Biology Exam Review

Unit 1: Biochemistry

Functional Groups

1. Hydroxyl (Alcohols)

2. Carbonyl (Aldehydes or Ketones)

3. Carboxyl (Carboxylic acid)

4. Amino (Amines)

5. Sulfhydryl (Thiols)

6. Phosphate (Organic Phosphates)

Chemical Bonding

Hydrogen Bonding

• Water forms weak bonds with each other (Making it polar)

• Due to oxygen being positively charged, it attracts more electrons that it shares with Hydrogen

• Electrons spend more time near oxygen

• Hydrogen Bonding involves bonds to highly electromagnetive atoms

Covalent bonds: Electrons being shared between two atoms

Ionic Bonds: Positively charged ion bonds with a negatively charged ion

Intramolecular forces: Ionic or covalent

Intermolecular forces

• Dipole-Dipole: the positive end of one polar molecule and the negative end of another attracts each other

• London Dispersion: Electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles

Dehydration vs. Hydrolysis

Dehydration: The removal of a water molecule when two molecules join

Hydrolysis: The splitting of a large molecule by adding water

Macromolecules

Carbohydrates(C₆H₁₂O₆)

• Made of Carbon, Hydrogen, and Oxygen

• Used for short term energy storage and cellular respiration

• Monosaccharides (Fructose, Glucose, Galactose): Monomer containing a carbonyl and multiple hydroxyls

• If the carbonyl is at the end, it is an aldose. If not, it is a ketose

• Dissacharides: two monosaccharides formed by a glycosidic linkeage

  • E.g. Glucose + Glucose = Maltose

• Polysaccharide: polymer of many monosaccharides

  • Starch: Energy store in plants

  • Glycogen: energy store in the liver and muscles

  • Cellulose: structural components of plant cell walls

  • Chitin: used for exoskeleton

Lipids

• Made of Carbon, Hydrogen, and Oxygen

• Used for long term energy storage, insulation, organ cushoning, and nerve impulses

• Glycerol: three carbon skeleton with a hydroxyl attached

• Fatty acid: Carboxyl with a long hydrocarbon tail

• Triglyceride: three Fatty acid’s and one glycerol joined together by an ester linkage

• Saturated fats: has no carbon-carbon double bond, solid at room temperature, found mostly in animals

• Unsaturated fats: Contains one or morecarbon-carbon double bond, liquid at room temperature, found mostly in plants

Proteins

Functions

• Enzymes (catabolyze metabolic reactions)

• Antibodies and bloodclotting

• Motion

• Component of the cell membrane

• Structural support

• Transport

• Made of the same sets of 20 monomers (Amino acids)

• Polymer is polypeptides

• Made of a hydrogen, A carboxyl group, an amino group and an R chain

• Polypeptides are made through a Peptide Bond via dehydration

Primary Structure: long sequence of amino acids Secondary structure: Amino acids form hydrogen bonds along the backbones

Tertiary Structure: R group to R group bonds (and R group to backbone bonds)

Quaternary Structure: Aggregation of two or more polypeptides

Denature: the unfolding of proteins due to extreme conditions (temperature and pH)

Nucleic Acids (RNA and DNA)

• Directs growth and development of organisms

• Monomer is nucleotides

Nucleotide components

• Pyrimidines: single ringed structures (Cytosine, Thymine, and Uracil)

• Purines: double ringed structures (Adenine and Guanine)

• Pentose Sugar: deoxyribose (DNA) or ribose (RNA)

• Phosphate group

• The connection of the sugars and phosphate creates a polynucleotide via phosphodiester linkage

• Adenine bonds with Thymine or Uracil, Guanine bonds with Cytosine

Enzymes

• Speeds up reactions and acts as a Catalyst (Chemical agent that changes the rate of reactions)

Functions

• Lowers the activation energy for a reaction to occur

• Provide a favourable space for the breaking/forming of bonds

• Promotes the conversion of reactions into products

• Enzymes binds to susbtrates at an active site, forming an enzyme-substrate complex

