Unit 2 QCAA

Question 1

define disease

Answer 1

Any deviation from the normal structure or function of an organ/system

Question 2

identify difference between infectious vs non-infectious diseases

Answer 2

Infectious - transmitted from one to another

Non-Infectious - caused by genetic and lifestyle factors

Question 3

define pathogen

Answer 3

a causative agent of disease

Question 4

define prion

Answer 4

type of protein that can trigger normal brain proteins to fold abnormally (cause neurodegenerative diseases)

Question 5

define virus

Answer 5

• make of DNA or RNA, coated with protein shell (capsid)

- depend on other cells to reproduce (NON-LIVING)

Question 6

define bacteria

Answer 6

prokaryotic organisms (pathogenic bacteria cause disease)

Question 7

define fungi

Answer 7

eukaryotic organisms that secrete enzymes to externally digest before absorbing the nutrients

Question 8

define protists

Answer 8

eukaryotic organisms, usually dont cause disease, but there are some that are pathogenic parasites that infect organisms to reproduce

Question 9

define parasite

Answer 9

organisms that live on or in another (host) and obtain nourishment at the expense of the host

Question 10

identify and describe virulence factors

Answer 10

Adherence factors:

• ability to adhere to host cells
• bacteria resist physical removal by producing fimbriae or pili, non-fimbrial adhesins and biofilm-producing glycocalyx

Invasion factors:

• ability of pathogen to enter host tissues, multiply and spread to other tissues
• eg. secrete enzymes to break down collagen, hyaluronic acid (‘glue’ holding cells together) to enter

Capsules:

• allow pathogens to resist host immune defence by preventing phagocytes from adhering to them
• antibodies cannot reach surface of bacteria to bind, therefore cannot initiate phagocytosis

Toxins:
- damage host tissues and be either endotoxins or exotoxins

Lifestyle Changes:

• change pathogenicity dependent on environmental changes
• eg. viruses switch between lytic and lysogenic cycles
• eg. fungal spores remain inactive until soil conditions become more favourable

Question 11

identify modes of disease transmission

Answer 11

• direct contact
• body fluids
• contaminated food/water
• disease-specific vectors (eg. mosquitos carrying malaria)

Question 12

describe recognition of self vs non-self

Answer 12

• MHC markers on surface of host cells label as ‘self’, no not attacked by immune system
• antigens on pathogens are recognised as ‘non-self’, because different from MHC markers on host cells

Question 13

innate vs adaptive immunity

Answer 13

Innate:
- general/non-specific
Adaptive:
- specific to certain antigen
- developed through life
- involves B and T lymphocytes

Question 14

give examples of physical and chemical defences of plants against pathogens

Answer 14

Physical defences:
- waxy cuticle
- bark/woody stems
Chemical defences:
- production of toxins harmful to pathogen (eg. insecticide pyrethrin)
- production of defensins with antimicrobial properties

Question 15

identify barriers of the innate immune response in vertebrates

Answer 15

• skin, mucus, cilia, saliva, tears, gastric acid

Question 16

explain the inflammatory system

Answer 16

• immune cells go to site of infection
• vasodilation –> more cells can get to infection
• mast cells secrete histamine and prostaglandins (cause vasodilation and increase permeability of capillaries)
• phagocytes engulf pathogen and display antigens
• natural killer cells destroy infected host cells

Question 17

Explain Humoral Response (B cells)

Answer 17

• effector B cells (plasma cells) - secrete specific antibodies to bind with antigen
• memory B cells - when activated by antigen, divide rapidly to produce plasma cells to secrete antibodies

Question 18

explain the cell-mediated response (T cells)

Answer 18

• helper T cells - activate B cells, phagocytes and cytotoxic T cells
• Cytotoxic T cells (killer T cells) - destroy infected host cells with chemicals
• Memory T cells - survive for many ears and very quickly create cytotoxic and helper T cells when exposed to pathogen again

Question 19

describe and give examples of passive and active immunity for both naturally and artificially acquired immunity

Answer 19

Passive - antibodies gained via placenta or breastfeeding (natural) or via antibody serum injection (artificial)
Active - natural exposure to pathogen (natural) or vaccination (artificial)

Question 20

identify factors that facilitate in the transmission of disease

Answer 20

• local, national and global movement of humans
• natural movement of animals via migration
• via water and wind

Question 21

identify factors affecting immunity (within pathogen and community)

Answer 21

• persistence of pathogens within host
• transmission mechanism
• proportion of populated immunised (herd immunity)
• mobility of individuals in affected population

Question 22

identify strategies to control spread of disease

Answer 22

- personal hygiene measures (wash hands, masks)
Community level:
- contact tracing and quarantine
- school and workplace closures
- reduction of mass gatherings
- temperature screening
- travel restrictions

Question 23

describe homeostasis and how it is maintained

Answer 23

• homeostasis maintained through feedback loops
• feedback loops - recognise stimulus, receptors, control centre, effector, and communication pathways (hormonal and nervous)

Question 24

recognise the sensory receptors, and which type of stimuli they detect

Answer 24

• mechanoreceptors (tough, pressure, hearing, equilibrium, position, acceleration)
• thermoreceptors (temperature)
• chemoreceptors (taste and smell)
• nociceptors (pain, physical/chemical damage to tissues)
• osmoreceptors (water volume)
• photoreceptors (light intensity)

