BIOLOGY IGCSE

Ultrafiltration

Allows small molecules to pass through e.g glucose and urea

Larger molecules e.g proteins remain in bloodsteam

What happens in selective reabsorption?

Mitochondria release ATP

Against concentration gradient

Selective reabsorption

Sodium ions and glucose are reabsorbed via active transport at a the proximal convoluted tubule

Loop of Henlé

Causes more water to be reabsorbed into the blood

Long loop of Henlé = more concentrated urine

Antidiuretic hormone

Hormone which controls the volume of urine produced

Cortex

Contains many blood vessels + nephrons

Nephrons

Microscopic tubules that produce urine

Adaptations of the nephron:

Many mitochondria to provide energy for active transport

Diabetes?

Cannot control glucose levels, often high

Not all glucose can be reabsorbed into blood

Glucose end ups in urine

Osmoregulation

The process by which organisms regulate the balance of water and salt in their bodies to maintain proper fluid balance and prevent dehydration or overhydration.

Excretion

The removal of metabolic waste from the body

If the body is dehydrated

More ADH is released

Collecting duct becomes more permeable to water

Water leaves into the bloodstream

Lower volume of concentrated urine

Filtrate

Urea

Glucose

Water

Salts

ADH

Controls water excreted

Travels in the plasma

Alcohol

• less ADH

• More urine

• Dehydrated

• Hangover

Ecstasy

• more ADH

• Less urine

• Thirsty

• Lungs drown

Dandelions

• less ADH

• More urine

Cornea

Transparent; no blood vessels, oxygen diffuses it from outside air

Refracts light , allows light into the eye

Iris

Controls how much light enters the pupil

Pupil

Gap in iris that allows light pass through to the lens

Lens

Changes shape to focus light onto the retina

Rod cells

Sensitive to light, can only see black and white

I.e can’t see colour in the dark

Cone cells

Sensitive to colour of light, allow us to see colour

Fovea

Area of retina with high concentration of cone cells, provides sharp vision

Optic nerve

Transmits impulses to the brain

Virtreous humour

Maintains shape of eye and attaches to retina

Aqueous humour

Maintains pressure in eye and nourishes cornea

Ciliary muscles

Help change the shape of of the lens in accommodation

Adaptations of neurones

Adapted to carry electrical impulses from one point to another

They are:

Long

Thin

Many branched connection to allow them to pass information

Sclera

Tough outer coat of the eye

Chloroid

Dark layer, pigmented to prevent light form being reflected around the eye

Nervous system (vs encodrine/hormonal system)

• sends fast impulses

• Short lived effect

• Localised effect

Endocrine system (vs nervous system )

• hormones in bloodstream

• Slower

• Longer-lasting

• Generalised effect

In bright light:

• circular muscles contract

• Radial muscles relax

• Pupil constricts

In dim light:

• circular muscles relax

• Radial muscles contract

• Pupils dilate

Photosynthesis word equation

Carbon dioxide + water —> glucose + oxygen

Photosynthesis process

Converts light energy too chemical energy

Factors affecting photosynthesis

Light intensity, concentration carbon dioxide, temperature

When stomata open

Water moves into guard cells

Cells become turgid

When stomata close

Water moves out of guard cell

Cells become flaccid

Limiting factor

The factor that prevents the rate of reaction from increasing

Leaf adaptions for photosynthesis

Large surface area; many chloroplasts

Upper epidermis

Transparent and allows light through

Waxy cuticle

Prevents water loss by evaporation

Palisade mesophyll

Contains many chloroplasts; main site of photosynthesis

Spongy mesophyll + air spaces

Allows diffusion of carbon dioxide into and oxygen out of the leaf

Lower epidermis, guard cells + stomata

Allows diffusion of carbon dioxide into and oxygen out of the leaf

Magnesium ion function

Component of chlorophyll

Magnesium ion deficiency

Yellowing

Nitrate ion function

Amino acids, DNA, chlorophyll

Nitrate ion deficiency

Stunted growth, yellowing

Test for starch

Iodine

POSITIVE: BLUE-BLACK

NEGATIVE: YELLOW-BROWN

Test for glucose

Benedict’s solution

1. Add water to test tube

2. Add Benedict’s solution

3. Heat in beaker

   POSITIVE :BRICK-RED

   NEGATIVE : BLUE

Test for protein

Biuret’s solution

Positive: PURPLE

Negative: BLUE

Test for lipid

Ethanol

POSITIVE: CLOUDY

NEGATIVE: COLOURLESS

Carbohydrate elements

Carbon, hydrogen, oxygen

Lipids elements

Carbon, hydrogen and oxygen

Protein elements

Carbon, hydrogen, oxygen, nitrogen (sulfur)