Lock and Key model: outdated hypothesis determining how enzymes are locks that fit into a specific substrate (key)

Induced fit hypothesis: Active site of an enzyme is a pocket where a substrate fits (Determined by the four protein structures)

Factors affecting enzymes

1. Enzyme and Substrate Concentration

   • A low substrate concentration creates a faster conversion of products due to the excessive enzyme capacity

     • Vice-versa will create a slower conversion as enzymes are occupied

   • Reactions will speed up with there are more enzymes added

2. Enzyme Inhibitors

   • Inhibitors competes with subtrates for an active site, making them not converted into products

3. Allosteric Regulation

   • Inhibitor binds to an allosteric site and changes the shape of an enzyme

   • Changes the activity of the enzyme

4. Temperature and pH

   • Enzymes work at a specific temperature and pH range. Too much heat can either speed up collision or weaken bonds (or denature)

Cell Transport

Isotonic: equal amounts of water into and out of the cell

Hypotonic: net movement of water into the cell (Causes cells to burst aka. Lysis)

Hypertonic: net movement of water out of the cell (Causes the cells to shrink aka. Plasmolysis)

Active Transport: movement of substances against the concentration gradient (Low concentration to High concentration)

• Achieved through a cell membrane protein (E.g. Sodium/Potassium Pump)

Diffusion: movement from a high concentration to a low concentration area

Pinocytosis: cells intake a small drop of ECF

Phagocytosis: cells intake large molecules and organic matter

Endocytosis:

Plasma Membrane

Proteins and Functions

• Integral/Intrinsic: provides structural support, recognizes cells through binding to protein sites of other cells, signaling, and transport

• Peripheral: connected to other proteins

• Glycoproteins: Enters and communicates with the cell

Unit 2: Metabolism

Part 1: Cellular Respiration

Structure of mitochondria

• Matrix: where cellular respiration occurs (Pyruvate Oxidation, Krebs Cycle)

• Outer and inner member membrane(Electron transport chain)

• Intermembrane space

Oxidation vs. Reduction

• Oxidation: Atom loses an electron

• Reduction: Atom gains an electron

• Endothermic: absorption of heat energy

• Exothermic: release of heat energy

• Endergonic: absorption of energy (Free energy is positive and nonspontaneous)

• Exothermic: release of energy (Free energy is negative and spontaneous)

