Sarah's Biology Exam Notes PDF

# Biology Exam Review ## Unit 1: Biochemistry ### Lesson 1: Chemical Bonding - **Stability** - Atoms react to achieve stability, usually results in the release of energy (and a lower energy state). - Combine = complete valence shell = stable, form chemical bonds. - Compound molecule:...

# Biology Exam Review ## Unit 1: Biochemistry ### Lesson 1: Chemical Bonding - **Stability** - Atoms react to achieve stability, usually results in the release of energy (and a lower energy state). - Combine = complete valence shell = stable, form chemical bonds. - Compound molecule: chemical bond 2+ atoms. - Formation = release energy -$A + B \rightarrow AB + ENERGY$ - Break, energy added -$AB + Energy \rightarrow A + B$ - **Types of bonds:** 1. **Ionic** : metal + non-metal, transfer of electrons - Oxidation - loss of electrons, usually when atoms with less than 4 electrons in their outer shell (H, Na, Ca, etc.) - Reduction - gain of electrons, opposite of above. (O, Cl, S, etc.) 2. **Covalent**: non-metal + non-metal, sharing electrons - Single, double, triple bonds. 3. **Hydrogen bonds**: O end polar molecule attracted to the + end of another polar molecule. 4. **Van der Waals**: London dispersion & dipole-dipole: any intermediate attraction. ### Lesson 1: Chemical Bonding (continued) - **Electronegativity** - Increases left to right, decreases top to bottom. - Left side doesn't often accept electrons, right does. - **Electronegativity difference:** - Less than 0.5 = covalent bonds. - Between 0.5 and 1.7 = polar covalent bond. - Greater than 1.7 = ionic bond. - **Moving electrons against the gradient (O to C) requires energy (stored, like Photosynthesis).** - **Moving electrons down the gradient (C to O) releases energy (cellular respiration).** ## Lesson 2: Plasma Membrane - **Plasma membrane:** - What leaves/enters the cell. - Membrane is a double layer of water repellant molecules. - **Cell wall:** - Support plant tissue, made of fully permeable wall or cellulose. - **Nucleus:** - Double membrane w/ pores, controls cell via expression of genes. - **Ribosomes:** - Produce proteins. ## Lesson 2: Organelles - **Rough ER:** - Protein synthesis, packaging into vesicles. - ER form network of tubules with maze structures. - Rough, presence of ribosomes. - Proteins from here are secreted out. - **Golgi apparatus:** - Modification of proteins for secretion. - **Vacuole:** - Storage area (plants, amino acids & sugars). - **Lysozyme:** - Vesicles that form on Golgi apparatus. - Digestion of old organelles. - **Mitochondria:** - Site of aerobic respiration. - Matrix is site of Krebs cycle. - **Chloroplast:** - In plants only, this is the site of photosynthesis. ## Lesson 3: Water - **Important properties of water:** 1. **Ice Formation:** - Forms regular crystal structure when solid. - Ice is less dense than liquid water. 2. **Surface tension:** - Hydrogen bonds cause water to have high surface tension (important for aquatic organisms). 3. **Adhesion and Cohesion:** - Water easily attaches itself to other polar molecules. 4. **Organizes Non-polar molecules.** 5. **High Specific Heat Capacity.** ## Lesson 4: Functional Groups - **Functional groups are clusters of atoms that behave in particular ways no matter what the rest of the molecule is like.** - **Saturated:** - $HO -\overset{O}{C} -C - C- H$ $H H H H$ - **Unsaturated:** - $HO -\overset{O}{C} -C=C =C=C-C-H$ $H H H H$ - **Organic compounds containing an OH are called alcohols.** - **Hydroxyl (alcohols)**: $R-OH$ - **Aldehyde (aldehydes)**: - $R-\overset{O}{C}-H$ - **Carbonyl (Ketones)**: - $R-\overset{O}{C}-R$ - **Carboxyl (carboxylic acids)**: - $ R-\overset{O}{C}-OH$ - **Amino (amines)**: - $R-\overset{H}{N}-H$ - **Ether (carbs)**: - $R-O-R$ - **Ester (fats)**: - $R-\overset{O}{C}-OR$ - **Phosphate (nucleic acids)**: - $R-O-\overset{O}{P}-O$ - $O$ - **Sulfhydryl**: - $S-R$ - **Amino acids/proteins** ## Lesson 4: Functional Groups (continued) - **Carbs:** Sugar, starch, cellulose. - **Proteins:** Albumen, fibrinogen, actin. - **Lipids:** Cholesterol, waxes, oils. - **CARBS:** - **Monosaccharides:** glucose, galactose, fructose - **Glucose structure:** - $H$ $C$ $O$ $H$ $HO-C-H$ $HO-C-H$ $H-C-OH$ $H-C-OH$ $CH_2OH$ - **Condensation:** - $R-\overset{O}{C}-H + H -O-\overset{O}{C}-R \longrightarrow R-\overset{O}{C}-\overset{O}{C}-R + H_2O$ - **Hydrolysis is opposite.