Enzymes and Digestion Flashcards
What are the seven food groups? How do you remember these?
carbohydrates (starch and gluose)
protein
lipids (fats and oils)
fibre
vitamins
minerals
water
Careless Pauline Let Finnian Vaporise My Water
What are simple sugars called?
monosaccharides
What are complex sugars called?
polysaccharides
What is starch made of?
thousands of glucose molecules
Give an example of a simple sugar (monosaccharide)
glucose
Give an example of a complex sugar (polysaccharide)
starch
What are carbohydrates?
they include simple sugars (monosaccharides) such as glucose and complex sugars (polysaccharides) such as starch (which is made of thousands of glucose molecules)
What are elements of glucose?
Carbon
Hydrogen
Oxygen
(C, H, O)
What is the formula for glucose?
C6H12O6
What is the equation for respiration?
glucose + oxygen —> carbon dioxide + water + ATP
C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP
What is the function of glucose?
short-term energy supply which is used in respiration
What are some sources of glucose?
e.g. in fruits, sweets
What are elements of starch?
Carbon
Hydrogen
Oxygen
(C, H, O)
What is the structure of starch?
thousands of glucose molecules
What is the function of starch?
short-term energy storage which is broken down into glucose for respiration
What is the function of starch in plants?
stores starch
What is the function of starch in humans?
eat foods containing starch which broken down into glucose in digestion
What are some sources of starch?
e.g. in bread, potatoes, pasta, rice
If you need a quick burst of energy what food should you eat and why?
eat food containing glucose (instead of starch) as it doesn’t need to be digested and can be absorbed into the bloodstream directly
What are the elements of protein?
Carbon
Hydrogen
Oxygen
Nitrogen
Sulphur
(C, H, O, N, S)
What is the structure of proteins?
chains of amino acids (20 different types)
What is the function of proteins?
there are a variety of functions:
needed to maintain cell function
needed to grow and repair cells and tissues
What are some sources of proteins?
e.g. meat, fish, eggs, dairy
What is the function of proteins in enzymes?
enzymes speed up chemical reactions in your body, e.g., the breakdown of food or respiration
What is the function of proteins in muscles?
muscle proteins called actin and myosin enable all muscular movement
What is the function of proteins in cellular messengers?
receptor proteins on the cell membrane transmit signals to other proteins inside cells
What is the function of proteins in antibodies?
antibodies are proteins that help defend your body against harmful microbes
What is the function of proteins in hairs and nails?
a protein called keratin forms your hair and fingernails
What is the function of proteins in the brain and nerves?
ion channel proteins control nervous system signalling by allowing ions in and out of nerve cells
What is the function of proteins in blood?
the haemoglobin protein carries oxygen in your blood to every part of your body
Complete this gapfill:
Lipids are good for … energy … - the body generally uses … first and stores … and …. If we run out of … our body breaks down the … and uses it as fuel for … - it is like a reserve energy source
Lipids are good for long-term energy storage - the body generally uses carbohydrates first and stores lipids and fat. If we run out of carbohydrates our body breaks down the fat and uses it as fuel for respiration - it is like a reserve energy source
What are the elements of lipids?
Carbon
Hydrogen
Oxygen
(C, H, O)
What are the subunits of lipids?
glycerol and three fatty acids
What is the function of lipids?
long-term energy storage
What are the types of lipids?
they include fats (solid at room temperature) and oils (liquid)
What are some sources of lipids?
e.g. butter, dairy, oil, nuts
What are some sources of lipids (fats)?
e.g. butter
What are some sources of lipids (oils)?
e.g. olive oil
What are elements of fibre?
Carbon
Hydrogen
Oxygen
(C, H, O)
What is the structure of fibre?
thousands of glucose molecules
What is the function of fibre in plants?
makes up plant cell walls (cellulose)
What is the function of fibre in humans?
humans cannot digest fibre, but eating fibre helps to keep the digestive system healthy and to prevent constipation
What are some sources of fibre?
e.g. vegetables, fruit
What is fibre made of?