Glycolysis

• Breaking down glucose into 2 pyruvate molecules

• Net Yield: 2 ATP, 2 NADH

1. Hexokinase used towards glucose makes Glucose-6-phosphate

2. Phosphoglucoisomerase used towards G6P makes Fructose-6-phosphate

3. Phosphofructokinase used towards F6P makes Fructose-1, 6-Bisphosphate

4. Aldolase is used to make Dihydroxyacetone Phosphate

5. Isomerases is used to make Glyceraldehyde-3-Phosphate

6. Triose Phosphate Dehydrogenase is used to make 1, 3-Bisphosphoglycerate

7. Phosphoglycerokinase is used to make 3-Phosphoglycerate

8. Phosphoglyceromutase is used to make 2-Phosphoglycerate

9. Enolase is used to make Phosphoenol pyruvate

10. Pyruvate Kinase is used to make Pyruvate

Pyruvate Oxidation

• Pyruvate turns into acetyl-CoA

• Net Yield: 2 NADH

Krebs Cycle

• The production of ATP, NADH, and FADH₂ with acetyl-CoA

• Net Yield: 2 ATP, 6 NADH, 2 FADH₂

1. Citrate synthetase is used to make Citrate

2. Aconitase is used to make Isocitrate

3. Isocitrate dehydrogenase is used to make Alpha-ketogluterate

4. Alpha-Ketogluterate dehydrogenase is used to make Succinyl-CoA

5. Succinyl-CoA synthetase is used to make Succinate

6. Succinate dehydrogenase is used to make Fumarate

7. Fumarase is used to make Malate

8. Malate Dehydrogenase is used to make Oxaloacetate

Electron Transport Chain

• Series of transport proteins and electron carriers forming H₂O when oxidized

• Net Yield: 2 NADH from glycolysis makes 4-6 ATP

  • 2 NADH from Pyruvate Oxidation makes 6 ATP

  • 6 NADH and 2 FADH₂ makes 22 ATP

  • Total: 32-36 ATP

ETC Proteins/Complexes: NADH Dehydrogenase Complex, Ubiquinone, Cytochrome b-c complex, Cytochrome c, cytochrome oxidase complex, ATP Synthase

• NADH and FADH₂ passes their electrons to complexes

  • NADH to NADH Dehydrogenase Complex, FADH₂ to Ubiquinone

• Final electroon acceptor is Oxygen (2H⁺ + 2 electrons + ½ O₂ = H₂O)

• ETC is Exergonic, which pumps Hydrogen from matrix to intermembrane space and gets transported through each complex

• ATP Synthase: makes ATP from ADP and P_i

• Chemiosmosis: using stored energy of an electrochemical gradient and the ATP Synthetase to generate ATP

Fermentation

• Generation of some ATP without oxygen

• Alcohol: pyruvate is converted to ethanol (2 Pyruvates = 2 acetaldehydes + 2 CO₂)

  • (2 Acetaldehydes + 2 NADH + 2 H+ = 2 Ethanol + 2 NAD+)

• Lactic acid: pyruvate is reduce to lactate (2 Pyruvates + 2 NADH = 2 Lactate + 2 NAD)

Part 2: Photosynthesis

• Pigments: substances that absorb light (photons)

• The colour we see is NOT absorbed, but reflected by the pigment

• Examples: Chlorophyll a (P680 and P700)

• Light Harvesting Complex: consist of various pigment molecules that are bound to proteins

Noncyclic Electron Flow

• Energy transfer through photosystems

• Step 1: Photosystem II absorbs a photon of light striking a pigment molecule. It boosts its electrons to a higher energy level. Electron reaches P680 making it excited and transfers to the primary electron acceptor

• Step 2: Z proteins splits water to release O₂

• Step 3: Excited electron passes through an Electron Transport Chain (Plastoquinone, Cytochrome complex, and plastocyanin)

• Step 4: Electron falls to a lower energy level for the synthesis of ATP

  • This is noncyclic phosphorylation

• Step 5: photon strikes Photosystem I pigment P700, boosting the electron level

• Step 6: Primary Electron Acceptor passes electron down to the second ETC (Ferredoxin and NADP Reductase)

Cyclic Electron Flow

• When ferredoxin donates back an electron to plastoquinone (repeats continually by moving through the membrane)

• Occurs when a plant has enough NADPH

• Energy from light converts to ATP without the oxidation of H₂O or reduction of NADP+ to NADPH

Calvin Cycle

• ATP and NADPH converts CO₂ to sugar

• Production of Glyceraldehyde-3-phosphate (G3P)

  • Calvin cycle must occur three times to produce G3P

• 6 CO₂+Glucose

1. Carbon Fixation: CO₂ attaches to Rubilose Bisphosphate (RuBP) by the catalyzation from rubisco

   • The product is too unstable and splits in half to make two molecules of 3-phosphoglycerate

2. Reduction: Each 3-phosphoglycerate recieves a phosphate group to form 1, 3-Bisphosphoglycerate

   • Product is reduced by NADPH to make G3P

3. Regeneration: Carbon skeletons of 5 G3P are rearranged to 3 RuBP

C4 Plants

• Physically separated Calvin cycle and light reactions, O₂ is not exposed by rubisco

• CO₂ is limited, C4 Cycle feeds CO₂ to rubisco

CAM Plants

• Opens stomata at night, allowing CO₂ to enter and minimize H₂O loss

• Converts malate which is stored till day

Unit 3: Molecular Genetics

Gene: Functional and physical unit of heredity passed from parent to offspring

• Carries a code (information) for making a specific protein

Allele: variant form of a gene

DNA Structure

• In a form of a double helix (Found by Rosalind Franklin)