** - **Polysaccharides are very large, generally insoluble.** - **Too large to pass through pores of membranes.** - **Excellent storage units.** - **Summary of types:** - **Monosaccharides:** 1 sugar (glucose, galactose, fructose) - **Disaccharides:** 2 sugars (maltose, sucrose, lactose) - **Polysaccharides:** many sugars (starch, cellulose, glycogen, pectin) - **LIPIDS** - **Not soluble in water, hydrophobic because of large number of C-H bonds (non-polar, can't form hydrogen bonds).** - **Yield about twice as much energy as carbs/proteins.** - **Glycerol has 3 hydroxyl joins with 3 fatty acids.** - **Condensation rxn:** - $H$ $C$ $H$ $H-C-OH$ $HO-C-R$ $H$ $H$ - $H-\overset{O}{C}-R + H-O-\overset{O}{C}-R \longrightarrow H-\overset{O}{C}-\overset{O}{C}-R + H_2O$ $H$ $H-C-OH$ $HO-C-R$ $H$ $H$ $H$ - **Glycerol + 3 fatty acids = triglyceride + 3 water (ester bond)** ## Lesson 4: Functional Groups (continued) - **LIPIDS (CONT.)** - **Saturated fats:** - Solid at room temperature, two H each C, no double bonds. - **Unsaturated fats:** - Liquid at room temperature, double bonds. - **High level of saturated fats means [amount] flowing through blood vessels, could clog to walls and cut off blood supply (atherosclerosis).** - **Functions:** 1. **Energy storage:** fats in animals, oils in plants. 2. **Heat insulation:** layer under the skin called subcutaneous, insulates, not a triglyceride. 3. **Buoyancy:** Less dense than water, helps to float! 4. **Sex hormones** 5. **Vision pigment.** ## Lesson 5: Cell Membrane - **Proteins:** $C, H, O, N, S$ (sometimes) - **Functions:** - **Structural molecules:** bone, muscle, membranes. - **Enzymes:** metabolic systems. - **Antibodies:** immune system. - **Hormones:** regulate body activities. - **Blood proteins:** blood clotting. - **Source of energy (last resort).** - **Need 20 amino acids, body can make 12, other 8 essential amino acids.** - **Two categories of proteins:** - **Fibrous:** - Insoluble, physically strong. - Very strong. - Long polypeptide chains arranged in extended parallel forms. - E.g.: keratin, hair, nails. - **Globular:** - Soluble in water. - Diffuse readily. - Polypeptide chains tightly folded, spherical or globular shapes. - E.g.: enzymes, hormones. - **Protein structure:** - $H$ $R$ $O$ $||$ $H-N-C-C-OH$ $H$ - **Amino** - **Carboxyl** ## Lesson 4: Functional Groups (continued) - **Proteins (cont.)** - **Four levels of protein structure:** - **Primary structure:** - Sequence of amino acids laid in row. - **Secondary structure:** - 3-D arrangement of the polypeptide, strong presence of H bonds cause helix formation. - Alpha helix. - **Tertiary structure:** - Molecule becomes twisted on itself. - **Quaternary structure:** - If two or more protein units become associated with each other. ## Lesson 4: Functional Groups (continued) - **Nucleic acids, long polymers made up of nucleotides.** - **Made up of:** - **DNA:** 1. **Five carbon sugar.** 2. **Phosphate group ($PO_4$).** 3. **Nitrogen containing base.** - **Purines:** adenine and guanine (large, double ringed). - **Pyrimidines:** cytosine and thymine (small, single ringed). - **A (adenine) + T (thymine)** - **G (guanine) + C (cytosine)** - **RNA** - **U (uracil) + A (adenine)** - **G (guanine) + C (cytosine)** - **Types of RNA:** 1. **mRNA** 2. **tRNA** 3. **rRNA** 4. **snRNA** ## Lesson 5: Cell Membrane - **Membrane structure:** 1. **Phospholipid bilayer:** polar, hydrophilic phosphate heads outwards, non-polar hydrophobic fatty acids facing in the middle. 