CHECK
What are minerals?
inorganic substances (salts) needed by the body in small amounts
What are some examples of minerals?
calcium, iron, magnesium, iodine
What is the function of minerals (calcium)?
to make healthy bones
What is the function of minerals (iron)?
blood - needed to make haemoglobin (molecule in Red Blood Cells)
What are some sources of minerals (calcium)?
e.g. milk
What are some sources of minerals (iron)?
e.g. meat and liver
What are vitamins?
organic substances needed by the body in small amounts
What are some examples of vitamins?
Vitamin A, Vitamin C, Vitamin D
What is the function of vitamins?
to take part in important chemical reactions in the body
What are some sources of vitamins (Vitamin A)?
e.g. carrots
What are some sources of vitamins (Vitamin C)?
e.g. oranges and lemons (citrus fruit)
What are some sources of vitamins (Vitamin D)?
e.g. milk
How much of the body is water?
about 67%
What is the formula for water?
H2O
What is the function of water?
to carry substances around the body and replace lost water
What are some sources of water?
e.g. drinks, vegetables (cucumber which is 95% water and tomatoes)
What is the function of carbohydrates?
short-term energy supply
What is the function of protein?
cell function, growth and repair of cell tissues
What is the function of lipids?
long-term energy storage and supply
What is the function of fibre?
to keep the digestive system healthy and prevent constipation
What is the function of vitamins?
to take part in important chemical reactions in the body
What is the function of minerals?
to make healthy blood, bones and other tissues
What is the function of water?
to carry substances around the body and replace lost water
Complete this gapfill:
We can test for glucose using …. If glucose is present, the colour will change from … to … when heated.
What should you use to heat for the colour change to happen?
We can test for glucose using Benedict’s reagent. If glucose is present, the colour will change from blue to brick red when heated.
To heat, use a bunsen burner or water bath
What is the colour gradient for the amount of glucose present when tested with Benedict’s reagent (from a lot of glucose present to little)?
red
orange
yellow
green
blue
Complete this gapfill:
We can test for starch using …. If starch is present, the colour will change from … to …/…
We can test for starch using iodine. If starch is present, the colour will change from brown to blue/black
Complete this gapfill:
We can test for protein using … (= copper sulphate + sodium hydroxide). If protein is present, the colour will change from … to …
We can test for protein using Biuret reagent (= copper sulphate + sodium hydroxide). If protein is present, the colour will change from light blue to purple
The substance tested for is starch. Complete the table:
Solution used:
Colour of solution at start:
Colour of solution at end:
Heat required?:
Solution used: iodine
Colour of solution at start: yellow
Colour of solution at end: blue/black
Heat required?: no
The substance tested for is glucose. Complete this table:
Solution used:
Colour of solution at start:
Colour of solution at end:
Heat required?:
Solution used: Benedict’s reagent
Colour of solution at start: blue
Colour of solution at end: red
Heat required?: yes
What is a balanced diet?
the right balance of different food groups providing the body with all essential nutrition and the right amount of energy (calories)
What is malnutrition?
a condition resulting from eating a diet that does not contain the right amount of nutrients
it happens when your diet is unbalance long-term
What is undernutrition and starvation?
not ontaining enough nutrients/calories
What are the causes of undernutrition and starvation?
e.g. not eating enough
What are the symptoms of undernutrition and starvation?
underweight
weakness
loss of fat and muscle tissue
What is overnutrition and obesity?
taking in too many nutrients/calories
What are the causes of overnutrition and obesity?
overeating
genetic
What are the symptoms of overnutrition and obesity?
weight gain
excess fat
heart disease
diabetes
What is BMI?
(body mass index)
= a measure of body fat based on height and weight
Who does BMI apply to?
adult men and women
How do you calculate BMI?
weight (kg) ÷ height (m)2
What are the BMI values for adults?