• Contains a phosphate group, deoxyribose sugars, and a nitrogenous base

• Phosphate is attached to the sugar of one nucleotide, creating a backbone of alternating Phosphate and sugars

• Nucleotide consists of purines (Adenine and Guanine), and pyrimidines (Cytosine, Thymine, Uracil)

• Complementary Base Pairs: Adenine makes two hydrogen bonds with Thymine, Guanine makes three hydrogen bonds with Cytosine

RNA Structure

• Single Strand

• Phosphate group, ribose sugar, nitrogenous bases

DNA Replication

• Semiconservative process where a daughter cell gets a copy of a genome

• Begins at the origin of replication, where short stretches of DNA have a specific sequence that proteins recognize

• Replication bubble: made when proteins bind to sites in DNA

• Replication fork: Y-shaped region at the end of the Replication Bubble

Enzymes Used (also in order of steps)

1. Helicase: untwists the double helix model

2. Single-strand binding proteins: binds to unpaired DNA

3. Topoisomerase: relieves strand by breaking and rejoining strand

4. RNA Primer: short stretch of RNA nucleotides made by primase

5. DNA Polymerase III: adds DNA nucleotides to the RNA primer

6. DNA Polymerase I: replaces RNA nucleotides with DNA nucleotides

7. Ligase: forms a bond between DNA fragments to previous fragments (glue)

8. Okazaki Fragments: discontinuous segments

New DNA Strand Synthesis

• DNA Polymerase III adds DNA nucleotides that comes from a Nucleoside Triphosphate

• Hydrolysis of pyrophosphate (molecule released when nucleotide is added) becomes two P_i

Anti-parallel Elongation

• DNA Polymerase is only able to add nucleotides in the 3’ end

• Strand elongates only in the 5’-3’ direction

Leading Strand

• DNA Polymerase III adds nucleotides to the 3’ end of the growing strand

• Synthesizes a complementary strand by elongating in the 5’-3’ end

Lagging Strand

• DNA Polymerase III works away from the replication fork

• Strand is discontinuous and occurs in segments (Okazaki fragments)

Proofreading and Repairing DNA

• Base pair mistakes occurs at a rate of 1/10,000 base pairs

• DNA Polymerase proofreads and removes wrong nucleotides

• Nucleoside incision repair: the enzyme nuclease cuts a segment of a damaged strand

• DNA Damage: occurs from reactive processes (X-rays, UV Light, Emissions)

• Mismatch repair: enzymes fix incorrectly paired nucleotides

Protein Synthesis

Transcription

• Turning DNA into RNA in the nucleus

1. Initiation

   • RNA Polymerase unwinds DNA and binds at the prometer (a sequence of DNA at the start of the gene)

   • TATA Box: Section of DNA with a high percentage of Adenine and Thymine. Enables the binding of RNA Polymerase (Two hydrogen bonds needed to open)

2. Elongation

   • RNA Polymerase adds nucleotides to the 3’ end of the growing strand

   • RNA is made using the 3’-5’ strand (the template strand), while the 5’-3’ strand is the coding strand

3. Termination

   • RNA Polymerase recognizes a termination sequence (A protein-coding gene that ends transcription)

   • Can be a string of Adenines that are transcribed to Uracils in RNA

Post-transcriptional Modifications

• Newly transcribed RNA is now pre-RNA and is vulnerable to be attacked by RNA digesting enzymes

• Poly(a) tail: modification where pre-RBA acquires a chain of 50-250 adenines to the 3’ end by the help of poly-A-polymerase

• 5’ cap: modifications where pre-RNA acquires 7 Guanines at the 5’ end to prevent itself from hydrolytic enzymes

• Exons (Coding regions) and Introns (non-coding regions) are transcribed but makes dysfunctional. Introns are deleted by RNA splicing

