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Biology > 3.3 Organisms exchange substances with their environment > Flashcards

3.3 Organisms exchange substances with their environment Flashcards

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1
Q

How do larger organisms combat a small SA:V ratio?

A
  • Specialised exchange surfaces
  • Specialised shape of animal
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2
Q

Why do smaller organisms not require specialised exchange systems?

A
  • They have a small mass, so a large SA:V ratio
  • They have a short diffusion distance
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3
Q

Which organism, large/small, loses the most heat energy and why?
How may they adapt to this?

think: adaption of haemoglobin

A
  • Small organisms as they have a larger SA:V ratio
  • Haemoglobin has lower affinty for oxygen, more oxygen unloaded at respiring tissue, more respiration, more thermal energy released to stay warm
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4
Q

Describe the structure of fish gills.

A
  • Gill raker and gill arch
  • Gill filaments along the gill arch, each filament has many lamallae present on it
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5
Q

How are fish gills adapted for a large SA?

A

Many lamallae on gill filaments

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6
Q

How are fish gills adapted for a short diffusion distance?

A

Lamallae have a thin epithelium

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7
Q

How are fish gills adapted to maintain a steep concentration gradient?

A

Countercurrent flow across the lamallae, water always flows by deoxygenated blood

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8
Q

How do fish create a constant flow of water to maintain a steep concentration gradient for gas exchange?

A

Buccal pressure pump:
- Increase volume of buccal cavity, lowers the pressure so water flows in
- Decrease volume of buccal cavity, increasing pressure so water flows out across the gills

Ram ventilation:
- Forcing water into the mouth by swimming with an open mouth

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9
Q

Describe gas exchange in an insect.

A
  • Air enters trachea through spircales
  • Oxygen then diffuses into tracheoles and tracheole ends, down the concentration gradient
  • Tracheole ends are in direct contact with respiring tissue
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10
Q

How do insects prevent water loss?

A
  • They can open and close their spiracles
  • They have water at the tracheole ends which lowers the difference in water potential so that water does not move out of cells
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11
Q

How is an insect’s tracheal system adapted for gas exchange?

A
  • Many highly branched tracheoles and tracheole ends so there is a large SA and short diffusion pathway
  • Rymthic pumping of insect body by muscles forcing air in and out, mainting steep conc. gradient
  • Tracheoles have thin walls so short diffusion pathway
  • Water in tracheole ends moves into tissues when activity increases so there is a shorter diffusion pathway for the gases
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12
Q

Why does water in the tracheole ends of insects diffuse into tissues as activity increases?

A
  • Insect may respire anaerobically when there is less oxygen, this produces lactic acid
  • This decreases the water potential in cells, so water diffuses into cells by osmosis
  • This decreases the diffusion pathway for gases, so more oxygen diffuses into respiring tissue
  • Less anaerobic respiration, less lactic acid produced so less water moves into tissues
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13
Q

Describe the structure of the lungs. By what pathway do gases enter?

A
  • Gas enters lungs through the trachea and then the bronchi
  • It then travels to alveoli by the bronchioles
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14
Q

How are the lungs adpated for a large SA?

A

Many small alveoli which have a spherical and folded shape

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15
Q

How are the lungs adapted for a short diffusion distance of gases?

A
  • Only 1 cell thick epithelial and endothelium layer of cells between the alveoli and capillaries
  • Both layers made up of squashed cells
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16
Q

How are the lungs adapted to maintain a steep concentration gradient?

A
  • Countercurrent flow of blood, so that air always meets more deoxygenated blood
  • Constant flow of blood from capillary networks
  • Lungs constantly ventilated
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17
Q

What tissue surrounds the trachae and why?

A

Cartilage
- Protects the trachae from damage and collapse over changes in pressure

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18
Q

What cells line the bronchi? What is the function of each one?

A

Goblet cells:
- Release mucus to catch any dust and pathogens before they enter the lungs

Ciliated cells:
- Hairs waft mucus up the trachea, towards the mouth

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19
Q

What tissue is found in alveoli and what is its purpose?

A

Elastic fibres
- Stretches and recoils, allowing alveoli to strech during inhalation

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20
Q

Why is liquid surfacant on alveoli important?