Question 25

explain catabolism vs anabolism

Answer 25

catabolism - break down molecules into smaller | anabolism - build up (synthesis) smaller molecules into larger

Question 26

explain why changes in metabolic activity alter optimum conditions for enzymes

Answer 26

- metabolic activity produces heath and CO2 - affect pH levels - higher temps and extreme pH denature enzymes

Question 27

identify types of nerve cells

Answer 27

- sensory (detects stimuli, sends internal or external sensory information to CNS) - interneuron/relay neuron (in CNS, link sensory and motor, in brain to process info) - motor neurons (carry impulses from CNS to effectors --> muscles or glands)

Question 28

differentiate between sensory and motor neuron structure

Answer 28

Motor: - soma at one end - dendrites connect directly to soma - longer axon - axon connects to effector Sensory: - soma in centre of cell - dendrites connect to ends of axon - shorter axon - axon connects to receptor

Question 29

explain the process of passage of nerve impulse (action potential, and synapse transmission)

Answer 29

Action Potential: - resting potential at approx. -70mV, inactive and polarised (sodium on outside, potassium inside - negative inside overall) - when stimulated, membrane increases Na+ permeability, Na+ floods into cell, neuron briefly depolarised - if reaches threshold limit (-55mV), more Na+ enters - once action potential reaches around +30 - +40mV, Na channels close, neuron repolarises with inside becoming more negative again - hyperpolarisation - when repolarising, becomes slightly too negative before returning to resting potential - refractory period - time when neuron is repolarising, cannot generate another action potential Synaptic Transmission: - action potential stimulates neurotransmitters contained in capsules in the synaptic knob to fuse to presynaptic membrane and diffuse across synaptic cleft through exocytosis - neurotransmitters bind to receptors on postsynaptic neuron, triggering new action potential

Question 30

describe hormones

Answer 30

- chemical compounds that act as intercellular messengers to regulate various metabolic functions - relay messages to cells displaying specific receptors for each hormone - travel through circulatory or lymphatic system

Question 31

explain cell's sensitivity to specific hormone

Answer 31

- cell can change the concentration of specific hormone receptors on its membrane - upregulation - when hormone concentration in low, cell increases concentration of receptors on surface - downregulation - when hormone concentration is high, cell decreases concentration of receptors on surface

Question 32

describe signal transduction mechanism in hormonal system

Answer 32

- hormone binding to receptor activates signal transduction | - signal transduction alters cellular activity (change permeability of membrane, alter gene expression)

Question 33

define endotherms vs exotherms

Answer 33

endotherms - heat produced and temp maintained internally, not reliant on external environment exotherms - body temp dependent on external environment

Question 34

identify thermoregulatory mechanisms of endotherms (structural features, behavioural responses, physiological mechanisms, homeostatic mechanisms)

Answer 34

Structural Features: - brown adipose tissue (turn food into body heat by non-shivering thermogenesis) - increased no. mitochondria per cell (release more metabolic heat) - insulation (fur, feathers or fat layers) Behavioural Responses: - kleptothermy (sharing of metabolic thermogenesis with another animal - huddling) - hibernation (slow metabolism, breathing, drop temp to conserve energy in winter) - aestivation (state of lowered metabolism and dormancy similar to hibernation, but in summer, not winter) - torpor (hibernation, but shorter periods, sometimes just through night or day) Physiological Mechanisms: - vasomotor control (vasoconstriction or vasodilation in peripheral blood vessels) - Evaporative heat loss - Countercurrent heat exchange (heat transferred from warmer artery blood to colder venous blood from limbs - Thermogenesis/metabolic activity (shivering creates energy from ATP, or non-shivering with more mitochondria to create heat energy) Homeostatic mechanisms: - increase certain hormones to affect metabolism - insulin increases glucose in cellular respiration, creating energy

Question 35

define osmoconformers vs osmoregulators

Answer 35

Osmoconformers - isotonic with salinity of environment, do not regulate salt and water concentration themselves Osmoregulators - actively regulate salt and water concentration, independent of environment

Question 36

Identify osmoregulatory mechanisms (structural features, behavioural responses, physiological mechanisms, homeostatic mechanisms)

Answer 36

Structural features: - animals have differing lengths of loop of Henle Behavioural responses: - drink more when dehydrated - move to shade Physiological mechanisms: - specialised cells in gives can actively absorb or secrete salts (aid in moving between fresh and salt water) Homeostatic mechanisms - ADH increases reabsorption of water, making urine more concentrated (increase ADH when dehydrated, decrease ADH when too much water)

Question 37

identify osmoregulatory mechanisms in plants (based on environments)

Answer 37

General: - waxy cuticle on upper and lower epidermis - abscisic acid (ABA) produced in roots when soil is dry and translocated to leaves --> close stomata to reduce water loss Hydrophytes (aquatic): - little need for support or transport tissue - water absorbed through leaves - waxy cuticle to repel excess water, not to prevent evaporation Halophytes (salt water): - glands to actively secrete/remove salt - root level exclusion (roots structured to exclude 95% salt in soil) - tissue partitioning (concentrate salts in certain leaves which then fall off) Mesophytes (only moderate water needed): - large root masses - leaves - broad, thin, waxy cuticle - most stomata on underside - produce abscisic acid Xerophytes (dry conditions): - leaves - small, hard, thick cuticle, sunken stoma - fine hairs trap humid air, decrease evaporation - deep root system to reach water table