• Spliceosome: complex formed between pre-mRNA and small nuclear ribonucleproteins that binds to introns and removes them

Translation

• Turning mRNA into a polyeptide in the ribosome with tRNA

• Codon: 3 base pairs for an amino acid in the 5’-3’ order

tRNA: small RNAs that are 70-90 nucleotides long

• Picks up amino acids in the cystol and deposits in the ribosome

• Structure: Has regions that base pair with themselves forming four double-helical segments

  • Contains an anticodon at the tip (3 nucleotide segment that pairs with a codon in mRNA)

    • Example: mRNA codon: 5’ AAG tRNA codon: 3’ UUC

Wobble Hypothesis: pairing of the anticodon with the first two nucleotides are precise, but the third has flexibility and codes for the same amino acid

• Aminoacylation: the addition of an amino acid to tRNA

  • Catalyzed by 20 aminoacyl-tRNAs that drives its energy to form a peptide bond

Ribosomes: made up of rRNA (ribosomal RNA) and ribosomal proteins

• Facilitate the coupling of tRNA anticodons with mRNA codons

Binding sites to tRNA molecules

• A-site: aminoacyl site holds the incoming aminoacyl-tRNA that is carrying the next amino acid to the growing polypeptide chain

• P-site: Peptidyl site holds the tRNA that is growing the polypeptide chain

• E-site: Exit site is where tRNA leaves the ribosome

3 Stages of Transcription

1. Initiation

   • Initiator tRNA has the anticodon specific to the codon AUG (start codon). The tRNA carries methionine (now called Met-tRNA)

   • Met-tRNA forms a complex that binds to the mRNA at the 5’ cap

   • Large ribosomal subunit binds to the mRNA and met-tRNA is automatically in the P-site

2. Elongation

   • Step 1: Hydrogen bonding forms between the mRNA codon under the A-site at the anticodon carrying the amino acid

   • Step 2: Second tRNA attaches to the codon at the A-site of the ribosome

     • Methionine is cut off from the P-site tRNA and attached to the tRNA in the A-site

     • Growing polypeptide chain is attached to the tRNA in the A-site

   • Step 3: Ribosomes moves to the next codon on the mRNA (tRNA moves from the A-site to the P-site, Steps repeat)

3. Termination

   • Ribosome reaches a stop codon (UAA, UAG, UGA) to stop elongation

   • A protein release factor binds to the A-site to release the newly formed polypeptide

Regulating Gene Expression

Lac Operon: regulates lactose metabolism

Trp Operon: regulates tryptophan production

• Both are controlled by negative feedback loops

Lac Operon

• Consists of a promoter, an operator(controls transcription), and coding regions for enzymes

• Lac repressor is a gene upstream that controls the production of lactose-metabolizing proteins by sensing lactose levels

• Lac repressor binds to the operator when lactose is absent, making it active. This stops RNA Polymerase from attaching to the promoter that blocks the production of lactose metabolizing enzymes

Trp Operon

• Same structures as Lac Operon (promoter, operator, coding regions)

• When tryptophan is absent, the repressor is inactive and allows RNA Polymerase to bind to the promoter, which transcribes the genes to make tryptophan

• When tryptophan is present, tryptophan acts as a corepressor and activates the repressor proteins (binds to promoter and stops RNA pol from transcribing genes)

Genetic Mutations

Causes of Mutations

• Induced: chemicals and radiation

• Spontaneous: Inaccurate DNA Replication

Small scale mutations

Point Mutations

1. Substitution: one base pair is replaced by another

2. Insertion: A single base pair is added

3. Deletion: A single base pair is removed

4. Inversion: Two adjacent base pairs are swapped

Single Nucleotide Polymorphisms (SNPs): Differences in DNA caused by Point mutations

