3.1.2 Transport in Animals Flashcards
How are erthrocytes specialised?
- Biconcave shape - increases their SA:V ratio
- No nucleus - more space to hold more haemoglobin so they can carry more O2
- Small size, flexible so can fit through capillaries
How are neutrophils specialised?
- Multi-lobed nucleus - can squeeze through small vessels easily
- Cytoplasm contains many lysosomes with enzymes to attack pathogens
How are sperm cells specialised?
- Acrosome releases digestive enzymes to break through the egg membrane
- Flagellum allows for quick movement to the egg
- Contain many mitochondria to have the energy to swim
How are palisade mesophyll cells specialised?
- Contain chloroplasts for photosynthesis - can move through cytoplasm to absorb more light
- Rectangular shaped cells - package closely together
- Thin cell walls - increases rate of diffusion
- Large vacuole to maintain turgor pressure
How are root hair cells specialised?
- Microscopic size - penetrate easily between soil particles
- Large SA:V ratio
- Thin surface layer
- Concentration of solutes maintains the concentration gradient for water uptake
How are guard cells specialised?
Can change shape to control the amount of water that leaves and the gases that enter. Become turgid with water and open, become flaccid (lose turgor pressure) due to lack of water so return to regular closed shape. Inner wall of the cell is less flexible than outer wall, so it becomes bean shaped.
How is the squamous epithelium specialised?
Very thin - only one cell thick
How is the ciliated epithelium specialised?
Hair like structures (cilia) move in rhythmic manner. Goblet cells release mucus to trap any unwanted particles
How is the cartilage specialised?
Contains elastin and collagen - allows for flexibility and structural strength
Why do organisms need a circulatory system?
- SA:V ratio to remove/absorb substances via diffusion (large diffusion distance)
- Metabolic activity too high to rely on diffusion
- Products require elsewhere to where they’re made
- Need to remove waste products
- Need to obtain amino acids, glucose, oxygen, water etc from environment
What features affect the efficiency of an exchange system?
- Surface Area
- Diffusion distance
- Concentration gradient
How do the following factors contribute to an efficient exchange system: large SA, thin layer and good blood supply?
Large SA: increases rate of diffusion
Thin layer: reduces diffusion distance
Good blood supply: maintains concentration gradient
State some adaptations of the lungs
- Many alveoli - together give high SA
- Large network of capillaries surrounding alveoli - higher SA, increased exchange
- Thin alveoli epithelium and capillaries one cell thick - short diffusion distance
- Alveolar and capillary walls are close together
- Ventilation maintains high concentration gradient
- Ciliated epithelial cells and goblet cells clear airways to alveoli (present in bronchioles)
- Constant blood supply - maintains high concentration gradient
Describe the structure and function of the trachea
Structure: Lined with goblet cells and ciliated epithelia, made up of incomplete rings of cartilage and smooth muscle (provides strength and support to keep open)
Function: Smooth muscle can contract to decrease diameter - propels air upwards from lungs (helps when coughing)
Describe the structure and function of the bronchi
Structure: made up of cartilage and smooth muscle, lined with goblet cells and ciliated epithelia
Function: Provide a pathway for O2 to enter and CO2 to leave the lungs. Smooth muscle relaxes to increase diameter to allow more air to flow into the lungs.
Describe the structure and function of the bronchioles
Structure: No cartilage, walls consist of smooth muscle, lined with goblet cells and ciliated epithelia. Inhaled air supports shape - smooth muscle contracts, bronchioles constrict, smooth muscle relaxes, bronchioles dilate
Function: Ensure each alveoli is filled with air
Describe the structure and function of the alveoli
Structure: Squamous epithelial cells make up wall, also consist of collagen and elastin fibres - allow stretch to draw in and return to resting to release air (elastic recoil). Inner surface coated in thin layer solution of water, salts and lung surfactant - remains inflated, decreases surface tension so inflation is easier
Function: exchange of gases with blood - supply oxygen to blood and remove carbon dioxide
Describe the mechanism of ventilation
Inspiration: Diaphragm contracts, moves downwards. Intercostal muscles contract - ribs up and out. Volume of thorax/lungs increases, pressure decreases below atmospheric pressure
Expiration: Diaphragm relaxes, domes upwards. Intercostal muscles relax - ribs down and in. Volume decreases, pressure increases above atmospheric pressure
What happens to facilitate forcibly exhaling?
Internal intercostal muscles contract, pulling ribs down fast and abdominal muscles contract to force diaphragm up
Define vital capacity
Maximum amount of air that can be breathed out after the maximum inhalation - sum of inspiratory and expiratory reserve volumes, and tidal volume.
Define tidal volume
Volume of air breathed in and out in a normal breath, usually 15% of the vital capacity
Define inspiratory reserve volume
Maximum volume of air breathed in above normal
Define expiratory reserve volume
Maximum volume of air breathed out above normal
How do you calculate ventilation rate?
Tidal volume x breathing rate (min)
What are the methods of measuring lung capacity?
