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A-levels > Biology UNIT 3-Gas exchange, Organisms, Exchange of substances & Environments > Flashcards

Biology UNIT 3-Gas exchange, Organisms, Exchange of substances & Environments Flashcards

1
Q

What is the importance of some inorganic ions?

A

Phosphorus- phosphate ion in ATP and phospholipids.

Sodium- Sodium ions in nerve impulses and absorption of glucose & water and muscle contractions.

Iron- Iron ion in haemoglobin

Hydrogen- Hydrogen ion affects pH for enzyme activity

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2
Q

What is a xerophyte?

A

Plants that have adapted to living in areas where water is short in supply. Without adaptations the plants would become desiccated and die.

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3
Q

What is an extremeophile?

A

An organism that has adapted to an extreme environment

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4
Q

What are the main adaptations found in a xerophyte?

A
  • Thick waxy cuticle
  • Rolling up of leaves
  • Hairy leaves
  • Stomata in pits or groves
  • Reduced SA:Volume ratio in leaves
  • Needle like leaves
  • Concertinaed stems.
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5
Q

How does rolling up of leaves prevent water loss?

A

Rolling leaves protects the lower epidermis and traps still moist air within the rolled up leaf. This area then has a high water potential and as there is no water potential gradient between the inside and outside of the leaf, no water is lost.

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6
Q

How do hairy leaves prevent water loss?

A

Hairs trap still moist air close to the surface of the leaf.

This reduces the water potential gradient so less water is lost via evaporation.

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7
Q

How does the waxy cuticle prevent water loss?

A

Forms a water proof barrier. The thicker the cuticle the less water is lost.

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8
Q

How do sunken stomata prevent water loss?

A

Traps still moist air near the leaf surface to reduce the water potential gradient.

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9
Q

How does a reduced SA:Volume ratio prevent water loss?

A

Leaves which are circular and have small cross sections have reduced water loss compared to broad fat leaves.

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10
Q

How does insects use gas exchange to respire without breathing?

A

Spiracles- holes in exoskeleton are openings which lead to tracheae which take in air.
Tracheae branch into smaller tracheoles.
Tracheoles terminate into fluid so oxygen can diffuse into fluid and carbon dioxide can diffuse into tracheoloes.

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11
Q

How are xerophytic insects adapted for gas exchange?

A
  • Slightly larger air sacs
  • Closed spiracles (prevents water loss)
  • Use oxygen form the air sacs.
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12
Q

How are hydrophylic insects adapted for gas exchange?

A
  • Use air sacs for buoyancy
  • Can store oxygen in air sacs
  • Chitinous projections outside spiracles create and area of localised humidity to prevent water loss
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13
Q

Explain how fish gills are adapted for gas exchange

A

On the gills are filaments which have a large surface area. On each filament are lamellae with tiny blood capillaries passing blood through them. The lamellae increase the surface area as well as ensure that the direction of blood flow is always opposite to the water flow allowing for a maintained concentration gradient.

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14
Q

What is counter current flow in a fish?

A

In a fish, the arrangement of water flowing past the gills is opposite to the direction of blood flow. This means that there is always a higher oxygen concentration in the water and therefore there is a maintained concentration gradient for diffusion of oxygen to occur and diffuse into the blood.

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15
Q

Define breathing rate and tidal volume

A

Breathing Rate- Number of breaths inhaled in a given time. (eg. breaths per min)

Tidal Volume- Volume of air you inhale in one breath.

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16
Q

What is the equation for pulmonary ventilation rate?

A

Ventilation rate = Tidal volume / Breathing rate

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17
Q

What happens during inspiration (breathing in)?

A
  • Inspiratory (external) intercostal muscles contract and pull the ribs up and out.
  • Diaphragm moves down and flattens as it contracts
  • Volume in thoracic cavity increases
  • Pressure in thoracic cavity deacreases.
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18
Q

What happens during Expiration (breathing out)?

A
  • Expiratory (internal) intercostal muscles contract and pull ribs down and in.
  • Diaphragm moves up and domes as it contracts
  • Volume in thoracic cavity decreases
    Pressure in thoracic cavity increases
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19
Q

What do epithelial cells do?

