Exchange (Chapter 6) Flashcards
Do smaller animals have a high surface area to volume ratio?
No they have a higher surface area to volume ratio
Do single celled organisms have mass transport systems and exchange organs?
NO- substances can diffuse directly into (and out of) the cell across the cell surface membrane. As diffusion rate is quick due to the small distance the substance has to travel.
Do multicellular animals have exchange organs and mass transport systems?
Yes
Why do multicellular organisms need exchange organs and mass transport systems?
Diffusion is slow because:
Some cells are deep in the body
Larger animals have a low surface area to volume ratio
How does body size affect heat exchange?
If an organism has a large volume its surface area is then relatively small. This makes it harder for it to lose heat from its body. And vice versa …
How does the shape of an animal affect heat exchange?
Animals with a compact shape have a small surface area relative to their volume- minimising heat loss from their surface. And vice versa
What depends on an animal being compact?
Temperature of its environment
List 4 other adaptations which aid exchange (that’s isn’t about body size/ shape)
- Small desert animals have kidney structure adaptations so that they produce less urine to compensate for their high SA:V which makes them loose water via evaporation
- To support high metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods eg. Seeds
- Smaller mammals may have thick layers of fur or hibernate when it gets cold
- Larger organisms living in hot regions- eg. Hippos, spend all day in water and elephants have large ears to increase surface area
What three adaptations do exchange surfaces usually have?
Large surface area : volume
Thin- providing a short diffusion pathway
Maintain a steep concentration gradient
Why can single celled organisms exchange gases across their body? (Via diffusion)
Relatively large surface area, a thin surface and a short diffusion pathway
So no need for a gas exchange system
What system do fish use for gas exchange?
Counter current system
Describe how fish use a counter-current system for gas exchange? (5)
- Water, containing oxygen, enters the fish through its mouth and passes out through the gills.
- Each gill is made of lots of thin plates called gill filaments, which give a large SA:VOL for exchange of gases.
- The gill filaments are covered in lots of tiny structures called lamella, which increase the surface area even more.
- The lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
- Blood flows through the lamellae in one direction and water flows over in the opposite direction. It maintains a large concentration gradient between water and the blood. Conc gradient of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.
What do insects use to exchange gases?
Tracheae
What are insect tracheae?
Microscopic air filled pipes
Explain insect gas exchange
Air moves into tracheae through pores on the surface called spiracles
Oxygen travels down the concentration gradient towards the cells
Tracheae branch off into tracheoles (which have thin permeable wall) and go to individual cells.
Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into atmosphere
What do insects use to move air in and out of the spiracles?
Rhythmic abdominal movements
Describe the structure of a dicotyledonous plants leaf (top to bottom)
Waxy cuticle
Upper epidermis
Palisade mesophyll
Xylem and phloem (in vein)
Spongy mesophyll
Lower epidermis
Stomata and guard cells
Waxy cuticle
What gas do plants need for photosynthesis?
CO2
How are mesophyll cells adapted for gas exchange?
Large surface area
How do gases enter a leaf?
Through stomata
How are stomata controlled?
Guard cells can control wether stomata are open (for gas exchange) or closed (to stop water loss)
How do insects control water loss?
If they are loosing too much water, they close their spiracles using muscles. They also have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracles, which reduce evaporation.
How do plants reduce water loss?
Stomata open in day for gas exchange.
Water renters guard cell, making them turgid, which opens the stomata pore. If plant starts to get dehydrated, the guard cell will loose water and become flaccid, which closes the pore.
What are xerophytes?
They are plants adapted for life in warm, dry or windy habitats where water loss is a problem.
List 4-5 xerophytic adaptations
- Stomata sunk in pits that trap moist air, reducing concentration gradient of water between lead and air. This reduces amount of water diffusing out of the leaf and evaporating away.
- Layers of hairs on the epidermis- to trap moist air around stomata
- Curled leaves with stomata inside, protecting them from the wind.
- Reduced number of stomata, fewer places for water to escape
- Waxy, waterproof cuticles on leaves and stems to reduce evaporation
Why do humans need to get oxygen into the blood?
For respiration
Explain the structure of the lungs
Trachea
Bronchi
Bronchus
Bronchioles
Alveoli
What work together to move air in and out of the lungs?
Rib cage
Intercostal muscles
Diaphragm
What does ventilation consist of?
Inspiration and expiration
Is inspiration active?
Yes it requires energy
Explain the steps of inspiration (breathing in)
External intercostal and diaphragm contract
Causes rib cage to move upwards and outwards. Diaphragm flattens increasing volume of thoracic cavity. (Where lungs are)
Lung pressure decreases (to below atmospheric pressure)
Air flows into trachea :)
Does expiration require energy?
No- passive process
Explain expiration (breathing out)
External intercostal muscles and diaphragm relax
Rib cage moves downwards and inwards and diaphragm becomes curved again
Volume of thoracic cavity decreases, causing air pressure to increase (to above atmospheric pressure)
Air forced down pressure gradient out of the lungs
Can expiration be forced?
