2) Structure and functions in living organisms - nutrition Flashcards
Photosynthesis
Endothermic reaction in which energy from sunlight is transferred to the chloroplasts in green plants
-absorbed by chlorophyll
carbon dioxide + water –> oxygen + glucose
Glucose in plants
-source of energy in respiration
-Produce starch for storage
-Synthesise lipids for an energy source in seeds
-To form cellulose to make cell walls
-Produce amino acids (used to make proteins) when combined with nitrogen and other mineral ions absorbed by roots
Photosynthesis equation
Carbon dioxide + water –light–> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
Limiting factors of photosynthesis
Something present in the environment in such short supply that it restricts life processes
-temperature
-light intensity
-carbon dioxide concentration
Limiting factors of photosynthesis - temperature
-lower - less kinetic energy particles have, fewer successful collisions occurring over a period of time
-higher - increases the kinetic energy of particles, increase likelihood of collisions between reactants and enzymes which results in the formation of products
-At higher temperatures - enzymes can be denatured – this reduces the overall rate of photosynthesis
Limiting factors of photosynthesis - light intensity
-required for photosynthesis
-more light - faster rate
-This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
Limiting factors of photosynthesis - carbon dioxide concentration
-required for photosynthesis
-more carbon dioxide, the faster rate
-This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
Structure of leaf
-waxy cuticle
-upper epidermis
-palisade mesophyll
-spongy mesophyll
-lower epidermis
-guard cell
-stomata
-vascular bundle
-xylem
-phloem
Waxy cuticle
Protective layer on top of leaf, prevents water from evaporating
Upper epidermis
Thin and transparent to allow light to enter palisade mesophyll layer underneath
Palisade mesophyll
Column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
Spongy mesophyll
Contains internal air spaces that increases the surface area to volume ratio for the diffusion of gases (mainly CO2)
Lower epidermis
Contains guard cells and stomata
Guard cell
Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
Stomata
Where gas exchange takes place
-opens during the day, closes at night
-evaporation of water takes place
-found in greater concentration on underside of leaf to reduce water loss
Vascular bundle
Contains xylem and phloem to transport substances to and from the leaf
Xylem
Transports water and dissolved minerals from the roots to the rest of the plant and also provides physical support.
Phloem
Transports sucrose and amino acids around the plant
Plant - adaptations for photosynthesis
-Large surface area of leaf - increase absorption of light
-epidermis is thin and transparent - more light to reach the palisade cells
-thin cuticle made of wax - protects the leaf without blocking sunlight
-palisade cell layer at the top of the leaf - maximizes absorption of light
Mineral ions - plants
-magnesium
-nitrate
Magnesium - plants
-needed to make chlorophyll
-deficiency - causes yellowing between the veins of leaves
Nitrates - plants
-source of nitrogen to make amino acids
-deficiency - causes stunted growth, yellowing of leaves
Practical - starch testing
-Destarch the plant by placing it in a dark cupboard for 24 hours
1. Heat a plant leaf in boiling water for 30 seconds - kill the leaf, stop any more chemical reactions
2. Add leaf to boiling ethanol in a water bath for a few minutes - turns it white
3. Dip into water bath again to soften
4. Spread onto a white tile
5. Add iodine solution from a pipette
6. Part of the leaf that contains starch will turn the iodine blue/ black
Practical: light and photosynthesis
- Destarch a plant
- Cover part of a leaf with a lightproof paper/ foil
- Place the plant in a bright light for several hours
- Test the leaf for starch using the 4 step starch test
- The area which was covered in foil will not turn blue-black
Practical: chlorophyll and photosynthesis
- Destarch a variegated plant (partly green and white)
- Place the plant in bright light for several hours
- Test the leaf for starch using the 4 step starch test
- The white part of the leaf will not turn blue-black
Practical: carbon dioxide and photosynthesis
- Destarch a plant
- Expose one leaf to sodium hydroxide, which will absorb carbon dioxide from the surrounding air
- Expose another leaf to water - not absorb CO2
- Place the plant in bright light for several hours
- Test both leaves for starch using the 4-step starch test
- Leaf exposed to sodium hydroxide will not turn blue black
Food groups
-Carbohydrates
-Proteins
-Lipids
-Dietary Fibre
-Vitamins
-Minerals (mineral ions)
-Water
Balanced diet
-consists of all of the food groups in the correct proportions
-Having an unbalanced diet can lead to malnutrition
Carbs - source, function, lack of, too much
-potatoes, rice
-used by the body for respiration to release energy
-hypoglycemia
-type 2 diabetes
Lipids - source, function, lack of, too much
-cheese, eggs, oils
-make cell membranes/ insulation/ protection of organs/ energy store
-anorexic
-obesity
Proteins - source, function, lack of, too much
-meat, fish, egg
-needed for growth and repair of tissues
-cachexia
-cause liver to be overworked
Vitamin A - source, function, lack of, too much
-fish oil, carrots
-maintains retina in your eye
-vision loss
-liver damage
Vitamin C - source, function, lack of, too much
-citrus fruits
-sticks cells lining the surface to make connective tissues
-scurvy
-kidney stones
Vitamin D - source, function, lack of, too much
-fish liver oil, dairy products
