Organisms Exchange Substances With Their Environment Flashcards
(119 cards)
1
Q
Why do cells need to exchange substances with their environment?
A
- cells need oxygen and nutrients e.g. glucose
- organisms need to excrete waste products
- heat needs to be exchanged as most organisms need to stay at the same temperature.
2
Q
What is metabolism?
A
The sum total of all chemical reactions that happen in the body/ cells. Including respiration.
3
Q
What is a byproduct of respiration?
A
Heat
4
Q
Why do warm blooded animals do more respiration?
A
To maintain body temperature.
5
Q
What is the total oxygen requirement of an organism correlated to?
A
It’s total volume
6
Q
Why do larger organisms require more oxygen?
A
Larger/ more cells, therefore requiring more energy for cellular processes.
7
Q
What is the rate of absorption of gasses by an organism correlated to?
A
The size of its surface area. Larger membrane would mean more molecular movement.
8
Q
Why must the volume always be at 1 when showing the relationship between surface area and volume?
A
Allows direct comparison between organisms of different sizes.
9
Q
By which process do single-celled organisms exchange gases across their body surface?
A
Simple diffusion
10
Q
Why do single-celled organisms have a fast diffusion rate?
A
- they are small and so have a short diffusion pathway
- they have a large SA:Vol ratio due to their small volume compared to the surface area of their cell surface membrane.
11
Q
What are the disadvantages of larger organisms having lower SA:vol ratios?
A
-diffusion is too slow as some cells are deep within the body
-a large volume of animals has requirements too high for the available surface area.
12
Q
Why do multicellular organisms have an increased metabolic demand?
A
They have more cells
13
Q
Why do multicellular organisms have a slower rate of diffusion?
A
-large diffusion distance to inner most cells
-lower SA:vol ratio
14
Q
What adaptations have multicellular organisms evolved to increase surface area?
A
Some organisms have evolved to have a body shape which maximises their surface area. E.g. by being flattened or elongated.
15
Q
Give examples of specialised exchange organs that organisms have developed to maximise gas exchange and transport.
A
-Gills in fish and amphibians, folded into lamella
-lungs in mammals folded into alveoli
Both increase surface area for exchange
16
Q
Give an example of a specialised delivery system that organisms have developed to maximise gas exchange and transport.
A
Th oxygen diffuses into the circulatory system (mass transport) to deliver gasses directly to cells.
17
Q
What have insects developed for gas exchange and transport?
A
Tracheal system
18
Q
What is the tracheal system?
A
Series of specialised tubes in direct contact t with cells. They also maintain a small size to maintain a short diffusion distance. Tubes carry o2 directly to cells.
19
Q
The epithelial cells that line the small intestines are adapted for the absorption of glucose. Explain how (5 marks)
A
1.Microvilli provide a large / increased surface area;
2.Many mitochondria produce ATP / release or provide energy (for active transport);
3.Carrier proteins for active transport;
4.Channel / carrier proteins for facilitated diffusion;
5.Co-transportof sodium (ions) and glucose or symport / carrier protein for sodium (ions) and glucose;
6.Membrane-bound enzymes digest disaccharides / produce glucose;
20
Q
Covert 2cm2 to mm2
A
200mm2
21
Q
Convert 1.5×10^-8m2 to um2
A
15000um2
22
Q
Convert 5×10^3 dm3 to cm3
A
5000000cm3
23
Q
5×10^6 cells in 20cm3, how many in 3mm3
A
750 cells
24
Q
List examples of substances exchanges with the environment
A
- oxygen and carbon dioxide
- urea/ ammonia
- heat
25
Why do smaller animals have a higher metabolic rate (per gram of body mass)?
In order to maintain a constant body temperature , they do more chemical reactions, such as respiration which release heat to maintain body heat.
26
Why do smaller animals radiate more heat per cm3?
They have a larger SA:Vol ratio
27
How does surface area:vol correlate to heat loss depending on animal size?
Smaller animals have larger SA:Vol ratio compared to larger animals. This means that they radiate more heat per cm3
In order to maintain a constant body temperature, therefore, smaller animals have a higher metabolic rate per gram of body mass
These chemical reactions release heat which is used to maintain body heat.
28
How have organisms that live in hot climates adapted to stay cool? Give an example
- increase SA:vol ratio
- can include smaller body size, larger ears, longer faces and longer noses.
