Energy, Control & Continuity

Energy, Control & Continuity

Contents • Energy Supply • Photosynthesis • Respiration • Survival and Coordination • Homeostasis • Nervous Coordination • Analysis and Integration • Muscles as Effectors • Inheritance • Variation • Selection and Evolution • Classification

Energy Supply • ATP (adenosine triphosphate) is required for endothermic processes but can be re-synthesised when coupled to exothermic processes: ATP ADP + Pi • ATP is synthesised across the inner membranes of the mitochondria and chloroplasts so they are adapted to give max. surface area. Energy for ATP synthesis is supplied by ATP-ase enzymes that are powered by a proton gradient • NADH (NADPH in photosynthesis) and FADH2 are reduced coenzymes that are used to carry electrons to a different part of the organelle

Photosynthesis • Occurs in two stages: 1) Light dependent reactions - photon hits chlorophyll molecule in PS II and excites electron. Photolysis of H2O into oxygen, protons and electrons is triggered - released electrons pass through series of electron carriers before reaching PS I - at PS I, electrons are excited again by incident photons. They pass through ferredoxin electron carrier - Electrons can either travel back to plastoquinone, powering proton pump or reach NADP reductase enzyme where NADP+ ions are reduced to NADPH -Proton gradient powers production of ATP from ATP-ase enzymes in thylakoid membrane

Photosynthesis 2) Light independent reactions - rubisco enzymes catalyses the fixing of the CO2 molecule to the 5-carbon ribulose biphosphate - decays into two 3-carbon molecules of phosphoglycerate - ATP from LDR is used to form diphosphoglycerate - NADPH used to reduce this to GALP - one molecule of GALP is removed per 3 molecules of CO2 and the rest are modified into (i) ribulose phosphate and (ii) ribulose biphosphate

Aerobic Respiration • Occurs in four stages: - Glycolysis in the cytoplasm - Link reaction in the matrix - Krebs cycle in the matrix - Electron transport chain on the cristae

Survival and Coordination • Human body is controlled by two major systems: 1) Nervous system 2) Endocrine system • These systems are linked together by the hypothalamus • Reflex arc is an instant uncontrolled action: - sensory neurone  relay neurone  motor neurone • Postural reflex, e.g. knee jerk, maintains position and body control without conscious adjustment

Homeostasis • Endocrine glands produce hormones (peptides, proteins, lipids) which fit into specific receptor molecules on target cells to trigger a change in intercellular activity • Homeostasis: maintenance of constant internal body environment. Two systems are involved: 1) Sympathetic nervous system (stimulates) 2) Parasympathetic nervous system (inhibits) • Postitive feedback: homeostatic mechanism increases the change and brings factor further from resting level • Negative feedback: homeostatic mechanism reverses the change and restores factor to resting level

Homeostasis • In the dermis, there are receptors to different stimuli: 1) thermoreceptors 2) pacinian corpuscles 3) meissner’s corpuscles 4) free nerve endings • For thermoregulation, there are two types of organism: 1) endotherms (produce and maintain body temp.) 2) exotherms (rely on environment to maintain body temp.)

Thermoregulation • Hypothalamus maintains thermoregulation • Temp too high: - sweating, blood moves to surface so heat radiates away, hairs fall so heat is not trapped, muscles become inactive • Temp too low: - sweating stops, shivering starts (muscles vibrate), blood is drawn away from surface, raised hairs trap air • Thyroid gland controls metabolic rate  iodine is essential

Blood Glucose Level • Pancreatic Islets of Langerhans maintain blood glucose level - Hyperglycaemia (too much blood glucose) - Hypoglycaemia (too little blood glucose) - Gluconeogenesis occurs in times of starvation (glucose production from lipid/protein sources)

Ultrafiltration: blood filtered under pressure  produces a filtrate identical to tissue fluid • Selective reabsorption: reabsorption of useful substances back into blood stream • Loop of Henle: reabsorbs water • Osmoreceptors in the hypothalamus: monitor osmotic blood concentration • Baroreceptors in the circulatory system: monitor blood pressure

The Eye • Light entering eye: focused on retina - cornea does most refraction. Cornea and vitreous humour have the same refractive index - lens fine focuses using ciliary muscles: Distant object: ciliary muscles relax, ligaments tighten  lens becomes flat and thin Close-up object: ciliary muscles contract, ligaments relax  lens becomes more spherical and fat • Iris controls pupil size: Dim light: radial muscles contract, circular muscles relax  pupil dilates Bright light: radial muscles relax, circular muscles contract  pupil constricts

The Eye • Rods respond to dim light, responsible for peripheral vision. Contain the visual pigment, rhodopsin • Cones respond to bright light, responsible for central and colour vision. Contain the visual pigment, iodopsin • Rods – low visual acuity • Cones – high visual acuity • Trichromatic theory = red, blue and green cones. Each detects different wavelength of light

Nervous Coordination Sensory neurones Motor neurones Intermediate neurones Predominantly in nervous tissue Myelinated neurones: Myelin sheath speeds up impulse Non-myelinated neurones: No myelin sheath

Nervous Coordination • Glial cells: - packed between neurones to form neuroglia tissue: a) provides mechanical support and electrical insulation b) Schwann cells are specialised glial cells, forming myelin sheaths c) control nutrient and ionic balance. Break down neurotransmitters • Nissl tissues: - contained in neurones: a) generate enzymes involved in impulse transmission and synthesis of trophic factors b) regulate growth and differentiation of nervous tissue

