UNIT 7 Human Nutrition & Digestive System Flashcards
Exam ques, notes
Describe how food is moved along the small intestine [2]
peristalsis [1]
muscle contraction ABOVE food pushes it forward [1]
5 MARKER.
Explain the differences in the average number of mitochondria in each type of cell
SO:
- state definition of mitochondria
-what it does
-focus on one esp the easiest and cover all possible logical arguments
📌mitochondria are site of aerobic respiration ;
release energy ;
red blood cells need space, for haemoglobin ;
red blood cells, are moved in the blood
red blood cells, take up oxygen by diffusion ;
so no energy needed for active transport ; 📌
[heart / intestine (cells), respire more ;
heart (cells) (continuously) contract ;
epithelial cells need more energy ;
active transport in the small intestine ;]
The blood that flows from S enters a vein.
Name the vein that transports blood away from the small intestine
main blood vessel that takes blood from the small intestine to the liver.
hepatic portal (vein)
Cell T is an example of the cells that form the surface of the villi.
Explain why there are many microvilli on cell T
give a large surface area (of membrane) ;
to increase absorption ;
by diffusion/ by active transport ;
Describe and explain how the structure of a villus is adapted for its function [4]
microvilli;
microvilli provide large surface area;
epithelium one cell thick ;
aiding diffusion;
good blood supply ;
(good blood supply) to maintain a steep concentration gradient ;
Explain the role of mechanical digestion.
breaks up food into small(er) pieces ;
without chemical change;
by teeth/muscles ;
to mix (with digestive juice) ;
increases surface area ;
for enzyme action ;
Explain how chemical digestion differs from mechanical digestion. [3]
chemical digestion breaks bonds and uses enzymes, making the insoluble food molecules soluble
mechanical digestion increases surface area of food so it can be churned
Some of the cells on the surface of the villi secrete mucus for protection.
Suggest what the villi need to be protected against.
enzymes ;
(stomach) acid ;
physical damage/AW ;
parasites /(named) pathogens / toxins ;
The small intestine is lined by many villi. 1st diagram: longitudinal section of a villus.
2nd: cross-section of same villus at V-W (through there)
Name P, Q, & R structures
P - epithelium (like outside layer of the villus)
Q - blood capillary (smaller structures around the main lacteal/lymphatic vessel through the middle, from cross section look like smaller circles not in centre)
R - lacteal (in cross section largest circle in centre + the running tube-looking structure through villus)
Epithelium
outside layer in villi
Fat is particularly difficult to digest as it is not water soluble and forms spherical globules in the alimentary canal.
Diagram - showing what happens to fat globules when mixed with bile.
[Fat globules - 2 big circles and many small ones, an arrow from big to small.]
i) Name the process shown
ii) Explain the advantage of the process shown [2]
i) emulsification
(emulsifying fat)
ii)
INCREASES SURFACE AREA
for action of LIPASE/enzyme(s)
Describe balanced diet
EXAM QUES: Explain the term balanced diet [3]
provides sufficient energy for needs AND provides nutrients in correct amounts
provides materials for metabolism
SOURCES & GENERAL FUNCTIONS
Carbs. Functions?
- Starch
- Simple sugars
E.g. of starch (carbs)?
Functions: Usually the primary nutrient for producing energy using respiration.
E.g’s: Bread, potatoes, pasta, rice
E.g. of simple sugars (carbs)
Sweets, cakes, biscuits
Fats/lipids. E.g.s?
Butter, oils, cheese
Fats needed to? 3 functions
⭐ Make cell membranes of cells
⭐ Store energy
⭐ Produce fat tissue to stay warm
Protein - e.g’s?
Meat, fish, milk, eggs & beans
Protein - needed for? 2 functions
⭐ Growth (getting bigger by growing new cells)
⭐ Repair (replacing damaged or worn out cells)
Vitamins (C & D)
Vitamin C - EXAMPLES?
🔗 Citrus fruit (lemon, orange, lime)
🔗 Kiwifruit
🔗 Capsicum
Vitamin C - FUNCTION?
⭐ Used in creating connective tissue, blood vessels, bones & cartilage
⭐ Required for wound healing
Severe Vitamin C deficiency results in…?
Scurvy
Vitamin D - EXAMPLES?
🔗 Fatty fish
🔗 Egg yolks
🔗 Mushrooms
🔗 MAIN source: sunlight
Vitamin D - Function?