- e.g. camels have long legs and a long neck to increase SA:vol ratio, thin fur and a hump storing fat to provide water.
29
How have organisms that live in cold climates adapted to stay warm? Give an example
- adapted to reduce SA:Vol ratio
- decreases loss of heat by radiation and helps maintain internal body temperature.
- may include larger body size, smaller ears,and compact facial features.
- e.g. artic fox has small ears, small body, compact facial features and thick fur.
30
Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Use your knowledge of SA:Vol ratio to explain the higher metabolic rate of a mouse compared to a horse.
Mouse:
1. Smaller so larger SA:Vol ratio
2. more/faster heat loss per gram
3. Faster rate of respiration releases more heat.
Allow converse for horse
31
How are single-celled celled organisms adapted for gas exchange?
Large SA:Vol ratio and short diffusion pathway
32
By which process do single celled organisms exchange gasses across their body surface?
Simple diffusion
33
How are larger organisms adapted for gas exchange?
Have specialises gas exchange surfaces, e.g. lungs, which have:
a large SA for diffusion
Thin surface, short diffusion pathway
Maintainence of steep diffusion gradient
34
Explain the advantages for larger animals having a specialised system that facilitates oxygen uptake.
1.larger organisms have smaller SA:vol ratio
2. Overcomes long diffusion pathway
35
What is the gas exchange process in insects?
-oxygen diffuses in tracheae through spiracles down a concentration gradient.
-the tracheae are lined with rings of chitin to prevent collapsing during ventilation.
- tracheae splits into branches called tracheoles, not lined in chitin (more permeable) branches provide large SA.
- tracheae are in direct contact with body cells and are thin (short diffusion pathway)
36
Why is the tracheae lined with chitin?
Prevents it from collapsing during ventilation.
37
Why are tracheoles not lined in chitin?
So they are permeable.
Makes them the site of has exchange insects
38
What are features/ adaptations of gas exchange in insects?
Short diffusion pathway:
Tracheoles in direct contact with insect body cells
Insects are small so sort diffusion pathway from spiritual to respiration tissues
Tracheoles are thin
Concentration gradient
Cells respire using oxygen so Concentration gradient remains low
Body can be moved by muscles to move air so maintains conc gradient for oxygen and co2
Large SA
Tracheoles are very branched.
39
How is water loss prevented in insects?
-exoskeleton made out of chitin, impermeable so reduces water loss by evaporation from insects tissue.
-exoskeleton covered in waxy cuticle which is waterproof
- spircles lined by hairs which trap water vapour around spiracle. Reduces WP gradient.
- insects can open and close spirales
40
Describe how single celled organisms exchange respiratory gasses.
Why is this method only possible in very small organisms?
-simple diffusion on their surface
-smaller animals have a larger SA:Vol ratio so faster rate of diffusion and a shorter distance from exchange surface so shorter diffusion pathway
41
An insect lives in air. Describe how the insects is able to obtain oxygen and limit water loss. 6 marks
Prevent water loss:
-waxy cuticle so waterproof
-exoskeleton made out of chitin, impermeable
-spiracles open and close and lined with hairs which absorb water
Obtain oxygen:
Enters through spiracles into trachea lined with rings of chitin to prevent collapsing during ventilation.
Branches of into tracheoles not lined with chitin, permeable. Site of gas exchange.
Short diffusion pathway as tracheoles are in direct contact with insect body cells and are thin.
Insects are small maintaining overall short diffusion pathway from spiracles to respirinf tissues.
Concentration gradient
Cells respire using oxygen so low oxygen levels. Muscles move air and so maintain conc gradient for o2 and co2
Large SA
Tracheoles are very branched
42
During excersize where does the fluid in the tracheoles move? Why?
Fluids diffuse into the tissue when active.
Activity causes metabolites e.g. lactic acid, to accumulate in tissues, making them hypertonic, so water moves into tissue by osmosis.
43
By which process is lactate produced?
Anaerobic respiration
44
Where does the fluid move when resting?
Diffuses back into the tracheoles (hypotinic)
45
Fluid in the end of tracheoles moves into tissue during ________.
-cells produce _______ by _________ respiration.
-_______ water potential.
-water moves ___ wp gradient via _______
-increases ______ In tracheoles and reduces ________ to draw more in.
-diffusion through air is ______
Exercise
Lactate
Anaerobic
Reduces
Down
Osmosis
Volume
Pressure
Faster
46
What is abdominal pumping?
