3A Exchange Flashcards
What is surface area?
The total area of the organism that is exposed to the external environment
What is volume?
The total internal volume of the organism (total amount of space inside the organism)
What happens to SA:V ratio when the overall size of an object increases and why?
It decreases because volume increases more rapidly than surface area
What benefits does a high SA:V have?
Large SA allows maximum absorption of nutrients and gases and secretion of gas products. Small V means the diffusion distance to all organelles is short
What happens as SA:V decreases?
Less SA for absorption of nutrients and gases and secretion of waste products, greater V results in longer diffusion distance to cells and tissues of the organism
What adaptations do large organisms have to facilitate exchange of substances to their environment?
A variety of specialised cells, tissues, organs and systems eg. gas exchange system, circulatory system, lymphatic system, urinary system, xylem and phloem
Which type of organisms don’t have transport systems and why?
Very small organisms eg. bacteria, protoctists and some worms. Their bodies are so small or so flat that they can rely on diffusion alone to get oxygen and release carbon dioxide
Give examples of very small organisms without transport systems
Amoeba (protoctista) and Cholera (prokaryotes/bacteria)
Why is the supply of oxygen important in organisms?
Organisms require ATP in order to carry out the biochemical processes required for survival. The majority of ATP is produced through aerobic respiration which requires oxygen
Why is the removal of carbon dioxide important in organisms?
Carbon dioxide is a toxic waste product of aerobic respiration, if it accumulates in cells/tissues it alters the pH
How does diffusion time increase when volume of a microorganism increases?
Chlamydomonas 20μm = 100 milliseconds for diffusion across 10μm radius
If it were 20μm diameter it would take 400 milliseconds for diffusion so it increases substantially
What is basal metabolic rate?
The metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving.
How can BMR be measured/estimated?
- oxygen consumption
- carbon dioxide production
- heat production
How are body mass and BMR of an organism related?
As mass gets greater, so does BMR. Therefore, a rhino consumes more oxygen in a period of time than a mouse.
How is SA:V ratio related to the BMR of an organism?
The BMR per unit of body mass is higher in smaller animals because they have a higher SA:V ratio so they lose more heat
Which different apparatus can be used for investigating metabolic rates in organisms?
- respirometers
- oxygen/carbon dioxide probes
- calorimeters
What do effective exchange surfaces in organisms have?
- large surface area
- short diffusion distance
- concentration gradient (maintained)
What do all insects possess?
A rigid exoskeleton with a waxy coating that is impermeable to gases.
What have insects evolved?
A breathing system that delivers oxygen directly to all organs and tissues of their bodies
What is a spiracle?
An opening in the exoskeleton of an insect which has valves.
What does a spiracle allow?
Allows air to enter the insect and flow into the system of tracheae
What are tracheae?
Tubes within the insect breathing system which lead to tracheoles (narrower tubes)
How do the tracheae in an insect stay open?
There are rings of cartilage that keep them open
Where is there a lot of tracheoles in insects and why?
A large number of tracheoles run between cells and into the muscle fibres - the site of gas exchange
In smaller insects, how does the tracheal system provide oxygen?
Sufficient oxygen is provided via diffusion in smaller insects
What is different in very active, flying insects’ tracheal systems compared to small insects?
Very active, flying insects need a more rapid supply/intake of oxygen. They create a mass flow of air into the system by:
- closing the spiracles
- using muscles to create a pumping movement for ventilation
What occurs during the flight of insects in their tracheoles?
The water found at the narrow ends of the tracheoles is drawn into the respiring muscle (by osmosis) so gas diffuses across quicker
What is the difference between a dicotyledonous plant and a monocotyledonous plant?
The first leaf in a monocotyledonous plant is just one eg. grass, however there is two leaves in the first germination of a dicotyledonous plant eg. roses or magnolias
Why must plants have adequate carbon dioxide?
In order to carry out photosynthesis, leaves have adaptations to aid uptake of carbon dioxide
Why do leaves of plants need adaptations to aid uptake of carbon dioxide?
