exam

Question 1

test for starch

Answer 1

starch is placed on spotting tile
a drop of yellow brow iodine is added
will change blue black in presence of starch

Question 2

test for glucose

Answer 2

glucose and distilled water
benedicts’ sol added(few drops)
water bath and boil
blue will change to brick red

Question 3

test for protein

Answer 3

biurets solution
protein and distilled water
pale purple

Question 4

test for lipid

Answer 4

pipette used to add one drop of oil
ethanol
water
white layer forms

Question 5

describe how energy content of food can be measured

Answer 5

mass of food sample is found
measured vol of 20cm3 water is placed in a boiling tube
tube is supported by stand and clamp
temperature of water is recorded
food is speared on end of mounted needle and held on to a bunsen burner flame until it catches fire
needle is used to hold burning food under boiling tube of water
this is continued,relighting if the flame goes out until the food can no longer burn
thermometer is used to stir gently so heat is evenly distributed and final temp is recorded
energy in joules per gram=
(final temp-initial temp)x20gx4.2/mass of food(g)
errors:(heat lost in test tube and water
distance between food and water not equal)

Question 6

describe the process of transcription

Answer 6

happens in the nucleus
in a chromosome part of the DNA helix unwinds and unzips so the 2 strands separate exposing the bases along the template strand
DNA forms framework and mRNA is formed
building blocks of mRNA are RNA nucleotides
they line up according to the complementary base pair rule
mRNA leaves nucleus and moves in to cytoplasm through the pores of the nuclear membrane
DNA helix then zips up again

Question 7

describe the process of translation

Answer 7

takes place at ribosome
first tRNA binds to bind at mRNA does so at start codon
another tRNA brings an anticodon which binds with next codon on mRNA
bonds form between first and second amino acid process is ongoing forming a polypeptide
at end of chain is stop codon

Question 8

what are the differences between DNA and RNA

Answer 8

DNA is a double helix RNA is a single strand
DNA contains the sugar deoxyribose RNA contains ribose
RNA contains the base uracil instead of thymine

Question 9

where does protein synthesis take place

Answer 9

cytoplasm of cell

Question 10

tough outer coat of eye, visible white coat

Answer 10

sclera

Question 11

transparent window which allows light to enter eye

Answer 11

cornea

Question 12

coloured ring of tissue

Answer 12

iris

Question 13

hole which lets light through

Answer 13

pupil

Question 14

dark layer underneath sclera which contains many pigment cells and blood vessels

Answer 14

choroid

Question 15

place where light energy is converted to nerve impulses at back of the eye

Answer 15

retina

Question 16

nerve which carries impulses to brain

Answer 16

optic nerve

Question 17

place where cones are concentrated

Answer 17

fovea

Question 18

what are the adv of having 2 eyes

Answer 18

cancelling blind spot
wider field of vision
stereoscopic vision
better sense of distances

Question 19

what are the changes that occur that allow distant objects to be seen

Answer 19

ciliary ms relax
suspensory ligaments are pulled tight
lens flat

Question 20

state cause, result and method of correction for long sight

Answer 20

cause: lens not convex enough or eyeball too short
result: light focused beyond retina
method of correction: convex lens to converge light before it enters the eye

Question 21

state cause, result and method of correction for short sight

Answer 21

cause: lens too convex or eye ball too long
result: light focused short of retina
method of correction: concave lens to converge lens before it enters the eye

Question 22

discuss the differences between regular and irregular astigmatism

Answer 22

regular: occurs when surface of cornea or lens is not perfectly spherical but rounder in one direction than the other
person’s eye will be in focus in one direction but not the other
corrected by glasses or lenses
irregular: curvature of cornea or lens is in more than one direction
corrected by lenses only

Question 23

what is a cataract and how is it treated

Answer 23

a condition in which the lens becomes cloudy and opaque so person is unable to see
can only be treated by surgery
lens is replaced by artifical lens

Question 24

roles of vitamins+deficiency

Answer 24

A:making chemical in retina and protects eye surface
deficiency: night blindness
B1: helps with cell respiration
def: beri beri
B2:helps with cell respiration
def: poor growth and dry skin
B3:helps with cell respiration
def: pellagra(dry red skin, poor growth, and digestive disorders)
C:sticks together lining surfaces such as the mouth
def: scurvy
D: helps bone absorb calcium and phosphate

Question 25

state the differences between sperm and ovum

Answer 25

sperm: motile
smaller 
no stored nutrients
either x or y chr
has tail
acrosome present 
ovum: cant move
larger
stored nutrients
only x chr
no tail
acrosome not present