A ventilation mechanism to replace air in trachea
47
What happened when the abdomen is compressed?
Increases pressure (compared to atmosphere) Air containing higher levels of co2 is forced through the abdominal spiracles out of the trachea.
Force air out. Vol decrease. Pressure increase. Moves air out via abdomen.
48
What happens when abdomen is expanded?
An expanded abdomen lowers pressure (compared to atmospheric) Air containing higher levels of o2 is forced through the thoracic spiracles into the trachea.
Force air in. Vol increase. Pressure decrease. Moves air in thorax.
49
Why do insects do abdominal pumping?
To increase air flow In and out of the body.
50
An increase co2 concentration causes the spiracles to...
(Decrease in o2...)
Open (to release co2 and Obtain o2)
Negates
51
Why does the concentration of o2 decrease when spiracles are closed?
Oxygen is used up in respiration, therefore diffuses from trachea to tissues.
O2 is unable to enter organism.
52
Why is spiracles being closed most of the time an advantage for insects that live in dry conditions?
To prevent water loss.
53
Why have fishes developed a very efficient method of gas exchange?
Water has a lower oxygen conent than air, and diffusion rates are slower in water than air.
54
How do gills have a short diffusion pathway?
Gills have a single layer of epithelial cells and the capillaries within the girls have a single layer of endothelial cells.
55
How do gills have a large surface area?
The Gills are folded into filaments, and these are further folded into lamellae.
56
How do the gills maintain a concentration gradient?
The gills have lots of blood capillaries.
Blood in the capillaries flows in the opposite direction to flow of water over the gills- this is called counter current flow.
57
How does the counter current flow work?
Water and blood flow in opposite directions so the diffusion gradient between the adjacent flows is maintained over the whole lamellae surface
58
What is a concurrent flow?
Water and blood flow in the same direction. There is not a concentration gradient along the whole length of the lamellae as equilibrium (of oxygen) is reached
59
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water.
Some other species of insect have larvae that are simular size and shape to damselflylarvae and also live in water. These larvae do not actively hunt prey and do not have gills.
Explain how the presence of gills adapts the damselfly it's way of life.
Gills provide a larger SA:vol ratio ,so more space for diffusion of oxygen to cells.
As it is actively hunting it needs to respire alot to release energy, so more oxygen is needed.
60
A student calculated that the leaf contained 300 stomata per mm2. How many stomata per um2?
Use standard form.
3×10^-4
61
Under 10x objective lens the diameter of the field of view is 0.4mm
A.What is the area?
B. There are 40 stomata in this view. Calculate the number of stomata per mm2
A. 0.127mm2
B. 318
62
Where do plants exchange gas?
Surface of mesophyll cells via stomata.
63
What gasses are needed by plants, and why?
-co2, needed for photosynthesis, o2 is a waste gas.
-o2, needed for respiration
64
How does co2 enter a plant?
Diffuses into leaves down a concentration gradient through pores in the surface of the leaf called stomata.
65
How are mesophyll cells adapted for gas exchange?
Tall and long shape increases surface area
66
How have leaves adapted to have a large surface area?
Large, flat leaf
Tall, long palisade mesophyll cells
67
How have leaves adapted to have a short diffusion pathway?
Thin leaf
Air spaces
68
How have leaves adapted to have a concentration gradient?
Mesophyll cells use the carbon dioxide, maintaining a low concentration at the mesophyll cells.
69
What causes the stomata to open?
More k ions, lowers wp. Water comes out making guard cells turgid, opening stomata.
Cell wall becomes thickened (doesn't stretch as well)
70
What causes the stomata to close?
Less k ions, higher water potential, water exits cells, guard cells become flaccid (plasmolysed)
71
How do plants lose water? By which process is this?
Plants lose water through their stomata by diffusion/ evaporation.
Process: transpiration
72
How can plants reduce water loss?
-stomata can close when the guard cells lose water and become flaccid
-leaf is covered in hydrophobic waxy cuticle (reduces water loss via evaporation)
-most stomata on lower surface of leaf (reduces water loss by evaporation out of stomata)
73
What type of plants are adapted to hot and dry conditions?
Name an example.
Xerophytes. E.g. Marram grass.
74
What further adaptations do xerephytes have to reduce water loss?