<18 underweights
18-25 normal weight
>25 overweight
>30 obese
How can we know if someone is overweight or obese?
calculate their BMI
however, BMI is not always useful as it is only fine for average people
What are deficiency diseases?
not enough of a particular food group (i.e. unbalanced diet)
What are some deficiency diseases?
night blindness
scurvy
rickets
anaemia
kwashiorkor
goitre
What are the causes of night blindness?
deficiency in Vitamin A —> degeneration of rod cells in the retina
rod cells enable us to see
What are the symptoms of nighblindness?
poor vision in low light levels
What is the cause of scurvy?
deficiency in Vitamin C
What are the symptoms of scurvy?
poor wound healing
bleeding, particularly in gums
loss of teeth
fatigue
What are the causes of rickets?
deficiency in Vitamin D or calcium; lack of sunlight
What are the symptoms of rickets?
brittle bones
bow legs
poor teeth
What is the cause of anaemia?
deficiency in iron
the body will lack Red Blood Cells and won’t be able to transport oxygen efficiently
What are the symptoms of anaemia?
low energy levels
lethargy
dizziness
What is the cause of kwashiorkor?
deficiency in protein
What are the symptoms of kwashiorkor?
swollen belly
poor muscle growth
weight loss
What is the cause of goitre?
deficiency in iodine
What are the symptoms of goitre?
swollen lump in thyrdoid glanf
slow metabolism
What is the energy in food used for?
movement, body heat and growth
What is the energy process for eating food?
food (chemical energy) —> respiration —> movement (kinetic energy), body heat (heat energy), growth and repair (chemical energy)
What happens if you take in too much energy?
you gain weight
What happens if you take in too little energy?
weight loss
What does how much energy we need depend on?
activity levels
temperature
age
What does one calorie equate to?
1 calorie = quantity of heat energy required to raise the temperature of 1g of water by 1oC
What is the equation for 1 joule?
1 joule = 4.2 x calories
(e.g. 100 cal = 420J)
What is the equation for food energy (calories)
food energy (calories) = mass of water (g) x temperature rise (oC)
What is the equation for food energy (calories ÷ grams)
food energy (calories ÷ grams) mass of water (g) x temperature rise (oC) ÷ mass of food
Do you think the BMI is always a good measure of obesity?
no
it is only good for average people
it cannot, e.g., take into account muscle weight
How could you treat deficiency symptoms?
taking supplements
incorporate the deficiency into your diet –> eat more e.g. Vitamin A if you suffer from night blindness
Why do you think scurvy was particularly prominent amongst sailors?
cannot eat fresh fruit (e.g. oranges) as they do not have access to them
Why would people suffering from anaemia have low energy levels and feel dizzy?
deficiency in iron —> body will lack Red Blood Cells and won’t be able to transport oxygen efficiently —> lack of oxygen for respiration
What kind of people might be at risk of developing Kwashiorkor in the UK?
vegans (although they can take B12 supplements)
people with an unbalanced diet
Who needs more energy and why?
male or female
male
on average their proportions are bigger
Who needs more energy and why?
child who exercises or child who doesn’t exercise
child who exercises
respiring and losing energy
Who needs more energy and why?
70 year old or teenager
teenager
growing
Who needs more energy and why?
cycle dispatch rider or receptionist
cycle dispatch rider
respiring and losing energy
Who needs more energy and why?
girl in summer or girl in winter
girl in winter
cold —> needs to retain body heat
Who needs more energy and why?
woman who is pregnant or woman who is not pregnant
woman who is pregnant
eating for two
How can people avoid putting on weight? What are the options?
avoid added sugar as it is not a necessary dietary requirement
balanced diet and exercise
In what way will a boy’s body who has just eaten a Twix use up energy while sitting watching tv?
respiration
heat
digestion
Design an experiment to find out how the energy content differs in food
weigh the food so the mass is known
use a calculator to detect and measure the temperature in the water before and after burning the food with a thermometer
use a temperature change to work out the energy change of the food
repeat the experiment three times with each type of food
measure the temperature once the food is completely burned off
use the same mass of water and foo
make sure to wear goddles for safety
How do you measure the energy content of food in the lab? What is the independent variable, the dependent variable and the two control variables?
