BIOLOGY IGCSE 🚨🚨🚨

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

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: 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

Alcohol

• less ADH

• More urine

• Dehydrated

• Hangover

Ecstasy

• more ADH

• Less urine

• Thirsty

• Lungs drown

Dandelions

• less ADH

• More urine

Osmosis

The movement of water across a partially permeable membrane from an area of high to low concentration

e.g soaking potatoes

Diffusion

The movement of particles from an area of high to an area of low concentration

e.g spraying perfume

Hypotonic Solution

Less Solute, more water

Water moves into the cell

Hypertonic solution

Water moves out of cell

More solute, less water

Isotonic Solution

Water moves in and out of the cell at the same rate

Active Transport

The movement of a substance against the concentration gradient from low to high concentration. This requires energy

e.g mineral ions in a root hair cell

test for starch

Iodine solution

Orange if present

Test for lipids

Cloudy if present

Test for glucose

Benedict’s solution

Green if some present

orange if lots present

Test for protein

Biurets solution

Lilac if present

How is the small intestine adapted

Large surface area

Villi

Rich blood supply for diffusion

Short distance for diffusion

Enzymes

Biological catalysts- speed up a chemical reaction

Made of protein

Carbohydrase

Breaks down disaccharides and polysaccharides into monosaccharides (simple sugars)

Amylase

Breaks down carbohydrates in the salivary glands in the mouth

Lipase

Breaks down lipids into glycerol+ fatty acids

Substrate

Complementary shape to the active site

Enzyme substrate complex

Where reaction happens

Optimum pH

7.5

What affect does pH and temperature have on enzymes

Denatures

Nucleus

Contains genetic material

Controls cell activities

Cytoplasm

Where chemical reactions take place

Jelly like substance

Supports cell structure

Permanent Vacuole

Contains cell sap

Keeps cells rigid to support plant

Mitochondria

Site of respiration

Cell wall

Made of cellulose

Strengthens the cell and provides support

Chloroplasts

Contains chlorophyll which is needed for photosynthesis

Ribosomes

All proteins needed for the cell are synthesised (made) here

Cell membrane

Controls the movement of substances in and out of the cell

Specialised Cells

Cells that are differentiated to perform a particular function

Root hair cells

Long thin hair like structure

Large surface area

No chloroplasts

Palisade cells

Large surface area

Many tightly packed chloroplasts for photosynthesis

Sperm cell

Digestive enzymes in head

Long tail

many mitochondria

Red Blood Cells

Bi concave shape

Haemoglobin

Stem cells

Undifferentiated cells

Used for repairing damaged cells

Arteries

Carry blood away from heart

Carries deoxygenated blood

No valves

Thin layer of muscle

Small lumen — high pressure

Capillaries

Connects arteries and veins

Carries both oxygenated an deoxygenated blood

No valves

Thin walls for diffusion

Low blood pressure allows fo the exchange of materials

Veins

Carries blood back to the heart

Carries deoxygenated blood

Have valves to stop the backflow of blood

Thin layer

Large lumen

Blood flows at low pressure