-helps bones absorb calcium
-weak bones/ muscles
-excess of calcium
Water - function, lack of, too much
-maintains osmosis in cells/ provides solvent for enzymes and food molecules/ component of blood plasma
-dehydration
-overhydration
Dietary fibre - source, function, lack of, too much
-vegetables, fruits
-gives muscles of gut something to push against as the food moves through the intestine
-constipation
-bloating
-diarrhea
Variations in dietary requirements
-age
-activity
-pregnancy
Variations in dietary requirements - age
-the amount of energy young people need increases towards adulthood - needed for growth
-energy needs for adults decrease as they age
Variations in dietary requirements - activity levels
-more active, more energy required for movement as muscles are contracting more, respiring faster
Variations in dietary requirements - pregnancy
-energy requirements increase
-energy needed to support the growth of the developing fetus
-larger mass mother needs to carry
-extra calcium, iron needed to help build bones, teeth, blood of fetus
Digestion definition
A process in which relatively large, insoluble molecules in food (such as starch, proteins) are broken down into smaller, soluble molecules that can be absorbed into the bloodstream and delivered to cells in the body
Digestive system
mouth - oesophagus - stomach –pancreas/liver/gall bladder– small intestine (duodenum/ ileum) - large intestine (codon/ rectum) - anus
Digestive system - mouth
-where mechanical digestion takes place
-teeth chew food to break it into smaller pieces and increase SA:Vol
-amylase enzymes in saliva digest starch into maltose
-food shaped into bolus by the tongue
-lubricated in saliva so it can be swallowed easily
Digestive system - oesophagus
-tube that connects the mouth to the stomach
-contractions take place to push the food down without relying on gravity
Digestive system - stomach
-food is mechanically digested - churning actions
-chemically digested - protease enzymes break down protein
-hydrochloric acid - kill bacteria in food, provide optimum pH for protease enzymes to work (pH 2)
Digestive system - pancreas
-produces digestive enzymes
-pushed them into the small intestine in the form of pancreatic juices
Digestive system - liver
-produces bile
Digestive system - gall bladder
-stores bile until it is released into the small intestine
Bile
-neutralises acid from the stomach as it is alkaline
-emulsifies fats which help give fat a larger surface area for digestive enzymes to work on
Digestive system - duodenum
-Food is mixed with digestive enzymes and bile
-continued digestion of carbohydrates and protein, begins digestion of lipids
Digestive system - ileum
-completes digestion of carbs and proteins into simple sugars and amino acids
-absorption of single sugars, amino acids, fatty acids, glycerol into the blood stream
Digestive system - colon
-undigested/ undigestable food passes through here, large intestine absorbs excess water
-watery due to secretions from the stomach, pancreas, gall bladder
Digestive system - rectum
Where feces is stored
Digestive system - anus
Where feces leaves the alimentary canal
Assimilation
the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
Egestion
the passing out of food that has not been digested or absorbed (as faeces) through the anus
Peristalsis
-a mechanism that helps moves food along the alimentary canal
-muscles in the walls of the oesophagus create waves of contractions which force the bolus along
-Circular muscles: contract to reduce the diameter of the lumen of the oesophagus or small intestine
-Longitudinal: contract to reduce the length of that section the oesophagus or the small intestine
Other adaptations for helping food move along the alimentary canal
-mucus produced - continually lubricate the food mass and reduce friction
-dietary fibre - provides roughage required for the muscles to push against during peristalsis
Enzymes to break down carbohydrates
-carbohydrases - carbs to simple sugars (e.g. glucose)
-amylase - made in the salivary glands, pancreas, small intestine - breaks down starch into maltose
-maltase - breaks down maltose into glucose
Enzymes to break down lipids
-lipases - lipids to glycerol and fatty acids
-lipase enzymes are produced in the pancreas and secreted into the small intestine
Adaptations of the small intestine
-very long
-highly folded surface with millions of villi (tiny, finger like projections)
-peristalsis
Villi in the small intestine adaptations
-A large surface area - Microvilli on the surface of the villus further increase the surface available for absorption
-A short diffusion distance - The wall of a villus is only one cell thick
-A steep concentration gradient
-The villi are well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
-A lacteal (lymph vessel) runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
-Enzymes produced in the walls of the villi assist with chemical digestion
-The movement of villi helps to move food along and mix it with the enzymes present
Practical: energy content of a food sample
- Use the measuring cylinder to measure out 25cm3 of water and pour it into the boiling tube
- Record the starting temperature of the water using the thermometer
- Weigh the initial mass of the food sample
- Set fire to the sample of food using the bunsen burner and hold the sample 2cm from the boiling tube until it has completely burned
- Record the final temperature of the water
- (Once cooled) weigh the mass of any remaining food and record
- Repeat the process with different food samples
Calculating energy transferred
(mass of water (g) x 4.2 x temperature increase (°C)) ÷ (mass of food (g))