fill a boiling tube with water (10cm3) - the amount of water is a control variable
measure the temperature at the start
measure the mass of food - the type of food is the independent variable, the mass of the food is a control variable
mount the food on a mounted needle (or into a fireproof dish)
set fire to the food into it until it catches alight
hold the burning food underneath water until it is burned
measure the temperature of water at the end - the temperature of the water is the dependent variable
calculate the energy in food
Label this structure of the digestive system
What is the function of the mouth?
starting point of digestion
What is the function of the teeth?
break up food particles mechanically in mouth
What is the function of the tongue?
mixes food with saliva
What is the function of the oesophagus?
transport of food to stomach
What is the function of the stomach?
storage and digestion of food (initial digestion)
What is the function of the duodenum (small intestine)?
main digestion of food
What is the function of the pancreas?
secretes digestive juiced and enzymes into duodenum to enable digestion
What is the function of the gall bladder?
site of bile storage
What is the function of the liver?
site of bile salt production
What is the function of the ileum (small intestine)?
main absorption of nutrients
digested food moved to the ileum
What is the function of the large intestine?
absorption of water
material that has not been digested and absorbed moves along the large intestine - food is compacted
What is the function of the rectum?
temporary storage of faeces
undigested and compacted material enters the rectum
What is the function of the anus?
defecation
How does food move along the digestive system?
peristalsis
What is peristalsis?
a series of wave-like muscle contractions in the wall of the oesophagus and the small and the large intestine that moves food along the dgestive system
How is food absorbed into the blood stream?
the ileum is lined by thousands of villi
nutrients are absorbed into the blodstream by diffusion
blood concentration is kept high as in the ileum food molecules are constantly supplied through peristalsis and in the bloodstream the absorbed molecules are taken away through blood flow
Why do we need the digestive system?
- digestion (breakdown) of food molecules
- absorption (uptake) of food molecules into the bloodstream
Can you swallow when standing on your head? Why?
yes
peristalsis helps food move along - not controlled by gravity but controlled by muscles
Which part of the digestive sysem is affected when you suffer from diarrhoea?
large intestine (absorption of water) —> diarrhoea is very watery
How is absorption in the digestive system made efficient?
large surface area
short diffusion distance
high concentration gradient
How is a large surface area achieved to make absorption efficient?
the ileum is lined by thousands of villi
many microvilli on each cell of the villus wall
How is a short diffusion distance achieved to make absorption efficient?
villus wall is thin (one layer of cells thick)
blood vessels are directly under the villus wall
How is a high concentration gradient achieved to make absorption efficient?
continuos flow of blood which requires nutrients
peristalsis brings along food constantly
At the end of the ileum, there is a … concentration graidient. Why?
at the end of the ileum, there is a low concentration graidient
this is because there are fewer nutrients
active transport happens at the end of the ileum
What is digestion?
the breakdown of food
Why does food need to be digested?
only small molecules can be absorbed (= diffuse) across villi into the bloodstream
some molecules are too large and cannot move across the ileum into the bloodstream
Complete this table for the food molecule water:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: no - absorbed directly into the bloodstream
What are they broken down into?: N/A
Enzyme involved: N/A
Complete this table for the food molecule glucose (carbohydrate):
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: no - absorbed directly into the bloodstream
What are they broken down into?: N/A
Enzyme involved: N/A
Complete this table for the food molecule starch (carbohydrate):
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: yes
What are they broken down into?: glucose molecules
Enzyme involved: carbohydrase (amylase and maltase)
Complete this table for the food molecule protein:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: yes
What are they broken down into?: amino acids
Enzyme involved: protease
Complete this table for the food molecule lipids:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: yes
What are they broken down into?: one glycerol molecule and three fatty acids chain
Enzyme involved: lipase
Complete this table for the food molecule fibre:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: cannot be digested
What are they broken down into?: N/A
Enzyme involved: N/A
Complete this table for the food molecule vitamins:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: no
What are they broken down into?: N/A
Enzyme involved: N/A
Complete this table for the food molecule minerals:
Are these digested?:
What are they broken down into?:
Enzyme involved:
Are these digested?: no
What are they broken down into?: N/A
Enzyme involved: N/A
What three food molecules are digested?
