2 Nutrition Flashcards
What is photosynthesis?
Converts light energy into stored chemical energy used by organism for respiration and making other biological molecules
How do plants photosynthesise?
plants use carbon dioxide and water to make glucose and oxygen
What does photosynthesis require?
light energy, absorbed by chlorophyll
what is the word and balanced chemical equation for photosynthesis?
carbon dioxide + water → glucose + oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
What is glucose used for in plants?
Making carbohydrates:
* starch for storage
* sucrose for transport
* fructose, found in fruits
* cellulose (cell walls)
Making DNA
Making Amino acids:
* joined together to make proteins
Making Lipids:
* e.g. to make cell membranes and oils in seeds
Making chlorophyll
What factors affect the rate of photosynthesis?
carbon dioxide concentration
light intensity
temperature
What is the factor in shortest supply called?
the limiting factor
What happens to rate of photosynthesis if you increase carbon dioxide concentration?
increases rate
more molecules to collide with enzymes
eventually reach point when adding more has no effect as lack of energy
What happens to rate of photosynthesis if you increase light intensity?
increase rate
more energy for reaction
at high light intensities a different factor is limiting
(graph levels off)
What happens to rate of photosynthesis if you increase temperature?
speeds up reaction
enzymes and substrates have more kinetic energy and collide more often
too high temps, rate decreases and reaction stops as enzymes become denatured
Describe the structure of a leaf
waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
guard cell
stomata
What does waxy cuticle do?
reduces water loss
what does the upper epidermis do?
transparent and contain no chloroplasts to allow light in to palisade cells
how are palisade cells specialised for photosynthesis?
long and thin and tightly packed.
large numbers of chloroplasts - maximises absorption of sun energy
main site of photosynthesis
how is spongy mesophyll specialised for photosynthesis?
air spaces to allow diffusion of CO₂ and O₂ to photosynthesising cells
How are stomata specialised for photosynthesis
allow gases to diffuse into air spaces of leaf. provides short diffusion distance for carbon dioxide
How do the guard cells work?
Day - stomata open
more light, more photosynthesis, more sugars produced in guard cells. Lowers water potential so water moves into guard cells by osmosis, opening stomata
What does the xylem do?
transports water from roots to leaves. provides short diffusion distance for water to diffuse into the photosynthesising cells
What does the phloem do?
transport sugars made in photosynthesis to other parts of the plant
Where do plants get mineral ions from?
absorbed through roots
What mineral ions do plants absorb?
nitrates
magnesium
phosphates
What do plants use nitrates for?
required to make amino acids and nucleic acids (DNA and RNA)
What do plants use magnesium for?
required to make chlorophyll
What do plants use Phosphates for?
required to make nucleic acids
part of cell membrane
What symptoms do plants show when they have a deficiency in nitrates?
stunted growth
What symptoms do plants show when they have a deficiency in magnesium?
yellow leaves
What symptoms do plants show when they have a deficiency in Phsophates?
poor root growth
purple younger leaves
How do you test a leaf for starch?
place leaf in boiled water for 2 mins - kills leaf (denature enzymes - stops reactions)
heat ethanol in warm water and place leaf in ethanol for 2 mins (extracts chlorophyll as ethanol dissolves lipids)
put leaf in boiled water for 15 seconds (softens leaf for penetration of iodine)
spread leaf on tile and put few drops of iodine
leaf turns blue/black
Describe experiment for how light intensity effects photosynthesis
test tube with pondweed (stem cut at angle) in sodium hydrogen carbonate solution
leave for 5 mins to acclimatise
10 cm from light source
count bubbles
repeat different distances
What should a balanced diet contain?
Carbohydrates, Proteins, Lipids, Minerals, Vitamins, Water and Fibre
What foods are carbohydrates?
Bread, potatoes, rice, cereals, fruit
What are carbohydrates used for?
fuel for respiration
What foods are proteins?
Meat, eggs, fish, quinoa, quorn
What are Proteins used for?
growth and repair of cells and tissues
Fuel for respiration
What foods are lipids?
Butter, cooking oil, cream, avocados
What are lipids used for?
store of energy
fuel for respiration
How is glucose stored in plants and animals?
starch in plants
glycogen in animals
What is energy used for in the body?
Heart beating, transport nutrients and repair cells.
30% used for walking, talking, running