A
  • Lowers the surface tension
  • Prevents the collapse of alveoli during exhalation
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21
Q

What happens when you inhale?

A
  • Diaphragm muscles contract and flattens
  • External intercostal muscles contract causing the ribs to move up and out
  • This increases the volume of the thorax
  • Pressure decreases so air flows in
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22
Q

What happens when you exhale?

A
  • Diaphragm muscles relax and dome
  • External intercostal muscles relac causing the ribs to move down and in
  • This decrease the volume of the throrax
  • Pressure increase and air is forced out
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23
Q

How is the mechanism for exhalation different when at rest to when you are exercising?

A

At rest:
- External intercostal muscles relax
- Elastic fibres in alveoli recoil
- Diaphragm relaxes and domes

Exercising:
- Internal intercostal muscles contract
- Abdominal muscles contract

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24
Q

What impact do the following diseases have on the lungs:
a) Asthma
b) Idiopathic Pulmonary Fibrosis
c) COPD/emphysema

A

a) Inflammation of bronchi, narrows the tubes temperorarily
b) Scarring of tissue, thick scars increase the diffusion distance and damage the elastic fibres and their ability to recoil
c) Elastic fibres in alveoli broken down, surface area of alveoli and recoil impacted

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25
Q

What is digestion?

A

When larger molecules of food are hydrolysed by enzymes into smaller, more soluble molecules that can be absorbed.

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26
Q

How does the body physically breakdown food and why is this important?

A
  • Churning of food by stomach and mastication (chewing/tearing)
  • Increases the surface area for chemical breakdown of food (enzymes, digestive juices)
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27
Q

Where is pancreatic juice made and secreted?
What enzymes are found in pancreatic juice?

A
  • Made in pancreas, secreted into small intestine by pancreatic duct
  • Lipase, endopeptidases, exopeptidases, amylase
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28
Q

Where are intestinal juices made and secreted?
What enzymes are found in intestinal juices?

A
  • Made in duodenal glands, secreted into small intestine
  • Maltase, sucrase, lactase, endopeptidase, dipeptidase
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29
Q

What 3 enzymes hydrolyse proteins, what does each enzyme release and how?

A

Endopeptidases:
- Hydrolyse peptide bonds in the central region of the protein
- Produces shorter peptides which increases SA for exopeptidase action

Exopeptidases:
- Hydrolyse peptide bond on the terminal amino acid
- Producing dipeptidases or some single amino acids

Dipeptidases:
- Membrane-bound
- Hydrolyse single peptide bond in a dipeptide
- Producing single amino acids

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30
Q

How is starch broken down in the body?

A
  • Salivary amylase in mouth hydrolyses the starch to produce maltose
  • Amylase in intestinal juices hydrolyses any remaining starch
  • Membrane-bound maltase hydrolyses maltose into glucose
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31
Q

How are lipids digested?

A
  • Lipids emulsified by bile salts
  • Increased SA for action of lipase
  • Lipase hydrolyses ester bond and produces monolgycerides and fatty acids
  • Which associate with bile salts to form small lipid droplets, micelles
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32
Q

Where is bile produced, stored and then secreted?

A
  • Produced in liver
  • Stored in gall bladder
  • Secreted into the small intestine by the bile duct.
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33
Q

What is the function of bile?

A
  • Neutralises the acid from the stomach, creating optimum conditions for hydrolytic enzymes
  • Emulsifies fats, larger SA for lipase activity
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34
Q

What is absorption?

A

The movement of small, soluble digested molecules into the blood/lymph through cells lining the intestinal wall.

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35
Q

How are the epithelial cells lining the small intestine adapted for the absorption of molecules?

A
  • Many small foldings of cell membrane (microvilli) which increase SA
  • Mitochondria (ATP) for active transport of molecules
  • Many carrier proteins fro co-transport/active transport
  • Many carrier/channel proteins for facilitated diffusion
  • Co-transport of glucose/amino acids with Na+
  • Membrane-bound enzymes (maltase, sucrase, lactase)
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36
Q

How are villi adapted to increase the efficiency of absorption?