⭐ Helps to absorb calcium from your diet. Needed to maintain healthy strong bones
Severe Vitamin D deficiency results in…?
Rickets
Minerals: calcium, iron
Calcium - EXAMPLES?
Milk, cheese, fish with bones
Calcium - FUNCTIONS?
Needed for maintaining healthy bones, preventing blood clotting & muscle contractions
Iron - e.g.s
Red meat, whole grains, leafy greens
Iron - functions
⭐ Required for making haemoglobin in red blood cells, used to bind oxygen
Dietary fibre [largely complex carbs body can’t digest] - e.g.s
fruits, vegetables
Dietary fibre - functions
Ensures food moves through your intestines at the correct rate/a good pace
Water - functions
⭐ Acts as a solvent for cellular reactions, circulatory system, digestion, etc.
⭐ Helps to maintain body temperature [high SHC]
Identify in diagrams & images the main organs of the digestive system, limited to:
(a) alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum and
ileum) & large intestine (colon, rectum, anus)
(b) associated organs: salivary glands, pancreas, liver & gall bladder
Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to:
[JUST FOR UNDERSTANDING]
(a) ingestion –
(b) digestion –
(c) absorption –
(d) assimilation –
(e) egestion –
a) the taking of substances, e.g. food & drink, into the body
b) the breakdown of food
c) the movement of nutrients from the intestines into the blood
d) uptake and use of nutrients by cells
e) the removal of undigested food from the body as faeces
Mouth & Salivary Glands
What do teeth do? What do salivary glands do? Which enzyme? Starch to maltose to glucose.
EXPLAIN:
Teeth grind food into small pieces, INCREASING surface area.
Salivary glands release saliva.
Saliva contains amylase enzyme which breaks down starch into maltose. Another enzyme, maltAse, breaks down maltose to glucose.
Part of a starch molecule.
⭐ AMYLASE ⭐
➡ Maltose molecules (disaccharides)
⭐ MALTASE ⭐
➡ Glucose molecules (monosaccharides)
Back of mouth, ball called bolus. The bolus is pushed down the oesophagus by rings of muscles that contract by peristalsis.
What is peristalsis?
Contraction of muscles
Stomach
Main organ where food DIGESTED
Muscles CHURN the food (physical). Enzymes are added (e.g. pepsin).
Hydrochloric acid is added, further digesting food
Small intestine
Function?
What happens here?
Made from?
Villi [[adaptations, microscopic villi, diffusion w/ S.A.]]?
Capillaries [[diffusion w/ distance, function]]?
Lacteal [[function, concentration gradient]]?
⭐ Region where nutrients are absorbed; ⭐ Where soluble food molecules are absorbed into the blood stream
⭐ Made from microscopic villi that help increase the internal surface area OF THE SMALL INTESTINE so more nutrients can be absorbed more quickly.
Villi (which INCREASE INTERNAL SURFACE AREA) line the small intestine - gives small intestine a LARGE SURFACE AREA, increasing the RATE OF DIFFUSION, making it faster [higher S.A. = faster rate of diffusion]
Capillaries reduce the diffusion distance. [shorter distance = faster rate of diffusion]
Capillaries TRANSPORT water, amino acids, sugars, etc.
Lacteal (in middle) absorbs fats. Blood flowing maintains steep concentration gradient. [larger concentration gradient = faster diffusion]
Small intestine [TWO]
3 parts: ILEUM, jejunum, DUODENUM
Food out of stomach enters the duodenum where bile & digestive enzymes are added to further digest the food.
[digestive processes continue as food enters jejunum]
FOOD will then pass into the ileum where the majority of nutrients are absorbed.
Large intestine
What enters the LI?
Function?
Mainly indigestible food & water enter the large intestine
Function: absorb water back into the body
Rectum & anus
for DEFECATION. Function? What is the anus?
Faeces, the waste food, is stored in the rectum ready to be released by peristalsis
The anus is the opening at the end of the digestive system
Liver & gall bladder
Function?
Liver PRODUCES BILE which helps to DIGEST LIPIDS
Gall bladder STORES the BILE until it is released into the SMALL intestine.
Pancreas. Function?
⭐ Produces enzymes involved in digestion [ protease, lipase & amylase are produced ]
⭐ Produces insulin & glucagon, hormones that regulate blood sugar levels
Define physical(/mechanical) digestion
What does it do?
