bio - things to learn

explain the process of how bile emulsifies fats and why and what it does to stomach acid and why

• fat droplets don’t mix well with water, so it’s hard for lipase enzymes to break them down into fatty acids and glycerol

• bile emulsifies (breaks down) large fat droplets into small ones, increasing surface area leading to faster digestion

• bile is alkaline and stomach acid is acid, this means bile neutralises it which means it’s no longer harmful

explain how proteins are broken down and excreted into urea

• proteins are broken down into amino acids

• these can be used for growth and repair but the body doesn’t need excess

• the liver removes the nitrogen part first, making ammonia which is toxic - deamination

• the ammonia is converted into urea, which is much less harmfull

• urea is carried through the blood in plasma, before being transported to the kidneys and filtering out as waste in urine during excretion

• the bladder passes out urine

how are villi adapted for absorbtion of food molecules

• villi line the walls of the small intestine, they absorb molecules from the digested food in the bloodstream

• they have extra projections caalled microvilli - inc sa

• they are large - inc sa

• they are one cell thick - shorter diffusion pathway

• they have a good blood flow - contain a network of capillaries that absorb nutrients into the blood quickly

• they can use active transport when molecules in the blood is low

what happens in plant cells when excess glucose is made?

inside plant cells, glucose molecules are joined together to make starch, starch is insoluable so doesn’t effect the water balance in the cell, the starch is stored (in roots, chloroplasts and tubers) until more glucose is needed, then it is converted back

how are the lungs adapted for gas exchange?

• large surface area as they contain lots of alveoli

• alveoli and capillary walls are only one cell thick which gives a short diffusion pathway into and out of the blood

• lots of capillaries surrounding the alveoli so good blood flow which gives a steep concentration gradient

• the lining of the alveoli is moist to dissolve gasses

• breathing maintains the concentration gradient which aids diffusion

what is the concentration gradient for oxygen and CO2 in the lungs?

oxygen - high conc in lungs, low conc in blood

CO2 - high conc in blood (waste product from respiration in cells) low conc in lungs

explain what happens when anaerobic respiration is used during and after vigourous excercise

during - body uses anaerobic bc oxygen can’t be supplied quick enough to the mucles

after-

• lactic acid builds up - can cause pain and muscle fatigue

• la is transported to the liver by blood

• liver breaks down la into glucose - which can be used for energy or stored as glycogen for later

• oxygen debt is repaid as breathing rate stays deeper

• heart pumps faster for a while to deliver oxygen and remove waste products (co2)

• sweating and inc blood flow helps body temp return to normal

what is the purpose of nitrate ions?

provides nitrogen which can be used for

• making amino acids which can make proteins needed for growth, repair, enzyme production and chlorophyll production

• can be used to make nucleic acids which are used in DNA

• without it the plant becomes stunted and yellow leaves

they are converted into ammonium ions in a controlled way, so the plant doesn’t produce toxic ammonia

what is the purpose of magnesium ions?

• helps make chlorophyll

• aids healthy leaf development

• can cause chlorosis (yellow leaves) and stunted growth without it

why does an increase of glucose made in the guard cells increase water taken in by osmosis and cause the guard cells to swell?

• Photosynthesis in guard cells makes glucose

  • In sunlight, guard cells photosynthesise and produce glucose.

• Glucose increases the solute concentration in the guard cells

  • This makes the water potential inside the guard cells lower (more concentrated).

• Water moves in by osmosis

  • Because the water potential is now lower inside the guard cells, water from surrounding cells enters by osmosis (from high water potential to low).

• Guard cells become turgid

  • The water makes the guard cells swell and bend, opening the stomata so gases (like CO₂) can enter for photosynthesis

what happens to gas exchange when it’s dim light?

• no net exchange of carbon dioxide or oxygen with the air

• (because) rate of respiration equals rate of photosynthesis

• carbon dioxide produced in respiration is used for photosynthesis

• no (extra) carbon dioxide is absorbed from the air

•oxygen produced by photosynthesis is used in respiration

• no (extra) oxygen is absorbed from the air

what is the food test for starch?

• Add a few drops of iodine solution to food sample

• Turns blue-black if starch is present.

• Stays orange-brown if no starch

what is the food test for sugars?

• Add Benedict’s solution and heat in a water bath for 5 minutes.

• Turns green, yellow, or brick red depending on sugar amount.

• Stays blue if no sugar.

what is the food test for proteins?

• Add Biuret solution to the food sample.

• Turns purple if protein is present.

• Stays blue if no protein

what is the food test for lipids?

• Add Sudan III stain to the food.

• Red layer forms on top if fat is present

what is starch, sugars, proteins and lipids broken down into?

st - glucose

su - glucose

pr - amino acids

li - fatty acids and glycerol - 3:1