6: Exchange Flashcards
Name some examples of exchange
Oxygen - aerobic respiration
Nutrients
Waste products - carbon dioxide and urea
Heat
What is SA:V?
Surface area to Volume ratio
SA : V
Volume value is always equals to 1
How do smaller to larger animals SA:V ratio compare?
Smaller animals have a higher SA:V
Larger animals have a smaller SA:V
How do unicellular cells exchange?
Large SA:V ratio
Adv. can happen more directly & easily
Simple diffusion can occur through one membrane
Loses more energy to heat
What are the features of an exchange surface?
High SA:V ratio - increases rate of collisions with exchange surface
Thin layer - short diffusion pathway length
Movement of external & internal environment - maintains a steep conc. gradient
Selectively permeable membrane
Why is diffusion too slow in multi-cellular organisms?
Some cells are deep within the body - long diffusion pathway
Low SA:V
What does heat loss depend on?
Surface area
High SA:V means high rate of heat loss
Causes high metabolic rate & exchange rate
What is the diffusion equation?
Diffusion α (SA x difference in concentration)/ length of diffusion path
α = related to
How does gas get to the body cells in insects?
Spiracles -> Trachea -> Tracheoles -> Muscle fibre
What is the trachea?
Internal network of air-filled pipes in insects
What are tracheoles?
Small dead-end tubes
Fluid filled at the ends next to muscle fibre
Extend throughout all the body tissues
How does a diffusion gradient affect in the tracheal system?
Muscle fibre cells use O2 for aerobic respiration
Creates a conc. gradient for O2 to diffuse to cells
CO2 produced creates a conc. gradient to cause it to diffuse to the atmosphere
Is diffusion faster in gas or liquid?
Gas - less molecules to hit therefore moves faster
How is mass transport done in insects?
Contractions of muscles can squeeze the trachea
Enables mass movement of air
This is also the movement of the external environment
Why are the ends of the tracheoles filled with water in insects?
Anaerobic respiration produces lactate
Lactate is soluble and lowers water potential in cells
Water moves into cells from tracheoles by osmosis
Vol. of water decreases in tracheoles and draws air further into them
Diffusion is in gas phase rather than liquid
Increases rate at which air moves but leads to greater water loss
What is a spiracle?
Tiny pores on the body surface
Can be opened or closed by valves
When open water can evaporate but gas exchange can occur
What is the limitation of the tracheal system?
Relies on diffusion
Requires short pathway
Therefore requires small size of insects
Why are hairs found in the spiracle?
Traps moist air & humidity
Lowering concentration gradient so water cannot diffuse out as easily
Where is a gill found?
Behind the head of the fish
What are the gill filaments?
Thin plates which have a large SA for exchange of gases
Stacked in a pile
What is a gill lamellae?
Gill filaments covered with them, at right angles
Contain lots of blood capillaries
Thin surface later of cells to speed up diffusion
What is the counter-current flow system?
Blood flows through lamellae in one direction
Water flows over them in the opposite direction
Maintains a large conc. gradient
Why does counter-current flow system work?
Larger conc. of oxygen in water than blood
Maintains conc. gradient as water moves over lamellae
What is the main surface of gas exchange in plants?
Mesophyll cells
They have a large SA
What are the pores in the plant called?
Stomata
When do the stomata open and close?
Open in the day - when photosynthesis occurs
Closed at night
Where are the stomata found?
Bottom side of the plant - in the shade so less evaporation
Guard cells turgid when H2O available - opens stoma
Flaccid when less H2O available - closes stoma
Name some adaptations of gas exchange in plants?
No cells far from stoma - short diffusion pathway
Air spaces in mesophyll - gases can easily come in contact with cells
Large SA of mesophyll cells - rapid diffusion
How are insects adapted to reduce water loss?
Small SA:V ratio - minimise area over which water is lost
Waterproof covering - waterproof cuticle prevents water loss
Spircales - valve can be closed to reduce water loss
What is a xerophyte?
Plants specifically adapted in warm, dry or windy habitats, where water loss is a problem
Why are stomata sunken in pits and hairy leaves?
Traps moist air - high water potential therefore reduces conc. gradient
Reduces the amount of water diffusing out of leaf and evaporating away
Why are leaves rolled up in xerophytes?
