Biochemistry

1. Ions in Biological Systems

1.1. ions can consist of just one element or can be polyatomic

1.2. IONS

1.2.1. an atom that has lost or gained electrons to obtain a full valance shell

1.3. CATION

1.3.1. when an atom loses electrons and becomes positively charged

1.4. ANION

1.4.1. when an atom gains electrons and becomes negatively charged

1.5. ions are necessary for the function of living cells

2. Functional Groups

2.1. a group of atoms attached to a molecule that gives it certain physical and chemical characteristics

3. Structures and Shapes of Molecules

3.1. MOLECULAR FORMULA

3.1.1. shows the number of each type of atom in an element or compound

3.2. STRUCTURAL FORMULA

3.2.1. 2D shows the different atoms of a molecule are bonded together

3.3. SPACE-FILLING & BALL-AND-STICK MODLES

3.3.1. 3D molecular models

4. Lipids

4.1. LIPIDS

4.1.1. FUNCTIONS

4.1.1.1. long-term energy storage

4.1.1.2. insulation against heat loss

4.1.1.3. cushion major organs

4.1.1.4. structural components of cell membranes

4.1.2. biological molecules composed of carbon, hydrogen and oxygen atoms with many energy-rich carbon and hydrogen bonds

4.1.3. as a result of the large number of carbon and hydrogen bonds, lipids are hydrophobic and are not soluble in water

4.1.4. molecules can be identified as lipids if they have 2 or 3 hydrocarbon chains or the quadruple ring structure of steroids

4.2. TRIGLYCERIDES

4.2.1. FATTY ACID

4.2.1.1. number of carbon atoms and bonding between carbon atom varies

4.2.2. made from 3 fatty acids and 1 glycerol by a condensation reaction (3 ester linkages)

4.2.3. have 3 hydrocarbon tails

4.2.4. there are two parts to a fatty acid

4.2.4.1. carboxyl group that is acidic

4.2.4.2. an unbranched hydrocarbon chain

4.3. FATS

4.3.1. solid at room temperature because of saturated fatty acids

4.4. OILS

4.4.1. liquid at room temperature because of unsaturated fatty acids

4.5. SATURATED FATTY ACID

4.5.1. all of the carbon atoms in the chain are connected by single covalent bonds

4.6. UNSATURATED FATTY ACID

4.6.1. contain one or more double bonds between carbon atoms in the chain, more hydrogens could be added by removing double bonds

4.7. MONOSATURATED

4.7.1. only one double bond

4.8. POLYUNSATURATED

4.8.1. two or more double bonds

4.9. CIS UNSATURATED

4.9.1. hydrogen atoms are bonded to carbon atoms on the same side of the double bond

4.10. TRANS UNSATURATED

4.10.1. hydrogen atoms are bonded to carbon atoms on opposite sides of a double bond

4.11. ENERGY STORAGE

4.11.1. ADIPOSE TISSUE OR FAT

4.11.1.1. anatomical term for loose connective tissue composed of adioocytes

4.11.1.2. main role is to store energy in the form of fat

4.11.1.3. cushions and insulates the body

4.11.2. MASS ADVANTAGE OF LIPIDS

4.11.2.1. energy per gram released from lipids is 2x the amount released per gram from carbohydrates

4.11.2.2. same amount of energy adds 1/2 as much body mass of fat

4.11.2.3. lipids are 6x more efficient

4.11.3. fats or oils and glycogen and starch are both used by living organisms as stores of energy

4.11.4. the seeds of plants contains starch or oil

4.12. PHOSPHOLIPIDS

4.12.1. LIPID BILAYER

4.12.1.1. main component of cell membranes

4.12.1.2. made of phospholipids

4.12.2. similar to triglycerides

4.12.3. have 2 fatty acids and a phosphate group instead of the 3rd fatty acid

4.12.4. hydrophilic "head" is polar because of the phosphate group

4.12.5. hydrophobic "tail" is non-polar because of the C-C and C-H bonds

4.13. STEROID

4.13.1. CHOLESTEROL

4.13.1.1. structural component of the cell membrane in animals and the precursor of steroid hormones