The atmosphere is only made of around 0.036% carbon dioxide so efficient gas exchange is necessary
Describe the function of a plant’s waxy cuticle
Reduces water loss from the leaf and plant in general
Describe the function of a plant’s upper epidermis
Layer of tightly packed cells that protects the leaf and aids in reducing water loss also
Describe the function of a plant’s palisade mesophyll layer
A layer of elongated cells containing chloroplasts in which most of the photosynthesis occurs in a leaf
Describe the function of a plant’s spongy mesophyll layer
A layer of cells that contains a network of air spaces that allows for gas exchange and flow of gases needed for photosynthesis
Describe the function of a plant’s stomata
Pores (usually on the underside) which allow air to enter and exit the leaf
Describe the function of a plant’s guard cells
They open and close the stomata to prevent water loss
Describe the function of a plant’s lower epidermis
The underside of the leaf containing guard cells and stomata which allow carbon dioxide and oxygen to enter and exit respectively as well as releasing excess water
Describe the mechanism of leaves in a dicotyledonous plant
- when guard cells are turgid (full of water) the stoma remains open allowing air to enter
- the air spaces within the spongy mesophyll allow carbon dioxide to rapidly diffuse into cells
- carbon dioxide is used up in photosynthesis by cells containing chloroplasts: MAINTAINS CONCENTRATION GRADIENT
- no active ventilation is required as thinness of the plant tissues and the presence of stomara helps to create a short diffusion pathway
Describe the structure of stoma
- small pores mainly on the underside of the leaf
- surrounded by guard cells
- most open during the day and close at night
- some show a constant rhythm of opening and closing even when kept in constant conditions
Why do stoma generally close?
When a plant suffers water stress
What may be different in desert plants’ stoma?
They open at night and close during the day
What do stoma do?
They control the flow of gases and evaporation of water by opening and closing
What exchange is essential for the survival of organisms?
The exchange of gases from the atmosphere, oxygen for respiration and carbon dioxide for photosynthesis
Describe some vital functions of water
- it’s a solvent that facilitates transport of essential nutrients
- extreme water loss can lead to death
Why does there need to be compromises between adaptations for gas exchange and minimal water loss?
Scientists have observed that adaptations in organisms that reduce water loss negatively affect gas exchange and vice versa
What are small ground insects prone to and why?
- prone to drying out
- surrounded by air
What do insects have that makes gas exchange difficult?
- insects have a rigid, waterproof exoskeleton that prevents water loss
- water proof waxy coating of exoskeleton makes gas exchange by diffusion very difficult
What have insects evolved and what does it consist of?
- they have evolved a breathing system known as the tracheal system
- consists of many tubes that carry oxygen to all cells and tissues
What are spiracles?
- openings in the exoskeleton of an insect connected to the tracheal system
How are moving gases involved in the gas exchange of insects?
- most insects can use their body muscles to squeeze their tracheae and air sacs
- this forces air out
- when muscular tension is released, fresh air is drawn into the large tracheae
How are tracheoles significant in insects’ gaseous exchange?
- spiracles open into large tracheal tubes
- tracheal tubes lead to ever-finer branches
- branches penetrate to every part of the body
- at their extreme ends (tracheoles) they may be less than one micrometer in diameter and are filled with liquid
- every cell in insect’s body is adjacent or very close to the end of a tracheole
Describe some adaptations for gas exchange within insects
- large surface area (lots of tracheoles)
- moist surface (tracheoles contain fluid)
- thin walls- one cell thick (short diffusion distance)
- trachea extend close to every singe body cell (insects are small)
Why are the hairs around the spiracle significant?
- maintain humidity
- make shallower conc grad of water
- prevents air movement so reduces water vapour loss
What is a xerophytic plant?
A species of plant that has adaptations to survive in an environment with little liquid water
Describe some adaptations xerophytic plants have to conserve water
- few stomata
- sunken stomata
- hairs surrounding stomata
- needle-shaped or small leaves
- waxy cuticle
Where are cacti typically found?
Deserts of the USA
Describe the adaptations of leaves on cacti
- leaves have become spines which don’t photosynthesise
- photosynthesis occurs in green stem which possess chloroplasts
Describe the adaptations of the cacti stem
- stem has thick cuticle and large diameter
- allows water storage
- low SA:V ratio
Describe the adaptations of the roots in a cacti
- has both shallow and deep penetrating roots
- gives access to all available water
Where is marram grass typically found?
Sand dunes
How are marram grass leaves well adapted to minimise water loss?
