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Exchange & Transport Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Relate the structure of xylem to their function.

A

Long continuous columns of dead tissue - allow transportation of water.
Contain pits - allow water to move sideways between vessels.
Thickened with tough substance - provide structural support

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2
Q

Relate the structure of phloem to their function.

A

Sieve tube elements - transport sugars around the plant.
Companion cells - active transport of sugars into tubes.
Cytoplasms linked by plasmodesmata - allow flow of substances between cells.

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3
Q

Explain what is meant by the apoplastic pathway.

A
  1. A method of osmosis
  2. Through root hair cells
  3. Water moves through cell walls and intercellular spaces
  4. Can only be used until water reaches Casparian strip
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4
Q

Explain what is meant by the symplastic pathway.

A
  1. A method of osmosis
  2. Through root hair cells
  3. Water moves through cytoplasm
  4. Water must be actively transported into cells
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5
Q

Explain the cohesion-tension theory.

A
  1. Water molecules form hydrogen bonds with each other
  2. This causes them to stick together (cohesion)
  3. Surface tension of water creates sticking effect
  4. As water is lost through transpiration — more can be drawn up the stem from the roots
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6
Q

How does root pressure affect water movement.

A
  1. High mineral content gives root a low water potential
  2. There is strong osmotic flow into roots
  3. Creates a weak push effect
  4. Moving water from roots into stem
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7
Q

How does temperature affect rate of transpiration.

A
  1. Higher temperature increases random motion and rate of transpiration
  2. Therefore increasing rate of transpiration
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8
Q

How does humidity affect rate of transpiration?

A
  1. High humidity means water content of air outside leaf is high
  2. Reduces concentration gradient
  3. Decreases rate of transpiration
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9
Q

How does wind affect rate of transpiration?

A
  1. Lots of air movement blows moist air away room leaves
  2. Creates steep concentration gradient
  3. Increases rate of transpiration
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10
Q

Summarise the mass-flow hypothesis.

A
  1. Sugar loaded into sieve tubes via active transport
  2. Lowers water potential
  3. Causes water to move in from xylem
  4. Hydrostatic pressure causes sugars to move
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11
Q

Give evidence for mass-flow hypothesis.

A
  1. Sap is released when stem is cut
    Therefore must be pressure in phloem
  2. Higher sucrose concentration in the leaves than the roots
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12
Q

Give evidence against the mass-flow hypothesis.

A
  1. Not all solutes move at the same speed

2. There is bidirectional movement in the sieve tubes

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13
Q

Relate the structure of arteries to their function.

A
  1. Thick, muscular walls
  2. Handle high pressure without tearing
  3. Elastic tissue allows recoil
  4. Narrow lumen maintains pressure
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14
Q

Relate the structure of capillaries to their function.

A
  1. Walls once cell thick - short diffusion pathway
  2. Narrow - can permeate tissues and RBCs can lie flat against wall - effectively delivering oxygen to tissues
  3. Highly branched - large surface area
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15
Q

Why are two pumps (left and right) needed instead of one?

A
  1. Maintain blood pressure around whole body
  2. When blood passes through capillaries (lungs)
  3. Pressure drops therefore would not flow strongly enough to reach whole body
  4. Therefore it is returned to heart to increase pressure
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16
Q

Describe what happens during cardiac diastole.

A
  1. Atrium and ventricle relaxed
  2. Pressure in chambers drops
  3. SL valves in aorta and PA close to prevent back flow
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17
Q

Describe what happens during atrial systole.

A
  1. Atria contracts
  2. AV valves open
  3. Blood flows to ventricles
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18
Q

Describe what happens during ventricular systole.

A
  1. Ventricles contract
  2. SL valves open + AV valves close
  3. blood flows from V to arteries
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19
Q

What are the advantages of a double circulatory system?

A
  1. Concentration gradient maintained so deoxy and oxy blood don’t mix
  2. High blood pressure to body tissues
  3. Low blood pressure to lungs - prevents capillary damage
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20
Q

Why does blood need to clot? (Thrombosis)

A
  1. Prevents blood loss when vessels are damaged
  2. Prevents entry of disease-causing microorganisms
  3. Framework for repair
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21
Q

Describe the cascade of reactions leading to clot formation.