2. **Integral/channel proteins:** one side of phospholipid bilayer to the other, transport substances, large molecules across membrane. 3. **Cholesterol:** binds to lipid in plasma membrane, ↑ fluidity. 4. **Peripheral proteins** 5. **Receptor proteins** - **Diffusion:** - Caused by kinetic energy, random direction. - From high to low concentration (source to sink) 1. **Simple/lipid diffusion:** - So small, pass through membrane with little resistance. - O2, CO2, H2O 2. **Facilitated:** - Large molecules pass via channel proteins. - Large, globular structures. - **Active transport:** - Requires energy to function. - Source of energy is ATP from the cell, respiration. - Low to high concentration, against concentration gradient. - Diagram showing ways molecules move across a cell membrane: - **Simple diffusion:** small, non-polar molecules. - **Transport proteins:** facilitated. - **Active transport:** against gradient, needs energy (ATP) ## Lesson 5: Cell Membrane (continued) - **Osmosis:** - Passive movement of molecules across a partially permeable membrane from a low solute to a high solute concentration. - Water tends to go low to high. - **Concentrated = hypertonic (water moves here)** - **Dilute = hypotonic** - **Diagram of hypertonic, hypotonic, and isotonic solutions.** - **Membrane fusion:** - When two membranes (e.g., vesicle and cell membrane) merge together. - **Endocytosis:** brings in substances. - Engulfs external materials. - **Exocytosis:** removing substances. - Cell expels substances, e.g., secretion hormones, waste. ## Lesson 6: Energy and Metabolism - **Energy: ability to do work.** 1. **Kinetic:** actively doing work (motion). 2. **Potential:** ability to work (stored). - **Adenosine Triphosphate (ATP)** - 3 phosphate groups. - 5 carbon sugar (ribose). - Nitrogenous base (adenine). - **Exergonic Reactions:** - **Release energy:** - Products contain less energy than reactants. - **E.g., respiration: $C_6H_{12}O_6 + 6O_2 \longrightarrow 6CO_2 + 6H_2O + energy$** - **Reactants** **Products** - **Endergonic Reactions:** - **Absorb energy:** - Products contain more energy than reactants. - **E.g., photosynthesis.** - **Activation Energy:** - Speed of reaction depends on amount of activation energy. - Catalysts lower amount of activation energy required by putting stress on bonds so they're easier to break. ## Lesson 7: Enzymes - **Enzymes:** protein catalysts, are not consumed. - Speed up a reaction by lowering activation energy. - Act on a substrate, bind to at specific sites. - **Factors affecting enzyme activity:** 1. **The effect of temperature:** - **Diagram of rate of reaction vs. temperature.** - **(a) ↓ temperature = ↓ rate of reaction** - **(b) Optimum temperature = max rate of reaction.** - **(c) Rapid increase in temperature = denatured enzyme.** 2. **The effect of pH:** - **Diagram of rate of reaction vs. pH.** - **(a) Enzyme active site charges shape.** - **(b) Optimum pH = rate of reaction.** - **(c) T pH = ± H+ = enzyme active site charges, ↓ rate of reaction.** 3. **Effect of substrate concentration:** - **Diagram of rate of reaction vs. concentration.** - **(c) Full saturation of the active sites by substrate.** ## Lesson 7: Enzymes (continued) - **Coenzymes:** organic substances that carry molecules from one enzyme to another. - **Cofactors:** inorganic substances needed for some enzymes to function. - **Competitive inhibitors:** - Similar shape to substrate. - Can enter the active site and block normal substrate from binding. - To reverse, increase substrate concentration. - **Noncompetitive inhibitors:** - Attach to another site on the enzyme. - Cause changes in enzyme shape. - Enzyme loses affinity for substrate. - **E.g., DDT inhibits enzymes of the nervous system.