The breakdown of
food into smaller pieces without chemical change
to the food molecules
mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum
🔗 Physical digestion increases the surface area of food for the action of enzymes in
chemical digestion; exposed to saliva & enzymes and broken down more quickly
Identify in diagrams and images the types of human teeth: incisors, canines, premolars and molars
check
Describe the structure of human teeth, limited
to:
- enamel,
- dentine,
- pulp,
- nerves,
- blood vessels
and - cement,
[gums]
AND
Understand that teeth are
embedded in bone and the gums
- Enamel: Hard outer layer of the crown. The hardest substance in the body.
- Dentine: not as hard as enamel. It forms the bulk of the tooth. If there are gaps in the enamel that expose the dentine to the outside, or enamel is very thin, your teeth will be sensitive.
- Pulp: soft tissue, contains blood capillaries and nerve supply to the tooth.
- Nerves: in the pulp
- Blood vessels: in the pulp
- Cementum: also known as cement. The layer of bone-like tissue covering the root. Not as hard as enamel.
TEETH ARE EMBEDDED IN BONE AND THE GUMS.
Chemical digestion - define
Role?
the break down of large insoluble molecules into small soluble molecules
the role of chemical digestion in producing small soluble molecules that can be absorbed
Describe the functions of enzymes as follows:
(a) amylase breaks down starch to …
(b) proteases break down protein to …
(c) lipase breaks down fats and oils to …
a) simple reducing sugars
amylase breaks down starch to maltose to glucose.
b) protein to AMINO ACIDS
c) fatty acids and glycerol
_____ water is absorbed from the _____________ but that some is also absorbed from the
_______
MOST
water is absorbed from the
SMALL INTESTINE
but that some is also absorbed from the
COLON
Incisors. Function?
Incisors - chisel-shaped for biting and cutting
Canines. Function?
Canines - pointed for tearing, cutting, holding and biting food
premolars
& molars
Function?
- 4 incisors consecutively, 2 canines bracketing that altgt, 2 premolars & 3 molars EACH on both sides
Premolars and molars - larger, flat surfaces with ridges at the edges for chewing and grinding up food
Molars - do most chewing work
Premolars - help incisors & canines GRIND & MIX FOOD
ROLE of Bile
What is bile?
role of bile in emulsifying fats and oils to increase the surface area for [faster] chemical digestion by enzymes
bile is an alkaline mixture that
neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action
3 main types of enzymes:
Carbohydrases - AMYLASE
Lipases - LIPASE
Proteases - PEPSIN
digests carbs - AMYLASE
digests lipids - LIPASE
digests proteins - PEPSIN
The digestion of starch (by amylase & maltase) in the digestive system:
Carbohydrases, E.G. amylase.
Produced by? Produced in? /
Where is it secreted and where do they act?
Function?
[Amylase produced by salivary glands]?
⭐ Amylase also produced in the pancreas & secreted into the duodenum
⭐ amylase breaks down starch to maltose. Maltase breaks down maltose to glucose on
the membranes of the epithelium lining the
small intestine
Lipase.
Where is it secreted and where do they act?
Function?
⭐ Produced in the pancreas & secreted into the duodenum
⭐ Digests lipids into glycerol & fatty acids
Protease E.G. pepsin
Where is it secreted and where do they act?
⭐ Pepsin is found in the stomach. Digests PROTEINS to AMINO ACIDS.
structures secrete enzymes that digest proteins: stomach, pancreas
Trypsin produced where? Secreted where?
Function?
Trypsin; produced in PANCREAS
Secreted into DUODENUM
Digests proteins to amino acids
The digestion of protein by proteases in the digestive system:
Pepsin - optimised for?
Optimised for acidic conditions, as stomach contains hydrochloric acid
pepsin breaks down protein in the acidic conditions of the stomach
Trypsin - optimised for?
Optimised for slightly alkaline conditions after bile neutralises the hydrochloric acid in the duodenum of small intestine
trypsin breaks down protein in the alkaline conditions of the small intestine
Functions of hydrochloric acid
in gastric juice
⭐ killing harmful
microorganisms in food
⭐ providing an acidic
pH for optimum enzyme activity
The bacterium Salmonella enterica can cause severe food poisoning and the lining of the
alimentary canal may be damaged. In these cases absorption of digested food products cannot easily take place.
Which region of the alimentary canal is most affected?
ileum
Which treatment is best for a person with persistent diarrhoea?
A drinking a solution of sugar and salt
B drinking pure water
C eating more fibre
D eating protein such as boiled eggs
A
Which substance catalyses the breakdown of fats to fatty acids and glycerol?
lipase
A person ate food X. Food X was not affected by enzymes until it reached the duodenum.