A
  1. Platelets attach to exposed collagen
  2. Thromboplastin releases
  3. Conversion of inactive prothrombin to active thrombin
  4. Thrombin catalysed conversion of fibrinogen into fibrin
  5. Fibrin forms network of fibres trapping RBC, platelets etc.
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22
Q

Describe the process of atheroma formation.

A
  1. Endothelium is damaged
  2. Increased risk of clotting
  3. Inflammatory response
  4. WBCs, cholesterol, fibres build up and harden
  5. Narrow arteries - restricted blood flow - increased blood pressure
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23
Q

What causes atherosclerosis and how can the risks be reduced?

A
  1. Diet, high BP, physical inactivity

2. Stop smoking, regular exercise, dietary changes

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24
Q

How does myogenic stimulation of the heart work?

A
  1. Depolarisation originates in Sinoatrial Node
  2. Spreads through atria (atrial systole)
  3. Stimulates the AV node
  4. AVN passes depolarisation into Bundle of His
  5. B of H splits into two Purkyne Fibres causing ventricular systole
25
Q

What are the main components of blood?

A
  1. Erythrocytes
  2. Leucocytes
  3. Plasma
26
Q

What is the cardiac cycle?

A

A series of contractions and relaxations that occur in the heart during one heart beat.

27
Q

What is tissue fluid?

A

Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which surrounds cells.

28
Q

What does each element of an ECG represent?

A
  1. P-waves - atrial systole caused by SAN
  2. QRS complex - ventricular systole
  3. T-wave - systole as ventricles depolarise (diastole)
29
Q

Name all types of leucocytes.

A

Granulocytes - granules in cytoplasm that take up stain, loved nuclei

  1. Neutrophils
  2. Eosinophils
  3. Basophils

Agranulocytes - no granules in cytoplasm, unlobed nuclei

  1. Monocytes
  2. Lymphocytes
30
Q

Describe the structure and function of erythrocytes.

A
  1. Haemoglobin, no nucleus, bioconcave disc shape, large surface area
  2. Carries oxygen form lungs to all cells
31
Q

Describe the structure and function of leucocytes.

A
  1. Larger than erythrocytes, can change shape, nucleus, granules (granulocytes)
  2. Defend body against infection
32
Q

Describe functions of specific leucocytes.

A

Lymphocytes - release antibodies, engulf pathogens
Eosinophils - contain enzymes to detoxify foreign proteins
Neutrophils - engulf foreign material
Monocytes - respond to inflammation

33
Q

Describe the function of plasma.

A
  1. Contains water, proteins, hormones
  2. Delivers them to cells
  3. Makes 55% of blood
34
Q

How does atherosclerosis affect health?

A

Increases risk of cardiovascular disease

E.g stroke, heart attack, angina

35
Q

What types of pressure influence formation of tissue fluid?

A
  1. Hydrostatic pressure - higher at arterial end of capillary than venous end
  2. Oncotic pressure - changing water potential of capillaries as water moves out
36
Q

How is tissue fluid formed?

A
  1. As blood pumps through small vessels
  2. Hydrostatic pressure is greater than oncotic pressure
  3. Fluid moves out of capillaries
  4. Exchanges substances with the cells
37
Q

What happens to excess tissue fluid?

A
  1. Removed from vessels into lymphatic system

2. Returned to blood near the heart

38
Q

Describe the structure of haemoglobin.

A
  1. Globular
  2. Water soluble
  3. 4 polypeptide chains
  4. Each carrying a haem group
39
Q

Describe the role of haemoglobin.

A
  1. Present in RBC
  2. O2 binds to haem groups
  3. Carried around body to respiring tissues
40
Q

How does partial pressure of oxygen affect oxygen-haemoglobin binding?

