Paper 2 Knowledge Gaps: Content Flashcards
What is the test for reducing sugars?
Benedicts test
What is the method for testing reducing sugars?
Add Benedict’s reagent to the food and boil in a water bath
What change takes place to indicate the presence of reducing sugars in its test?
Goes from blue to a brick red precipitate
What is the test for starch?
Iodine test
Describe change that occurs to indicate the presence of starch
Goes from orange to blue black
Name the test for amino acids/ proteins
Biuret
Describe change that occurs to indicate the presence of protein
Goes from blue to lilac after adding the biuret reagent
Name the test for fats
Ethanol emulsion test
Describe the test for fats
Add ethanol to the food to dissolve the fat then add water.
Describe the colour change that occurs to indicate the presence of fat
Colourless to white emulsion
What is the route that the blood takes to become purified?
- blood is transported to the kidney through the renal artery
- blood is filtered at a high pressure and the kidney selectively reabsorbs any useful materials, eg: glucose, mineral ions and water. Any excess is sent to the ureter for excretion and eventually the bladder
- the purified blood eventually returns to circulation via the renal vein
What is the role of the kidney?
To regulate the levels of salt, ions and urea in the blood
What is urea and when is it produced?
- produced in the liver when excess amino acids are broken down
- main waste product removed in urine
- as it is not reabsorbed by the kidney
What occurs during kidney failure?
When both kidneys stop working, causing a build-up of waste substances
How does dialysis work?
- unfiltered blood is taken from a blood vessel in the arm, mixed with blood thinners / an anti-coagulant to prevent clotting and pumped through the dialysis machine
- inside the machine, blood and the dialysis fluid are separated by a partially permeable membrane
- the blood flows in the opposite direction as compared to the dialysis fluid, allowing for the creation of a concentration gradient for the exchange of substances occur
What are the stages the kidney works in?
- filtration
- selective reabsorption
- formation of urine
Describe what happens in filtration
- blood passes into the kidney’s many capillaries
- blood under high pressure at the start of the nephron, which helps the ultrafiltration of the blood
- small molecules are squeezed out and pass into the nephron tubule called the Bowman’s Capsule
–> Small molecules: urea, water, ions, and glucose - large molecules too big to fit through the wall and will remain in the blood
Where does filtration happen?
Glomerulus
Where does selective reabsorption happen?
proximal convuluted tubule
Describe selective reabsorption
- kidneys must reabsorb the useful molecules that just got filtered out
- allows those that are not needed to pass out and form urine
- reabsorption of water and ions occur in the loop of Henle and collecting areas of the tubule
Describe what happens during the formation of urine
- molecules that aren’t reabsorbed continue along the nephron tubule as urine
- this eventually passes down the bladder
- urine exits in the ureter
What molecules are reabsorbed by the kidney during reabsorption?
- all of the glucose initially filtered out
- as much water as the body requires to maintain a constant water level in the blood plasma
- as many ions as the body needs to maintain a constant balance of mineral ions in the blood plasma
What are the adaptations of a nephron?
- large surface area of contact between nephron and capillaries
- cell membrane of first convoluted tube has folds (microvilli) increasing the surface area
- cells that use active transport have lots of mitochondria
- cells of bowman’s capsule and glomerulus capillaries have spaces making them leaky
What does ADH do if the water potential is too high?
- less ADH is released from the pituitary gland
- making the collecting duct less permeable to water
- leads to more water being released in urination
What does ADH do if the water potential is too low?
- more ADH is released from the pituitary gland
- making the collecting duct more permeable to water
- less water remains in the tubule + more entering blood surrounding the tubule
- less water is released in urination
Explain the effect of the negative feedback system when the thyroxine levels in the blood are low
- stimulate the hypothalamus to release TRH
- which causes the release TSH by the pituitary gland
- this hormone triggers the release of thyroxine by the thyroid
- causing the blood levels to return to normal
Explain the effect of negative feedback when the thyroxine levels in the blood are high
- hypothalamus inhibits the production of TRH
- stopping production of TSH
- stopping the thyroxine from being released
- so blood levels can return to normal
What is the symbol equation for photosnythesis?
6Co2 + 6H20–> C6H12O6 + 6O2
What equation is used to link distance and light intensity together?
light intensity is directly proportional to 1/distance^2
What happens during transpiration?
- plant opens its stomata to let in carbon dioxide
- water on the cell surfaces of the spongy mesophyll and the palisade mesophyll evaporate
- and diffuse out of the leaf
- as water molecules are attracted to each other when some molecules leave the plant the rest are pulled up through the xylem
- this results in more water uptake from the soil
- forming a continuous stream of water within the xylem vessels
What are the adaptations of xylem vessels?
- made up of ‘dead’ cells (hollow, no cytoplasm)
- lignin deposited in spirals which helps the cells withstand the pressure from the upwards movement of water
- cells that make up the xylem lose their end walls to form one continuous long tube
- lack of cell walls means the water speed remains unaffected
- tiny pores allow water and mineral ions to enter and leave
What are the adaptations of a sieve cell?
- no nuclei for more space
- has a perforated end so one cytoplasm connects to the next
- only have some cytoplasm for space, therefore these cells are alive
What is the role of a companion cell?
- provides energy to the sieve cells
- pumps sucrose in and out of sieve cells
What adaptations do plants have for dry weather?