Nervous Coordination • When impulse is not transmitted: - charge (resting potential) across axon membrane = -70mV • When impulse is transmitted: - action potential is a brief reversal of resting potential • All-or-None rule: - stimulus needs the minimum intensity to initiate an action potential. Below this, there is no impulse • Impulse takes place over: - temporal or spatial summation

Nervous Coordination • Synapses: - are gaps between neurones to control impulses chemically - release neurotransmitters that diffuse across synaptic cleft and trigger action potential in membrane - once it reaches post-synaptic neurone, enzymes break it down and it diffuses back across synapse • Neurotransmitters used in the human body are: - acetylcholine (motor neurones) - noradrenaline (sympathetic synapses) - serotonin, dopamine (in brain)

Nervous Coordination • Synapses: - are effected by drugs: Hallucinogens (LSD) mimic actions of other neurotransmitters Nicotine is addictive Curare and atropine block acetylcholine Muscarine mimics acetylcholine

Analysis and Integration • Central Nervous System: 1) Spinal Cord 2) Hindbrain 3) Midbrain 4) Forebrain • Cerebral Cortex: 1) Sensory areas 2) Motor areas 3) Association areas • Visual Cortex: 1) Simple cells 2) Complex cells 3) Association areas

Analysis and Integration • Brain and spinal cord protected by: 1) Bone (skull and vertebral column) 2) Spinal and cranial meninges 3) Cerebrospinal fluid • Opposing functions of sympathetic & parasympathetic divisions of the ANS: 1) Iris 2) Ciliary muscle 3) Lacrimal gland 4) Urinary bladder wall

Muscles are Effectors • Skeletal muscles occur in antagonistic pairs, held together by connective tissue with a tendon at each end attached to the bones • Collagen is a fibrous protein in tendons and bones that prevent them from breaking or stretchy • Arthropods have exoskeletons as their cuticle. This must be shed to grow • Skeletal muscle consists of muscle fibres, each containing many myofibrils • Sliding filament hypothesis of muscle contraction is like a ratchet mechanism

Inheritance • Genotype: combination of alleles • Phenotype: observable features of an organism • Gene: length of DNA for a characteristic • Chromosome: long DNA molecule • Locus: position of a gene on a chromosome • Allele: alternative form of a gene • Homozygous: both alleles are the same (both dom, both rec) • Heterozygous: alleles are different (dominant & recessive)

Meiosis: First Division

Meiosis: Second Division

Chromosomes Humans have 23 pairs of chromosomes: 22 pairs of autosomes Final pair determines sex – XX or XY Ova have X chromosome, sperm determines X or Y

Alleles • Homozygous dominant (AA) – dominant allele expressed • Homozygous recessive (aa) – recessive allele expressed • Heterozygous (Aa) – dominant allele expressed • Codominant alleles: IA & IB are A & B proteins, I0 = no proteins - I0I0 = blood group O - IAIA or IAI0 = blood group A - IBIB or IBI0 = blood group B - IAIB = blood group AB (codominance) • Parents AABB and aabb  F1 will all be AaBb  F2 will give 9:3:3:1 ratio of phenotypes

Sex-Linked Inheritance • Occurs when the gene occurs on the sex chromosomes • Males cannot be carriers, if the faulty allele is on the X chromosome, as they will only have one copy of the gene. • Men tend to be much more affected, as women must have both faulty alleles, whereas men only need have one - red/green colour blindness: recessive on X chromosome - pattern baldness: dominant on Y chromosome - haemophilia: recessive on X chromosome

Genetic Variation Two types: • Discontinuous: usually coded for by one gene - specific outcome, e.g. hair colour • Continuous: usually polygenic - many outcomes, e.g. mass, height Caused by: • Variation during meiosis • Mutations • Environmental factors

Genetic Variation Gene frequencies are predicted by the Hardy-Weinberg • Total frequency for phenotype, p and q: p + q = 1 • p2 + 2pq + q2 = 1, whereby: p2 = frequency pf AA 2pq = frequency of Aa q2 = frequency of aa • Assuming: large population, random breeding, no natural selection, no allele mutations

Selection • Natural Selection (selection pressure) • Organisms whose genes give them an advantage for survival - more likely to survive, reproduce and pass genes on • Feature arises by random mutation, and survival determines whether feature is passed on through population • Artificial Selection • Breeding is controlled for certain characteristics - new breeds but not new species • When no selection pressure, characteristics are best suited for the environment in which an organism lives

Species • A population or group of similar organisms that can reproduce to produce fertile offspring • New species evolve by: - isolation - natural selection - speciation • Evolution relies strongly on immigration and emigration • Evidence for evolution: fossil records, common blood pigments, similar larval forms (annelids and echinoderms), similar embryological development in mammals, fish and reptiles

Classification • Kingdom • Phylum • Class • Order • Family • Genus • Species • Canis domesticus: Canis = genus, domesticus = species • Genus has an upper case 1st letter: Canis • Species has a lower case 1st letter: domesticus

Classification • Five kingdoms of living organism: • Kingdom Animalia - multicellular eukaryotes, heterotrophic nutrition, radial or bilateral symmetry • Kingdom Plantae – multicellular eukaryotes, cellulose cell walls • Kingdom Fungi – eukaryotes that reproduce by spore production • Kingdom Protoctista – e.g. amoeba • Kingdom Prokaryotae – no nucleus, circular DNA

Summary • Energy Supply • Photosynthesis • Respiration • Survival and Coordination • Homeostasis • Nervous Coordination • Analysis and Integration • Muscles as Effectors • Inheritance • Variation • Selection and Evolution • Classification

Energy, Control & Continuity