** - **Some enzymes posses allosteric sites (receptor sites)** - An activator will stimulate enzyme activity. - An inhibitor will inhibit enzyme activity (it stabilizes inactive form of the enzyme). ## Unit 2: Metabolism ### Lesson 1: Cellular Respiration - **ATP Functions:** - Active Transport. - Catabolic Reactions. - Muscle contractions. - Nervous system transmissions. - **Sources of ATP** 1. **Substrate level phosphorylation:** - Formation of ATP with energy-yielding process (exergonic). - $ADP + P + energy (from exergonic rxn) \longrightarrow ATP$ - **Anaerobic is only 2% efficient!** 2. **Chemiosmotic ATP generation (oxidative phosphorylation):** - ATP generated when protons move back through the membrane via proton "pumps", now, most ATP is made. - **(a) If source of energy from light - Photosynthetic phosphorylation.** - **(b) If from oxidation of food- Oxidative phosphorylation (slower, indirect than substrate level). Aerobic respiration is 38.3% efficient.** ### Lesson 2: Pyruvate Oxidation and the Krebs Cycle - **P.O.** - In mitochondrial matrix. - **Stage 2:** 1. One of the three carbons in pyruvate is cleaved off and released as carbon dioxide. 2. Remainder called an acetyl group, becomes associated with a carrier molecule called Coenzyme A. 3. Produces acetyl-CoA (fuel for Krebs). 4. This rxn is coupled with the reduction of NAD+ to form NADH. - **Krebs Cycle** - **Stage 4:** 1. Cycle begins when acetyl-COA (2C) combines with oxaloacetate (4C) to form citrate (6C). 2. Citrate is converted to isocitrate (6C). 3. Isocitrate becomes oxidized, reducing NAD+ to NADH, releases one molecule of $CO_2$, forming α-ketoglutarate (5C). 4. α-ketoglutarate is oxidized, reducing NAD+ to NADH, remaining 4C attaches to Co-A and forms succinyl-CoA. 5. Succinyl-CoA converted to succinate, GTP transfers to ADP to make ATP. 6. Succinate oxidized to fumarate (4C), reducing FAD to FADH2. 7. Fumarate is hydrated (add $H_2O$) to form malate. 8. Malate is oxidized to oxaloacetate, reducing NAD+ to NADH. ### Lesson 4: Electron Transport Chain - **Stage 4:** - Electrons donated by NADH and FADH, transported through the chain. - NAD+ accepts two $e^-$, one $H^+$. FAD is two $e^-$, two $H^+$. 1. **NADH dehydrogenase accepts electrons, then passed to peripheral protein called ubiquinone, then integral protein called bcl complex, then peripheral protein called cytochrome c, then cytochrome oxidase complex. ** 2. **Final electron acceptor is oxygen (as it's very electronegative). Oxygen combines with 2 $e^-$ and 2 $H^+$ to form H2O (water produced, oxygen consumed).** 3. **FADH$_2$ doesn't have the right shape to bind with NADH dehydrogenase so it goes through ubiquinone.** - **NADH gives 3$H^+$ into intermembrane space = 3 ATP. ** - **FADH$_2$ gives 2$H^+$ = 2 ATP.** - **Chemiosmosis:** - Molecules called NADH and FADH release energy. - $H^+$ ions pile up on one side of membrane. - They can only make it back by crossing ATP synthase. - ATP synthase creates ATP as $H^+$ flows through it. ## Lesson 5: Anaerobic pathways - **Anaerobic is without oxygen.** - The body doesn't have an unlimited amount of NAD+. - Organisms must continuously recycle NAD+ - If unavailable, $H^+$ are transferred by ethanol fermentation or lactic acid fermentation. - **Fermentation:** metabolic process converts sugars to acids, gases, and/or alcohol. - Happens when NAD+ is not available, so $H^+$ are transferred by: 1. **Ethanol fermentation:** (prokaryotes, bacteria/yeast) - NADH transfers H atoms to acetaldehyde to form ethanol. - This regenerates NAD+ (required for glycolysis to continue). 2. **Lactic acid fermentation:** (eukaryotes) - When there isn't enough $O_2$ present for the ETC to function. - NADH transfers H atoms to pyruvate in cytoplasm. - Pyruvate converts to lactate after exercise, lactate is oxidized back to pyruvate. ## Lesson 6: Photosynthesis - **Photosynthesis: process of converting light → chemical.