Digestion and Exchange Flashcards
What is surface area? How do you calculate it?
Refers to the outside area of an object, e.g. it is the area around the outside of a cell or organism. Length x height
What is volume? How do you calculate it?
The amount of space inside of the object, e.g. it is the space inside a cell or organism. Length x depth x height
What is surface area to volume ratio and how do you calculate it?
An object’s Surface Area to Volume Ratio (SA:V) is like a way of describing how close every internal part of it is to its surface. Dividing an object’s surface area by its volume
How do unicellular/very simple organisms get oxygen and other substances?
Diffuse through their outer membrane
Do unicellular organisms have a high or low SA:V?
High
Give two reasons why diffusion is too slow in multicellular organisms for them to exchange substances.
Have small SA:V so many cells will have no surfaces exposed to the outside. Diffusion distance is too large to get from outside to all cells in the centre of the organism.
How do multicellular organisms get oxygen and other substances?
Exchange systems – e.g respiratory and circulatory
Name four substances that all organisms must exchange with their environment
Oxygen, nutrients, carbon dioxide, urea, water
Do large animals have a higher or lower SA:V than small animals?
Lower
Will the rate of heat loss at a given temperature be greater for an animal with a high or low SA:V?
Small animals with high SA:V will lose more heat
Explain how an animal’s shape can help control its temperature.
Increasing SA:V increases heat loss, decreasing SA:V decreases heat loss as diffusion distance will be greater. Examples: Large organisms with low SA:V often have large ears which increase their surface area allowing them to lose more heat. In warm environments. Animals in cold environments are often streamlined with a compact body shape giving a smaller SA:V.
Give two adaptations a small organism could have to survive in a cold environment.
Streamlined, compact body shape, thick layers of fur or blubber. May hibernate
Give two adaptations a large organism could have to survive in a hot environment.
Kidney structure adaptations so that they produce less urine to compensate for water lost through evaporation. Large ears which increase their surface area allowing them to lose more heat. May be nocturnal
How is the small intestine adapted for absorption of nutrients?
Thin epithelial walls, large surface area from villi and microvilli. Lots of capillaries around villi and muscular mixing helps to maintain concentration gradient
What are carbohydrates broken down into during hydrolysis?
disaccharides and then monosaccharides
What is the role of amylase?
Hydrolyses starch into maltose
Where is amylase produced?
salivary glands and pancreas
How are epithelial cells in the ileum involved in the digestion of carbohydrates?
they have membrane bound disaccharidase enzymes.
What are the three disaccharide enzymes?
Maltase, sucrase and lactase
Explain how monosaccharides are absorbed across the ileum epithelium
Glucose and galactose are actively transported using sodium ions through co-transporter proteins. Fructose is absorbed by facilitated diffusion through a different transporter protein
How are ileum epithelial cells adapted for absorption of carbohydrates?
Microvilli (folded membrane) which increase the surface area for diffusion further. Many mitochondria to provide energy and carrier proteins for active transport of glucose and galactose. Many channel proteins for facilitated diffusion of fructose.
What is a hydrolysis reaction?
Where water is added to break a covalent bond
What is the product of complete hydrolysis of proteins?
Amino acids
What is the role of protease enzymes?
To breakdown proteins in a series of hydrolysis reactions
What is the role of endopeptidases?
Hydrolyse peptide bonds within a large protein (polypeptide) to create smaller polypeptide chains
Describe the action of exopeptidases
Hydrolyse terminal peptide bonds (between amino acids on the ends of a polypeptide chain) to remove individual amino acids and create smaller polypeptide chains
Where are dipeptidases found?
Membrane-bound of ileum cells
How are sodium ions are involved in the absorption of amino acids?
Needed for co-transport. Sodium ions are actively transported out of the ileum cells so that they diffuse back in down their concentration gradient with amino acids
What are lipids broken down into during hydrolysis?
Monoglycerides and fatty acids
What is the role of lipase?
To hydrolyse ester bonds between fatty acid chains and glycerol to break down lipids
Where are lipase enzymes made and where do they act?
Made in pancreas, act in the small intestine
Describe how bile enters the small intestine
Bile salts are produced by the liver and stored in the gall bladder which releases them into the small intestine.
How do bile salts help the digestion of lipids?
Bile salts help to break down large fat globules by emulsifying them into smaller droplets. This helps to speed up the action of lipases by increasing the surface area of lipids that can be exposed to the enzyme.
What is a micelle?
Monoglycerides and the fatty acids attached to the bile salts
How are the products of lipid digestion absorbed?
Micelles hit epithelial cells, monoglycerides and fatty acids diffuse across the cell membrane where they are transported to the ER and reform into triglycerides. In the golgi they bind with cholesterol and proteins and are packaged to form chylomicrons which travel in a vesicle to the cell membrane and are exocytosed from epithelial cell. Chylomicrons enter lacteals which transport them away from the small intestine to cells to be used.
How does mass transport of oxygen occur in insects?
Contraction of muscles through abdominal pumping enabling mass movements of air in and out
What is the advantage of having water at the end of tracheoles?
In periods of high activity, anaerobic respiration will create lactate which will reduce the water potential of respiring cells causing them to take up water by osmosis. This loss of water from the tracheoles means gas is further inside them.