4.13.2. TESTOSTERONE

4.13.2.1. responsible for secondary sexual characteristics in males

4.13.3. ESTROGEN

4.13.3.1. regulates sexual and reproductive functions in females

4.14. WAXES

4.14.1. lipids consisting of long carbon chains that are solid at room temperature

4.14.2. waxes are present on the skin, fur, feathers and exoskeleton of animals

5. Nucleic Acid

5.1. NUCLEOTIDES

5.1.1. DNA and RNA are the two types of nucleic acid

5.1.2. they are both polymers of subunits called nucleotides

5.1.3. consists of pentose sugar, phosphate group and a nitrogenous base

5.2. NITROGENOUS BASES

5.2.1. organic molecule with a nitrogen atom that has chemical properties of a base

5.2.2. the main biological function of a nitrogenous base is to bond nucleic acids together

5.2.3. non-polar

5.3. PHOSPHODIESTER BONDS

5.3.1. covalent bonds between the pentose sugar of one nucleotide and the phosphate of the next one

5.4. ANTIPARALLEL

5.4.1. strands run alongside each other but in the opposite direction, one 5' to 3' and the other 3' to 5'

5.5. HYDROGEN BONDS

5.5.1. two strands are linked by H-bonds between their bases

5.5.2. only two base pairs will form H-bonds: A-T and C-G

5.5.3. A and T form 2 H-bonds

5.5.4. C and G form 3 H-bonds

6. Biochemical Reactions

6.1. NEUTRALIZATION

6.1.1. NEUTRALIZATION REACTION

6.1.1.1. an acid reacts with a base to produce a water and a salt

6.1.1.2. double displacement reaction

6.1.1.3. acid + base -> water + salt

6.1.2. ACIDS

6.1.2.1. substances that release H+ ions when they dissolve in H2O

6.1.2.2. tend to increase the concentration of hydrogen ions in an aqueous solution

6.1.2.3. the greater the H+ ion concentration, the lower the pH will be

6.1.3. BASES

6.1.3.1. substances that releases OH- ions when they dissolve in H2O

6.1.3.2. increase the concentration of OH- ions

6.1.3.3. the higher the pH, the more basic the solution will be

6.1.4. PH SCALE

6.1.4.1. indicates the concentration of hydrogen ions in H2O

6.1.4.2. it ranges from 0 to 14

6.1.4.3. acids have a pH of less than 7

6.1.4.4. bases have a pH of greater than 7

6.1.4.5. neutral substances have a pH of 7

6.1.4.6. the concentration of H+ ions and OH- ions is equal at a pH of 7

6.2. OXIDATION-REDUCTION REACTIONS

6.2.1. REDOX-REACTIONS

6.2.1.1. based on electron transfer

6.2.1.2. the two reactions occur at the same time

6.2.2. OXIDATION

6.2.2.1. gain of O, loss of H, the loss of e-

6.2.3. REDUCTION

6.2.3.1. loss of O, gain of H, the gain of e-

6.3. CONDENSATION AND HYDROLYSIS

6.3.1. CONDENSATION

6.3.1.1. "dehydration synthesis"

6.3.1.2. monomers of biological molecules are joined together to form polymers

6.3.1.3. enzymes remove an OH group from a functional group on one molecule and an H atom from another molecule

6.3.1.4. an H2O molecule and a covalent bond between the two molecules is formed

6.3.2. HYDROLYSIS

6.3.2.1. the opposite of a condensation reaction

6.3.2.2. H2O is required to break the covalent bond between two monomers

6.3.2.3. enzymes add an H atom from a H2O to one monomer and an OH group to another monomer