A
  • Thin walls reduce diffusion distance
  • Good supply of blood vessels and lymph system to maintain steep concentration gradient
  • Many foldings of cell membrane (microvilli) to increase SA
  • Muscles move food around mainting diffusion gradient
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37
Q

How are glucose molecules/amino acids absorbed at the intestinal epithelial cells?

A
  • Co-transport with Na+ ions
  • Na+ actively transported into blood, lowers concentration in the cells
  • Na+ diffuses (facilitiated) into cells with glucose
  • Glucose diffuses into blood down concentration gradient (facilitated diffusion)
38
Q

How are lipids absorbed at the intestinal epithelial cells?

A
  • Fatty aicds and monoglycerides associate with bile salts to form micelles
  • Micelles transport products to epithelial cell surfaces, releasing the monolgycerides and fatty acids
  • Simple diffusion into cell (small, non-polar)
  • Smooth ER produces triglycerides
  • Packaged at golgi apparatus with lipopteins/cholesterol to form chylomicrons
  • Exocytosis, enter lacteals and then bloodstream
39
Q

What is the structure of haemoglobin?

A
  • Globular protein, has a quaternanry structure
  • 4 polypeptide chains held together by disulphide bonds
  • 2 alpha-globin and 2 beta-globin chains
  • Each sub-unit has a prosthetic haem group (containing Fe 2+, which oxygen reversibly binds to)
40
Q

What are the adaptions of an erythroycyte?

A
  • No nucleus, more space for haemoglobin
  • Biconcave shape for a large SA
  • Small cell that can pass through capillaries
41
Q

What is formed when oxygen binds to haemoglobin?

A

Oxyhaemoglobin

42
Q

What order is it easiest to load oxygen molecules onto haemoglobin and why?

A

1st: hardest, must change shape in order to fit O₂
2nd/3rd: easiest, shape has changed (positive cooperativity)
4th: difficult, smallest probability of collision as only 1 empty haem group remains

43
Q

Where does haemoglobin associate and dissociate oxygen and why?

A
  • Haemoglobin assocated in lungs and dissociated at respiring tissue
  • High partial pressure of O₂ in lungs, low pp of O₂ in respiring tissue
44
Q

In which environments would you find haemoglobin with a high/low affinty for O₂?
What might the metabolism be for an organism in each environment becuase of this?

A

High affinity = readily loads O₂, low O₂ environment (low metabolism)
Low affinty = readily unloads O₂, high O₂ environment (high metabolism)

45
Q

On an oxygen dissocaition curve, to what side would the line for lower affinity and higher affinty lie?

A

Lower affinty = right
Higher affinity = left

46
Q

On an oxygen dissocaition curve, to what side would the line for lower affinity and higher affinty lie?

A

Lower affinty = right
Higher affinity = left

47
Q

What impact does high pressure of carbon dioxide have on oxygen association?

A

Bohr shift:
- More carbonic acid forms, lowers pH
- H+ ions interact with haemoglobin tertiary structure, breaking hydrogen/ionic/disulphide bonds
- Tertiary structure changes, binding site changes shape, oxygen cannot bind
- Lower affinity for oxygen, more readily dissociated at respiring tissue

48
Q

When there is increased activity, what happens tothe oxygen dissociation curve?

A

Curve shifts to the right
- Haemoglobin has lower affinity for O₂
- More readily dissociates at respiring tissue, more O₂ available for aerobic respiration

49
Q

How does haemoglobin differ across organisms?

A
  • Haem groups are the same
  • The four polypeptide chains can differ however
50
Q

What is the effect of altitude on haemoglobin?

A

High altitude = low pp of O₂
- Higher affinity for O₂
- Allows for suffiicient saturation at low pp

51
Q

What are the adaptions of foetal haemoglobin?

A
  • Has a higher affinity for oxygen
  • Has to compete with mother to get O₂ from her blood
52
Q

Describe the human circulatory system.

A
  • Closed double circulatory system
  • Pulmonary and systemic circulatory systems
  • Blood passes through the heart twice
53
Q

What is the difference between an open and closed circulatory system?

A

Open (insects) = blood not contained in blood vessels, pumped directly into body cavities

Closed (fish, mammals) = blood pumped around body in continuos network of blood vessels

54
Q

What is needed in an efficient circulatory transport system?