- leaves can roll up to reduce the exposure of surfaces to wind
- rolling of leaf provides deep grooves which protect the stomata
- the exposed surface has no stomata and a thick cuticle
- inner surface of the leaf possesses a large number of hairs
Describe the trachea
- airway connecting mouth and nose to bronchi
- lined with mucus secreted by Goblet cells within cilia
- cilia sweep microorganisms and dust away from the lungs
Describe the lungs
- central part of the respiratory system
- where gas exchange occurs
Describe the bronchi
- at the bottom of the trachea
- similar structures but narrower
- lead to bronchioles
Describe the bronchioles
- narrow tubes (less than 1 mm)
- carry air from the bronchi to the alveoli
- no cartilage so could collapse
Describe the alveoli
- site of gas exchange
- tiny sacs with thin walls and large surface area to volume ratio for efficient gas exchange
Describe the capillary network within the human gas exchange system
- extensive capillary network surrounding alveoli
Describe cartilage rings
- along the trachea (tracheal rings)
- help support the trachea and ensure it stays open whilst allowing movement and flexion
Describe the ciliated epithelium
- specialised tissue along the trachea
- each cell has small projections of cilia
Where are goblet cells found?
Found scattered throughout the ciliated epithelium
Describe how the goblet cells are involved in the human gas exchange system
- they are mucus-producing cells that secrete mucus which traps dust, bacteria and other microorganisms
- mucus swept along by cilia upwards and is swallowed
- mucus and microorganisms are destroyed by acid in the stomach
Describe the wall of the alveoli
- they have a lining of thin and squamous epithelium
- forms a structure of the alveolar wall and so is very thin and permeable for easy diffusion of gases
Describe how smooth muscle is involved in the human gas exchange system
- found throughout the walls of bronchi and bronchioles
- helps regulate the flow of air into the lungs by dilating when more is needed and constricting if less is needed
Describe how the network of capillaries is involved within the human gas exchange system
- carbon dioxide diffuses out of capillaries and into alveoli to be exhaled while oxygen diffuses the other way to be carried around the body
- capillaries have the diameter for only one red blood cell to travel through at a time which ensures there is sufficient time for gas exchange
What occurs at the alveolar epithelium?
- the exchange of carbon dioxide and oxygen occurs between the alveoli and the capillaries in the lungs
- simple diffusion process
Describe some features of the alveoli
- large quantity
480-500 million in the average adult
SA = 40-75 metres sq. - thin walls
one cell thick for short diffusion distance (cells are also flattened- squamous epithelial cells) - extensive capillary network
constant blood flow maintains conc grad
What does ventilation and blood flow ensure within the human gas exchange system?
- ensures there’s always a higher conc of oxygen in the alveoli than in the blood
- breathing refreshes the air in the alveoli
Where does carbon dioxide go in the blood?
Diffuses into the plasma
Where does oxygen go in the blood?
Binds to the haemoglobin in red blood cells
What happens in the thoracic cavity when inhaling?
- volume in chest increases
- air pressure in lungs decreases until it’s slightly lower than the atmospheric pressure
- air moves down pressure gradient and lungs fill with air
Describe the mechanism of inhaling while at rest
- diaphragm contracts and flattens
- increases chest volume
Describe the mechanism of inhaling when exercising
- external intercostal muscles contract
- moves ribcage upwards and outwards
What happens in the thoracic cavity when exhaling?
- volume in chest decreases and pressure increases
- forces air out
Describe the mechanism of exhaling when at rest
- external intercostal muscles relax
- recoil of elastic fibres surrounding alveoli forces air out
- diaphragm becomes dome shaped
Describe the mechanism of exhaling when exercising
- internal intercostal muscles contract to pull the ribcage down and back
- abdominal muscles contract to push organs into the diaphragm
- this increases pressure and causes forced exhalation
What is the formula for calculating PVR?
PVR (pulmonary ventilation rate)
= tidal volume x breathing rate
What is tidal volume?
The volume of air in each breath
What is vital capacity?
The maximum volume of air a person can exhale after a maximum inhalation
What is residual volume?
The volume of air that can’t ever be expelled
What is total lung capacity?
The total volume of air in the lungs after a maximum inhalation
What is breathing rate?
The number of breaths taken per minute
What is breathing rate also known as?
Ventilation rate
What is oxygen consumption?
The volume of oxygen used by the body
What is Fick’s law?
rate of diffusion is proportional to:
(diff in concs x SA)/thickness of membrane
Describe some effects of lung disease
- affect structure of alveolar walls
- damage airways involved in ventilation
When does cancer occur?
