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
What is energy measured in?
KJ Kilojoules
PAPER 2 How can we measure amount of energy in food?
burning it and seeing how much heat energy is released
measure 25cm³ of water in boiling tube - record starting temperature
food lit over bunsen then held under water to heat.
If food stops burning, relight until no longer burn
Measure finishing temp and calculate change
What does iron do?
forms part of haemoglobin which binds to oxygen
What foods have iron in them?
Red meat, Liver, Spinach
What deficiency disease is iron related to?
Anaemia
What does Calcium do?
Needed to form bones and teeth
What foods have calcium in them?
Milk and dairy products, fish, fresh vegetables
What deficiency disease is related to calcium?
rickets
How is vitamin A used in the body?
Making chemical in the retina and also protects the surface of the eye
What is the effect of deficiency of Vitamin A?
Night blindness and damaged cornea
What foods have vitamin A in them?
Fish liver oil, liver, butter, carrots
How is vitamin C used in the body?
Needed for cells and tissues to stick together
What is the effect of deficiency of vitamin C?
scurvy
What foods have vitamin C in them?
fresh fruit and vegetables
How is vitamin D used in the body?
Needed to absorb Calcium and Phosphate ions from food
What is the effect of deficiency in vitamin D?
rickets, caused by weak bones
What foods have vitamin D in them?
Dairy products, oily fish
What is water used for in the body?
an essential solvent , used to transport components of blood and is crucial for temperature regulation e.g. sweating
What is fibre?
plant material you can’t digest, mainly chemical called cellulose.
What is fibre used for in the boyd?
Helps movement of food through the intestine, preventing constipation and bowel cancer
What foods are good sources of fibre?
fruit and vegetables, grains (wheats, oats etc.) as they contain cellulose
How do energy requirements vary for different people?
Teenagers need lots of energy for growth - more energy need at younger ages
Higher activity levels need more energy e.g. builder requires more energy then office worker
Pregnant women also require more energy
What is the alimentary canal?
Mouth, Oesophagus, Stomach, Pancreas, Small intestine, Large intestine
What is ingestion?
Taking food in through mouth and swallowing
What is digestion?
Breaking down large insoluble molecules into smaller more soluble molecules
What is absorption?
Movement of small soluble molecules out of the gut and into the blood by diffusion and active transport
What is egestion?
passing out undigested food through anus
What is assimilation?
Building larger biological molecules from the small soluble molecules, in all cells
What is the first structure in the alimentary canal?
Mouth and oesophagus
Ingestion takes place
What is mechanical digestion in mouth and oesophagus?
food broken into smaller peices in mouth by chewing. Increases surface area for enzymes and also prevents discomfort when swallowing
What is chemical digestion in mouth and oesophagus?
Saliva is released into mouth by salivary glands. Makes food easier to swallow and contains enzyme amylase which breaks down starch into maltose
How do you swallow food?
food shaped into ball by tongue and moved to back of mouth. Ball called bolus. Blocked from entering trachea
How is food pushed down the Oesophagus?
by peristalsis
Food also moved along by peristalsis in small intestine and large intestines
muscles push food down:
Circular muscles contract behind bolus pushing along
Longitudinal muscles contract making oesophagus wider
What do gastric glands in stomach do?
gastric glands in the stomach wall secrete enzyme pepsin, which begins process of digesting proteins into peptides (shorter chain amino acids)
What does contraction of the stomach cause?
mixing of contents of the stomach, maximising contact between enzymes and food
What are pepsins optimum working conditions?
acidic pH
conditions in stomach are acidic due to release of hydrochloric acid by gastric glands
very low pH which would burn through stomach if no mucus lining
What does hydrochloric acid in stomach do?
kills many bacteria and fungi which may be present in food we eat
What does the small intestine do?
digestion and absorption
What are the parts of the small intestine?
duodenum and ileum
What is the duodenum?
final site of chemical digestion
Pancreas makes several enzymes and secretes them into duodenum
What enzymes are secreted into the duodenum?
Trypsin: protein to peptide
Amylase: starch to maltose
Lipase: lipid to glycerol and 3 fatty acids
What do the duodenum walls contain?
glands which make enzymes and secrete them into duodenum: maltase and peptidase
What does maltase break down?
maltose into glucose
What does peptidase break down?
peptide into amino acids
Where is bile produced and stored?
produced in liver and stored in gall bladder
Where is bile used?
released into duodenum through bile duct
What is bile used for?
neutralises stomach acid. Enzymes in duodenum work best at pH 7-8
emulsifies lipids - breaks large droplets into smaller droplets, increasing the surface area for lipase to digest the fats
What does food enter after the duodenum?
ileum
What happens in the ileum?
absorption
has many folds and covered in villi
How are small soluble molecules absorbed in the ileum?
through villi and some absorbed by diffusion
glucose absorbed via active transport using ATP
How is rate of diffusion increased in ileum?
Large surface area - folding of ileum, villi and microvilli
Short diffusion distance - villi walls are 1 cell thick
High concentration gradient - provided by capillary network and lacteals removing absorbed molecules
What are the sections of the large intestine?
colon and rectum
What happens in the colon?
reabsorption of water
What happens in the rectum?
faeces stored and egested from anus
What is excretion?
removal of waste substances produced by chemical reactions - e.g. carbon dioxide removed by lungs and urea removed by kidneys and sweat
What digestive enzyme is found in the mouth?
amylase
What digestive enzyme is found in the stomach?
pepsin
what digestive enzymes are found in duodenum?
amylase
lipase
trypsin
maltase
peptidase
