Unit 10: Coordination and Control Flashcards

Question

Explain positive phototropism

Answer 1

Positive phototropism = grow towards the highest light intensity in their environment Benefit: increases the amount of light absorbed by a shoot’s leaves for use in photosynthesis

Answer 2

Phytohormone = plant hormone that helps control growth, development and responses to stimuli in plants 1. GROWTH - can either promote or inhibit growth by affecting rates of cell division and cell enlargement (i.e. gibberelin causing stem elongation) 2. DEVELOPMENT - promote or inhibit aspects of development (i.e. ethylene ripens fruits) 3. RESPONSE TO STIMULI - control tropisms (i.e. auxins control phototropism)

Answer 3

Auxin = phytohormone that promotes stem growth and causes differential growth response of phototropism. - enter cells by passive diffusion as long as its carboxyl group remains undissociated Auxin efflux carriers will move to the side that requires auxin, allowing auxin to be pumped into that side of the plant

Answer 4

Auxin promotes proton pump synthesis in the cell walls (apoplast) --> lowers pH of cell wall --> weakens crosslinks between cellulose microfibrils within cell wall --> cell wall can then elongate

Answer 5

Auxin is produced in shoot tips, transported down into roots in phloem Cytokinin is produced in root and transported up into shoots in xylem. If they work together, it is called synergism. Else: antagonism

Answer 6

When seeds are ready to be dispersed, the fruit ripens - colour changes from green - cell walls are partially digested, - softening fruit flesh - acids and starch converted to sugar (palatable) - volatile substances are synthesized to give fruit a distinctive scent Positive feedback: ethylene stimulates ripening, ripening fruits produce ethylene. Ethylene is also a gas --> so it affects nearby fruits

Answer 7

SIMILARITIES: 1. binding of ligand/substrate occurs at the specific site 2. shape + chemical properties of the ligand-binding/active site match ligand/substrate, preventing other substances from binding 3. receptors/enzymes are unchanged by the binding of a ligand/substrate, even if temporary changes to induce fit DIFFERENCES: 4. ligand released unchanged after bonded, but substrate is chemically converted into product and released

Answer 8

A change in the behaviour of a colony when its population density reaches a certain threshold More cells = more chemical messenger molecules. At certain density, enough molecules have been received to cause a change in activity = demonstrates interdependence EXAMPLE: Vibrio fischeri --> bioluminescence - when it reaches a certain population density, it will bioluminesce

Answer 9

All are functional categories of signalling chemicals in animals 1. HORMONES (i.e. insulin, glucagon, testosterone, estrogen) - come from endocrine glands - target cells have receptor proteins - long effect time 2. NEUROTRANSMITTERS (i.e. dopamine, seratonin) - only travel in the synapse - isolated to just that nerve junction - short effect time, because they are quickly removed from synapse 3. CYTOKINES (i.e. interferon) - proteins that act as chemical messages within cells/between nearby cells - can have multiple effects depending on binding site 4. CALCIUM IONS - not a biological molecule - with muscle fibres = calcium ions bind to a protein on actin to allow myosin heads to attach - neurons = causes the release of neurotransmitters from the presynaptic neuron

Answer 10

Both are small, soluble, and have a shape compatible with a receptor. HORMONES: steroids, amines, peptides NEUROTRANSMITTERS: amines, amino acids, esters, gases

Answer 11

Hormones have effect over LARGE distances because they are travelling through blood Neurotransmitters produce a localised effect between 2 neurons, because they are only travelling between 2 neurons

Answer 12

INTRACELLULAR RECEPTOR: Signalling molecule (steroid hormone) CAN enter the cell because it is hydroPHOBIC, so receptor protein is located IN the cytoplasm or nucleus (inside the cell), and have a surface of hydroPHILIC amino acids TRANSMEMBRANE RECEPTORS: Signalling molecule (non-steroid hormone) CANNOT enter the cell because it is NOT hydrophobic, so receptor protein is located ON the plasma membrane, has BOTH hydrophilic and hydrophobic amino acids