A

Enables the body to partition/compartmentalise organs and body parts,
They also protect deeper layers of tissue from injury or infection.

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20
Q

What is the role of the proper epithelium?

A

Covers and lines the outer and inner body parts.

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21
Q

What is the role of the glandular epithelium?

A

Forms glands and secretes hormones and other substances.

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22
Q

Define invagination?

A

The action or process of being folded in on itself and turned inside out.

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23
Q

Name the different types of epithelial cells?

A
  • Squamous cells- Flat with thin membranes for short diffusion paths
  • Cuboidal cells- Absorb nutrients and produce mucus/other substances
  • Columnar cells
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24
Q

What is ficks

A

Rate of diffusion = difference in concentration x Surface area / Thickness of diffusion pathway.

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25
Q

What are alveoli?

A

Small tiny air sacs of the lungs for rapid gaseous exchange.

Made up of squamous epithelial cells which enables the alveoli to have a short diffusion path.

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26
Q

What does the surfactant do?

A

Produces moisture to extend the concentration gradient to allow the oxygen to diffuse in at an increased rate.
Holds the alveoli open when we breathe.

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27
Q

How are the alveoli adapted for their function?

A

Moisture produced from surfactant increases concentration gradient for quick diffusion.
Squamous epithelial cells are flat and thin for an increased surface area and short diffusion pathway resulting in a high rate of diffusion.

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28
Q

What are the disaccharidases?

A
  • Maltase
  • Lactase
  • Sucrase
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29
Q

What does amylase break strach into?

A

Maltose.

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30
Q

What doe endopeptidases do?

A

Breaks the peptide bond in the middle of a polpeptide.

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31
Q

What do exopeptidases do?

A

Breaks the peptide bond at the ends of polypeptides.

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32
Q

What do dipeptidases do?

A

Breaks down dipeptides into amino acids.

33
Q

Which 4 enzymes digest carbohydrates?

A

Amylase
Maltase
Sucrase
Lactase

34
Q

How is glucose absorbed from the lumen of the small intestine into the blood stream at low and high concentrations of glucose?

A

High concentration- Glucose moves via facilitated diffusion

Low concentration- Glucose moves via sodium co-transport.

35
Q

How are amino acids absorbed from the lumen of the small intestine at low and high concentrations of amino acids?

A

High concentration- amino acids are absorbed by facilitated diffusion.
Low concentration- amino acids are absorbed by sodium co-transport

36
Q

Explain what happens in sodium co-transport.

A

The lumen has a high concentration of Na+ ions which bind to a carrier protein. Glucose also binds to the protein.
Another carrier protein moves the glucose from the epithelial cell via facilitated diffusion.
The Na+ ions are moved via the sodium potassium pump. (3Na+ and 2K+)

37
Q

How are lipids digested?

A

1) Fat droplets area emulsified by bile salts and then digested by lipase enzymes.
2) Free fatty acids and bile salts combine to form miscelles. The lipid soluble fat droplets pass through the membrane and bile salts move away.
3) In the cell triglycerides and proteins join forming chylomicrons which are exocytosed into the lacteal.

38
Q

How do Miscelles form and give some properties of them?

A

After digestion, monoglycerides and fatty acids associate with bile salts and phospholipids to form miscelles.

  • Transport poorly soluble monoglycerides and fatty acids to the epithelial cells to be absorbed
  • Contain fat soluble vitamins and cholesterol.
39
Q

What are Chylomicrons, how are they formed and what do they do?

A
  • Re synthesised monoglycerides and fatty acids form triglycerides.
  • Triglyceride is packaged in the ER and Golgi along with cholesterol and fat soluble vitamins into Chylomicrons.
  • Chylomicrons are lipoproteins specifically for transport of lipids in the circulation system
  • Chylomicrons are exocytosed.
40
Q

Where are Chylomicrons exocytosed to?

A 
The lacteal ( a vessel in the lymphatic system)
because these particles are too big for normal capillaries.
41
Q

What is haemoglobin?