- rolled leaf, leaf hairs, stomata in pits: traps water vapour close to leaves which increases humidity + reduces water loss
- spines instead of leaves: less surface area for water loss
- thick cuticle: less water loss
- stomata open at night: less water loss through evaporation
What adaptations do plants have for cold weather?
- losing leaves: less water loss where the ground frozen
- needle-shaped leaves: same as above
What adaptations do plants have for tropical weather?
- large leaves: more surface area for photosynthesis
- tall plants: to obtain more sunlight
What adaptations do plants have for waterlogged conditions?
- no air spaces in soil: lack of oxygen
- more spongy tissue in root to store oxygen
How are artificial auxins used?
- selective weedkillers: can kill weeds with broad leaves, which are the majority of them
- rooting powder: increase the development of roots in cuttings
- gibberellins (released during seed germination) can trigger artificial germination
- ethene is a plant hormone which can be sprayed to prevent early ripening
What is Fick’s Law?
A law that describes the relationship between the rate of diffusion and the three factors that affect it
rate of diffusion is directly proportional to (surface area x concentration difference)/ thickness of membrane
What are the adaptations of an alveoli?
- one cell thick, providing a short diffusion pathway
- capillaries provide a good blood supply, maintaining a concentration gradient for diffusion of substances
- small and arranged in clusters, which increases the SA:V ratio
What are the adaptations of platelets?
They can stop bleeding in two main ways:
- have proteins on their surface which allows them to stick together to breaks in a blood vessel and clump together
- secrete proteins that leads to a blood clot, therefore plugging a wound
- small fragments of cells
- no nucleus
What are the adaptations of arteries?
- carry blood under high pressure
- have thick muscular and elastic walls to pump and accommodate blood
- Connective tissue, which is a type of supporting tissue provides strength
- channel in the blood vessel that carries blood: lumen is very narrow
What are the adaptations of veins?
- carry blood under low pressure: so the lumen is wide
- have thin walls; less muscular than arteries
- have less connective tissue than arteries
- valves to ensure blood is flowing in the right direction
What are the adaptations of capillaries?
- One cell thick walls create a short diffusion pathway
- permeable walls so substances can move across them
What are the parts of a blood vessel?
- endothelium
- elastic fibres
- smooth muscle
- collagen
- valves
What is the role of endothelium?
Cells lining blood vessels to reduce friction
What is the role of elastic fibres?
Proteins that stretch and recoil for flexibility
What is the role of smooth muscle?
Contracts and relaxes to change the size of the lumen
What is the role of collagen?
Proteins that support the shape of the vessels
What are the types of arteries and what do they do?
- aorta: pumps blood from heart to body
- Pulmonary artery: blood from heart to lungs
- Coronary arteries: supply the heart with blood to use
What is the role of valves?
Structure that opens and closes to control blood movement
What are the types of veins and what do they do?
- vena cava: blood from body to heart
- pulmonary vein: blood from lungs to heart
Describe the process that blood goes through in the heart
- blood flows into the right atrium through the vena cava, and left atrium through the pulmonary vein
- The atria contract forcing the blood into the ventricles
- The ventricles then contract, pushing the blood in the right ventricle into the pulmonary artery to be taken into the lungs, and the blood in the left ventricle to the aorta to be taken around the body
- As this occurs, the valves close to ensure the blood doesn’t flow backwards
What is cardiac output?
The total volume of blood pumped out by the left ventricle every minute
How do we calculate cardiac output?
stroke volume x heart rate
Define stroke volume?
The volume of blood pumped out by the left ventricle during every contraction
Define heart rate
The number of beats per minute your heart produces and the same as the pulse rate
What is the importance of the carbon cycle?
- component of all organic molecules, many of which are responsible for sustaining life on Earth, such as glucose
- since there is only a limited amount of carbon available, the carbon cycle is an essential way of recycling the carbon we have available to us
Describe the carbon cycle
- Carbon removed from atmosphere through photosynthesis
- passed onto animals and decomposers due to feeding
- returned through respiration; in plants, animals and decomposing microorganisms
- additionally, returned by the combustion of fossil fuels
What are the four key processes of the nitrogen cycle?
- nitrogen fixation
- ammonification
- nitrification
- dentrification
Describe nitrogen fixation
Atmospheric nitrogen gas is converted into nitrogen-containing compounds such as ammonia, which forms ammonium ions (in solution) that can then be used by plants
What is nitrogen fixation carried out by?
- Nitrogen fixing bacteria
- Lightning
Describe nitrogen fixing bacteria
- found ‘free-living’ in soil and also in root nodules of certain plants (legumes)
- take n2 gas and change it into nitrates in the soil
How does lightning play a part in nitrogen fixing?
Splitting the bond between two atoms and turning them into nitrous oxides like N20 and NO2, which disolve in rainwater and ‘leach’ into the soil
Describe ammonification
Nitrogen compounds in waste products and dead organisms are converted into ammonia by decomposers
Describe nitrification
Ammonium ions in the soil are converted into nitrates by the nitrifying bacteria
Define decomposition
Breaking down and digestion of biological material by organisms called decomposers
Describe dentrification
Dentrifying bacteria use nitrates in the soil during respiration which releases nitrogen gas back into the atmosphere
How can we preserve food?
- drying food: adding salt/sugar (removes water)
- chilling/freezing (removes warmth required)
- pickling (changes pH)
- canning/ vacuum packing/ sealing in gases like N2 (prevents oxygen access)
- irradiation: kills decomposers