6.3.2.4. the large molecule splits into two smaller molecules

7. Enzymes

7.1. CATALYSTS

7.1.1. ACTIVATION ENERGY

7.1.1.1. the energy that is needed to start a chemical reaction

7.1.2. CATALYSTS

7.1.2.1. lower activation energy

7.1.2.2. allow reaction to proceed more rapidly

7.1.3. ENZYMES

7.1.3.1. macromolecular biological catalysts

7.1.3.2. speed up chemical reactions without being changed themselves (enzymes aren't used up)

7.1.3.3. control the rate of the reactions of metabolism

7.2. SUBSTRATES AND ACTIVE SITES

7.2.1. SUBSTRATE

7.2.1.1. a reactant in an enzymes - catalysed reaction

7.2.1.2. enzymes are globular proteins

7.2.2. ACTIVE SITE

7.2.2.1. special region on the globular protein (enzyme)

7.2.3. SUBSTRATE-SPECIFIC

7.2.3.1. most enzymes will only bind to particular substrates, molecules other than the substrate so not fit or are not attracted so do not bind (-ase)

7.2.3.2. catalysis only occurs if the substrates are in a liquid, so their molecules are in continual random motion (Brownian motion) and there is a chance of collisions between the substrates and the active site on the surface of the enzyme

7.2.4. ENZYME-SUBSTRATE COMPLEX

7.2.4.1. the intermediate formed when a substrate molecule interacts with the active site of an enzyme

7.2.4.2. the slight alteration in shape facilitates the enzyme - catalyzed reaction

7.2.4.3. after the reaction is completed, the product(s) are released and the active site returns to its original shape

7.2.4.4. the products are released from the active site

7.2.5. INDUCED FIT

7.2.5.1. the active site undergoes a slight conformational change to accommodate the substrate

7.2.5.2. intermolecular bonds, such as H-bonds, form between the enzymes and the substrate

7.2.6. CATALYTIC CYCLE

7.2.6.1. multiple step reaction mechanism

7.2.6.2. initial step entails binding one or more reactants

7.2.6.3. final step is release of the product(s) and regeneration of the catalyst

7.2.7. COFACTORS

7.2.7.1. inorganic metal ions that assists an enzyme by accepting or donating atoms to the reactions

7.2.8. COENZYMES

7.2.8.1. a non-protein, small, organic molecule that assists an enzyme

7.3. FACTORS AFFECTING ENZYME ACTIVITY

7.3.1. TEMPERATURE

7.3.1.1. enzyme activity increases as temperature increases

7.3.1.2. collisions between substrate and active site happen more frequently at temperatures due to a faster molecular motion

7.3.1.3. this occurs until proteins are denatured and stop working

7.3.2. pH

7.3.2.1. enzyme activity is reduced as pH decreases/increases from the optimum because the conformation of the enzyme is altered more and more

7.3.2.2. below/above a certain pH the acidity/alkalinity denatures the enzyme

7.3.3. SUBSTRATE CONCENTRATION

7.3.3.1. at low substrate concentrations, enzyme activity increases steeply as substrate concentration increases because random collisions between substrate and active site happen more often

7.3.3.2. at high substrate concentration has little effect

7.4. ENZYME REGULATION

7.4.1. NORMAL ENZYME ACTION

7.4.1.1. substrate bonds to enzyme via the active site to form an enzyme-substrate complex

7.4.1.2. the shape and properties of the substrate and active site are complementary, resulting in enzyme-substrate specificity

7.4.2. COMPETITIVE INHIBITION

7.4.2.1. involves a molecule, other than the substrate, binding to the enzymes's active site

7.4.3. COMPETITIVE INHIBITOR

7.4.3.1. a molecule structurally and chemically similar to the substrate that blocks the active site and thus prevents the substrate from binding

7.4.4. NONCOMPETITIVE INHIBITION

7.4.4.1. involves a molecule binding to a site other than the active site (allosteric site)

