vocab

phospholipids - is a molecule that composes the lipid membrane

• composed of a polar head

  • the head contains a negatively charged phosphate head

  • is hydrophilic, meaning it forms hydrogen bonds with water

• also has 2 hydrophobic, hydrocarbon tails

  • composed of non-polar, fatty acid chains

    • chains can be saturated or unsaturated

    • *remember if unsaturated then a kink will form

      • saturated fatty acids = high melting point = provides stability to membrane

      • unsaturated fatty acids = low melting point = provides fluidity to the membrane

simple diffusion - substances move from an area of high concentration to an area of low concentration

• the substances move down their concentration gradient

• the result will be equilibrium

• is also passive (doesn’t require input of energy)

integral proteins - a type of protein that’d embedded in the lipid bilayer & cannot be easily extracted from the membrane

• contain hydrophobic & hydrophilic regions

peripheral proteins - a type of protein located on the surface of the lipid bilayer

• only contains hydrophilic regions, no hydrophobic regions

osmosis - movement of water from an area of low solute concentration to an area of high solute concentration

• so water moves from outside of cell to inside of cell

• its kinda like diffusion

  • low solute concentration = high water concentration

  • high solute concentration = low water concentration

    • so water moves from high concentration to low concentration

• water movement continues until equilibrium is achieved (amount of solute is the same on both sides of membrane)

aquaporins - a type of integral protein that helps water move in & out of cell

• composed of 4 subunits which each hv a lining of specific hydrophilic side chains

• these allow water to move through the aquaporin, but dont allow ions

• are bidirectional (water can enter & exit cell)

• number of aquaporins is based on the amount of water that needs to move

facilitated diffusion - the movement of particles down their concentration gradient, with the help of carrier proteins & channel proteins

channel proteins - transmembrane proteins that form channels for the movement of polar molecules

• one example are ion channels

carrier proteins - transmembrane proteins that are involved in facilitated diffusion

• they will bind to the solute molecules (the molecules that’re being transported), undergo a conformational change & transfer molecules to other side of membrane

• are highly specific, as they hv sites specific for the solute or class of solute

• one example - glucose transporter (GLUT)

pump proteins - the transport protein involved in active transport

• uses ATP to move molecules against their concentration gradient (area of low concentration to area of high concentration)

active transport - the net movement of particles against their concentration gradient

• helps to:

  • take up essential nutrients

  • remove waste products from cell into extracellular fluid

  • maintain appropriate concentrations of ions in cells

• 2 types: direct & indirect

direct active transport - the energy released from an exergonic reaction (such as breakdown of ATP) is used to directly move molecules across the membrane

• these transport proteins are called ATPases or ATPase pumps

indirect active transport/cotransport - movement of one solute down its concentration gradient, causes another solute to move against its concentration gradient

• can check kognity for some examples (check b2.1.14-16)

glycolipids - covalent bonding of carbs to lipids results in glycolipids

• are amphipathic molecules

• typically located on exterior of cell membrane

• carbohydrate groups of this molecule are polar = extend into extracellular environment

• lipid component is non-polar = embedded in the membrane

glycoproteins - formed when there is covalent bonding between an oligosaccharide and protein molecules

• the carb groups often stick out into the extracellular environment

glycocalyx - a sticky layer formed by the carbohydrate groups of the glycolipids & glycoproteins that extend from the cell surface

• it aids in cell-to-cell recognition, cell adhesion, cell signalling & helps protect the cell’s surface

cholesterol - is an amphipathic steroid

• hydrophobic region is composed of 4 steroid rings & a hydrocarbon side chain

• hydrophilic region is polar hydroxyl group

• the hydrophilic & hydrophobic regions of the cholesterol interact with the hydrophilic & hydrophobic regions of the phospholipid molecule

  • this interaction helps hold the phospholipid molecule together

endocytosis - a moving process where substances are moved into cell

• cell membrane slowly invaginates & eventually engulfs the particles to be taken in

• the membrane then pinches to form a vesicle with the ingested particles

• can be phagocytosis or pinocytosis

phagocytosis - ingestion of large, solid particles

pinocytosis - ingestion of liquids

exocytosis - a moving process where substances are excreted out of the cell

• material that is removed will be enclosed in vesicles

• the vesicles move to plasma membrane & fuse with it, releasing the particles out of cell

ligand-gated channels - channels that open when a ligand binds to this channel

• when ligand is a neurotransmitter, this channel is called neurotransmitter-gated ion channels

sodium-potassium pump - are transmembrane pumps that’re found in cell membrane of all animals cells & involved in active transport

• generates energy through the hydrolysis of ATP

• this energy is used to power the movement of sodium & potassium ions against their concentration gradient

• also contributes to electrochemical gradient? higher concentration of K+ & lower concentration of NA+

• hv 3 binding sites for sodium & 2 for potassium

cell-adhesion molecules/CAMSs - crucial for cell adhesion

• they’re glycoproteins that organize the binding of cells to other cell, or to extracellular matrix

• different forms of CAM include: cadherins, integrins, selectins, & immunoglobin super family

• needed for formation of cell junctions

cell junctions - connect cells to each other

• important for enabling intracellular communication & transport

• play important roles in cell proliferation, cell migration & limit unregulated movement of substances between cells

• 3 main types: adhesive junctions, tight junctions & gap junctions

adhesive junctions - present in epithelial cells & cardiac cells

• often called anchoring junctions cuz they organize cell-cell adhesion in tissues to ensure structural stability & allow cells to withstand mechanical stress

tight junctions - are in epithelial cells

• form tight seal between 2 neighboring cells

  • this limits unregulated movement of molecules across barrier

gap junctions - present in multiple types of cells

• are intracellular channels that physically connect neighboring cells for movement of molecules

• aid in cell-cell transfer of small molecules