A

A Quaternary protein made of 2 beta and 2 alpha chains. Found in red blood cells and binds to oxygen to form oxy-haemoglobin.

42
Q

What is the Heme group

A

An Fe2+ group bound to each of the 4 chains. There are 4 heme groups which bind to the oxygen once it has diffused into the red blood cells.

43
Q

What happens when the oxygen binds to the heme group?

A

The bind changes the structure of the haemoglobin molecule so it has more affinity for oxygen molecules.
This means more oxygen molecules bind to the haemoglobin and so can be carried to tissues which area heavy respirers.

44
Q

What affect does carbon dioxide have on haemoglobin?

A

Carbon dioxide increases the acidity (carboxylic acid) which changes the structure of the haemoglobin molecule again.
This reduces the affinity the molecule has for oxygen and therefore the oxygen molecules are released.

45
Q

What is the order of blood flow through the heart?

A 
Vena cave
Right atrium
Right ventricle
Pulmonary artery to the lungs.
Pulmonary vein
Left atrium
Left ventricle
Aorta

Artioventricular valves- Atrium and ventricle
Semi-lunar valves- Ventricle and arteries.

46
Q

What is diastole, systole and what happens to blood flow?

A 
Diastole:
- Cardiac muscles relax
- Volume increases
- Pressure decreases
- Blood flows in from a higher pressure
Systole:
- Cardiac muscles contract
- Volume decreases
- Pressure increases
- Blood is forced out as there is a higher pressure
47
Q

What are the 3 stages in the cardiac cycle?

A

1) Atrial systole- blood is forced from the heart to the ventricles
2) Atrial diastole and ventricle systole- Blood is pushed from the ventricles to the arteries and the atria relax
3) Atrial and ventricle diastole- Blood is taken in via veins as the whole heart is relaxed.

48
Q

What is the equation for cardiac output?

A

Cardiac output = Stroke volume x Heart Rate

49
Q

What is the structure and function of the capillaries?

A

Structure:
- Small and build up a network of capillaries in most organs in the body.
- Walls are only 1 cell thick to allow exchange between the capillary.
Function:
- Supply tissue with components
- Remove waste from surrounding cells
- Exchange oxygen, carbon dioxide, water and salts between the blood and body tissue.

50
Q

What is the structure and function of the veins?

A 
Structure:
- Thin walls consisting of 3 layers
- Less muscle and elastic than arteries
- have valves preventing backflow
Function:
- Transports blood towards the heart
- Transports deoxygenated blood
- Low blood pressure due to the long journey the blood has undergone from the heart.
51
Q

What is the structure and function of the arteries?

A 
Structure:
- Very thick muscular walls
- Very strong elastic fibres able to stretch and recoil.
- Smooth muscle
- Narrow lumen
Function:
- Transports blood away from the heart
- Transports oxygenated blood only
- Pressure is high to conduct the blood.
52
Q

What is the structure and function of the arterioles?

A

Structure:
- Very little elastic tissue
- Thick layer of smooth muscle
Function:
- Reuglating blood flow from the arteries to capillaries by regulating resistance according to the metabolic needs.
- Can vasoconstrict ( increase contraction, decrease pressure)
- Can vasodilate (decrease contraction, increase blood flow)

53
Q

What is the structure and function of the venules?

A

Structure:
- very small veins
Function:
- Transport blood from the capillaries to the veins
- Release white blood cells at the site of infection

54
Q

Put in size order, Arteries,arterioles, veins, venules and capillaries

A 
Veins
Arteries
Arterioles
Venules
Capillaries
55
Q

What is tissue fluid?

A

The liquid part of blood which is forced out of the capillaries and washes over cells/tissues.

56
Q

Why does blood not back up between arterioles and capillaries? (or equivalent)

A

The number of capillaries and their total diameter of lumen is greater than the diameter of the arteriole and therefore the blood flow may be slower but the capacity is greater so blood doesn’t back up.

57
Q

How is tissue fluid removed from the blood?