PRACTICAL: the effects of light on gas exchange

• hydrogen carbonate indicator

• 4 test tubes

• Light + dark

• PURPLE +YELLOW

PRACTICAL: what happens to leaf placed in sunlight

• turns PURPLE

• Photosynthesis occurring faster than respiration

• Leaf is using up co2 faster than it is respiring

PRACTICAL: what happens to leaf placed in dark

• will turn YELLOW

• leaf is respiring faster than its photosynthesising

• Leaf is producing co2 faster than it is using it

PRACTICAL: testing green leaves for starch

• soften leaf in boiling water

• Ethanol

• Iodine

PRACTICAL: carbon dioxide is needed for photosynthesis

• bell jar 24hrs

• Soda lime/ sodium hydroxide absorbs carbon dioxide from air

• Test leaves for starch

PRACTICAL: effects of light intensity on oxygen production

• pondweed in water

• Move lamp to different distances

• Record the number of bubbles produced

Xylem function

• Transports water and minerals through the plants

Xylem structure

• Thickened walls of lignin

• dead cells - hollow tubes

Phloem function

• transports sugars (sucrose + amino acids)

Transpiration

Loss of water by evaporation from mesophyll cells

Cornea

Transparent; no blood vessels, oxygen diffuses it from outside air

Refracts light , allows light into the eye

Iris

Controls how much light enters the pupil

Pupil

Gap in iris that allows light pass through to the lens

Lens

Changes shape to focus light onto the retina

Rod cells

Sensitive to light, can only see black and white

I.e can’t see colour in the dark

Cone cells

Sensitive to colour of light, allow us to see colour

Fovea

Area of retina with high concentration of cone cells, provides sharp vision

Optic nerve

Transmits impulses to the brain

Virtreous humour

Maintains shape of eye and attaches to retina

Aqueous humour

Maintains pressure in eye and nourishes cornea

Ciliary muscles

Help change the shape of of the lens in accommodation

Adaptations of neurones

Adapted to carry electrical impulses from one point to another

They are:

Long

Thin

Many branched connection to allow them to pass information

Sclera

Tough outer coat of the eye

Chloroid

Dark layer, pigmented to prevent light form being reflected around the eye

Nervous system (vs encodrine/hormonal system)

• sends fast impulses

• Short lived effect

• Localised effect

Endocrine system (vs nervous system )

• hormones in bloodstream

• Slower

• Longer-lasting

• Generalised effect

In bright light:

• circular muscles contract

• Radial muscles relax

• Pupil constricts

In dim light:

• circular muscles relax

• Radial muscles contract

• Pupils dilate

Ultrafiltration

Allows small molecules to pass through e.g glucose and urea

Larger molecules e.g proteins remain in bloodsteam

What happens in selective reabsorption?

Mitochondria release ATP

Against concentration gradient

Selective reabsorption

Sodium ions and glucose are reabsorbed via active transport at a the proximal convoluted tubule

Loop of Henlé

Causes more water to be reabsorbed into the blood

Long loop of Henlé = more concentrated urine

Antidiuretic hormone

Hormone which controls the volume of urine produced

Cortex

Contains many blood vessels + nephrons

Nephrons

Microscopic tubules that produce urine

Adaptations of the nephron:

Many mitochondria to provide energy for active transport

Diabetes?

Cannot control glucose levels, often high

Not all glucose can be reabsorbed into blood

Glucose end ups in urine

Osmoregulation

The process by which organisms regulate the balance of water and salt in their bodies to maintain proper fluid balance and prevent dehydration or overhydration.

Excretion

The removal of metabolic waste from the body

If the body is dehydrated

More ADH is released

Collecting duct becomes more permeable to water

Water leaves into the bloodstream

Lower volume of concentrated urine

Filtrate

Urea

Glucose

Water

Salts

ADH

Controls water excreted

Travels in the plasma