A
  • Pressure pump (forces mass transport)
  • Closed system (to maintain pressure)
  • Suitable medium to transport molecules (aqueous solvent)
55
Q

How do you calculate cardiac output?

A

Cardiac output = heart rate x stroke volume

56
Q

What are the blood vessels that carry blood to and from the heart to the brain?

A
  • Carotid artery
  • Jugular vein
57
Q

What is the muscle that the heart is made, what is special about it?

A

Cardiac muscle
- It is myogenic

58
Q

Describe the structure of the heart?

A
  • 4 chambers: 2 atria and 2 ventricles
  • Septum seperating the two sides
  • Semi-lunar valves (pulmonary/aortic valves)
  • Atrio-ventricular valves
59
Q

From what blood vessels does blood enter and leave the heart?

A

Enters:
- Superior/inferior vena cava (deoxygenated)
- Pulmonary vein (oxygenated)

Exits:
- Pulmonary artery (deoxygenated)
- Aorta (oxygenated)

60
Q

How is the aorta adapted to its function?

A
  • Has elastic tissue, can stretch when ventricle contracts and recoil when ventricle relaxes
  • Thick artery wall to withstand pressure
  • Aortic valve to stop backflow
  • Smooth endothelium, reduces friction
61
Q

What is the function of the coronary arteries?

A

Transport oxygen glucose to cardiac muscle.

62
Q

What are the main stages of the cardiac cycle?

A

Diastole:
- Both chambers relaxed
- Pressure in ventricles lower than arteries (SL valves close)
- Atria fill with blood
- Pressure in atria greater than in ventricles (AV valves open)

Atrial systole:
- Atria contract

Ventricular systole:
- Ventricle walls contract
- Pressure in ventricles greater than atria and arteries (SL valves open and AV valves close)

63
Q

What are the 3 layers of a blood vessel?

A

Outer layer = epithelium
Middle layer = smooth muscle and elastic fibres
Inner layer = endothelium

64
Q

Why do blood vessels have a smooth endothelium layer?

A

Reduces surface of blood flow and friction

65
Q

What protein is found in the epithelium of arteries and veins, and why?

A

Collagen = tough, fibrous protein
- High tensile strength
- Helps blood vessels withstand high pressure of blood
- Prevents bursting

66
Q

Describe the structure of arteries.

A
  • Narrow lumen
  • Thick layer of smooth muscle and elastic tissue
67
Q

What is the purpose of elastic fibres in arteries?

A
  • Elastic fibres stretch, allowing the artery wall to expand around high pressure blood
  • Elastic fibres recoil to maintain blood pressure alongside the narrow lumen
68
Q

Describe the structure of veins.

A
  • Wide lumen
  • Valves (prevent backflow)
  • Thin layer of smooth muscle and elastic fibres
69
Q

Describe the structure of capillaries.

A
  • Very small lumen
  • One cell thick endothelium
  • Pores
  • Capillary networks called capillary beds
70
Q

For what 2 reasons is it important that the pressure of blood is low when it reaches capillaries?

A
  1. Blood moving slow enough to allow time for molecules to be exchanged
  2. Stops capillaries bursting as they do not have a thick wall
71
Q

How does the body decrease pressure between the arteries and capillaries?

A
  • Blood enters capillary beds from arteries
  • Capillary network has a larger area.
72
Q

Explain 2 advantages of capillaries being narrow.

A
  1. Slows down blood flow
  2. Shorter diffusion pathway out of capillary
73
Q

How does tissue fluid form?

A
  • Water and smaller metabolites move into tissue fluid from a high to low hydrostatic pressure
  • Larger proteins remain in the blood, water leaves so water potential in capillary decreases
  • Some water returns to the capillary by osmosis at the venule end, the rest enters the lymph
74
Q

What happens to the tissue fluid when someone has hypertension?

A
  • High blood pressure so higher hydrostatic pressure in capillary
  • More water forced into tissue fluid
  • Less water returns to capillary at venule end as there is a higher hydrostatic pressure
  • Build-up of tissue fluid
75
Q

What is the function of the lymph system?

