Organisms Exchange Substances With Their Environment Flashcards
Describe the relationship between size and surface area to volume ratio
Increase size results in a decrease in surface area to volume ratio
List the four organisms that gas exchange occurs in
Fish
Insects
Humans
Plants
Describe the gas exchange in single celled organisms.
Occurs in the tracheal system
Spiracles- opening in exoskeleton with valves to allow air to enter
Trachea- tubes that lead to tracheoles
Tracheoles- extend to organs which deliver the oxygen
What is the order of the tracheal system and how does it work?
Spiracles- opening in exoskeleton that allows air to enter
Trachea-tubes that extend to tracheoles
Describe the adaptations of fish for gas exchange
Gill arch attached to gill filaments to increase surface area
Rows of lamellae to also increase surface and form network of capillaries
What is the counter current principle in fish?
Water flows in opposite direction to blood to ensure a favourable concentration gradient
Describe the adaptations of plants for gas exchange
Waxy cuticle- prevents water loss
Palisade mesophyll- layers of elongated cells with chloroplast which speeds up photosynthesis
Stomata- pores on underside which allows air to enter and leave
Guard cells- control the opening and closing of stomata
Explain the differences between gas exchange in terrestrial insects and xerophytic plants
Insects:
Air enters through spiracles and moves down trachea into tracheoles.
Rhythmic abdominal movements causes the air to move in and out of the spiracles
Plants:
Air enters through stomata and diffuses through the air spaces within the sponges mesophyll allowing co2 to diffuse rapidly
List the gross structure of the human gas exchange system
Nose
Trachea
Lungs
Bronchi
Bronchioles
Alveoli
Describe the structure and function of the alveoli
Tiny sacs with thin walls to enable sufficient gas exchange (short diffusion pathway)
It is the main site of gas exchange in the lungs
Describe the structure and function of the bronchioles
Narrow tubes which carry air from bronchi to alveoli
Describe the structure and function of the bronchi
Bronchi lead to bronchioles
Describe the structure and function of the trachea
Airway that leads from mouth to nose then to bronchi.
Lined with mucus-and cilla which sweeps the mucus away.
Describe the structure and function of the lungs
Central part of the respiratory system where gas exchange takes place
What are the features of the alveolar epithelium?
Large number of alveoli- increases surface area for co2 and o2 to diffuse
Thin walls- short diffusion pathway
Extensive capillary network- constant flow of blood
Describe inhalation in the human body
Volume of thorax increases
Air pressure decreases
Diaphragm flattens and contracts
External intercostal muscles contract
Ribcage moves up and down
Describe exhalation in the human body
Volume of thorax decreases
Air pressure increases
Diaphragm becomes domed
External intercostal muscles relax
Internal intercostal muscles contract
Ribcage moves down and back
What is digestion?
Process where large insoluble biological molecules are hydrolysed into smaller soluble ones in order to be absorbed across the cell membrane
What polysaccharide is used for the digestion of carbohydrates?
Amylase
What polysaccharide is used for the digestion of lipids?
Lipase
Name the three enzymes that take part in the digestion of proteins
Endopeptidases
Exopeptidases
Dipeptidases
Explain the differences between the position of the three enzymes that digest proteins
- Endopeptidase hydrolyse proteins into smaller proteins
- Exopeptidase hydrolyse the ends of the chain to produce dipeptides
- Dipeptidase hydrolyse into amino acids
How are amino acids and monosaccharides absorbed?
Co transport
What is the role of micelles in the absorption of lipids?
Enables the lipid digestion products to be transported to the small intestinal surface for absorption
What is haemoglobin?
A group of chemically similar molecules found in many different organisms
What is the role of haemoglobin?
It’s responsible for binding oxygen in the lungs and transporting oxygen to the tissue to he used in aerobic metabolic pathways
Describe the structure of haemoglobin
- Globular protein
- quaternary (made of 4 polypeptide chains)
- 4 game groups so 4 or 8 oxygen molecules can bind
Name the three factors affecting haemoglobin binding
- Temperature
- Hydrogen ions
- Carbon Dioxide
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
As the partial pressure increases, the number of oxygen molecules bound by Hb increases, increasing the saturation of Hb
How does the partial pressure of carbon dioxide affect the oxygen-haemoglobin binding?
Shifts curve to the right as it decreases pH
Therefore becomes more acidic by increasing concentration of H+ ions which causes haemoglobin to distort and affinity of oxygen decreases which increases oxygens unloading
How does saturation of haemoglobin affect oxygen-haemoglobin binding?
More saturated means less oxygen can bind as haemoglobin’s binding sites are occupied
Explain why oxygen binds to haemoglobin in the lungs
So it has the ability to transport oxygen around the body to the respiring cells
One oxygen bonds to the iron in haemoglobin so one molecule is able to carry a maximum of four oxygen molecules
What do oxyhaemoglobin curves show?
How many oxygen molecules are bound to haemoglobin at different partial pressures of oxygen
How does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?
Shifts curve to the right as produces more H+ ions (water and CO2 react and produces carbonic acid) therefore it’s more acidic. Lower pH causes change in the structure of haemoglobin decreasing affinity of O2 but increasing unloading of O2
Describe the gross structure of the heart, including all chambers and ventricles
Vena cava
Rift atrium
Tricuspid valve
Right ventricle
Pulmonary artery to lung
Pulmonary vein
Left atrium
Bicuspid valve
Left ventricle
Aorta
Describe the blood flow in the heart
Deoxygenated blood enters the heart through the vena cava
Travels to the right atrium then through the tricuspid valve into the right ventricle
The blood travels out the pulmonary artery and travels to the lungs to be oxygenated
Oxygenated blood now travels in through the pulmonary vein and into the left atrium then through the bicuspid valve into the left ventricle out the heart though the aorta which travels around the body to the respiring cells
Explain the structure and function of the arteries
Arteries carry blood away from the heart at high pressures
Outer layer made of collagen- strengthens vessels to withstand the pressure
Elastic layers- stretch and recoil to compensate for high blood flow
Smooth muscle- reduces friction
Explain the structure and function of the arterioles
Carry blood from arteries to capillaries
Similar to arteries but have smaller lumen
Higher muscle but thinner elastic than arteries
Explain the structure and function of the veins
Carry blood towards the heart
Thin walls made of collegen
Valves to prevent back flow of blood
Explain the formation of tissue fluid and how it returns to the circulatory system
High hydrostatic pressure in the capillaries cause tissue fluid to leak out into the blood stream
The gradient in water potential causes tissue fluid to move back into the capillaries and excess water is absorbed by the lymphatic system
What is the structure and function of the xylem vessel
Long hollow tubes made up of dead cells called lignin
Transports water and mineral ions
Explain the structure and function of the phloem vessel
Made of
•companion cells
•sieve tube elements (living cells joined end to end to form sieve tubes)
•sieve plates (contain lots of holes to allow substances to pass through)
Transport sucrose and amino acids from source (where it’s made) to sink (where it’s used)
Explain the mass flow hypothesis in plants
Hydrogen ions pump from companion cell into source by active transport
A co transporter moves hydrogen ions and sucrose from the source to the companion cell
Sucrose diffuses from companion cell into sieve tube elements (low water potential as more sucrose)
H2O moves from xylem to phloem sieve tube element via osmosis which increases water potential (less sucrose more water)
Water moves down sieve tube from high to low concentration
Sucrose eaves sieve tube element into sink
Water potential increases now so H2O move back into xylem by osmosis
What is translocation?
How organic substances move around the plant from source to sink