** - $6CO_2 + 6H_2O + light energy \longrightarrow C_6H_{12}O_6 + 6O_2$. - Takes place within chloroplasts. - Needs water ($H_2O$), carbon dioxide ($CO_2$), light energy. - **Characteristics of light:** - Photons that travel in waves. - Short wavelengths have higher energy, long wavelengths have lower energy. - When electrons are struck by a photon, contact will boost electrons to a higher energy level. - **Chloroplast structure:** - Thylakoids contain pigments, increase surface area. - Stroma is ground substance inside. - Grana and stacks of thylakoids are connected by lamellae. - **Chlorophyll a and b both absorb blue and red better than yellow and green.** - Ethyl group. - Carbonyl. ## Lesson 7: Light Reactions - **Occur in the thylakoid membrane of chloroplasts.** - **Non-cyclic:** 1. **Photons hit PSII, exciting electrons.** 2. **Moves through electron transport chain.** 3. **To replace electrons that the chlorophyll lost, water splits and its electrons go there (i.e., $H_2O$, O produced.** 4. **After ETC, they go to PSI; light excites again.** 5. **Accepted by NADP+, also accepts hydrogen to become NADPH.** - **Diagram of the non-cyclic light reactions.** - **Cyclic:** - **Diagram of cyclic light reactions.** ## Lesson 8: Dark Reactions - **Calvin Cycle.** - Occur in the stroma of the chloroplast.. 1. **Carbon fixation.** - $CO_2$ combined with rubisco (RuBP). - Splits into two 3-C molecules of 3-PGA. 2. **Reduction.** - 3-PGA molecules are phosphorylated by ATP, and NADPH reduces 1,3-BPG to G3P, Some G3P leaving (only 1 for every 6 G3P produced). 3. **Regenerating RuBP.** - ATP rearranges five G3P (3C each) into 3 RuBP (5C each). ## Unit 3: Molecular Genetics ### Lesson 1: Molecular Genetics - **DNA:** - Stands for deoxyribonucleic acid. - Only in nucleus. - Double helix structure. - Adenine joins thymine with double hydrogen bond. - Cytosine joins guanine with a triple hydrogen bond. ### Lesson 2: DNA Replication - **Somatic cells have twice as much DNA as reproductive cells.** - **Diagram showing DNA replication.** - **Leading strand:** 3' hydroxyl, stable. - **Lagging strand:** 5' hydroxyl, unstable. - **Parent strand.** 1. **Gyrase initiates the unwinding of DNA. ** 2. **Helicase preps the DNA by breaking the H bonds between strands.** 3. **Single-stranded-binding proteins attach to the strands to keep them apart** 4. **DNA polymerase III adds nucleotides to each template strand.** 5. **RNA primase adds RNA nucleotides to form RNA primers to signal DNA polymerase III where to start.** 6. **DNA polymerase I replaces the RNA primers and proofchecks.** 7. **Okazaki fragments produced on lagging strand sealed with ligase** ### Lesson 3: RNA - **RNA:** - Stands for ribonucleic acid. - Base uracil replaces thymine. - Single stranded. - **Types of RNA:** 1. **Ribosomal RNA (rRNA)** - Makes up the structure of the ribosome. - Place where polypeptide chains are synthesized during protein formation. 2. **Transfer RNA (tRNA)** - Bind to specific amino acids and bring them to the ribosome where they are attached to mRNA. 3. **Messenger RNA (mRNA)** - Long molecule that copies the DNA template, travels from the nucleus to the ribosome. 4. **Small nuclear RNA (snRNA)** - Involved in the removal of introns. ### Lesson 4: Transcription and Translation - **Transcription:** - **Diagram showing transcription** - **DNA** - **Antisense/template strand, one copied.** - **Sense/coding, other strand** - **Transcription in the nucleus.** - **Initiation:** - RNA polymerase has to know where to start and what direction to go in, so it's directed to a particular DNA sequence (TATA region) and binds to something called the promoter to start, the DNA then unwinds. - **Elongation:** - RNA polymerase works in the 5' to 3' direction, and it slides along the template DNA strand, as the complementary bases pair up, RNA Polymerase links nucleotides. - **Termination:** - RNA Polymerase comes to a stop when it gets to TATA rich region, terminator. - Pre-mRNA is released. - **Modification:** - **Introns (non-coding regions)** are spliced (splicesomes). - **Guanine cap** is added to the 5' end. - **Poly A tail** is added to the 3' end. ### Lesson 5: Translation - **Translation in the cytoplasm, on ribosomes.