7.4.5. ALLOSTERIC SITE

7.4.5.1. located elsewhere than the active site

7.4.5.2. a conformational change to the enzyme's active site occurs when an inhibitor binds to it

7.4.6. FEEDBACK INHIBITION

7.4.6.1. a common way biochemical pathways are regulated

7.4.6.2. the product of the last reaction of the pathway is a non-competitive inhibitor of the enzyme that catalyzes a reaction at the beginning of the pathway

7.4.7. ACTIVATOR

7.4.7.1. a molecule that binds to an allosteric site causing a conformational change in the enzyme

7.4.7.2. increases enzyme activity

8. Membrane Transport

8.1. DIFFUSION

8.1.1. FACTORS AFFECTING THE RATE OF DIFFUSION

8.1.1.1. Concentration gradient

8.1.1.2. surface area

8.1.1.3. length of diffusion path

8.2. SIMPLE & FACILITATED DIFFUSION

8.2.1. PARTIALLY PERMEABLE

8.2.1.1. membranes allow some substances to diffuse through but not other

8.2.2. SIMPLE DIFFUSION

8.2.2.1. diffusion of substances between the phospholipids molecules in the membrane

8.2.3. CHANNEL PROTEIN

8.2.3.1. cylindrical-shaped

8.2.3.2. allow ions and polar molecules to pass through them

8.2.3.3. the shape and size of the hole determines what type of substance can pass through it

8.2.4. CARRIER PROTEINS

8.2.4.1. bind to specific and undergo a change in shape as they transport these molecules across the cell membrane

8.3. SOLUTION

8.3.1. SOLUTE

8.3.1.1. a substance that is dissolved in a liquid (solvent)

8.3.2. SOLVENT

8.3.2.1. a liquid in which particles dissolve

8.3.3. SOLUTION

8.3.3.1. a mixture of solute and solvent

8.4. MOVEMENT OF WATER

8.4.1. OSMOSIS

8.4.1.1. the movement of water through a selectively permeable membrane from the side of high water concentration to low water concentration

8.4.1.2. occurs until equilibrium is achieved

8.4.2. AQUAPORINS

8.4.2.1. transmembrane proteins that facilitate diffusion of H2O

8.5. OSMOLARITY

8.5.1. ISOTONIC

8.5.1.1. osmolarity outside the cell equals molarity inside the cell

8.5.1.2. there is no net movement of water

8.5.1.3. cell maintains it's shape

8.5.2. HYPOTONIC

8.5.2.1. osmolarity outside the cell less than inside the cell

8.5.2.2. water travels into cell/tissue by osmosis

8.5.2.3. pressure inside the cell rises

8.5.3. HYPERTONIC

8.5.3.1. osmolarity outside the cell greater than osmolarity inside the cell

8.5.3.2. water travels out of cell/tissue by osmosis

8.5.3.3. pressure inside cell drops

8.5.4. PLASMOLYSIS

8.5.4.1. shrinking of cytoplasm in plant cells due to water loss, membrane retracts from cell wall

8.5.5. CRENATION

8.5.5.1. shrinking in animal cells due to water loss

9. Active Transport and Membrane Assisted Transport

9.1. PRIMARY ACTIVE TRANSPORT

9.1.1. PROTEIN PUMPS

9.1.1.1. a substance that is dissolved in a liquid (solvent)

9.2. SECONDARY ACTIVE TRANSPORT

9.2.1. SOLVENT

9.2.1.1. a liquid in which particles dissolve

10. Chemistry in Living Systems

10.1. ELEMENTS

10.1.1. pure substances that cannot be broken down into simpler substances

10.1.2. 6 important elements form the building blocks of life

10.1.2.1. carbon

10.1.2.2. oxygen

10.1.2.3. hydrogen

10.1.2.4. nitrogen

10.1.2.5. phosphorus

10.1.2.6. sulfur

10.2. ATOMS

10.2.1. the smallest particles of elements that can exist by themselves

10.2.2. all atoms of an element have the same number of protons and electrons

10.3. ISOTOPES

10.3.1. atoms of an element that have the same number of protons but differ in mass because they have different numbers of neurons