If mutations affect the regulation of mitosis in cells
When do tumours occur within lung cancer?
- if a mutation occurs in oncogenes of the bronchial epithelial cells
- causes uncontrolled mitosis which creates a mass of cells in the lumen of airways
What happens to a tumour of lung cancer over time?
- tumour gets larger
- no programmed cell death
- develops its own blood supply (vascularisation)
How does a tumour of lung cancer affect lung function?
- squeezes against blood vessels
- enters lymphatic system
State symptoms of lung cancer
- coughing blood
- persistent cough
- coughing lots of mucus
- wheezing
- back/shoulder pain
- sudden weight loss
- breathing difficulties
What does COPD stand for?
Chronic obstructive pulmonary disease
What does COPD involve?
- includes a range of lung-based diseases
eg. asthma, chronic bronchitis, enphysema
State some symptoms of COPD
- shortness of breath
- chronic/persistent cough
- chest tightness
- wheezing
- difficulty breathing whilst exercising
What happens when goblet cells in the ciliated epithelium become enlarged in a person with COPD and what does this result in?
- they produce more mucus
- this destroys cilia in the trachea so they can’t sweep mucus away from the lungs
What happens when mucus containing bacteria and dust blocks narrow bronchioles?
- causes coughing, scar tissue and infection
- infection attracts phagocytes
What do phagocytes release and what damage can this enzyme do in someone with COPD?
- elastase
- damages elasticity of alveolar walls
What happens when there isn’t enough elastin in someone with COPD?
- the alveoli break down and may burst
What happens when alveoli burst in someone with COPD?
- creates large air spaces in alveoli and patients become wheezy and breathless
- many need constant oxygen to survive
State 2 well known risk factors in relation to lung disease
- pollution
- smoking
Describe how pollution is a risk factor relating to lung disease
- car exhaust fumes and burning of fossil fuels
- can be hard to avoid in modern society (especially in urban areas)
Describe how smoking is a risk factor relating to lung disease
- much easier to control and measure than pollution
- can record number of cigarettes per day and for how many years
Describe the chemicals that cigarettes consist of
- tar- a carcinogen
- nicotine- an addictive substance which narrows blood vessels
- carbon monoxide- reduces the oxygen-carrying capacity of the blood
Describe the effects of smoking on air passages
- tar destroys cilia which causes a buildup of mucus
- potentially leads to bronchitis as bronchi lining becomes irritated
Describe the effects of smoking on the alveoli
- tar contributes to the breakdown of alveolar walls
- this merges the walls together and creates an insufficient SA:V ratio
- this leads to less gas exchange
- tar can build up and form a layer on alveolar cells which can increase diffusion distance
How may smoking cause enphysema?
- lower SA:V ratio means less gas exchange and reduces efficiency of gas exchange
- this can cause enphysema because less oxygen is carried in blood
- makes exercise difficult
What did the 1930s have in relation to lung disease and smoking?
Large numbers of lung cancer patients were heavy smokers
Describe the Doll and Hill study
- prospective study carried out
- over 50 years, they monitored smoking habits and mortality rates of 34000 male doctors
Why were doctors used in the Doll and Hill study?
They felt they would get more reliable feedback
What information was collected for the Doll and Hill study?
- how many cigarettes a day
- past smoking history
etc
Describe the results of the Doll and Hill study
- smoking increases mortality from lung disease and lung cancer
- greater intensity of smoking = higher increased mortality
- increases mortality rate from other cancers (mouth, throat etc.)
- giving up reduces mortality from lung cancer, other cancers and lung diseases
What year was the Doll and Hill study carried out?
1951
What is a risk factor?
Any factor correlating with an increased chance of suffering from a condition/disease
What is incidence?
The number of cases of a disease that occur within a particular group of people within a given time
Describe a prospective study
- using data as it becomes available
- beneficial and more accurate
- time consuming
Describe a retrospective study
- past data
- unreliable, data may be forgotten or altered
- quicker
Why may data collecting be difficult?