starch (carbohydrase)
protein
lipids
How is food digested?
mechanical digestion (teeth and tongue)
chemical digestion (enzymes)
What are enzymes?
proteins that speed up chemical reactions (for example, the breakdown of food molecules)
biologial catalysts
What would happen without enzymes?
we would starve
How do enzymes work in digestion?
each enzyme binds to a particular molecule (called their substrate) and breaks it down into products
without an enzyme the breakdown of a molecule would be much slower
enzymes are specific to a particular molecule (i.e. each enzyme can only bind to one type of molecule)
different enzymes are needed to catalyse different reactions
Does the body need one type of enzymes or lots of different enzymes?
lots of different enzymes
How is starch digested?
starch is digested into maltose and glucose by carbohydrase enzymes called amylase and maltase
How are proteins digested?
protein is digested into amino acids by the enzyme protease
How are lipids digested?
lipids are digested into glycerol and fatty acids by the enzyme lipase
What enzyme breaks down carbohydrates?
carbohydrase
What enzyme breaks down proteins?
protease
What enzyme breaks down lipids?
lipase
What enzyme breaks down maltose?
maltase
What enzyme breaks down starch (amylose)?
amylase
In the test for glucose the solution needs to be heated. Give two precautions you would use to heat the solution safely
tie your hair back so it does not catch fire
tuck bags and chairs under the table so you can’t trip and fall into the flame or the water bath
What is the name of the reagent used to test for protein?
Biuret reagent
Using Biuret reagent, Jill tested two foods, A and B, for protein. A had no protien but B did. What are the colours she obtained for A and B?
A: light blue
B: purple
A student wants to test some food samples for glucose. Choose two pieces of appartus the student should use out of the following options:
test tube
Bunsen burner
microscope
funnel
Bunsen burner
test tube
What is the name of the reagent the student should use to test for glucose?
Benedict’s reagent
Using Benedict’s reagent, what would the colour change be for a food that contains glucose?
at the start of the test: blue
at the end of the test: brick red
A student decided to test a food sample to see if it contained starch. Name the reagent the student should use and what colour changes would be observed if starch was present
reagent: iodine
colour change: brown to blue/black
What is the test solution and colour of positive result for lipids?
test solution: water and ethanol
colour: cloudy white
Why would you crush a food sample when testing for a simple sugar?
to increase the surface area
What reagent would you use to test a food sample for a simple sugar?
Benedict’s reagent
Why is a water bath used when testing a food sample for a simple sugar instead of heating the test tube directly with a Bunsen burner?
so it heats the whole sample evenly, not just the base
Why would you leave a heated food sample for two minutes before observing a colour change?
to allow the sample to heat up
Two food samples were tested. Complete this table:
The colour of reagent A at the start:
Colour of reagent A at the end for a food sample containing glucose:
Colour of reagent A at the end for a food sample containing protein:
The colour of reagent A at the start: blue
Colour of reagent A at the end for a food sample containing glucose: brick red
Colour of reagent A at the end for a food sample containing protein: purple
Label this diagram of a calorimeter
How do you use a calorimeter to determine the energy in food?
first, the food is wieghed so we know the mass of it
the food is then placed and burned in a metal chamber that sits inside a well-insulated vessel fo water
the food is lit using the ignition wires
the heat released by burning the food is transferred to the water which surrounds the food chamber
the increase in temperature of the water and the measured mass of both the food and the water are used to determine the heat released by the substance
Use the graph to describe the changes in the mass of the rats in Group A from day 18 to day 50
the mass stays constant and then rises
Use the graph to describe the changes in the mass of the rats in Group B from day 18 to day 50
the mass rises and then falls
What conclusions can you draw as to the effect of milk on the growth of the rats in Hopkins’ experiment?
milk is needed for growth as it contains calcium/ vitamins
milk is needed everyday
Suggest why Hopkins swapped the diets after 18 days
to show the change due to milk, not the differences between groups (rats)
To enable a valid comparison to be made between the two groups, other variables need to be kept the same. Suggest two such variable and explain how it could be kept the same
temperature: keep the room thermostat and the same temperature
genetic differences: same species of rats
Which vitamin helps with night vision and what is a source of this vitamin?