Rolled leaf shape as upper epidermis is facing inwards to trap humid air.
Reduced leaf surface area for transpiration.
Sunken stomata, humid air is trapped reducing water potential gradient between inside leaf and humid trapped air.
No stomata on exposed lower surface.
Hairs, trap moist air.
Thick cuticle, waxy covering reduced evaporation.
75
Outline the pathway of oxygen to get to the blood.
-oxygen enters the trachea
-then travels to the bronchus
-which splits of into branches called bronchioles
-which lead to alveoli on the ends
-then through the alveolar epithelium
-into the capillary endothelial
-finally into the blood
76
How are alveoli adapted to have a large surface area?
-many alveoli which are folded, providing a large SA.
77
How are alveoli adapted to have a short diffusion pathway?
Alveolar epithelium (tissue made of epithelial cells) and capillary endothelium (tissue made of endothelial cells) are one cell thick.
Cells are also squamous (flattened)
Provides a short diffusion pathway for o2 and co2 between air and blood.
78
How are alveoli adapted to maintain a steep concentration gradient?
-many capillaries close to alveoli to maintain good blood supply and maintain steep conc. Gradient.
-well ventilated to bring o2 to surface and take co2 away (breathing) to maintain a steep conc gradient for o2 and co2
-both ensure higher (o2) inside alveoli.
79
What controls the movement of air in and outif the lungs?
The diaphragm and internal/ external muscles contrat to change the volume in the thorax, so change the air pressure. Air moves from higher to lower air pressure.
80
What happens when we breath in?
-The external intercostal muscles contract SO rib cage moves up and out.
-The internal intercostal muscles relax
-The diaphragm contracts SO it flattens
-ribcage movement and flattened diaphragm increases the volume of the thorax SO pressure decreases below atmospheric pressure.
-this causes air to move into the lungs, down a pressure gradient.
81
What happens when we breath out?
-External intercostal muscles relax SO ribcage moves down and in.
-Internal intercostal muscles contract (forced expiration)
-Diaphragm relaxes SO it becomes dome shaped.
-Ribcage movement and Diaphragm shape decreases the volume of the thorax SO pressure increases above atmospheric pressure.
-This causes air to move out of the lungs down a pressure gradient.
82
Describe and explain the mechanism that causes lungs to fill with air.
1. Diaphragm (muscle) contracts and external intercostal muscles contract.
2.this causes the volume to increase and the pressure to decrease in the thorax.
3.Air moves down a pressure gradient
83
How does forced expiration occur?
-internal intercostal muscles contract pulling the rib cage further down and in.
-external intercostal muscles and diaphragm relax.
84
What is pulmonary tuberculosis? (Don't have to know this)
List an example effect on lung function.
-bacterial infection. The immune system builds hard tubercles around bacteria in the lungs which damages the gas exchange surface.
-volume breathed in decreases.
85
What is fibrosis?
List an example effect on lung function.
-after exposure to asbestos or dust. Thick non-elastic sca tissue forms.
-volume breathed in decreases as does the volume exhaled per breath. Gas exchange is reduced as diffusion distance across scale tissue is longer.
86
What is asthma?
List an example effect on lung function.
-Airways are irritated and inflamed. Smooth muscle lining the bronchioles contract and more mucus is produced.
-Airflow is severely reduced so volume of air exhaled per second reduces.
87
What is emphysema?
List an example effect on lung function.
-caused by smoking or air pollution as particles are trapped in the alveoli. Inflammation attracts phagocytes, and enzymes break down the elastin in the alveolar wall. Alveoli can not now recoil.
-destruction of the alveolar walls reducing surface area for gas exchange. Increasing ventilation rate to compensate.
88
What happens during digestion?
-large, insoluable biological molecules are hydrolysed to smaller,more soluble molecules that can be absorbed across cell membranes.
89
What can catalyse the breakdown of biological molecules?
-digestive enzymes, which are produced by specialised cells in mammals to catalyse the breakdown.
Enzymes are specific to substartes so different enzymes are needed.
90
How does food travel through the digestive system?
-enters through mouth (PH 7-8)
-salivary glands produce enzymes (amylase)
-travels down oesophagus
-to the stomach (PH 2, which denatures amylase)
-travels into small intestines, pancreas secretes enzymes had produces alkaline fluid neutralising PH to 7-8. Liver also produces bile responsible for neutralising PH.
-travels to large intestines.