A
  1. Partial pressure of O2 increases
  2. Affinity of haemoglobin also increases
  3. Oxygen binds tightly to haemoglobin
  4. When partial pressure is low - O2 is released from haemoglobin
41
Q

Explain the Bohr effect.

A
  1. Partial pressure of CO2 increases
  2. Conditions become acidic
  3. Haemoglobin changes shape
  4. Affinity of haemoglobin decreases
  5. O2 is released from haemoglobin
42
Q

What do oxyhaemoglobin dissociation curves show?

A
  1. Saturation of haemoglobin with oxygen (%)
  2. Plotted against partial pressure of oxygen (kPa)
  3. Curves further to left show haemoglobin has higher affinity than O2
43
Q

How does the Bohr effect alter the position of an oxyhaemoglobin dissociation curve?

A
  1. Curve shifts to the right

2. Haemoglobin’s affinity for O2 has decreased

44
Q

How does myoglobin differ from haemoglobin?

A
  1. Only 1 haem group
  2. Very high affinity for O2 even at low partial pressure
  3. Found in muscle cells of mammals with high metabolic demands
45
Q

How does foetal haemoglobin differ from adult haemoglobin?

A
  1. Partial pressure of O2 is low when it reaches the foetus
  2. Foetal haemoglobin has higher affinity for O2
  3. Allows both mother and child’s O2 needs to be met
46
Q

Name 3 features of an efficient gas exchange system.

A
  1. Large surface area
  2. Short diffusion distance
  3. Steep concentration gradient, maintained by blood supply or ventilation
47
Q

Name and describe the main features of an insect’s gas transport system.

A
  1. Spiracles - openings on the body’s surface
  2. Tracheae - large tubes extending through body tissues
  3. Tracheoles - smaller branches dividing off the tracheae
48
Q

How are insect’s adapted for gas exchange?

A
  1. Spiracles can open or close to regulate diffusion
  2. Muscles in trachea allow mass movement of air in and out
  3. Tracheoles highly branched to provide large surface area
49
Q

Name and describe the 2 features of a fish’s gas transport system.

A
  1. Gills - made of filaments and supported by arches

2. Lamellae - folds that cover filaments, water passes over them due to pressure from floor of mouth

50
Q

How are fish adapted for gas exchange?

A
  1. Gills - made of many filaments, covered by lamellae, high surface area
  2. Countercurrent exchange system - water and blood flow in opposite directions, water is always next to blood of lower O2 concentration (steep gradient)
51
Q

Define passive transport an give examples.

A
  1. Movement of particles down a concentration gradient
  2. No energy required
  3. Diffusion, facilitated diffusion, osmosis
52
Q

Define facilitated diffusion and give the type of substances that use this.

A
  1. Movement of particles
  2. From high to low
  3. Through carrier or channel protein
  4. Charged particles because cell membrane repels them
53
Q

Define water potential.

A
  1. Tendency of water to move by osmosis

2. Pure distilled water has highest potential of 0

54
Q

How might certain properties of a molecule affect how its transported?

A
  1. Solubility - lipid-soluble molecules pass membranes easily
  2. Size - smaller molecules diffuse faster
  3. Charge - charged molecules can’t diffuse by simple diffusion
55
Q

Define active transport.

A
  1. Movement of molecules
  2. From low to high
  3. Energy is required
  4. Uses carrier proteins
56
Q

How does ATP release energy?

A
  1. ADP is phosphorylated to form ATP
  2. Requires energy which is stored in the molecule
  3. ATP is hydrolysed
  4. Energy is released
57
Q

How does an organism’s size relate to their surface area to volume ratio?

A
  1. The larger the organisms

2. The lower the SA:V

58
Q

How does surface area to volume ratio affect transport of molecules?

A
  1. The lower the SA:V ratio
  2. Further distance molecules need to travel
  3. To reach all parts of organism
  4. Diffusion alone is not sufficient
59
Q

Why do larger organisms require mass transport and specialised gas exchange surfaces?

A
  1. Small SA:V means substances can’t easily enter cells
  2. Mass transport and exchange surfaces
  3. Facilitate exchange of substances

Biology (3 decks)

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