** - **Initiation:** - Starting point. - tRNA binds to mRNA and moves it along until it reaches the start codon (AUG). - tRNA carrying amino acid methionine attaches, anticodons join with codons of mRNA. - **Elongation:** - Peptide bond forms between 1st and 2nd amino acid. - A site is entry site for new tRNA. - P site is when the growing polypeptide chain is attached to exit (E) site. - First tRNA then moves to exit site - **Termination:** - Stop codon reached, polypeptide is released and forms into proper shape and begins to act as a functional protein. - **Diagram of the ribosome.** ## Lesson 6: Genes and Their Regulation - **Four types of control:** 1. **Transcriptional:** controls what gene is transcribed and the rate it is transcribed. 2. **Post-transcriptional:** changes to mRNA within the nucleus. 3. **Translational:** controls how often and fast translation occurs. 4. **Post-translational:** prevents proteins from becoming active. - **Enzyme induction:** - **Lac operon encodes for:** - Repressor. - Promoter. - Operator. - LacZ. - LacY. - LacA. - **Inducible enzymes are synthesized as a result of genes being turned ON.** - **Substrate is inducer, no substrate = repressor binds operator, prevents RNA polymerase, enzyme production is inhibited.** - **Diagram of the lac operon.** - **Lactose binds to the lactose repressor and the repressor binds to the promoter.** - **End product repression**: - Regulator gene synthesizes inactive repressor. - If end product is short in supply, inactive repressor doesn't bind. - **Diagram of trp operon.** - **If plentiful, the repressor becomes active, binds to the operator and prevents mRNA transcription.** ## Lesson 7: Mutations - **Mutations** - Chemical mutagens: mimic correct nucleotide bases but don't pair properly during DNA replication. - Removes part of nucleotide, improper pairing. - **Types of Mutations:** - **Silent mutations:** don't have any effect on the function of the cell. - **Missense mutations:** occur when the codon is changed to call for the wrong amino acid in a protein. - **Nonsense mutations:** occur when a normal codon is replaced by a stop codon, disrupting protein synthesis. - **Point mutations:** - **Base pair substitution:** change in only one base pair. - **May or may not be serious, e.g., sickle cell anemia**. - **Frameshift mutations:** deletion or addition of 1+ base pairs (not multiples of 3) - **Very dramatic, not easily corrected.** - **Types of mutations:** - Deletion, duplication, insertion, inversion, translocation - **Actions of the total genotype:** 1. **Multiple effects of single genes:** - Single gene ruck up has many effects. - E.g.: frizzling, defective feathers = poor heat insulation = body issues. 2. **Interaction of genes:** - Expression of any trait influenced by a large # of genes. 3. **Environmental influences:** - Gene action may be controlled by the environment. - E.g.: no sun = ↓ chlorophyll produced. ## Unit 3: Metabolism ### Sequencing Practice: - **Original strand:** - 5'GGCTACACT3' - **When drawing it, do the reverse in 5' to 3'. ** - **Options in DIDATP?** - 5'A3' - 5'AGTGTA3' - 5'AGTGTAGCC3' - **Original:** 5'GGCTACACT3' - **Reverse:** 3'CCG AUG UGA5' - **Flip (translation):** - 5'AGU GUA GCC3' - Serine, Valine, Alanine ## Unit 4: Homeostasis ### Lesson 2: Excretory System - **Kidney is the osmoregulator of the body.** - **Functional unit is the nephron.** - Works on solutes (urea and sodium chloride). - **Diagram showing the nephron.** - **1. Proximal tubule:** - Isn't permeable to sodium, urea, but permeable to water. - Cells filled with mitochondria, the cell respires. - Most water is recovered here, [**ACTIVE TRANSPORT**] - **2. Descending loop:** - Cells are thin, have mitochondria. - Impermeable to salt/urea, permeable to water, water moves via osmosis to surrounding tissues. - **3. Ascending loop:** - Not really permeable to water, permeable to sodium and chloride ions, higher up [**Active transport**] to pump out NaCl. - **4. Distal tubule:** water diffuses out by osmosis. - **5. Collecting duct:** permeable to urea. - **6. Bladder:** urine stored, impermeable to urea. - **Summary of nephron processes:** 1. **Filtration** of plasma in Bowman's capsule. 