Transcript Energy, Control & Continuity

Energy, Control & Continuity
Contents
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Energy Supply
Photosynthesis
Respiration
Survival and Coordination
Homeostasis
Nervous Coordination
Analysis and Integration
Muscles as Effectors
Inheritance
Variation
Selection and Evolution
Classification
Energy Supply
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ATP (adenosine triphosphate) is required for endothermic
processes but can be re-synthesised when coupled to
exothermic processes: ATP ADP + Pi
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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
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NADH (NADPH in photosynthesis) and FADH2 are reduced
coenzymes that are used to carry electrons to a different
part of the organelle
Photosynthesis
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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
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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
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Human body is controlled by two major systems:
1) Nervous system
2) Endocrine system
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These systems are linked together by the hypothalamus
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Reflex arc is an instant uncontrolled action:
- sensory neurone  relay neurone  motor neurone
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Postural reflex, e.g. knee jerk, maintains position and body
control without conscious adjustment
Homeostasis
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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
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In
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3)
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the dermis, there are receptors to different stimuli:
thermoreceptors
pacinian corpuscles
meissner’s corpuscles
free nerve endings
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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
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Hypothalamus maintains thermoregulation
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Temp too high:
- sweating, blood moves to surface so heat radiates away,
hairs fall so heat is not trapped, muscles become inactive
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Temp too low:
- sweating stops, shivering starts (muscles vibrate), blood is
drawn away from surface, raised hairs trap air
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Thyroid gland controls metabolic rate  iodine is essential
Blood Glucose Level
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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)
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Ultrafiltration: blood filtered under pressure  produces a
filtrate identical to tissue fluid
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Selective reabsorption: reabsorption of useful substances
back into blood stream
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Loop of Henle: reabsorbs water
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Osmoreceptors in the hypothalamus: monitor osmotic blood
concentration
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Baroreceptors in the circulatory system: monitor blood
pressure
The Eye
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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
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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
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Rods respond to dim light, responsible for peripheral vision.
Contain the visual pigment, rhodopsin
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Cones respond to bright light, responsible for central and
colour vision. Contain the visual pigment, iodopsin
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Rods – low visual acuity
Cones – high visual acuity
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Trichromatic theory = red, blue and green cones. Each
detects different wavelength of light
Nervous Coordination
Intermediate
neurones
Predominantly in
nervous tissue
Sensory
neurones
Motor
neurones
Myelinated neurones:
Myelin sheath speeds up impulse
Non-myelinated neurones:
No myelin sheath
Nervous Coordination
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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
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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
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When impulse is not transmitted:
- charge (resting potential) across axon membrane = -70mV
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When impulse is transmitted:
- action potential is a brief reversal of resting potential
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All-or-None rule:
- stimulus needs the minimum intensity to initiate an action
potential. Below this, there is no impulse
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Impulse takes place over:
- temporal or spatial summation
Nervous Coordination
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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
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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
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Analysis and Integration
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Central Nervous System:
1) Spinal Cord
2) Hindbrain
3) Midbrain
4) Forebrain
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Cerebral Cortex:
1) Sensory areas
2) Motor areas
3) Association areas
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Visual Cortex:
1) Simple cells
2) Complex cells
3) Association areas
Analysis and Integration
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Brain and spinal cord protected by:
1) Bone (skull and vertebral column)
2) Spinal and cranial meninges
3) Cerebrospinal fluid
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Opposing functions of sympathetic & parasympathetic
divisions of the ANS:
1) Iris
2) Ciliary muscle
3) Lacrimal gland
4) Urinary bladder wall
Muscles are Effectors
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Skeletal muscles occur in antagonistic pairs, held together by
connective tissue with a tendon at each end attached to the bones
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Collagen is a fibrous protein in tendons and bones that prevent
them from breaking or stretchy
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Arthropods have exoskeletons as their cuticle. This must be shed to
grow
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Skeletal muscle consists of muscle fibres, each containing many
myofibrils
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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)
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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
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Homozygous dominant (AA) – dominant allele expressed
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Homozygous recessive (aa) – recessive allele expressed
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Heterozygous (Aa) – dominant allele expressed
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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)
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Parents AABB and aabb  F1 will all be AaBb
 F2 will give 9:3:3:1 ratio of phenotypes
Sex-Linked Inheritance
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Occurs when the gene occurs on the sex chromosomes
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Males cannot be carriers, if the faulty allele is on the X
chromosome, as they will only have one copy of the gene.
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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
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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
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Total frequency for phenotype, p and q:
p+q=1
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p2 + 2pq + q2 = 1, whereby:
p2 = frequency pf AA
2pq = frequency of Aa
q2 = frequency of aa
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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
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Feature arises by random mutation, and survival determines
whether feature is passed on through population
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Artificial Selection
Breeding is controlled for certain characteristics
- new breeds but not new species
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When no selection pressure, characteristics are best suited for
the environment in which an organism lives
Species
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A population or group of similar organisms that can reproduce
to produce fertile offspring
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New species evolve by:
- isolation
- natural selection
- speciation
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Evolution relies strongly on immigration and emigration
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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
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Canis domesticus: Canis = genus, domesticus = species
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Genus has an upper case 1st letter: Canis
Species has a lower case 1st letter: domesticus
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Classification
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Five kingdoms of living organism:
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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
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Summary
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Energy Supply
Photosynthesis
Respiration
Survival and Coordination
Homeostasis
Nervous Coordination
Analysis and Integration
Muscles as Effectors
Inheritance
Variation
Selection and Evolution
Classification