Protects them from the wind
Traps moist air - high water potential therefore reduces conc. gradient
Why is there a thick cuticle in xerophytes?
Waterproof barrier - prevents the water loss from this route
Why is there a reduced SA:V ratio in xerophytes?
Reduces the surface area which allows water to leave the plant
Why is gas exchange required in humans?
Oxygen needed for aerobic respiration to release ATP
Carbon dioxide is produced in respiration and if builds up is harmful in the body
Why is a large amount of air required to be moved in or out of the human body?
Large organisms with large volume of living cells
Maintain a high body temp. which is related to high metabolic and respiratory rates
Why are the lungs located in the body?
Air is not dense enough to support and protect delicate structures
Body would lose a great deal of water
What is the route of the air going into the body?
Mouth/nostril Pharynx Epiglottis Larynx Trachea Bronchi Bronchioles Alveoli
What is the pharynx?
Part of the throat that air and food goes through
What is the epiglottis?
Flap which prevents the food from entering the trachea
What is the larynx?
After the epiglottis, where the vocal chords are found
What are the adaptation of the bronchioles?
C-shaped cartilage rings
Allows flexibility, gives structure when the pressure reduces
Made of smooth muscles and lined with ciliated epithelium and goblet cells
What is the adaptation of the trachea?
C-shaped cartilage rings
Allows flexibility, gives structure when the pressure reduces
Why is smooth muscle present in the bronchioles?
Allows them to constrict so they can control flow of air in and out of the alveoli
What is the alveoli?
Minute air-sacs at the end of bronchioles
Between alveoli collagen and elastic fibres allowing them to stretch as they fill with air
Alveolar membrane is the surface of gas exchange
What is ventilation in and out called?
Inspiration
Expiration
What things are used for ventilation?
Diaphragm
Internal and External intercostal muscles
Ribcage
What occurs in inhalation?
External intercostal muscles and diaphragm contract Causes ribcage to move up and out Thoracic cavity increases in volume Lung pressure decreases Air flows from high->low pressure Active process as requires energy
What is the diaphragm?
Sheet of muscles that separates the thorax and abdomen
Curved/concave when relaxed
Contracts to a downwards and flattened state
What occurs during passive expiration?
External intercostal and diaphragm relax Ribcage moves down and inwards Thoracic cavity decreases in volume Lung pressure increases Air flows out of the lungs
What is passive and active ventilation?
Passive doesn’t require any energy
Active requires energy
What occurs in active expiration?
External intercostal muscles relax and internal intercostal muscles contract
Pulling the ribcage further down and in
Intercostal muscles move in an antagonistic way
What does antagonistic movement mean?
When two sets of muscles is said to be moving in an opposing direction
What is tidal volume?
Volume of air normally taken in at each breath when the body is at rest - typically 0.5 dm3
What is breathing/ventilation rate?
The number of breaths taken in 1 minute - typically 12-20 breaths in healthy adult
What is pulmonary ventilation and what is it measured in?
Total volume of air that is moved into the lungs that is moved into the lungs during 1 minute
Measured in dm3 min-1
What is the equation of pulmonary ventilation rate?
Pulmonary ventilation rate = tidal volume x breathing rate
dm3 min-1 = dm3 x min-1
What is an alveolus made of?
Microscopic air sacs
Made from a single later of thin, flat cells called alveolar epithelium
How is there a short diffusion pathway in a human lung?
Diffusion is across thin squamous epithelium (one cell thick) and capillary cell wall
What is the advantage of having a thin pulmonary capillaries?
Slows RBCs - increasing time spent at the exchange surface and flattens them decreasing the short diffusion pathway
How are the lungs protected?
Delicate membranes internalised by ribs for protection
How does a large capillary and alveoli have a large SA?
Due to the large number of them
How is the movement of the environment done in the lungs?
External environment is managed by ventilation
Internal environment is managed by circulation
How is a moist coated inner surface of the alveolus advantageous?
Reduces surface tension
Enables gases to dissolve before diffuses to speed up movement
What is forced expiratory volume (FEV1)?
Max volume of air that can be breathed out in 1 second
What is the forced vital capacity (FVC)?
Max volume of air it is possible to breathe forcefully out of lungs after a really deep breath in
What are the processes in the digestive system?