Vitamin A
e.g. carrot
Which vitamin helps with skin and gum development and what is a source of this vitamin?
Vitamin C
e.g. citrus fruit; oranges
What does Vitamin D help and what is a source of this vitamin?
bone/tooth development
e.g. milk
Name the appartus a student could use to measure 20cm3 of water accurately
meauring cylinder
Calculate the enegery content of a biscuit in J using the formula:
energy content in J = rise in temperature in oC x volume of water in cm3 x 4.2
temperature of the water at the start = 18 oC
temperature of the water at the end = 33 oC
volume of water = 20 cm3
energy content in J = rise in temperature in oC x volume of water in cm3 x 4.2
= (33-18) x 20 x 4.2
= 15 x 20 x 4.2
= 1260
Five results using a boiling tube of water were different from each other. The student thought this was because different amounts of energy were lost and not transferred to the water. Suggest two reasons why the energy might not be transferred to the water
energy lost to surroundings
energy heating up glass, not water
Peter wants to find out if potato crisps contain as much energy as crispbread. Suggest three things he must do to make the experiment a fair test
same mass of food
same volume of water
burning food at the same distance from the test tube
What results will Peter get when he burns 1.0g of potato crisps instead of 1.0g of crispbread? Why?
the temperature change of water will be much greater because there is more energy in potato chips
Use the table to give two reasons for choosing crispbread rather than potato chips as part of a healthy and balanced diet
more fibre
less fat (less likely to gain weight)
Label this diagram of a villus
Label this diagram of villi
Why does bread start tasting sweet when you chew it for a long time?
the amylase in your saliva breaks down the bread into glucose - glucose is sweet
Design an experiment to find out if the digestion of starch is more efficient with compared to without enzymes
independent variable = the quantity of enxymes
choose a range of three enzyme quantities - none present, small quantity present, large quantity present
measure how long it takes for starch to be digested by using iodine to see whether glucoseis produced (if it is then the reagent will turn blue/black) - measure the time with a stopwatch
repeat the experiment three times for each quantity
do not change the mass of the starchy food or the temperature of the room in which the experiment takes place
keep the type of food constant
What is an enzyme?
proteins that speed up biochemical reactions
enzymes catalyse … (breaking down) reactions
enzymes catalyse … (building up) reaction
enzymes catalyse catabolic (breaking down) reactions
enzymes catalyse anabolic (building up) reaction
What do enzymes do to biochemical reactions? How do enzymes work?
enzymes speed up biochemical reactions up to 106x
enzymes work by lowering the activation energy (= energy needed to start a chemical reaction)
Each enzyme … to a particular molecule (…) and catalyses the conversion into the products
Enzymes are … for a particular … (i.e. each enzyme can catalyse … particular reaction)
Different enzymes are needed to catalyse … reactions
Each enzyme bind to a particular molecule (substrate) and catalyses the conversion into the products
Enzymes are specific for a particular substrate (i.e. each enzyme can catalyse only one particular reaction)
Different enzymes are needed to catalyse different reaction
Why are different enzymes are needed to catalyse different reactions?
to control reactions
otherwise you would use up all the energy in a cell and the cell would probably die
The amino acid chain of the protein (enzyme) … in a specific way and gives the protein its …
Part of the folded protein forms the … when the substrate is bound
The shape of the substrate … to the shape of the active site = fits like a key into a lock (= … model)
The amino acid chain of the protein (enzyme) folds in a specific way and gives the protein its shape
Part of the folded protein forms the active site when the substrate is bound
The shape of the substrate complementary to the shape of the active site = fits like a key into a lock (= lock and key model)
How does enzyme action work?