- Spirometer - breathe into airtight chamber filled with oxygen, soda lime removes CO2, trace recorded on revolving drum
- Peak flow meter - measures rate of air expulsion
- Vitalographs - peak flow meter, but graph produced of rate of expulsion
Describe the mechanism of ventilation in insects
Mechanical ventilation - muscular pumping of thorax/abdomen controls collapsible tracheae (increase/decrease air through system). Can close some spiracles to retain water. Tracheal fluid at end of tracheoles
What is the purpose of the tracheal fluid in insects?
When resting, bathes tissues to reduce water loss through the tracheae (lowers water potential gradient). When active, fluid diffuses into muscle cells to allow greater gas exchange (would be a barrier to O2 diffusion)
Describe the mechanism of ventilation in fish
Inspiration: open mouth, buccal cavity lowers, opercular cavity increases volume, opercular valve closes
Expiration: close mouth, buccal cavity moves upwards, opercular cavity decreases volume, opercular valve opens
Explain the mechanism of countercurrent exchange in fish
Water flow is in the opposite direction to blood flow - water with highest conc of O2 passes blood with lowest O2 conc, maintaining a constant high conc gradient
Describe the structure of gill filaments and lamellae
Gill filaments are sectioned into gill lamellae. Tips of filaments overlap, increasing resistance to water so water movement slows down, so more time for exchange
What two aspects further the efficiency of a fish’s gas exchange system?
Tips of gill filaments overlap
Countercurrent exchange
Explain the formation of tissue fluid
Arterial end - hydrostatic pressure higher than oncotic pressure - blood plasma (except rbcs and plasma proteins) forced out of capillary fenestrations to bathe tissues (forms tissue fluid).
Venous end - hydrostatic pressure lower than oncotic pressure (plasma proteins give high solute potential) - excess fluid diffuses back into capillaries (10% into lymph)
What are the differences in the composition of lymph, blood plasma and tissue fluid?
- Only blood plasma contains rbcs, platelets and plasma proteins. Tissue fluid and lymph contain wbcs
- Tissue fluid and lymph contain less hormones than blood plasma
- Blood plasma contains more amino acids and glucose than both
- Highest fatty acid level in lymph, none in tissue fluid
- Blood plasma contains more O2 than both
- Lymph contains more CO2 than both a
How is lymph transported?
One-way valves prevent the backflow of lymph - fluid transported through squeezing of muscles, returns to blood via veins under collar bone (clavicle).
Lymphocytes build up in lymph nodes.
What are the functions of the lymph system?
- Return excess fluid from tissues to blood
- Defend against diseases - lymph nodes filter lymph
- Absorb fats and fat-soluble vitamins from digestive system and put into blood
Explain the role of haemoglobin in transporting oxygen
High affinity at lungs - one binds to 4 O2 molecules. Initial binding changes shape of Hb, making subsequent binding easier (positive cooperativity).
Low affinity at respiring tissues, initial dissociation makes rest easier
Explain the role of haemoglobin in transporting carbon dioxide
At high partial pressures, CO2 diffuses into cytoplasm of rbcs - reacts with water to form carbonic acid (carbonic anhydrase catalyses) and this dissociates into H+ and HCO3-. HCO3- diffuses into plasma and Cl- into cytoplasm to maintain electrical balance (chloride shift). Hb accepts H+ to form haemoglobinic acid - acts as buffer
At low partial pressures, HCO3- diffuse back and react with H+ for reverse reaction of carbonic acid to CO2. Cl- diffuse back
What are the different ways CO2 is transported in the blood?
- 5% dissolves in plasma
- 10-20% binds with Hb to form carbaminohaemoglobin
- 75-85% reacts with water to form carbonic acid
What is the Bohr effect?
At higher partial pressures of CO2, the disassociation curve is more to the right as affinity for oxygen decreases
What is the significance of the different affinities of fetal and adult haemoglobin?
Blood oxygenated in placenta instead of lungs (foramen ovale open). Higher affinity than adult haemoglobin - must bind to oxygen at low partial pressures when it dissociates from adult haemoglobin. (Gamma sub-units give higher affinity)
What does an ECG trace measure?
Electrical differences in the skin due to the heart activity
What is tachycardia?
Heart rate exceeding normal resting rate (above 100bpm)
What is bradycardia?
Heart rate under normal resting rate (below 60bpm)
What is ectopic heartbeat?
Presence of frequent heartbeats out of normal rhythm
What is atrial fibrillation?
Abnormal rhythm from atria - categorised by rapid impulses (up to 400 contractions a minute)
What do the P, Q, R, S and T represent in the ECG trace?