Ingestion Digestion Absorption Assimilation Egestion
Is the contents of the digestive system internal or external?
External
What is an endocrine?
Chemicals which are secreted into the bodies systematic circulation
E.g Hormones
What is an exocrine?
Chemical which are secreted outside of your body
E.g tear ducts, gastro-intestinal tract
What forms of mechanical digestion are there in the digestive system?
Chewing/Mastication
Stomach churning
Small intestine/oesophagus - peristalsis
What is the purpose of the oseophagus?
Carries food from mouth to stomach
Smooth muscle pushes down food by peristalsis
What is peristalsis?
Smooth muscle causes wave like contractions creating a squeezing motion downwards
What chemical digestion is there is the digestive system?
Enzymes
Hydrochloric acid
What is the stomach?
Muscular sac with an inner layer that produces enzymes
Stores and digests food
Produces hydrochloric acid
What is the role of the large intestine?
Absorbs water
What is the rectum?
Final section of the intestines
Faeces stored here before being removed via the anus by egestion
What is the role of the oesophagus?
Smooth muscle - peristalsis
What is secreted in the stomach?
Pepsin secreted by chief cells
Goblet cells produce mucus for protective barrier against acid and proteases
HCl secreted
What affect does HCl have in the stomach?
Kill pathogens or bacteria
Break down ionic/hydrogen bonds to disrupt tertiary structure to make it primary
What are the salivary glands and the roles?
Situated near the mouth
Pass secretions via a duct in the mouth
Contains amylase which hydrolyses starch into maltose
What is the pancreas and its role?
Large gland situated behind the stomach
Produces pancreatic juice (exocrines)
Contains pancreatic protease, carbohydrases, and lipase
Secretes enzymes and alkaline salts
What is the role of alkaline salts?
Allows enzymes to work at their optimum pH by lowering pH
Emulsifies fats
What is the purpose of enzymes?
Hydrolyses a molecule into smaller sections and into their molecules
What does amylase do?
Hydrolyse glycosidic bond
Starch into maltose (disaccharides)
Produced in salivary glands, pancreas, and ileum
Optimum pH is 7
Why does amylase not work in the stomach?
Low pH would denature the enzymes
What is maltase, lactase, and sucrase?
Membrane bound disaccharidases in small intestine cells (enterocyte)
How are carbohydrates absorbed by the small intestine?
Diffusion or co-transport
How are proteins digested in the digestive system?
HCl denatures hydrogen and ionic bonds in proteins
Tertiary to primary like structure
Endopeptidases, Exopeptidases, and Dipeptidases break peptide bonds
Diffusion and co-transport
What are endopeptidases?
Hydrolyses peptide bonds in the central region of a protein
What are expopeptidases?
Hydrolyses peptide bonds on the terminal ends of the protein
What is a dipeptidase?
Membrane bound peptidases
Hydrolyses single peptide bonds in disaccharides
How is absorption in digestion follow the exchange principles?
Short diffusion pathway - only through enterocyte
Internal movement - blood flow takes away nutrients
External movement - peristalsis takes away food in the lumen
High SA - villi and microvilli
Membrane permeability - carrier/protein channel
What do lipases do to triglycerides?
Hydrolyse ester bonds from triglycerides -> monoglycerides + two fatty acids
What is the process of emulsification?
Bile salts break large droplets into smaller droplets
Where are bile salts made transported and stored?
Produced in liver
Stored in gall bladder
Transported in bile ducts
How are triglycerides absorbed into the enterocytes?
Emulsification by bile salts to form micelles
Lipase breaks down triglycerides to monoglycerides and fatty acids
Micelles break down and contents diffuse into enterocytes
Free fatty acids and monoglycerides repackaged in the endoplasmic reticulum into triglyceride
Chylomicron formed in the golgi body
Chylomicron goes by excocytosis into the lacteal
What is a chlyomicron?
Triglyceride + cholesterol + protein
Formed in golgi body
How is fructose absorbed?
Facilitated diffusion
Through a transporter protein
What is a micelles?
Small globules of monoglycerides and fatty acids
Very small with large SA:V
Must break down to diffuse across
How do spiracles work?
Can be opened or closed by valves
When open water can evaporate but gas exchange can occur
