Unit 3: Organisms Exchange Substances With Their Environment Flashcards
Why must organisms exchange substances
- their external environment is different to their internal environment
- in order to survive, transfer of substances across membranes must occur
What do organisms exchange
- respiratory gases
- nutrients
- excretory product
- metabolic heat
- water
What is surface area : volume ratio and why is it important
- difference between surface area of cell surface membrane and overall volume of cell
- the larger the animal, the lower SA:V
- surface must be large compared to volume for efficient gas exchange
What is the thorax
- lungs are housed in the thorax, an air-tight, dome shaped chamber formed by the ribcage and intercostal muscles
- thorax lined with a pleural membrane, secreting pleural fluid, which acts as a lubricant from blood plasma, maintaining surface tension and protecting lungs from friction
What is the diaphragm
- a sheet of muscle attached to the body wall at the base of the ribcage
- separates the thorax and abdomen
Flow of air from mouth into lungs
- inhaled at mouth or nose, pass through the trachea, pharynx and larynx
- trachea divides into two primary bronchi, one to each lung.
- bronchi divides into secondary bronchi, the bronchial tree.
- smallest bronchi divide into bronchioles, which terminate at the alveoli.
Trachea notes
- lined with cillates epithelial cells, which are hair-like cells that waft mucus to the back of the throat
- goblet cells produce mucus, which acts as a method of trapping dirt and pathogens
- trachea cells havw +-shaped cartilage disks which prevent collapsing
- smooth muscle controls diameter of the airway
Bronchiole notes
- leads from bronchi and go to alveoli
- mainly smooth muscles and epithelial cells
- larger bronchioles may have cartilage to maintain structure
Alveoli notes
- squamous epithelial tissue and elastic fibres
- adaptations: large SA, good blood supply, short diffusion distances
What is tidal volume
- the volume of air in each breath, usually between 0.4 - 0.5dm3 for adults
What is ventilation rate
- number of breaths per minute, around 15 per minute at rest
What is forced expiratory volume
- the maximum volume of air that can be breathed in and out
What is forced vital capacity
- the maximum volume of sir it is possible to breathe forcefully out of the lungs after a deep breath in
What is vital capacity
- the maximum air we can inhale and exhale
What is residual volume
- the volume of air left in the lungs after the strongest exhalation
What is total lung capacity
- vital capacity + residual volume, normally 5 - 6dm3.
What is pulmonary ventilation
- tidal volume x ventilation rate
Xerophytic adaptations
- stomata sunk in pits, to trap water vapour
- layer of hairs to trap water around stomata
- curled leaves to protect stomata from high speed winds
- reduced stomata so less water can escape
- thicker waxy cuticle to reduce evaporation
What are endopeptidases and examples
- break up large proteins into smaller polypeptides, by hydrolysing bonds in the middle
- trypsin, pepsin
What are exopeptidases
- break up dipeptides or amino acids off from the end of polypeptides
Digestion of carbohydrates
- amylase catalyses the breakdown of starch, which is chains of glucose
- hydrolyses glycosidic bonds to produce maltose
Digestion of disaccharides
- enzymes attached to the epithelium of the ileum
Digestion of lipids
- lipase enzymes catalyse breakdown of lipids into monoglycerides
- bile salts emulsify lipids into droplets
- micelles help the product of lipid digestion to be absorbed
What does the circulatory system consist of
- tubes called blood vessels
- a pump, the heart, keeps blood flowing through the vessels
- valves, in the heart and veins, prevent backflow of blood
What makes it double-circulatory
- blood passes through the heart twice, once as deoxygenated and once as oxygenated
Key features of a mass transport system
- a transport medium to transport necessary substances
- rapid enough movement to supply body and cells with what they need
- mechanisms to ensure blood flows in one direction
- via a system of vessels and tubes
What is myogenic contraction
- the heart can beat without input from the nervous system, if its cells stay alive
- muscle cells (myocytes) have a slight electrical charge across their membrane, when this charge is reversed it causes them to contract
- heartbeat is initiated in the sinoatrial node, also known as the pacemaker
- consists of contraction (systole) and relaxation (diastole)
Three steps of heart contraction
1) cardiac diastole - allows heart to refill with blood
2) atrial systole - pushes blood into ventricle
3) ventricular systole - pushes blood out of heart into aorta and pulmonary arteries
Heartbeat sounds
Ventricular systole - ‘lub’
Diastole - ‘dub’
Heartbeat valves
Ventricular systole:
- atrioventricular valves shut, because pressure in ventricle is higher than atrium
- semi lunar valves open, as pressure in ventricles is higher than in aorta
Diastole:
- semi lunar valves shut, because pressure in ventricle drops and aorta pressure is now higher
- atrioventricular valve opens as pressure in atria begins to increase as blood flows in.
Tissues in blood vessels
- elastic tissue stretches and recoils to maintain pressure
- muscle tissue contracts to reduce diameter of lumen
- endothelial tissue is smooth and reduces friction
