different concentrations 

    3. The dissolved substances can’t move across the membrane 

  • If solution on one side of the membrane has a higher concentration of dissolved substances than the other that means that side has a lower concentration of water 

  • Water will move across the membrane from areas of high concentration to areas of low water concentration 

  • Moves slowly across the membrane or rapidly through a channel protein 

  • The channel protein is a called aquaporin 

Hypotonic solution: the environment the cell is in lower concentration then the inside of the cell (in a blood cell water will move outside of the cells)

Isotonic solution: the concentration is equal on outside and inside the cell

Hypertonic solution: the environment has a high concentration then the outside of the cell

(In blood water will move into the cell)



Concentration gradients 

  • Occur when dissolved substances differ concentration in different areas usually on different sides of the cell membrane 

  • Arrow used to indicate their higher to lower directionality



Potential energy: energy of positions the potential of energy to be released

Ex: raised hammer (potential energy) the swinging of the hammer (kinetic energy)



Selective permeability: Some substances can pass through the membrane barrier much more readily than others

  • The ability of a substance to pass through is dependent on the size and the charge of the membrane  

  • All else equal, Smaller substances pass through cell membrane much faster than larger substances

  • All else equal, Uncharged and non polar substances pass through the cell membrane much faster than charged or polar substances 

  • Permeability is dependent on size and charge because of the substances interaction with the phospholipids

  • Transport proteins are used to move ions or molecules through a special channel in the membrane protein called facilitated diffusion 



Membrane channels: 

- Transmembrane proteins that function as tunnels and allow ions and other small molecules pass 

  • They form a channel or passageway that facilitates diffusion across the lipid bilayer 

  • Channels are extremely specific each ion/molecule has its own channel 

  • R groups: inside of the protein there are R-groups that have sizes and charges that allow specific ions to pass but others not to 

  • Few channels are open at all  times instead they have opening and closing door which is strictly regulated 

Transmembrane protein: Transmembrane proteins that function as tunnels and allow ions and other small molecules pass 

  • Called carries 

  • Carriers are mechanism for small molecules , which are too large to cross lipid bilayer

  • Each carrier transports specific molecule

  • Movement of the transported substances occurs via diffusion supporting passive transportation 

  • Carriers are heavily regulated, 

  • Carries stop working in inhibitors bind to them 

  • Carries don’t form an open channel for molecules to flow through 

  • The molecule binds to carrier when this happens the carrier changes shape and exposes the molecule to the inside of the cell where it can drop off and diffuse into the solution inside the membrane 

Membrane proteins 

  • Small non polar: easily pass through the membrane (O2,Co2,N2) 

  • Small polar: can pass with some difficulty across the membrane bilayer they benefit from the help of transporter channel proteins (water, ethanol,glycerol)

  • Large polar: have difficulty passing through the membrane need the help of transport glucose, nucleotides, amino acids)

  • Charged Ions (Na+ K+ Cl+)



ATP: Adenosine triphosphate  

  • 3 phosphate groups attached to 5 carbon on ribose

  • 4 negative charges (carries a lot of charge in small space)

  • When binds to molecules it creates a surge of energy that opens the correlating channel

  • Allows for ions and bigger molecules to flow down the concentration gradient passively

  • In the case for passive transport it only move the protein so that is opens but the transport is still passive because the flow doesn’t require energy  

Pumps: proteins that transport molecules through the membrane 

  • Are specialized meaning they only transport their specific molecules and change shape 

  • Can be turned off or on 

  • Transports substance against or up the concentration gradient 

  • They make active transport possible 

  • Pump is energized by atp which makes it possible for the molecules to be pushed against their concentration gradient