-exits through rectum- anus
91
How are carbohydrates digested?
-the mouth produces salivary amylase which hydrolysis glycosidic bonds in starch to form maltose.
-salivary gland produces amylase, PH is 7/8.
-the stomach has a PH of 2, so amylase is denatured
-pancreas produces amylase and alkaline fluid to neutralise HCl to PH 7/8
-liver also produces bile to neutralise PH.
-small intestines, pancreatic amylase hydrolysis glycosidic bonds in starch to form maltose.
-small intestines (ileum), disaccharides (e.g. maltase, sucrase and lactase) attached to the epithelial cells lining the ileum hydrolyse glycosidic bonds in disaccharides to form monosaccharides.
Amylase. Membrane bound maltase
Starch--------------> maltose------------------------------------> glucose
Mouth/ Small I. Small intestines
92
How are proteins digested?
-proteins are hydrolysed by 3 types of protease enzymes: endopeptididases, exopeptidases and dispeptidases into amino acids.
-endopeptidases hydrolyse bonds within a proteins. Some produced a pancreas and secreted into small I. Other types are produced by stomach cells and work in acidic conditions using HCl.
Hydrolyse long polypeptides into shorter polypeptides. Increasing the SA for exopeptidases and speeds up full hydrolysis of proteins.
-exopeptidases, produced by the pancreas and secreted into small I, hydrolyse the bonds at the end of proteins to remove single amino acids.
-Dipeptidases, located on cell surface membrane of epithelial cells in small I and seperate dipeptides into two amino acids.
____________________________exopepgidases__________________
Endopeptidases. Exopeptidases. Dipeptidases
Large polypeptides-------------------->smaller polypeptidases--------------->deptides--------------> amino acids
Stomach/small intestines. Small intestines. Small intestines
93
Two solutions often used to stain tissues are heamatoxylin solution and iodine solution.
Heamatoxylin stains DNA blue.
Iodine stains starch blue-black.
Why is heamatoxylin used to stain lung tissue and not iodine?
-there is no starch present in human lung tissue.
-nucleus in lung tissue cells contains DNA
94
How is the digestion of lipids different to the digestion of starch and proteins?
Lipids are not polymers so only need one enzyme to hydrolyse the ester bond.
Starch and proteins are polymers and so need multiple enzymes to hydrolyse them.
95
How are lipids hydrolysed?
Lipids are hydrolysed to monoglycerides and fatty acids. Catalysed by lipase.
96
Where is lipase produced and where does it work?
-produced by the pancreas
-works in the small intestines
97
What is the function of bile in the digestion of lipids? Where is bile produced and stored?
Bile salts produced by the liver emulsify large droplets of lipids into smaller droplets, creating a larger surface area for lipases to work on, increasing the rate in which ester bonds are hydrolysed.
Tye monoglycerides and fatty acids form micelles with the bile salts.
Bile. Lipase
Larger lipid----->smaller lipid-------------------->Monoglycerides and fatty acids (l- + =)
Small intestines
98
How can measuring the PH indicate lipid digestion?
Fatty acids make the solution more acidic. The father the PH change, the father the rate of hydrolysis (as lipids are broken down into fatty acids)
99
Why can't a PH buffer be used to measure rate of lipid digestion?
What should be used instead?
PH buffer would maintain a constant PH which is not desired in this type of investigation.
PH meter would be most accurate.
100
Why would the addition of bile result in a quicker decrease in PH when measuring lipid digestion?
Bile emulsifys lipids, increasing the SA for lipase to hydrolyse the lipids.
This means fatty acids are produced quicker and so PH decreases quicker.
101
What are micelles and what do they do?
-lipid droplet surrounded by bile.
-transport lipids to the epithelial cell membrane so the lipids can be absorbed. Micelles diffuse to cell membrane in the lumen of the small intestines.
102
How are maltose, sucrose and lactosebroken down, what into?
Maltose:
Maltose+ maltase -> 2× a-glucose
Sucrose:
Sucrose+ sucrase-> fructose + a-glucose
Lactose:
Lactose+ lactase-> galactose + a-glucose
103
How is starch, protein and lipids broken down?
Starch:
Amylose + amylase-> maltose
Disaccharides-> monosaccharides
Protein:
Long peptide + endopeptidase-> shorter peptides
Short peptide + exopeptidase-> amino acids + dipeptides
Dipeptide + dipeptidase-> amino acids
Lipids:
Triglyceride + lipase-> monoglycerides + fatty acids
104
What digestive enzymes does the stomach produce?