10.4. RADIOISOTOPES

10.4.1. isotopes that are unstable and emit radiation as their nucleus decays

11. Studying The Interactions of Molecules

11.1. BIOCHEMISTRY

11.1.1. the study of the properties and interactions of biologically important molecules

11.2. ORGANIC MOLECULES

11.2.1. carbon-based molecules, carbon atoms are usually bonded to each other and to hydrogen

11.3. INTRAMOLECULAR FORCES

11.3.1. chemical bonds, forces occurring between atoms within a molecule

11.3.2. covalent bonds are bonds within molecules that form when non-metal atoms share their valence electrons

11.4. ELECTRONEGATIVITY

11.4.1. refers to an atom's ability to attract electrons in a chemical bond

11.4.2. atoms with high EN attract electrons much more strongly than atoms with low EN

11.5. POLAR MOLECULES

11.5.1. have unequal sharing of the electrons in the covalent bond results in regions of partial positive charge and partial negative charge

11.5.2. ex) water

11.6. NON-POLAR MOLECULES

11.6.1. have equal sharing of electrons the covalent bond because the atoms have similar electronegativities

11.6.2. the polarity of biological molecules affects their nature and function in a cell

11.7. INTERMOLECULAR FORCES

11.7.1. forces between different molecules or between different parts of the same biological molecule

11.7.2. weaker than intramolecular forces

11.7.3. easily broken

11.7.4. London dispersion forces. hydrogen bonding, dipole-dipole

11.8. HYDROGEN BONDS

11.8.1. can form between the slightly positive hydrogen atoms of one water molecule and the slightly negative oxygen atom of another water molecule

11.8.2. weaker than covalent intramolecular bonds but collectively very strong

11.8.3. common in large biological molecules such as DNA

11.8.4. play an important role in 3D shape and function

11.9. HYDROPHILIC

11.9.1. substances that are attractive to water

11.9.2. form intermolecular bonds with water

11.9.3. ionic commands and polar molecules

11.9.4. many hydrophilic substances dissolve in water because their ions or molecules are more attracted to water than each other

11.10. HYDROPHOBIC

11.10.1. substances aren't hydrophilic

11.10.2. does not mean it is repelled by water

11.10.3. water molecules are more strongly attracted to each other than to the non-polar molecules of hydrophobic substances

11.10.4. insoluble in water

12. Carbohydrates

12.1. BIOLOGICALLY IMPORTANT MOLECULES

12.1.1. MACROMOLECULES

12.1.1.1. large molecules composed of repeating subunits that are bonded together covalently

12.1.1.2. carbohydrates, proteins, lipids and nucleic acids

12.1.2. POLYMERS

12.1.2.1. long molecules that are made up of smaller individual subunits linked together

12.1.3. MONOMERS

12.1.3.1. subunits

12.1.4. CARBOHYDRATE

12.1.4.1. hydrates of carbon

12.1.4.2. a molecule containing carbon, hydrogen and oxygen

12.1.4.3. usually with a hydrogen-oxygen atom ratio of 2:1

12.1.4.4. primarily used by living organisms as a source of energy

12.2. MONOSACCHARIDES

12.2.1. ISOMER

12.2.1.1. molecules with the same number and type of atoms but different structural arrangements

12.2.1.2. the molecules shown were D-ribose and D-glucose

12.2.1.3. the "D" indicates the right-handed versions

12.2.1.4. left and right-handed versions can exist but living organisms use only right-handed versions

12.2.2. simple sugar

12.2.3. consist of a single sub-unit (monomer)