substrate binds to active site
enzyme-substrate complex forms
reaction takes place
product no longer fits into active site and is released
enzyme is free to be used again
(Note: enzymes are not used up/changed during reaction)
What is catalase?
a detox enzyme
found in most living tissues
What is the equations for hydrogenperoxide being affected by the enzyme catalase?
hydrogenperoxide –(catalase)–> water + oxygen
H2O2 –(catalase)–> H2O + O2
oxygen is released very, very quickly
What must cells do to hydrogenperoxide?
cells must break down this toxic molecule into safe products
What is the effect of temperature of enzyme activity
- below optimum T
- optimum T
- above optimum T
- rate of reaction increases as temperature increases as there is more kinetic energy and therfore more collisions andmore enzyme-substrate complexes
- highest rate of reaction (around 37oC in humans)
- rate of reaction decreases rapidly as the enzyme denatures and the active site changes shape and therefore cannot bind
What is the effect of pH of enzyme activity
- optimum pH
- and 3. below/ above optimum pH
- highest rate of reaction
- and 3. rate of reaction decreases rapidly as the enzyme denatures and the active site changes shape
the rate of reaction lowers as you move away from the optimum pH
What is denaturation?
change in the shape of a protein
it is irreversible
Why do people die of fever?
enzymes denature at high temperature
respiration enzymes denature
Different enzymes have a … optimum pH
Different enzymes have a different optimum pH
Where does food digestion happen?
there are three areas where digestion happens:
mouth (teeth and tongue)
stomach
duodenum (small intestine)
Where is the first area that enzymes act in digestion?
the mouth
What type of digestion is in the mouth?
mechanical and chemical
What type of digestion is in the stomach?
chemical
What type of digestion is in the duodenum?
chemical
What digestion happens in the mouth?
starch is digested into maltose by the enzyme carbohydrase (amylase) made in the salivary glands
What is maltose?
a small carbohydrate consisting of two glucose molecules
What digestion happens in the stomach?
protein is digested into amino acids by the enzyme protease (pepsin) made in the stomach lining
the stomach is very acidic (ph = 2-3) and so pepsin works best at a low pH
What is pepsin?
special protease that only acts in the stomach - needed as the stomach is very acidic
Where does most digestion happen?
in the duodenum
What is digested in the duodenum?
starch
protein
lipids
How is starch digested in the duodenum?
starch is digested into maltose and glucose by amylase made in the pancreas and maltase made in the duodenum
How is protein digested in the duodenum?
protein is digested into amino acids by the enzyme protease (trypsin) made in the pancreas
In what pH does trypsin work best in?
a neutral pH
How are lipids digested in the duodenum?
lipids are digested into glycerol and fatty acids by the enzyme lipase made in the pancreas
lipase action is helped by bile produced in the liver and stored in the gall bladder
Is bile an enzyme?
no
What does bile do?
bile neutralises the pH when food exists the stomach - food moves out of the stomach at a low pH but lipase doesn’t work at a low pH so bile is needed so lipase can properly function
bile emulsifies (breaks down) lipids into droplets which increases the surface area helping lipase action - lots of little droplets have a big surface area which makes digestion of lipids by lipase much faster
What is starch broken down into?
maltose
glucose
Which enzyme is involved in the breakdown of maltose (starch)?
carbohydrase (amylase)
Which enzyme is involved in the breakdown of glucose (starch)?
carbohydrase (amylase and maltase)
Where is maltose (starch) digested?
mouth
Where is glucose (starch) digested?
duodenum
Where is amylase to breakdown maltose in the mouth produced?
salivary glands
Where is amylase to breakdown glucose and maltose in the duodenum produced?
pancreas
Where is maltase to breakdown glucose and maltose in the duodenum produced?
duodenum
What is protein broken dowin into?
amino acids
Which enzymes are involved in the breakdwon of amino acids?
protease (pepsin)
protease (trypsin)
Which protease works best at low pH and which protease works best in neutral pH?
low pH = pepsin
neutral pH = trypsin
Where are amino acids broken down by protease (pepsin) digested?
stomach
Where are amino acids broken down by protease (trypsin) digested?
duodeum
Where is protease (pepsin) produced?
stomach lining
Where is protease (trypsin) produced?
pancreas
What are lipids broken down into?
glycerol and fatty acids
Which enzyme is involved in the breakdown of lipids?
lipase
Where are lipids digested?
duodenum
Where is lipase produced?
pancreas
What do you need to have for a graph (similar to CORMMS)?