What was in food X?
fat
In which organs does the digestion of carbohydrates take place?
mouth &
small intestines
What is the result of a diet lacking iron?
A bleeding gums
B poor wound healing
C reduced number of red blood cells
D weak bones and teeth
C) reduced number of red blood cells
bleeding gums relates to…
lack of vitamin C
The activity of lipase is measured in four parts of the gut.
Which part has the most lipase activity?
duodenum
What is a function of the liquid produced by pancreas & going into duodenum?
to digest proteins to amino acids
[could be gastric juice, containing enzymes and hydrochloric acid, breaking down food.
this liquid contains enzymes like pepsin, which breaks down proteins into smaller strands called peptides, and hydrochloric acid, which creates an acidic environment to optimize pepsin function.]
The scientists concluded that food stays longer in the digestive systems of larger mammals compared with smaller mammals.
Discuss the evidence from Fig. 6.2 for and against the statement that food stays longer in the
digestive systems of larger mammals.
for:
positive correlation/ as (relative) body mass increases,
time in digestive system increases ;
any two or more figures from the graph ;
against: max 3 from
two/one/ few/ some (species), are outliers / anomalies ;
any figure(s) from the graph;
(description of) some mammals do not fit the, pattern/ trend ;
any example from the graph;
only information about 26 species of mammal/ small sample size ;
idea about unknown validity ;
- conversion of glucose
to glycogen - secretion of insulin
and glucagon
- liver
- pancreas
Explain the advantage of the process (emulsifying fat w/ bile) shown in Fig. 3.2.
[2]
increases surface area ;
for action of, lipase/ enzyme(s) ;
show how the uptake of glucose by cells and the concentration of
glucose in the blood respond when the two hormones are secreted.
Hormones: insulin, glucagon
uptake of glucose by cells & concentration of glucose in
the blood
decreases/stays same/increases?
when insulin secreted ;;
uptake of glucose by cells: increases
conc. of glucose in blood: decreases
/ glucagon ;;
cells: decrease
blood: increase/stay the same
State another hormone that influences the concentration of glucose in the blood.
adrenaline
Some people develop gallstones, made of cholesterol, that accumulate in the gall
bladder and the bile duct. Gallstones block the flow of bile.
Explain how gallstones can affect the digestion of fat.
less / no bile, secreted/released ;
(so) no/ less, bile salts ;
enter small intestine/ duodenum ;
no/ less, emulsification of fat ;
less / no, increased surface area of fat (globules /AW)
for lipase ;
slower/ harder, digestion ;
Cholesterol can also accumulate in the walls of the coronary arteries.
Explain the effects that this might have.
coronary heart disease/CHD/ heart attack / cardiac arrest/ angina/myocardial
infarction ;
reduced blood flow/ blockage of artery or arteries ;
damaged/hardened artery wall/ atheroma/ atherosclerosis ;
(blood) clot/ thrombus / thrombosis /(coronary) aneurysm ;
causes high blood pressure ;
reduced supply of, oxygen/nutrients, to heart tissue/muscle ;
muscle respires anaerobically ;
partially digested food is mixed with bile in…
the small intestine
most water is reabsorbed
small intestine
describe what happens to seal the wound in the skin
and repair the skin tissue. [5]
Platelets cause clotting.
Enzyme converts soluble fibrinogen to insoluble fibrin, forming a mesh to trap blood
and prevent blood loss, making a scab
[7]
Fig. 1.1 A shows a cell from the lining of the alimentary canal.
Fig. 1.1 B shows a cell from the lining of a kidney tubule.
List three substances that are absorbed by both cells
water
glucose
ions
Suggest the role of the muscle tissue shown in the villus
(contracts to) move villus ;
exposes villus to more food / changes surface area ;
increases absorption ;
increase diffusion
After two hours there was less water in the bag made from small intestine.
The volume of water in the bag made from small intestine decreased, but the volume in
the bag made from Visking tubing did not change.
Explain why.
lower water potential outside bag
water diffuses out of bag ;
by osmosis ;
Explain why water is added to food by the secretions [3]
for breakdown of (large / insoluble) food (molecules);
(used in) chemical digestion ;
solvent / for dissolving, enzymes and food ;
Explain why it is important that water is absorbed in the alimentary canal. [2]
prevents
loss of, large volume of / lots of water ;
loss of, ions / salts (in solution) ;