A
  • Transports chylomicrons from small intestine to bloodstream
  • Removes plasma proteins from the tissue fluid (lowering water potential) and returns them back to the bloodstream
76
Q

How does the lymph move through the lymphatic system?

A
  • Liquid moves along the larger vessels by compression from body movement
  • Valves stop backflow of the lymph
77
Q

How are the lymph capillaries different to the blood capillaries?

A
  • Lymph capillaries have larger pores, so larger proteins can enter
  • They have closed ends and valves
78
Q

Compare and contrast the phloem and xylem.

A
  • Both are involved in mass transport
  • Phloem is translocation (dissolved sugars), xylem is transpiration (water and mineral ions)
  • Phloem involves active processes and living cells
  • Xylem involves passive processes and dead cells
79
Q

Describe the structure of the phloem.

A
  • Sieve cells have no nucleus, few organelles and are perforated to allow for a continuos flow
  • Companion cells have many mitchondria (ATP) for active transport
80
Q

Describe the structure of leaf tissue.

from top to bottom

A
  • Waterproof cuticle
  • Upper epidermis
  • Palisade mesophyll layer
  • Xylem and phloem
  • Spongy mesophyll layer
  • Stomata and guard cells
  • Lower epidermis
81
Q

How is the leaf adapted for efficient gas exchange?

A
  • Large SA = spongy meosphyll layer creates air spaces for gases
  • Short diffusion pathway = thin plant tissue and stomata
  • Steep conc. gradient = photosynthetic cells use carbon dioxide immediately
82
Q

By what methods are water and mineral ions taken up into the plant?

A

Water = osmosis (passive)
Mineral ions = active transport (active) or facilitated diffusion (passive)

83
Q

What two pathways can water take to move across the cortex of a plant?

A

Apoplast:
- Diffusion
- Around the cells (cellulose cell walls)
- Faster

Symplast:
- Osmosis into cells
- Through cytoplasm/plasmodesmata/vacuole of cells
- Slower

84
Q

What are 4 advantages of transpiration?

A
  1. Water for metabolic reactions (photosynthesis)
  2. Keeps plant rigid, provides support
  3. Transports important mineral ions
  4. Cools plant, through evaporative cooling
85
Q

Explain how the transpiration stream works.

A
  • Water evaporates out of leaf/mesophyll cells through stomata
  • Lowers water potential of leaf/mesophyll cells
  • Water from xylem moves into cells, transpiration pull
  • Lower hydrostatic pressure in xylem in leaves and high hydrostatic pressure in roots, water pulled up xylem, tension created
  • Water molecules cohere due to hydrogen bonds between the molecules, creating continuous water column
  • Water molecules also adhere to the xylem wall
86
Q

What factors affect the rate of transpiration?

A
  • Temperature = KE and evaporation of water
  • Humidity = controls conc. gradient between air and leaf
  • Wind = removes water vapour in surrounding air
  • Light intensity = causes stomata to open/close
87
Q

What apparatus can you use to measure the rate of transpiration?

A

Potometer

88
Q

Where are dissolved sugars produced and transported?

A
  • Produced in leaves
  • Transported from stores to sinks (meristems, seeds, flowers, stems, roots)
89
Q

What form of sugar is transported in the phloem and why?

A

Sucrose
- Glucose is too reactive and would be broken down before it reaches the sink

90
Q

Describe the Mass Flow Hypothesis.

A
  • Sucrose actively transported into phloem sieve cells by companion cells using ATP
  • Lowers water potential in phloem and water enters by osmosis from xylem
  • Increase in hydrostatic pressure in phloem
  • Mass flow of phloem sap towards sink where sugars are being unloaded
91
Q

Describe 2 ways you can investigate translocation.

A
  1. Ringing experiments
    Ring of phloem/bark remoed from tree trunk, area above swells, liquid in swelling contains sugars, shows that when ploem is removed sugars cannot be transported
  2. Radioactive carbon dioxide
    Trace sugars, containg radioactive carbon, makes path of sugars visible under x-ray
92
Q

How do you calculate the surface area of a leaf?

A
  • Draw around the leaf on squared paper and count the number of squares to estimate the area
  • Multiply by two to get both sides of the leaf

Biology (10 decks)

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