12.2.4. contain only atoms of carbon, hydrogen and oxygen in the ratio 1:2:1

12.3. DISACCHARIDES

12.3.1. double sugar

12.3.2. pairs of monosaccharides are linked together by condensation

12.3.3. glucose + glucose -> maltose + H2O

12.3.4. glucose + galactose -> lactose + H2O

12.3.5. glucose + fructose -> sucrose + H2O

12.4. POLYSACCHARIDES

12.4.1. GLYCOSIDIC BOND OR LINKAGE

12.4.1.1. a type of covalent bond that joined a carbohydrate molecule to another group, which may or may not be another carbohydrate

12.4.2. STARCH

12.4.2.1. a polymer of a D-glucose

12.4.2.2. all of the glucose subunits in the same orientation

12.4.2.3. gives the polymer a helical shape

12.4.3. AMYLOSE

12.4.3.1. has only 1,4 linkages, unbranched

12.4.4. AMYCOPECTIN

12.4.4.1. has some 1,6 linkages, so branched

12.4.4.2. starch is used by plants to store glucose in an insoluble form that does not cause osmotic problems

12.4.4.3. by making the molecule branched, it is possible to load or unload glucose more rapidly as there are more points on a starch molecule to which glucose can be added or detached

12.4.5. complex carbohydrte

12.4.6. composed of long chains of monosaccharides

12.4.7. insoluble in water

12.4.8. the polysaccharides starch, cellulose and glycogen are all composed of glucose

12.4.9. CELLULOSE

12.4.9.1. unbranched polymer of B-D-glucose

12.4.9.2. the orientation of the glucose units alternatives

12.4.9.3. makes the polymer straight rather than curved

12.4.10. MICROFIBRILS

12.4.10.1. groups of cellulose molecules arranged in parallel with H-bond forming cross-links

12.4.10.2. have enormous tensile strength

12.4.10.3. basis of plant cell walls

12.4.11. GLYCOGEN

12.4.11.1. similar in structure to amylopectin

12.4.11.2. branched polymer of a-D-glucose

12.4.11.3. there are more 1,6 linkages than in amylopectin, so it is more branched

12.4.11.4. used by mammals to store glucose in liver and muscle cells

12.4.11.5. large amounts of glycogen can be stored because it is insoluble whereas if glucose was stored, it would cause water to leave the cells by osmosis and there would be danger of them bursting

13. Proteins

13.1. AMINO ACIDS

13.1.1. organic compounds containing amine and carboxyl functional groups, along with a side chain

13.1.2. monomer of protein

13.2. R-GROUP

13.2.1. variable group of amino acids

13.2.2. amino acids with hundreds of different R-groups could be produced in the laboratory

13.2.3. ribosomes are able to manufacture amino acids with 20 R-groups

13.2.4. an R-group can be as simple as a hydrogen or as complicated as a multiple ringed structure

13.3. POLYPEPTIDES

13.3.1. PEPTIDE BONDS

13.3.1.1. covalent bond formed in a condensation reaction between the amine group of one amino acid and the carboxyl group of the next

13.3.2. DIPEPTIDE

13.3.2.1. a molecule consisting of two amino acids linked together

13.3.3. POLYPEPTIDE

13.3.3.1. consists of many amino acids linked by peptide bonds, unbranched chain of amino acids

13.3.4. PEPTIDE

13.3.4.1. chain of fewer than 40 amino acids

13.4. PROTEIN STRUCTURE

13.4.1. PRIMARY STRUCTURE

13.4.1.1. linear sequence of HAs joined together by peptide bonds

13.4.2. SECONDARY STRUCTURE

13.4.2.1. H-bonds occur between the C-O of one AA and the N-H of a nearby AA in the polypeptide chain

13.4.3. TERTIARY STRUCTURE

13.4.3.1. primarily due to R-goup interactions such as ionic bonds, covalent bonds and H-bonds

13.4.3.2. very important to a protein's function

13.4.4. QUATERMARY STRUCTURE

13.4.4.1. fourth level of organization in proteins consisting of two or more polypeptide chains together in a specific arrangement