- ethical implications
- finding people with very similar lifestyles is hard
- expensive and time consuming
Describe how sample size is related to data
Larger sample = more reliable
Describe how individuals in the sample are related to data
Data should state who it’s about eg. if only 20-40 y/o women, won’t be accurate for others
Describe how levels of exposure are related to data
Should be paid attention to
Describe how the control group is related to data
Should be of similar age and background to those in other groups
Describe how statistical significance is related to data
Determine is differences between groups is large
Describe other factors/variables that are related to data
- genetics
- secondary exposure to smoking
- other factors eg. exercise
Describe relative risk
- % chances can be calculated for each group
- other people can then estimate theirs based on their lifestyle
Describe relative risk
- % chances can be calculated for each group
- other people can then estimate theirs based on their lifestyle
What is a correlation?
A relationship between variables
What is causation?
When one variable has an influence or is influenced by another
Describe the general process of digestion
- large insoluble molecules are hydrolysed into smaller soluble molecules which can be absorbed across cell membranes into the blood
How can digestion hydrolysis be quickened?
Enzymes catalyse the hydrolysis
What are smaller molecules used for after they have been hydrolysed in digestion?
To either:
- provide cells with energy
- build other molecules for cell growth, repair and function
Describe how proteins, carbs and lipids are hydrolysed in digestion
Proteins>amino acids
Carbohydrates>simple sugars
Lipids> fatty acids and glycerol
What body tissues are involved in the human digestive system?
Glands (salivary and pancreatic), stomach, small intestine, liver, large intestine
What do the pancreatic glands produce?
Digestive juices
What are the sites of digestion in the digestive system?
Small intestine and stomach
What does the liver produce?
Bile
What is the main site of absorption in the digestive system?
Small intestine
What is the site of water reabsorption?
Large intestine
Describe the path of digestion
mouth
salivary glands
oesophagus
stomach
small intestine
large intestine
Describe what happens in the mouth during digestion
- teeth increase surface area
- carbohydrate digestion begins here
- food is formed into a bolus by the tongue and lubricated with saliva for swallowing
Describe what happens in the oesophagus during digestion
- hollow tube with muscular walls from mouth to stomach
- contractions of the smooth muscle in its wall help move food towards stomach
Describe what happens in the stomach during digestion
- protein digestion begins here
- muscular tissue churns food mixing it with acid and enzymes
- acid unravels proteins and lowers pH which is optimal for stomach enzymes’ function
- low pH is bad for bacteria that may be present in food
What is the role of the glandular tissue in the stomach during digestion?
Produces enzymes and stomach acid
Name the 3 sections of the small intestine
- duodenum
- jejunum
- ileum
What is peristalsis?
The rhythmic contractions of the smooth muscle in the intestine wall that move the food along
Describe what happens in the small intestine during digestion
- carb, protein and lipid digestion occurs mainly in the duodenum
- soluble food molecules are absorbed into blood mainly through the jejunum and ileum
- ileum is long and lined with finger-like villi to increase surface area
- water absorption also occurs
Describe what happens in the large intestine during digestion
- any water remaining in undigested food (eg. cellulose found in plant fibre) is absorbed here along with vitamins and minerals
- undigested food material (faeces) is stored in the rectum and removed through the anus
Describe the enzymes involved in digestion
- substrate specific
- extracellular (work outside of cells)
What are the 3 main types of digestive enzymes?
- carbohydrases
- proteases
- lipases
Where does the digestion of carbs occur?
- mouth
- small intestine
What is the function of amylase?
- hydrolyses starch into maltose
How does maltose become glucose?
hydrolysed by maltase
Where is amylase made?
- salivary glands
- pancreas
- small intestine
Describe maltase
- found in cell-surface membrane of the epithelium cells of the small intestine
- hydrolyses the disaccharide, maltose
How are sucrose and lactose hydrolysed?
By sucrase and lactase respectively
What are sucrose and lactose?
Disaccharides
Describe the lining of the small intestine
- folded
- microvilli are present
- increases surface area for absorption
Describe the 2 types of starch
- amylose:
- straight chain
- only 1-4 glycosidic bonds
- amylopectin:
- branched
- 1-4 and 1-6 glycosidic bonds
Where does protein digestion begin and by what?
- in the lumen of the stomach by protease enzymes
Describe endopeptidase
- hydrolyses peptide bonds within protein chains
- secreted with HCl, lowers pH
- breaks down proteins
- produced in stomach and pancreas
- released in stomach and small intestine
How is pancreatic juice related to protein digestion?
- contains endopeptidases and exopeptidases
Describe exopeptidase
- hydrolyse at the ends of polypeptides
- produce dipeptides
- breaks down proteins
- produced in pancreas
- released in small intestine
Where are dipeptidase enzymes found and what is their function?
