paper 1 only

what are the chemical elements present in carbohydrates, proteins, and lipids

carbon, hydrogen, oxygen

proteins: carbon, hydrogen, oxygen, nitrogen

food test for glucose

• prepare a hot water bath

• add some BENEDICT’S SOLUTION to test tube

• place in water bath, leave for 5mins

pos = green → yellow → brick-red

food test for starch

• add iodine solution and gently shake tube

pos = browny-orange → blue-black/black

food test for proteins

• add BIURET SOLUTION and gently shake to mix

pos = blue → pink/purple

food test for lipids

• add couple drops of SUDAN (III) SOLUTION and gently shake

Sudan (III) solution stains lipids

pos = mixture separates out into two layers, top layer = BRIGHT RED

why do energy requirements vary in different people

activity level, age, pregnancy

def of diffusion

net movement of particles from an area of high conc to an area of low conc

def of osmosis

net movement OF WATER across a PARTIALLY PERMEABLE MEMBRANE from a region of high water conc to a region of low water conc

def of active transport

movement of particles against a conc gradient (area of low conc to an area of high conc) using energy released during RESPIRATION

how can you investigate osmosis

living system - potato cylinders in different sugar solutions

non-living system - visking tubingl

limiting factors of psyn

light, CO2 conc, temp

minerals needed for healthy growth

nitrates, phosphates, potassium

a bit of magnesium

why are nitrates needed for growth in plants

making amino acids and proteins which is needed for cell growth

not enough nitrates - stunted and older leaves will turn yellow.

why are phosphates needed for growth in plants

making DNA, cell membranes, respiration, and growth

not enough phosphates - poor root growth and older leaves turn purple

why is potassium needed for growth in plants

help enzymes for psyn and resp

not enough potassium - poor flower growth and discoloured leaves

why is magnesium needed for growth in plants

making chlorophyll

not enough magnesium - yellow leaves

which mineral ions cause yellow leaves if not enough

nitrates (older leaves) and magnesium

not enough potassium causes discolouration

what do xylem tubes transport

water and minerals from roots to shoots in the transpiration stream

what do phloem tubes transport

sucrose, amino acids from where they’re made in the leaves to other parts of the plant

what is the movement of food substances around a plant called

translocation

def for respiration

process of transferring energy from glucose, which happens constantly in every living cell

what is the indicator called in the investigating respiration practical

hydrogen-carbonate indicator

what are the lungs surrounded by

pleural membranes

describe breathing in

1. intercostal muscles and diaphragm contracts

2. thorax volume increases

3. this decreases the pressure, drawing air in

specialisation in alveoli for gas exchange?

• huge number gives very large SA

• moist lining - gases can dissolve

• very thin walls (1 cell thick) - gases don’t have far to diffuse

• great blood supply to maintain a high conc gradient

• permeable walls so gases can diffuse easily

what disease can smoking lead to

emphysema

function of arteries

carry blood away from the heart

function of capillaries

involved in exchange of materials at tissues

function of veins

carry blood to the heart

artery specialisation

• heart pumps blood at high pressure - strong and elastic walls

• elastic fibres allow arteries to expand

• walls are thick - contain layers of muscle to make them strong

largest artery in the body is the aorta

capillary specialisation

arteries branch into capillaries

• really tiny

• carry blood really close to every cell in body to exchange substances with them

• permeable walls - substances dissolve in and out

• supply food and oxygen and take away waste - CO2

• walls are usually only one cell thick - increases rate of diffusion by decreasing distance

vein specialisation

capillaries eventually join up to form veins

• blood is at lower pressure so walls don’t have to be as thick

• bigger lumen (hole in middle) to help blood flow

• have valves to keep blood flowing in right direction

largest vein in body is vena cava

right side of heart (top to bottom)

pulmonary artery

vena cava

right atrium

semi-lunar valve

tricuspid valve

right ventricle

left side of heart (top to bottom)

aorta

pulmonary vein

left atrium

semi-lunar valve

bicuspid valve

left ventricle

what 2 things control heart rate

exercise and hormonal system

pulmonary def

the lungs

hepatic def

the liver

renal def

the kidneys

right side of circulation system (top to bottom)

pulmonary artery

vena cava

hepatic vein

renal vein

left side of circulation system (top to bottom)

aorta

pulmonary vein

hepatic artery

hepatic portal vein (gut → liver)

renal artery

three main roles of the kidneys

1. removal of urea from blood

(urea is produced in the liver from excess amino acids)