Endopeptidase
105
What digestive enzymes does the pancreas produce?
Amylase, endopeptidases, exopeptidases and lipase
106
What does the liver produce, where is it stored and released to?
Liver produces bile, stored in gall bladder and released into duodenum.
107
Where is amylase produced?
Salivary gland and pancreas
108
Where is endopeptidases produced?
Stomach and pancreas
109
Where is exopeptidases produced?
Pancreas
110
Where is lipase produced?
Pancreas
111
How is the ileum adapted to ensure rapid absorption?
-very long and folded into villi. Increases the SA for absorption.
-each villas has a good capillary network, and a network of tubes called a lacteal, part of the lymph system. Both rapidly re,ove absorbed molecules, maintain a steep concentration gradient.
-lining of the ileum is made of one layer of epithelial cells and capillaries are one layer of endothelial cells, ensures short pathway for absorption.
112
What are adaptations of the epithelial cells?
- folded into microvilli, increasing SA
-membrane has more protein channels and carriers for more active transport, facilitated diffusion and co-transport.
-more mitochondria for more ATP production, allowing more active transport and co-transport.
-more ribosomes, RER and golgi for protein synthesis and modification, to produce more membrane proteins.
113
How are amino acids or monosaccharides taken into the epithelial cells, when high and low conc?
-when high concentration in ileum, they,ove in by facilitated diffusion
-when low concentration they are taken up by co-transport.
114
How is monosaccharides (e.g. glucose) and amino acids co-transported into the epithelial cell?
1. (3 ions of) Na+ is active transported out of the ileum into the blood using ATP. This produces a concentration gradient as low concentration of NA+ in cells.
2. NA+ diffuses down the gradient through a carrier protein/ co-transport protein into cell. It brings glucose/ amino acid with it by co-transport.
3. Glucose/ amino acid moves out of cell and into the blood by facilitated diffusion.
115
How does less/ no ATP have an effect absorption of digestion products?
No/less ATP (due to respiratory indicators or reduced respiration rate)
No/less NA+ activity transported out of cell
No/less of a concentration gradient between ileum and cell (as conc of NA+ in cell is higher)
Without a concentration gradient, NA+ will not be drawn in down a concentration gradient, so products cannot be co-transported, reducing rate of absorption.
116
What do micelles do?
Make the lipids soluble in the watery solution in the lumen of the ileum and transport the fatty acids and monoglycerides to the cell membrane of the epithelial cells.
117
Once at the cell membrane what do the micelles release, by which process do they cross the mebrane and what happens inside the epithelial cell to them?
Micelle releases the fatty acids and monoglycerides. As they are small and hydrophobic they cross the membrane by diffusion.
Once in the cell, triglycerides are reformed in the SER. The triglyceride is transported to the golgi where the triglyceride is added to a protein modifying it into a structure called a chylomicron, which is packaged into a vesicle and exported out of the cell.
The chylomicrons move into lacteals where they are transported around the body.
118
How are monoglycerides and fatty acids transported into the villi?
Bile salts create micelles with monoglycerides and fatty acids, transports them to the epithelial membrane to be absorbed by diffusion.
Triglycerides are reformed in the SER.
The golgi modifies lipids by adding proteins (lipoprotein) and Triglycerides, packaging into chylomicrons.
The chylomicrons are exported by exocytosis.
Chylomicrons are absorbed into the lacteals in the villi.
119
Describe the process involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (5 marks) ms 2020
1. Micelles contain bile salts and fatty acids/ monoglycerides
Ignore other correct components of micelles
2. Make fatty acids / monoglycerides (more) soluble (in water)
OR
Bring/ release/ carry fatty acids/ monoglycerides to cell/ lining (of the ileum)
OR
Maintain high(er) concentration of fatty acids/ monoglycerides to cell/ lining (of the ileum);
Accept lipid/fat for fatty acid/ monoglycerides
3. Fatty acid/ monoglycerides absorbed by simple diffusion.
Reject facilitated diffusion
Ignore if micelles themselves are being absorbed
4. Triglycerides (re)formed (in cells);
Accept chylomicrons form
5. Vesicles move to cell membrane;
Accept exocytosis for 'vesicles move'