Answer 13

TRANSDUCTION: sequence of interactions initiated by the ligand binding to receptor TWO MAJOR TYPES OF TRANSDUCTION PATHWAYS: 1. INTRACELLULAR: - ligand enters cell - binds to receptor - complex regulates gene expression 2. TRANSMEMBRANE PATHWAY - ligand binds with the receptor - receptor changes shape - produces secondary messenger molecules - causes changes inside the cell

Answer 14

Neurotransmitters are released from the presynaptic neuron. They bind to receptors on the post-synaptic neuron and cause sodium ion channels to open. Sodium then enters the cell via facilitated diffusion. --> changes the membrane potential from negative to positive Example: acetylcholine is a messenger between neurons and muscle fibers

Answer 15

GPCR: G-protein coupled receptor (transmembrane receptor protein) GDP: guanosine DIphosphate GTP: guanosine TRIphosphate when GDP bound to G protein = inactive when ligand binds to the receptor, GDP is replaced by GTP --> protein complex activates, disassembles and causes changes within cells

Answer 16

Epinephrine = NON STEROID hormone produced in the adrenal glands, so cannot enter cell when it binds with a G-protein, it causes a SECONDARY MESSENGER MOLECULE CASCADE -- ATP to be converted into a secondary messenger molecule called cyclic AMP (cAMP) - amplifies the effect example: hydrolysis of glycogen --> glucose

Answer 17

Kinase: enzyme that phosphorylates molecules by removing a phosphate group from ATP and adding it to a molecule Tyrosine Kinase: enzyme that transfers a phosphate group from ATP to tyrosine (a type of amino acid) in a protein EXAMPLE: binding of insulin to the transmembrane receptor protein tyrosine kinase are the 2 tails that extend into the cytoplasm -insulin cannot enter cell -insulin binds to the receptor, the tyrosine kinase with join and this causes a conformational change in the proteins -the vesicle that contains the proteins will fuse with the membrane (insertion of glucose transporters into the membrane -glucose can move into the cell

Answer 18

Intracellular receptors are hydrophobic so can enter the cell and bind to an intracellular receptor The hormone receptor complex will attach to the DNA in the nucleus and changes gene expression

Answer 19

OESTRADIOL GnRH --> secretion of LH and FSH --> travel through bloodstream and target tissue = ovary --> when follicles are acted upon by these hormones, they secrete oestradiol Oestradiol will travel BACK to hypothalamus and enter the hypothalamus cells, causing even more transcription and translation to take place --> MORE GnRH produced (positive feedback) PROGESTERONE target tissue in endometrium, progesterone will travel through bloodstream to these cells, will enter the cells and regulate genetic expression that thickens and intensifies nutrition value of endometrium

Answer 20

Negative feedback loop: - to maintain stable conditions - increasing concentrations of the end product inhibits further production - example is testosterone --> GnRH --> LH, travels via bloodstream to testes, triggering testosterone release --> travels to hypothalamus to INHIBIT GnRH production Positive feedback loop: - final product triggers more production of the product - example: oestradiol --> GnRH --> secretion of LH and FSH --> travel through bloodstream and target tissue = ovary --> when follicles are acted upon by these hormones, they secrete oestradiol Oestradiol will travel BACK to hypothalamus and enter the hypothalamus cells, causing even more transcription and translation to take place --> MORE GnRH produced (positive feedback)

Answer 21

Neurons = cells within nervous system that carry electrical impulses electrical impulses = electrical signal passed between 2 cells

Answer 22

membrane potential = voltage created by an imbalance of charges on either side of the membrane at rest: - inside of neuron is relatively negative (-70 mV [millivolts]) - Na+ are on the outside of the cell - this is established by active transport (sodium potassium pump), requires ATP and generating a CONC. GRADIENT --> sodium OUTSIDE and potassium INSIDE