P wave - atrial contraction (systole)
QRS wave - ventricular depolarisation and contraction (systole)
T wave - ventricular repolarisation (diastole)
Describe diastole of the heart
Heart is relaxed, blood at low pressure so blood enters atria and valves are closed
Describe atrial systole
Atria contract, so pressure higher in atria than ventricles - AV valves open due to pressure gradient, blood flows into ventricles
Describe ventricular systole
Ventricles contract, so pressure higher in ventricles than atria (AV valves are closed) - semi-lunar vales open, blood flows into aorta/pulmonary artery
Describe the cardiac cycle
Blood into atria from vena cavas/pulmonary vein - atria contract - pressure increase, AV valves open - blood into ventricles - ventricles contract - AV valves shut - pressure increase, semi-lunar valves open - blood into aorta/pulmonary artery - diastole
Describe how heart action is initiated and coordinated
- SAN cells depolarise - sends wave of depolarisation to muscle fibres so atria contract simultaneously (layer of non-conducting tissue stops it reaching ventricles)
- Wave travels via conductive fibres to AVN - creates 0.1s delay between atria and ventricles
- Wave travels down to Bundle of His, through septum to apex of heart, and up sides of ventricle via Purkyne fibres (wave travels to muscle fibres surrounding) causing contraction from apex up
How is cardiac output calculated?
Heart rate x Stroke volume
What are the differences between atria and ventricle walls?
Atria have thinner walls - pump blood a shorter distance and at a lower pressure.
Why is the left ventricle wall thicker than the right ventricle?
Has to generate a higher pressure from contraction to pump blood around most of the body
Why does hydrostatic pressure decrease further from the heart?
- Divisions into smaller vessels (more of them)
- Larger lumen of vessels away from heart
- Loss of plasma from capillaries
- Reduced resistance to flow due to wider lumen/more vessel divisions
State 3 advantages and 2 disadvantages of open circulatory systems
Advs: 1. Fewer vessels needed 2. Blood directly contacting cells 3. Less vulnerable to high pressures Disadvs: 1. Blood flow can't be varied 2. Steep diffusion gradients can't be maintained
State 3 advantages and 2 disadvantages of closed circulatory systems
Advs:
1. Can move under high pressure quickly
2. Blood returns to heart - re-pressurised
3. Can vary amount of blood at tissues
Disadvs:
1. Diffusion has to occur across vessels
2. More energy for blood distribution around body
State 1 advantage and 2 disadvantages of single circulatory systems
Adv: Less energy required to distribute blood
Disadvs:
1. Limited blood pressure - blood isn’t re-pressurised
2. Slower blood flow - can’t be as active
State 2 advantages and 1 disadvantage of double circulatory systems
Advs:
1. Most efficient - blood at high pressure, moves quickly
2. Organism can be very active
Disadv: requires more energy to distribute blood
Give examples of organisms with open circulatory systems
Most invertebrates (Insects and molluscs) - haemolymph is pumped from heart to haemocoel (body cavity) under low pressure
Give examples of organisms with closed circulatory systems
Vertebrates, Echinoderms (starfish, sea urchins)
Give examples of organisms with single circulatory systems
Fish - body weight is supported by water, so don’t need to regulate body temp. Reduces metabolic demands, allowing more activity
Give examples of organisms with double circulatory systems
Mammals - pulmonary and systemic circuit
Why do plants need transport systems?
- Size - more complex system to move substances around
- Small SA:V ratio when considering all parts of tree - can’t rely on solely diffusion
- High metabolic demands - organs that don’t photosynthesise require nutrients
What are dicotyledonous plants (dicots)?
Plants that make seeds containing two cotyledons (organs that act as food stores for embryo and form first leaves when germinating)
What is the difference between herbaceous and arborescent (woody) dicots?
Herbaceous - soft tissues, short life cycle
Arborescent (woody) - hard, lignified tissues, long life cycle
Name the tissues other than xylem and phloem within herbaceous dicots
Sclerenchyma, Parenchyma, Collenchyma - provide support via structural packing
Describe the structure of the xylem tissue
Non-living - made up of dead cells.
Xylem vessels are long, hollow structures comprised of several columns of fused cells.
Xylem parenchyma packs around vessels, storing food and containing tannin deposits (bitter-tasting chemical protecting from attack).
Xylem fibres are long cells with lignified secondary walls that provide extra mechanical strength, but don’t transport water
What are the different ways lignin can be laid down?
Rings, spirals or solid tubes with unlignified bordered pits
Describe the structure of the phloem tissue
Living
Sieve tube elements are many cells joined end-to-end to form hollow structure. Between cells there are perforated sections - sieve plates. Organelles break down - mature cells have no nucleus.
Companion cells join to sieve tube elements via plasmodesmata - provide life support
Supporting tissues, such as sclereids (cells w/extremely thick walls)
Describe the pathway of water into the roots and xylem
- Water diffuses into root hair cells via osmosis (mineral ions actively transported in lowers potential)
- Water moves through the root cortex cells to the root endodermal cells via the apoplast (cell walls) or symplast pathway (continuous cytoplasm)
- Water meets endodermis (layer of cells surrounding the vascular tissue - casparian strip (made of suberin) around each cell is waterproof , water in apoplast forced into symplast
- Minerals actively pumped into xylem produce water potential gradient - produces root pressure which gives water push up xylem (not the main factor)
Describe the process of transpiration
- Loss of water from the stomata pulls water up the xylem through capillary action
- Water has cohesive and adhesive forces (allow for capillary action) and moves in a continuous stream up the xylem - creates tension (cohesion tension theory)
- Water moves up xylem down pressure gradient