2. **Reabsorption** in PCT, LOOP, DCT. 3. **Secretion** - **Hormonal control of reabsorption:** - **Water permeability of the collecting duct is controlled by ADH (antidiuretic hormone)** - ADH determines if urine is dilute of concentrated. - **More water reabsorbed = more concentrated** - **Renin:** - A fall in blood pressure causes kidneys to release renin into blood. - Renin combines with angiotensin to: - Constrict afferent renal arterioles & peripheral blood vessels. - Adrenal glands release aldosterone to ↑ sodium and water reabsorption. - Sends a message to the brain to stimulate thirst. ### Lesson 3: Endocrine System - **Non-target hormones:** affect many cells - Growth hormone (GH)/somatropin. - Insulin. - Epinephrine/adrenaline. - **Target hormones:** - Parathyroid. - Gastrin. - **Two types of hormones:** 1. **Steroid hormones:** - Made from cholesterol (lipid compounds). - E.g., sex hormones, cortisol. - Soluble in fat. - Ring structure. - Can diffuse into cells from capillaries. - Bind to receptors in cytoplasm. 2. **Protein hormones:** - Made from proteins. - Soluble in water. - Linear structure. - Bind to receptors on the cell membrane. - E.g., Insulin, growth hormone, thyroxine ### Unit 4: Metabolism - **Lesson 3: Endocrine System (continued)** - **Key endocrine glands and hormones:** - **Prolactin:** - **FSH:** - **Anterior pituitary:** - **LH:** - **TSH:** - **Thyroid:** thyroxine. - **Adrenal cortex:** cortisol. - **Adrenal medulla:** adrenaline/norepinephrine, epi/norepi. - **Pancreas:** insulin/glucagon (controls blood sugar). - **Ovary:** estrogen/progesterone. - **Testes:** testosterone. - **Control:** - **Antagonistic controls:** some hormones stimulate, others inhibit. - **Feedback controls:** hypothalamus measures hormone release. - **Diagram showing relationship between hypothalamus and pituitary gland. ** ### Lesson 4: Hormones - **Hormones that affect blood sugar:** 1. **Insulin:** - ↓ blood sugar. - Produced in the beta cells of the islets of Langerhans in the pancreas. - Causes cells to become permeable to glucose. - Prevents hyperglycemia. 2. **Glucagon:** - ↑ blood sugar. - In alpha cells in islets of Langerhans pancreas. - Converts glycogen to glucose. - **Diabetes:** - **Type I** (unable to produce insulin). - **Type II** (adult, ↓ production, ↓ absorption of insulin). - **Type III** (gestational, in pregnant women/fetus). - **Stress hormones:** - **Adrenal glands:** superior to kidneys, made of cortex/medulla. - **Adrenal medulla:** epinephrine and norepinephrine. - **Adrenal cortex:** aldosterone and cortisol. ### Lesson 4: Hormones (continued) - **Fight or Flight:** - **Adrenal medulla:** - **Epinephrine:** - Alpha and beta receptors. - In arteries, heart, lungs, skeletal muscles. - ↑ blood sugar, ↑ heart rate, ↑ rate of heart pump. - **Norepinephrine:** - Only alpha receptors. - Found only in arteries. - ↑ blood sugar, ↑ heart rate, narrows blood vessels. - **Stressful event? Hypothalamus relays message to anterior pituitary gland, stimulating ACTH** - **ACTH → bloodstream → msg to adrenal cortex to secrete cortisol (slower but long lasting compared to epi/norepi).** - **Cortisol:** - ↑ blood sugar levels. - ↓ inflammation. - Monitors B.P. ### Lesson 5: Male Reproductive System - **Testosterone:** - Produced in interstitial cells of the testes. - Controlled by hypothalamus and pituitary gland. - **Functions of testosterone:** - Stimulates spermatogenesis. - Hair development. - ↓ voice. - ↑ muscle strength - Acne. - **Diagram showing the male reproductive system.** - **Testes:** reproductive organs responsible for making testosterone and sperm. - **Seminiferous tubules:** spermatozoa