Scale must be bigger than half of the available graph paper and both axes must be linear (e.g. 0, 10, 20, 30…)
Line straight (use a ruler), point to point
Axes must be the correct way around (x = independent, y = dependent)
Axes must be labelled correctly
Points must be plotted accurately (i.e. exaclty right to the number)
= SLAAP
Describe and explain the results from 100C to 45oC
as the temperature increases, the rate of carbon dioxide in bubbles per minute increases
this is because the molecules have more kinetic energy and collide more often
Describe and explain the results from 45oC to 80oC
as the temperature increases, the enzymes dentaure and the rate of carbon dioxide production decreases
The graph suggests that 45oC is the optimum temperature for the production of carbon dioxide. Describe how you could modify this experiment to test this hypothesis
more detailed temperature changes; use smaller intervals between 30oC and 50oC (N.B. you must include a range)
repeat the experiment
The rate of carbon dioxide production during an experiment was measured by counting the number of bubbles produced per minute. Explain why this is not a precise way to measure carbon dioxide production and suggest a more precise way of doing this
bubbles are difficult to count; collect the bubbles in a measuring cylinder
Which letter shows where bile is made?
F (the liver)
Explain how bile is involved in digestion?
bile neutralised the pH
bile emulsifies lipids into lots of little droplets which increases the surface area helping lipase action
In which part of the body is most villi found?
ileum (small intestine)
Explain how the structure of a villus is adapted for the absorption of the products of digestion
it has a large surface area with lots of capillaries
blood circulates to maintain the concentration gradient
the capillary walls are one single cell thick to allow for a short diffusion distance
From the diagram select the letter, or letters, that show where the change of pH 7 to 2 takes place
C
From the diagram select the letter, or letters, that show where the digestion of enzymes takes place
A, C, F
From the diagram select the letter, or letters, that show where absorption takes place
F, G, C, A
From the diagram select the letter, or letters, that show where egestion takes place
egestion = defecation
H
Describe two ways in which bile helps digestion
it neutralises the pH when the food exits the stomach
it emulsifies lipids into droplets
The horse is a mammal and the digestive system is similar to that of humans. Chose the correct letter to match each statement:
This is where plant food is chewed:
This is where faeces is stored:
This is where most villi are found:
This is where plant food is chewed: B
This is where faeces is stored: D
This is where most villi are found: C
Explain how food is moved along the oesophagus
peristalsis; muscle contractions in the wall of the oesophagus
Describe and explain the results shown by the graph
lipase works best with bile, least well in acidic solution and better in alkaline conditions
bile neutralises the pH
bile emulsifies fat
enzymes denature
What is the product of digestion of the maltose?
glucose
Name three macronutrients in the diet
protein
lipids
carbohydrates
Name two micronutrients in the diet
minerals
vitamins
Which mineral is found in meat and dark green leafy vegetables?
iron
What is fibre exaclty?
it is used to make cellulose - plant cell walls
Give one fact about the structure of starch
it is made up of many glucose subunits - coiled shape
What are molecules like after digestion?
small
soluble
Is liver part of the digestive system?
no
food doesn’t pass through it
What is the name for the tube that takes enzymes from the pancreas into the digestive system?
the pancreatic duct
Which two types of vessel are found inside veery villus?
lacteal
blood capillary
Desrcibe the surface of a villus
one layer of cells
have microvilli
3 samples of lipase were kept in 3 test-tubes
One has pH 2 buffer added, one has pH 7.5, and one had pH 9
Which pHs denature the lipase?
ph 9 and ph 2
Which enzyme breakdown hydrogen peroxide into water and carbon dioxide?
catalase
Recall this diagram about the digestive system