- within the cell surface membrane of the epithelial cells in small intestine
- they hydrolyse dipeptides into amino acids which are released into the cytoplasm of the cell
Describe the journey of polypeptides into amino acids and which enzymes are involved
- protein hydrolysed by endopeptidases into polypeptides
- polypeptide hydrolysed by exopeptidases into dipeptides
- dipeptides hydrolysed by dipeptidase into amino acids
Describe emulsification
- in the stomach, solid lipids are turned into a fatty liquid consisting of fat droplets
- when fatty liquid reaches small intestine, bile is secreted
- bile salts bind to the fatty liquid and break the fatty droplets into smaller ones via emulsification
What does bile contain?
Bile salts
Where is bile made and stored?
- made in the liver
- stored in the gall bladder
What does emulsification help with?
- increases surface area of the fatty droplets for action of digestive enzymes
What does lipase do after emulsification?
- lipase converts emulsified lipids into fatty acids and glycerol
Where does the digestion of lipids occur?
- only in the lumen of the small intestine
Where are lipase enzymes produced and secreted?
- produced in the pancreas
- secreted into the small intestine by the pancreas
Describe amylase
- breaks down carbs
- produced in the pancreas and salivary glands
- released in the mouth and small intestine
Describe maltase
- breaks down disaccharides
- produced in small intestine
- released in small intestine
Describe dipeptidase function and location
- breaks down dipeptides
- produced in small intestine
- released in small intestine
Describe lipase
- breaks down lipids
- produced in the pancreas
- released in the small intestine
Describe mechanisms of absorption
- digestion breaks down food into smaller, soluble molecules
- products are absorbed through the intestinal lining
- the absorption of amino acids and monosaccharides is similar via co-transport
- absorption of lipids is different
Describe the mechanism of absorption for amino acids and monosaccharides
- specific co-transport proteins found in cell membranes of epithelial cells of the ileum
- facilitated diffusion moves 2 molecules in 1:1 ratio down their concentration gradient
- conc grad of Na+ ions is maintained by Na+/K+ pump
Describe the process of absorbing glucose/amino acids in digestion
- sodium ions are actively transported out of epithelial cells via Na+/K+ pump into the blood
- this takes place in one type of carrier protein
- higher conc grad of sodium is maintained (more in lumen of intestine than epithelial cells)
- sodium ions diffuse into the epithelial cells down a conc grad through co-transport protein
- either amino acids or glucose molecules are carried in with sodium
- glucose/amino acids pass into the blood plasma by facilitated diffusion using another type of carrier, sodium is actively transported out again
Describe the absorption of triglycerides in digestion
- lipase digests lipid droplet into monoglycerides and fatty acids
- these then combine with bile salts to form micelles
- the micelles break down and feed a pool of dissolved monoglycerides and fatty acids
- the fatty acids and monoglycerides diffuse into the epithelial cell
- triglycerides are formed via the endoplasmic reticulum and they are packaged with fat-soluble substances into chylomicrons
- the chylomicrons exit the epithelial cell via exocytosis and enter the bloodstream via the lacteals
What are the products of lipid digestion?
- fatty acids
- glycerol
- monoglycerides
How are micelles formed?
- monoglycerides and fatty acids associate with phospholipids and bile salts to form micelles
How do micelles aid transport during lipid digestion?
- monoglycerides and fatty acids aren’t very soluble so micelles aid their transport to the surface of epithelial cells
Why is it good that the freely dissolved molecules of lipid digestion are non-polar?
- they can diffuse through the phospholipid bilayer
What is different about short fatty acid chains compared to longer ones during lipid digestion?
- short fatty acid chains:
- move directly into the blood via diffusion
- longer fatty acid chains:
- recombine with monoglycerides and glycerol to form triglycerides in the ER
- they are then packaged into lipoproteins called chylomicrons
What happens to the chylomicrons during lipid digestion?
- they are transported to a lacteal via exocytosis
- eventually the chylomicrons enter the bloodstream
Describe the structure of chylomicrons
- spherical ‘case’ made of phospholipids and lipoproteins
- hold non-polar triglycerides inside so they’re hidden from the aqueous environment of the cytoplasm and blood
- cholesterol and phospholipids are also found in chylomicrons