1. Missense mutations: changes in base pairs that make a different amino acid

   • Protein ends up either dysfunctional, function different, or beneficial

2. Nonsense mutations: base pair change results in a premature stop codon

   • Protein is incomplete and non-functional

3. Silent mutations: base pair change that doesn’t alter the function of the gene

   • DNA codes for the same amino acid, protein is unchanged

4. Frameshift mutations: insertion or deletion of nucleotides

   • Affects all amino acids leading to multiple missense or nonsense mutations

Large Scale Mutations

• Gene duplication: one or more genes copied to multiple regions of a chromosome

• Large scale deletion: Entire coding regions of DNA is removed

• Translocation: genes move from one chromosome to another

• Inversion: portion of DNA reverses direction within the genome

• Trinucleotide repeats: repeating sequences in the genome (E.x CAG CAG CAG)

Unit 4: Homeostasis

• The maintenance of a constant environment in the body

• Body maintains 1. Temperature 2. Water levels 3. Glucose concentration 4. pH levels

Negative Feedback systems

• Homeostatic control system with three components

• Receptor: detects a change in the body

• Control center: processes the information from the receptor

• Effector: creates a response

ADH Feedback mechanism: Increases blood osmotic pressure when there’s an increase of solutes in blood and decrease of water concentration

• Osmoreceptors: located in the hypothalamus that detects a change in blood osmotic pressure

• Control Center: hypothalamus shrinks due to water moving out of the cell. Sends nerves to the pituitary gland to release ADH in the blood stream

• Effector: Kidneys reabsorb water to dilute solute concentration, making more concentrated urine

Nervous System

Nerve signaling

Membrane Potential: electrical gradient across the membrane

• Anions (-): Concentrated inside the cell

  • Proteins, amino acids, sulfate inside, Cl outside

• Cations (+): Concentrated outside of the cell

  • K+ inside, Na+ outside

• Resting potential: -70mV

• Action potential: All or Nothing depolarization thats triggered if the potential reaches -55mV

Chemical Synapse

1. Depolarization: the action potential depolarizes the plasma membrane at the synaptic terminal

2. Ca2+ influx: Voltage gated Ca2+ channels open to allow Ca2+ into the presynaptic terminal

3. Vesicle fusion: The high Ca2+ concentration causes synaptic vesicles to fuse with the presynaptic membrane

4. Neurotransmitter release: Vesicles release neurotransmitters into the synaptic cleft

5. Receptor Binding: Neurotransmitters bind to receptors on ligand-gated ion channels on the postsynaptic membrane

Neuron Structure

• Dendrites: ends that receive information and conducts nerve impulses

• Cell body: contains the nucleus and other organelles

• Axon Hillock: junction between body and axon

• Axon: carries nerve impulses away from the cell and towards the neurons

  • Myelin Sheath: white coat of fatty protein that insulates the neruons to prevent itself from losing charged ions

  • Node of ranvier: Indentations between sections of myelin sheath

Central Nervous System

• Brain and spinal cord

• Gray matter: unmyelinated axons, cell bodies, and dendrites

• White matter: myelinated axons

Peripheral Nervous System

• Consists of nerves that carry information between the organs of the body and the CNS

• Somatic Nerves (Voluntary): controls skeletal muscles, bones, and skin

  • Sensory Somatic Nerves: relays information about the environment to the CNS

  • Motor Somatic Nerves: Initiates appropriate responses to external stimuli

• Automatic Nerves (Involuntary): manages the internal organs, smooth muscle, and cardiac muscle

  • Sympathetic Nervous System: prepares the body for stress

  • Parasympathetic Nervous System: restores normal balance

Brain Structure

• Brainstem: lower part of the brain containing the Medulla Oblongata, pons, and the midbrain

  • Maintains homeostasis, coordinates movement, and conducts impulses to and from higher brain centers

• Medulla and Pons: Controls automatic nerve functions (Breathing, digestion, swallowing)

  • Relays information to and from higher brain centers

• Cerebellum: coordinates motor activities and perceptual functions

  • Sends sensory information to the cerebrum via pons

• Thalamus: relays sensory information to the cerebrum

• Hypothalamus: regulates automatic activity and controls the pituitary gland

Excretory System

• Kidney: removes waste, maintains water balance, supplies blood in its renal artery, filters waste