Answer 23

depolarisation: membrane potential goes from negative to positive --> ions into the cell --> potassium ions will leave the cell afterwards repolarisation: membrane potential goes from positive back to negative --> when potassium ions leave the cell sodium potassium pump will move the sodium ions out and potassium ions in PROCESS: 1. voltage gated sodium ion channels open 2. sodium ions diffuse INTO the cell (facilitated diffusion) 3. depolarisation 4. voltage gated sodium ion channels close, and voltage gated potassium ion channels open 5. potassium ions diffuse out of the cell (facilitated diffusion) 6. repolarisation 7. sodium potassium pump re-establishes resting potential by actively pumping sodium ions out and potassium ions in nerve transmission occurs starting from dendrites and along the axon to the terminal. depolarisation in one part triggers depolarisation in the next part due to the opening of voltage-gated channels. this is called SELF-PROPAGATION

Answer 24

Average speed = 1m/s to increase speed: -larger axon diameter -myelination --> myelin sheath (the little knobs on the axon MYELINATED VS NON-MYELINATED NEURONS --> saltatory conduction occurs only in MYELINATED CONDUCTION --> myelin sheath insulates the electrical impulse, so it only has to jump from node to node --> 1 to 100m/s

Answer 25

Synapse = gap between cells through which signals are passed by neurotransmitters only 20nm wide occur between neurons and between neurons and effectors

Answer 26

1. Action potential (wave of positive voltage) reaches the end of the presynaptic neuron 2. Voltage gated calcium ion channels open 3. Calcium ions enter the presynaptic neuron (facilitated diffusion) 4. Ions force vesicles with neurotransmitters to fuse with the membrane 5. Neurotransmitters released into the synapse (exocytosis) 6. Neurotransmitters diffuse across synapse 7. Bind to receptors on the postsynaptic membrane 8. Ion channels open 9. If enough ions enter the postsynaptic cell, that generates an action potential 10. Neurotransmitter is removed from the synapse (either destroyed or moves back into presynaptic neuron)

Answer 27

Acetylcholine - responsible for carrying messages between neurons and muscles Enzyme that breaks down acetylcholine = acetylcholinesterase --> breaks down to acetyl and choline --> choline is reabsorbed by the presynaptic neuron to make more acetylcholine

Answer 28

Threshold potential = the membrane potential that must be reached in order for the voltage gated ion channels to open (-50mV) When sodium diffuses into the neuron, a wave of ion-channel openings occurs further down the axon

Answer 29

local current = movement of sodium ions between polarised and depolarised regions

Answer 30

Oscilloscope = can measure membrane potentials using electrodes

Answer 31

Occurs in myelinated sheaths, means the jumping of the nerve impulse from node to node to increase speed of impulses 1m/s to 100m/s

Answer 32

Exogenous chemical = something that enters the body from an external source can affect synaptic transmission (block or promote) EXAMPLES neonicotinoids: insecticides/pesticides --> binds to acetylcholine receptors, so cannot bind causes paralysis and death 1. pros: does not affect humans 2. cons: affects non-pest species (like bees) cocaine: -blocks the reuptake mechanism for dopamine to the presynaptic neuron -dopamine builds up -too many dopamine messages -stimulant/feelings of euphoria

Answer 33

Some neurotransmitters make the membrane even more negative (hyperpolarized), making it harder for nerve impulses to be sent Acetylcholine is an excitatory neurotransmitter. Gaba is an inhibitory neurotransmitter.

Answer 34

- an excitatory neurotransmitter from one presynaptic neuron is usually not enough to reach threshold potential in the postsynaptic neuron SUMMATION: when multiple releases of an excitatory neurotransmitter are needed to cause an action potential in the postsynaptic neuron -> neurotransmitters from diff neurons OR -> several neurotransmitters from the same neuron excitatory neurotransmitters MUST OUTNUMBER inhibitory neurotransmitters in order to reach threshold potential

Answer 35

sensory neurons have endings in the skin. action potential is initiated in response to pain carries the impulse to the spinal column, then to the brain brain sends an impulse along motor neurons to affect behaviour

Answer 36

consciousness is a property that emerges from the interaction of individual neurons in the brain. --> simultaneous awareness of many different things Sleep = reduced consciousness Anesthesia = unconsciousness