Yes ie. Blowing out candles
Where does gas exchange happen in the lungs?
Alveoli
Structure of alveoli?
Single layer of thin flat cells called alveolar epithelium
Lots of capillaries
How do alveoli increase the surface area of the lungs?
Huge number of alveoli, so big surface area for exchanging oxygen and carbon dioxide
Explain how oxygen gets into the blood via alveoli
Diffuses out of alveoli, across alveolar epithelium and capillary endothelium and into the haemoglobin in the blood.
How is co2 breathed out?
Diffuses from blood into alveoli then breathed out
How are the alveoli adapted for gas exchange?
Thin exchange surface- one cell thick so short diffusion pathway
Large surface area- large number of alveoli
Steep concentration gradient- of oxygen and carbon dioxide
Maintained via flow of blood and ventilation
What is a tidal volume?
Volume of air in each breath - usually between 0.4dm3- 0.5dm3 for adults
What is ventilation rate?
Number of breaths per minute - healthy person = 15 breathes
what is the forced expiratory volume?
Maximum volume of air that can be breathed out in 1 second
What is forced vital capacity?
Maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
List 4 lung diseases
Pulmonary tuberculosis
Fibrosis
Asthma
Emphysema
What do i need to be able to do surrounding lung disease?
Interpreting data please check out babe
Which two directions link it gas exchange?
Fish gills
Lungs
Insects
What are the ethical issues surrounding dissecting animals?
Morally wrong to kill animals just for directions, unnecessary killing. However most directions in schools, animals have already been killed for meat, and we use the organs.
Concerns animals used for directions not always raised in a humane way, eg overcrowding, lack of food etc. it is important to make sure looked after properly and killed humanely.
How do you dissect fish gills?
Gills located on each side of fish head, protected by a bony flap called an operculum supported by gill arches.
Push back operculum and use scissors to carefully remove gills. Cut each gill arch through the bone at top and bottom.
Why can we not absorb starch, proteins etc in food?
Too big to cross membrane so cannot be absorbed into blood.
List the two steps of breaking down polysaccharides
Polysaccharides —> disaccharides —> monosaccharides
Via hydrolysis
List two steps of breaking down fats
Fats —> fatty acids —> monoglycerides
Via hydrolysis
List the step of protein breakdown
Proteins —> amino acids
Via hydrolysis
How are carbohydrates broken down?
By amylase and membrane bound disaccharidases
Where is amylase produced?
Mouth (salivary glands)
Pancreases (which releases into small intestine)
What does amylase break down?
Starch into maltose
Involves hydrolysis of glycosidic bond
What are membrane bound disaccharidases?
Enzymes attached to the cell membranes of epithelial lining in the ileum. They break break down disaccharides into monosaccharides.
Via hydrolysis of glycosidic bond
List three disaccharidases
Maltase
Sucrase
Lactase
What do lipases do?
Catalyse breakdown of lipids into monoglycerides and fatty acids.
Via hydrolysis of ester bond
Where are lipases made?
Pancreas
Where do lipases work?
Small intestine
Where are bile salts produced?
Liver
What do bile salts do?
Emulsify lipids, which causes them to form small droplets
Why are bile salts sop essential?
Break down lipids into smaller droplets which have a much larger surface area. Meaning more area for enzymes (lipases) to work on
How are micelles formed?
Monoglycerides and fatty acids stick with bile salts to form them.
What are proteins broken down by?
Proteases or peptidases
What do proteases and peptidases do?
Hydrolyse peptide bond between amino acids breaking proteins into amino acids.
Where do endopeptidases act?
Hydrolyse peptide bond within a protein
List two examples of endopeptidases
(Where are these bad bois at?)
Trypsin and chymotrypsin and (pepsin)
Synthesised in pancreas and secreted in small intestine (only trypsin and chymotrypsin)
Where is pepsin released?
Stomach- by cells in stomach lining
Pepsin only works in acidic conditions- HCL
Where do exopeptidases work?
Hydrolyse peptide bonds at ends of protein molecules. They remove single amino acids from proteins.
What are dipeptidases?
Are exopeptidases which work specifically on dipeptides
What do dipeptidases do?
Separate two amino acids that make up a dipeptidases by hydrolysing the peptide bond
Where are dipeptidases located?
Cell surface membrane of epithelial cells in small intestine
How is the monosaccharide glucose and galactose absorbed in the ileum?
Active transport with sodium ions via a co transporter protein
How is the monosaccharide glucose absorbed in the ileum?
Facilitated diffusion through a different transporter protein
How do monoglycerides and fatty acids move accross the ileum?
Lipid soluble so diffuse directly across epithelial cell membrane
How do micelles help move monoglycerides and fatty acids towards epithelium?
They constantly break up and reform, they can release monoglycerides and fatty acids, allowing them to be absorbed.
(Whole micelles are not taken up)
How are amino acids taken up by the ileum?
Via co transport
(Look back)
