Exam Qs Flashcards
Explain the mechanisms for thermoregulation in humans
*The normal human body temperature is 37°C
*Peripheral thermoreceptors detect change in environment
*Supports conscious behaviour to avoid extreme temperatures through actions like wearing more clothing
*Hypothalamus sends signal to pituitary gland
*Pituitary gland releases TSH
*TSH stimulates thyroid to release thyroxin
*Thyroxin increases metabolic rate
*Random muscle contractions begin in order to generate heat
*Brown adipose tissue burns fat to generate waste heat
*White adipose tissue undergoes browning to also burn fat, while additionally acting as insulator
*Vasoconstriction occurs in order to preserve heat
Explain the relationship between temperature and enzyme activity
*As temperature increases, molecular motion also increases because there is more kinetic energy
*This increases frequency of collisions between enzyme and substrate
*Increasing the rate of reaction
*Until optimum temperature reached
*If temperature increases more, enzymes denature (because high temperature breaks H bonds, deforming the shape of the enzyme)
Distinguish between the thermal properties of air and water as
they relate to the habitat of animals.
*Water has a higher specific heat capacity than air
*Water requires more energy gain/loss to change temperature
*Water provides a more stable habitat to animals than air
*Water has a higher thermal conductivity than air
*More heat is transferred from organisms into water than from organisms into air
*Water is a good evaporative coolant and air is not
*Water animals must then have more body fat for insulation
Outline how water acts as a coolant when sweating
*Body’s internal temperature rises, hypothalamus detects it, signals for sweat glands to secrete sweat (mixture of water, Na+, Cl-)
*As sweat evaporates, hydrogen bonds are broken. This requires energy, and it uses the body’s excess thermal energy, thereby removing the heat from the skin with evaporation.
*Water’s high latent heat of vaporisation makes it more efficient at this, as it can absorb a large amount of heat for a relatively small amount of water.
Stem cells can be used to treat Stargardt’s disease. State one other condition treated
using stem cells.
*leukemia
*other diseases of the hematopoietic system
*skin burns
Explain the propagation of nerve impulses along the membrane of a neuron.
*Depolarization of one part of the axon triggers depolarization of the next part; this is called a local current
*There is diffusion of Na+ between depolarized and polarized part
*Resting potential reduced from -70mV to threshold potential at -50mV
*Sodium channels open when threshold potential reached
*Entry of sodium ions causes depolarization
*Saltatory conduction happens through the myelinated axons
Describe the secondary structure of proteins
*Polypeptide wound into an alpha helix shape
OR
*Polypeptide folded into a beta pleated sheet
*Stabilized by hydrogen bonds between C–O and N-H
*Are regular/unvarying
Outline the extension of the stem in plants
*Apical meristem divides through mitosis in the apex of the stem
*Auxin stimulates cell growth and enlargement
*Elongation of cells causes stem to grow
Explain transcription
*Transcription is the synthesis of mRNA from DNA
*Carried out by RNA polymerase
*RNA strand assembled on the template strand, copying the sense strand
*RNA polymerase uncoils the DNA strand, exposing the bases
*RNA polymerase binds to a promoter
*Complementary base pairing is the basis of copying base sequence
*Cytosine pairs with Guanine, but Thymine is replaced by Uracil, so Adenine pairs with Uracil
*RNA nucleotides linked together to form a strand
*3’ end of nucleotides linked to 5’ end of growing RNA strand
*Regulated by transcription factors
Distinguish between continuous and discrete variation, using examples
Continuous:
*Non distinct categories
(Many possible phenotypes)
*Multiple genes
*Environmental influences
*Height/weight/skin colour
Discrete:
*Distinct categories (Few possible phenotypes)
*Few influencing genes
*Not influenced by the environment
*Blood groups/number of eggs/eye colour
Outline the properties of water that make it an ideal transport medium in plants
*Water is polar,
*Which causes hydrogen bonds to form, and they’re very strong
*Cohesion happens between water molecules
*Cohesion allows tension to be created, thus causing upward movement against gravity
*Adhesion to cellulose cell walls generates tension in xylem, causing capillary rise
*Solvent for many substances
*Liquid at most temperatures, allowing it to flow
Distinguish between the xylem and the phloem of plants
Xylem:
*Transports water and mineral ions
*From roots to leaves
*Made of
-dead cells
-membrane present
-no organelles
*Hollow tube
*Lignified walls for support
*Pores that aren’t lignified to allow water passage from xylem vessel to xylem vessel, in case one is damaged
*Flows due to low pressure
*Thicker walls
*Wider lumen
Phloem:
*Transports photosynthesis products/sugars
*From source to sink (leaves to roots)
*Made of
-living cells
-membrane present
-some organelles
*Sieve plate/perforated walls present
*Flow due to high pressure
*Thinner walls
*Does not provide support
*Narrow lumen
Explain how the light-independent reactions of photosynthesis rely on the light-dependent reactions
Explain the production of antibodies in humans
*Antigens stimulate antibody production
*Antibodies produced by lymphocytes
*Macrophages engulf the pathogen and display the latter’s antigens on their surface
*T cells activated by macrophage displaying antigens
*Activated T cells activate B cell
*Activated B cell begins to divide by mitosis in order to produce clones of itself
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