2. adjustment of ion level sin blood

3. adjustment of water content in blood

3 main types of neurones

sensory, relay, motor

what does the central nervous system (CNS) consist of

brain, spinal cord only

what happens when receptors in a sense organ detect a stimulus

they send electrical impulses along sensory neurones to the CNS

the CNS sends electrical impulses to the effector along a motor neurone which then responds accordingly.

function of CNS

coordinate a response

needs a stimulus, receptor and effector

how does the nervous system bring about very rapid responses

information is transmitted using high speed electrical impulses

what is the connection between 2 neurones called

a synapse

• the nerve signal is transferred by chemicals (neurotransmitters) which diffuse across the gap

• these chemicals then set off a new electrical signal in the next neurone

source and role of adrenaline

• adrenal glands

• readies body for fight of flight

  • increases heart rate, blood flow to muscles and blood sugar level

source and role of insulin

• pancreas

• controls blood sugar level

  • stimulates liver to turn glucose into glycogen for storage

source and role of testosterone

• testes

• main male sex hormone

  • promotes male secondary sexual characteristics (e.g. facial hair)

source and role of progesterone

• ovaries

• supports pregnancy

  • maintains lining of uterus

source and role of oestrogen

• ovaries

• main female sex hormone

  • controls menstrual cycle and promotes female secondary sexual characteristics (e.g. widening of hips)

differences between hormones and nerves

nerves:

• fast message

• act for short time

• act on precise area

hormones:

• slower message

• act for long time

• act in more general way

def of homeostasis

maintenance of a constant internal environment (water content and body temp)

how is water lost from the body

• skin as sweat

• lungs in breath

  • kidneys as urine

when you’re too hot your skin…

• lots of sweat - evaporation - transfers energy from skin to environment

• blood vessels close to surface of the skin widen - VASODILATION - allows more blood flow near surface - can transfer energy into surroundings

• hairs lie flat

when you’re too cold your skin…

• very little sweat

• blood vessels near surface of skin constrict (VASOCONSTRICTION) - less blood flows near surface - less energy transferred to surroundings

• you shiver - increases rate of respiration - transfers more energy to warm body. (exercise does the same)

  • hair stand on end to trap an insulating layer of hair

higher SA:vol ratio

• organisms with bigger SA: vol ratios gain or lose heat faster as there is more area for the heat to transfer across

plant growth hormone: auxins

auxins control growth at the tips of shoots and roots, moving around the plant in solution.

• auxin is produced in the tips and diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips

• auxin promotes growth in the shoot, but actually inhibits growth in the root

• auxins are involved in the growth responses of plants to light (phototropism) and gravity (geotropism)

roots are…

POSITIVELY GEOTROPIC (grow towards gravity)

1. a root growing sideways will have more auxin on its lower side

2. auxin in root = inhibits growth. cells on top elongate faster, causing the root to bend downwards.

sexual reproduction def

where genetic information from two organisms is combined to produce offspring which are genetically different to either parent

haploid def

half the number of chromosomes in a normal cell (haploid number is 23)

what happens during fertilisation

• a male gamete fuses with a female gamete to form a zygote (fertilised egg)

  • zygote undergoes mitosis and develops into an embryo

mitosis

when a cell reproduces itself by splitting to form 2 cells with identical sets of chromosomes

meiosis

produces four haploid cells whose chromosomes are not identical