• Renal Cortex: outer layer of the kidney

• Medulla: inner layer beneath the cortex

• Renal pelvis: cavity connecting the kidney to the ureter

Nephron: functional unit of the kidney

• Bowman’s Capsule: encircles the glomerulus

• Glomerulus: capillaries in the Bowman’s Capsule that makes the first step of filtration

• Afferent Arteriole: blood supplying unfiltered blood from the body to the Glomerulus

• Efferent Arteriole: blood vessel carrying blood away from the Glomerulus to the rest of the body

• Proximal Tubule: connects the Bowmans capsule to the loop of Henle

• Peritubular Capillaries: reabsorbs essential ions and minerals from filtered blood

• Loop of Henle: U shaped portion connection the proximal tubule to the distal tubule

• Distal Tubule: connects the Loop of Henle to the ducts

Urine Formation

1. Filtration: blood to the Bowman’s Capsule at a fast rate

   • Bowman’s Capsule cells and the Glomerulus makes a selectively permeable membrane

   • Pores of the Glomerulus allows blood contents to enter the nephron (But large blood proteins aren’t allowed)

   • Amino group is removed when proteins enter, creating a by-product of ammonia

     • Ammonia + CO₂ = Urea

2. Reabsorption: transfer solutes and water to the blood

   • Begins in the proximal tubule where water, ions, and nutrients are transferred back into the interstitial fluid

   • Amino acids, glucose, nutrients, and salts are reabsorbed from the filtrate

   • Microvilli in the tubule increases the surface area for better reabsorption

   • Water concentration increases in the filtrate by osmosis

     • Aquaporins (water channels) in the Descending LoH enables more water reabsorption

   • Peritubular Capillaries allows reabsorbed substances while remaining filtrate thats high in Urea moves to the Loop of Henle

   • Ascending LoH: absorbs salt by passive diffusion, if concentration decreases it is absorbed by active transport

3. Secretion: transfer of materials from blood to nephron

   • Waste from blood and interstitial fluid are removed and secreted into the proximal tubule

   • H+ ions and detoxified substances are secreted in the nephron and excreted through urine

   • Distal Tubule secretes K+ and more H+ ions

   • Kidney secretes excess H+ ions when acidity rises

Endocrine System

• Hormone released by negative feedback

• Endocrine glands: Secrete hormones (Hormones regulate growth and speed or slow metabolism)

  • Regular endocrine glands: glands that act exclusively like endocrine glands (e.x. pituitary gland, pineal gland, thyroid gland, adrenal gland)

  • Tissues and Organs: structures that don’t function like glands, but still secretes hormones (e.x. hypothalamus, pancreas, thymus, ovaries & testes)

Steroid Hormones: lipid based hormones made of cholesterol

• Diffuses easily though the cell membrane (since its lipid soluble) and easily binds to the nucleus’ receptor

Water soluble hormones: Amino acid/protein based hormones

• Cannot diffuse through the cell membrane, but binds to the cell membrane’s receptor instead to activate cAMP. cAMP activates enzyme cascades

Posterior Pituitary

• Part of the nervous system that does NOT produce hormones

• Uses ADH and oxytocin (made by the hypothalamus)

• Hormone Travel: Hypothalamus produces ADH and Oxytocin in neurosecretory cells

  • Both hormones move down the axon and gets released into the blood when reaching the endings

Anterior Pituitary

• Produces its own hormones

• Releases 6 important hormones (TSH, ACTH, PRL, HGH, FSH, LH)

• Hormone Travel: Hypothalamus produces releasing or release inhibiting hormones that uses a network of blood vessels (The portal system)

  • Hormones stimulate the secretion of other hormones which are later released into the blodstream)

Dwarfism: less hGH Gigantism excess HGH in childhood Acromegaly: more HGH in adulthood