Answer 37

Maintaining stable internal conditions regardless of fluctuations in the external environment examples = body temp, blood pH

Answer 38

Homeostasis utilises negative feedback loops and uses energy but allows organisms to make use of a wider range of habitats

Answer 39

Cells of the pancreas -> exocrine glands = secrete substances through a duct -> endocrine glands = secrete hormones into the bloodstream ---> α cells = glucagon (secreted when low blood glucose levels) ------> stimulates conversion of glycogen to glucose ------> glucose levels return to normal ---> β cells = insulin (secreted when high blood glucose levels) ------> opens glucose channels to allow for uptake ------> stimulates conversion of glucose to glycogen ------> glucose levels return to normal

Answer 40

Diabetes = chronically elevated blood glucose levels TYPE I - Immune system attacks β cells, so little to no insulin is produced -> autoimmune to treat: insulin injections TYPE II - Decreased sensitivity to insulin due to lack of insulin receptors -> caused by lifestyle and genetics to treat: dietary changes to avoic peaks + exercise

Answer 41

peripheral thermoreceptors in the skin and central thermoreceptors predict temperature changes. hypothalamus monitors and interprets information from thermoreceptors and initiates a response TRH = thyrotropin releasing hormone TSH = thyroid stimulating hormone Thyroxine = a hormone that increases cellular metabolism (respiration) @ LOW TEMP -> Hypothalamus secretes TRH -> Pituitary secretes TSH -> Thyroid secretes Thyroxine -> Cellular metabolism increases, causing temp to increase Endocrine tissues: Muscle tissues: contractions generate heat Adipose tissues (fat cells): insulator to prevent heat loss , respiratory substrate for heat generation (respiration)

Answer 42

If COLD: - shivering - erection of hair - vasoconstriction (reducing blood flow to skin) - uncoupled respiration in brown adipose tissue --> No ATP produced, only heat If HOT: - sweating --> water has a high latent heat of vapourisation --> controlled by hypothalamus - vasodilation --> increases blood flow to skin

Answer 43

Osmoregulation = Keeping the osmotic concentration of body fluids within narrow limits --> Kidney carries out osmoregulation by varying the relative amounts of water and salts that are removed from the body in urine. Excretion = The removal of toxic waste products of metabolism from the body. --> kidney removes substances like urea

Answer 44

Glomerulus = fenestrated capillaries that allows filtrate to be separated from blood Bowman's capsule = captures filtrate from the glomerulus Proximal convoluted tubule = site of selective reabsorption

Answer 45

Afferent arteriole > efferent arteriole Creates high pressure, forces molecules out of the glomerulus, glomerular filtrate captured by Bowman's capsule Based on size and charge (not selective)

Answer 46

Recapture molecules from ultrafiltration - sodium ions (active transport) - chloride ions (active transport) - water (osmosis) - glucose (using cotransporter proteins by facilitated diffusion) special adaptations for this: microvilli (larger surface area), mitochondria (produce atp for active transport) molecules not reabsorbed: - urea and other toxins - salt - water

Answer 47

Medulla has high solute concentration Descending limb - water exits via osmosis Ascending limb - not permeable to water - sodium ions leave filtrate (active transport)

Answer 48

Hypothalamus monitors osmotic concentration in blood - can trigger the pituitary to release ADH (or not) ADH = antidiuretic hormone (increases permeability of the collecting duct by moving aquaporins to cell surface) So, when dehydrated, more ADH, more water leaves filtrate, more concentrated urine. Hydrated, NO ADH.

Answer 49

Arterioles: Vasoconstriction = reduce blood flow Vasodilation = increase blood flow BLOOD FLOW 1. SLEEP Brain: high Skeletal muscle: low Digestive system: variable Kidneys: low 2. RESTING BUT AWAKE Brain: moderate Skeletal muscle: moderate Digestive system: variable Kidneys: very high 3. EXERCISE Brain: high Skeletal muscle: very high Digestive system: low Kidneys: low