Why are the insect’s spiracles generally closed?
To prevent water loss.
What are the main structure of gills?
gill filaments
What increases the surface area of the gills?
they have lots of gill fillaments with lots of gill lamellae on them
Describe how counter current flow allows for effective gaseous exchange.
Blood flows in the opposite direction to water. Ensures there is always a diffusion gradient between water and the gills allowing maximum uptake of oxygen across the whole length of the gill
Explain how parallel flow decreases gaseous exchange.
Oxygen can only be absorbed by diffusion at the start where oxygen concentration in the water is higher than in the blood. Equilibrium is quickly reached.
What are the two process which require gases in a plant?
Photosynthesis and respiration
How is a leaf adapted for gas exchange?
1 - many small pores (stomata) for short diffusion pathway. 2 - lots of are spaces in the mesophyll layer for movement of gases 3 - Large surface area of mesophyll cells
During daytime, what is the exchange of gases in and out of the plant? Why?
Carbon dioxide in and oxygen out. Due to photosynthesis. Respiration doesn’t create enough carbon dioxide or use enough oxygen.
During night time, what is the exchange of gases in a plant? Why?
Carbon dioxide out and oxygen in. Respiration is still occurring, photosynthesis is not.
How are the gas exchange systems of plants similar to insects?
1 - The cells using the gases are close to the external air. 2 - Diffusion occurs in the gas phase, not water. 3 - Pores for air to enter and leave.
Where are stomata mainly found?
Bottom side of the leaf to limit evaporation and transpiration
What cell controls the opening and closing of stomata?
Guard cells
What is a disadvantage to having open stomata?
Excessive water loss
What is the name of the plants that are well adapted to dry environments?
Xerophytes
How do insects reduce water loss? Explain one example.
Small surface area to volume ratio, waterproof coverings, spiracles that can be opened and closed
What is the process known as when a plant loses water?
Transpiration
How does a thick cuticle reduce transpiration?
It is a waterproof barrier which increases diffusion distance
How does rolled up leaves reduce transpiration?
The stomata end up on the inside part of the leaf. this means water vapour becomes trapped and the air is saturated with water. It has a high water potential removing the water potential gradient between inside and outside the leaf.
How does having hairy leaves reduce transpiration?
These trap moisture near to the leaf, increasing water potential in the air, and reducing the water potential gradient. Less water is therefore evaporated.
How does having stomata in pits or grooves reduce transpiration?
Water vapour is trapped in the pit/groove. This increases the water potential in the air, and reduces the water potential gradient. Less water is therefore evaporated.
How does having a reduced surface area to volume ratio in the leaves of the plant reduce transpiration? What is a drawback of this adaptation?
The smaller the surface area to volume ratio, the slower the rate of diffusion. This slows evaporation. But has to be balanced against surface area for photosynthesis.
Suggest why must humans have a high rate of gaseous exchange?
Because they have a large volume of cells and have to maintain a high body temperature (related to high metabolic rate)
What is the lungs made up of?
Bronchioles and alveoli
What is the airway from the mouth/nose to the lungs?
The trachea
Why is the trachea supported by a ring of cartilage?
To prevent it collapsing when air pressure inside is low
What is the role of goblet cells and cilliated cells in the bronchi?
Goblet cells produce mucus to trap dirt/dust/pathogens. Cilliated cells waft the mucus back up the throat to be swallowed.
What allows the alveoli to stretch and recoil?
Elastic fibres
During inspiration which muscles contract and which relax?
External intercostal muscles and diaphragm contract. Internal intercostal muscles
During expiration which muscles contract and which relax?
Internal intercostal muscles contract. External intercostal muscles and diaphragm relax.
What happens to the rib cage during inhalation?
The ribcage moves upwards and outward increasing the volume of the thorax.
What happens to the ribcage during exhalation?
The ribcage moves downwards and inwards, decreasing the volume of the thorax.
What happens to the pulmonary (of the lungs) pressure during inhalation?
The pressure in the lungs (pulmonary) decreases as thoracic volume increases. Atmospheric pressure is greater, so air is forced into the lungs.
What happens to the pulmonary (of the lungs) pressure during exhalation?
The pressure in the lungs (pulmonary) increases as thoracic volume decreases. Atmospheric pressure is lower, so air is forced out of the lungs.
During normal breathing, how is air expelled from the lungs?
The elastic recoil of the lungs is generally enough, alongside the relaxation of the external intercostal muscles and diaphragm.
How do you calculate pulmonary ventilation?
pulmonary ventilation = tidal volume x breathing rate
What are the main risk factors for lung disease?
Smoking, air pollution, genetic make-up, infections, occupation.
What is COPD?
Chronic obstructive pulmonary disease.
What is the difference between correlation and causation?
Correlation is when one variable changes, there is a change in another variable. Causation is when one variable changes, it causes a change in the second variable.
Why can we not say that correlation is the same as causation?
There may be other factors at play that have created the correlation between the two variables. The may not affect each other, but have both been affected by something else.
What is the advantage of physical breakdown before chemical breakdown?
Increases surface area for chemical digestion
What reaction do digestive enzymes catalyse?
Hydrolysis
What are the two enzymes involved in starch digestion?
Amylase (starch -> maltose) and maltase (Maltose -> alpha glucose)