13.5. FUNCTIONS

13.5.1. STRUCTURAL PROTEINS

13.5.1.1. bones, tendons, skin, hair, nails, claws, beaks

13.5.2. TRANSPORT PROTEINS

13.5.2.1. help move molecules throughout the body and ions across the cell membrane

13.5.3. ENZYMES

13.5.3.1. have active sites that catalyst reactions

13.5.4. PIGMENTS

13.5.4.1. colour sensitive, absorb light waves of particular wavelengths/frequencies

13.5.5. HORMONES

13.5.5.1. travel dissolved in blood, binds specifically and reversibly to receptors in the membranes of body cells causing them to perform an action

13.5.6. ANTIBODIES

13.5.6.1. bind to antigen on specific cell (they regard as "foreign") to attack them

13.5.6.2. allows specific immunity

14. Cell Membrane

14.1. MODELS OF MEMBRANE STRUCTURE

14.1.1. THE DAVSON-DANIELLI MODEL

14.1.1.1. bilayer of phospholipids in the centre of the membrane

14.1.1.2. layers of protein on either side

14.1.2. SJ SINAER AND NICOLSON MODEL

14.1.2.1. current model

14.1.3. FLUID-MOSAIC MODEL

14.1.3.1. phospholipid bilayer (fluid) with embedded proteins and substances such as cholesterol (mosaic)

14.2. PHOSPHOLIPIDS

14.2.1. HYDROPHILIC

14.2.1.1. attracted to water, polar molecules forming ionic or hydrogen bonds with water molecules

14.2.2. HYDROPHOBIC

14.2.2.1. not attracted to water, non-polar molecules that repel water molecules

14.2.3. PHOSPHOLIPIDS

14.2.3.1. consist of two hydrophobic fatty acid "tails" and hydrophilic "heads"

14.2.4. AMPHIPATHIC

14.2.4.1. part of the molecule is hydrophilic and part is hydrophobic

14.3. MEMBRANE PROTEINS

14.3.1. INTEGRAL

14.3.1.1. permanently embedded

14.3.2. MONOTOPIC

14.3.2.1. penetrating the surface

14.3.3. PERIPHERAL

14.3.3.1. have a temporary association with the membrane

14.3.3.2. either attach to integral membrane proteins or penetrate the peripheral regions of the membrane bilayer

14.3.3.3. membrane proteins are diverse in terms of structure, function and position in the membrane

14.3.4. TRANSPORT

14.3.4.1. protein channels (facilitated) and protein pumps (active)

14.3.5. RECEPTORS

14.3.5.1. peptide-based hormones (insulin, glucagon, etc.)

14.3.6. ANCHORAGE

14.3.6.1. cytoskeleton attachment and extracellular matrix

14.3.7. CELL RECOGNITION

14.3.7.1. glycoproteins (carb chains), antigens

14.3.8. INTERCELLULAR JOININGS

14.3.8.1. tight junction (animal) and plasmodesmata (plants)

14.3.9. ENZYME ACTIVITY

14.3.9.1. metabolic pathways (electron transport chain)

14.4. CHOLESTEROL IN MEMBRANES

14.4.1. CHOLESTEROL

14.4.1.1. hydroxyl group makes the head polar and hydrophilic

14.4.1.2. carbon rings - it is not classed as a fat or an oil

14.4.1.3. non-polar tail

14.4.2. MEMBRANE FLUIDITY

14.4.2.1. the hydrophobic hydrocarbon tails usually behave as a liquid

14.4.2.2. hydrophilic phosphate heads act more like a solid

14.4.2.3. though it is difficult to determine whether the membrane is truly either a solid or liquid it can definitely be said to be a fluid

14.5. ENDOCYTOSIS & EXOCYTOSIS

14.5.1. SOLUTION

14.5.1.1. a mixture of solute and solvent