A

As the blood travels from arterioles to capillaries, there is a high hydrostatic pressure (water pressure) which forces the liquid part and all solutes of the blood out of the capillaries through the cell walls of capillaries and through the pores between cells.
This results in tissue fluid bathing cells.

58
Q

Why is a slow rate of flow in the capillaries a good thing?

A

A slow rate of flow of blood is good as it allows more time for diffusion to take place.

59
Q

Why is a small diameter of lumen in the capillaries a good thing?

A

More red blood cells are pushed up/ in contact with the walls of the capillaries.
therefore there is an increased surface area for exchange. This is more efficient.

60
Q

How does tissue fluid get back into the capillaries?

A

Water potential in the capillaries is lower (more negative) than outside in the tissue fluid.
Due to plasma proteins lowering water potentail
Therefore water will move (osmosis) from the tissue fluid and back into the capillaries.

61
Q

What happens to water which does not diffuse back into the capillaries?

A

Water which fails to move back into the capillaries will drain into the lymphatic capillaries and be taken back to the heart via lacteals and the lymphatic system.

62
Q

How does water move into the root hair cells of a plant?

A

Nitrates move into the cells roots by active transport.
This lowers the water potential within the root hair cell so there is a greater water potential outside the cell allowing the water to move into the hair cell by osmosis.

63
Q

What are the 3 ways water takes to get the xylem from the root hair cells?

A

Symplast pathway- water through cytoplasm
Vacuolar pathway- Water through vacuoles
Apoplast pathway- Through cell walls until it hits the casparian strip.

64
Q

What is the plasmodesmata?

A

Corridors for water to pass through from the root hair cells to the xylem.

65
Q

What is the Casparian strip?

A

A strip made from a waxy substance which diverts the water from the cell walls to the plasmodesmata.
Made of suberin.

66
Q

How doe water move into the xylem?

A

Active transport of ions into the xylem by the pericycle cells.
This lowers the water potential so water moves in via osmosis.

67
Q

How does water move up through the xylem?

A

Water moves up the xylem column via adhesion and cohesion. Due to there being a higher pressure at the bottom of the xylem and low pressure at the top.

68
Q

What factors affect transpiration rate?

A

High rate- Dry/windy/hot

Low rate- Wet/rain/still air/cold.

69
Q

What is a potometer used for?

A

Measuring the rate of transpiration.

70
Q

Define Translocation

A

The movement of amino acids, sugars and organic molecules through a plant.

71
Q

what is the role of the xylem and phloem?

A

Xylem- Moves water and nutrients ions in plants upwards.

Phloem- Moves sucrose/organic nutrients and amino acids in plants (bidirectional)

72
Q

What are sources and sinks?

A

Source- where sucrose is produced

Sink- Where sucrose is removed/ the cells which require sucrose.

73
Q

Give examples of sources and sinks in plants

A 
Source:
- Leaves
- Roots
Sinks:
- Roots
- growing regions.
74
Q

What is the mass flow hypothesis?

A

The idea that sugar is made via photosynthesis and then travels around the plant through the phloem.

75
Q

What is the structure of the phloem/companion cell?

A 
Phloem:
- Sieve plates
- living tissue
Companion cell:
- Lots of mitochondria
- Large nuclei.
76
Q

What is active loading?

A

Sucrose moving from sources to the phloem.

77
Q

Explain the process of active loading.

A

1) H+ ions actively transported out of the companion cell (but not into phloem)
2) H+ ions with sucrose diffuse back into companion cell via co-transport proteins.
3) Increased sucrose concentration allows diffusion out of the companion cell and into the phloem through plasmodesmata.
4) Increased sucrose concentration in phloem and lower water potential so water moves into phloem via osmosis. (high hydrostatic pressure)
5) Mass flow is causesd.

78
Q

How is sucrose removed from the phloem at sinks?

A

1) After water is in the phloem a hydrostatic pressure is generated.
2) Source- high hydrostatic pressure, Sink- low hydrostatic pressure, gives a gradient for sucrose to flow down.
3) Sucrose diffuse/actively transports out of the phloem which increases the water potential.
4) Water flows out via osmosis keeping the hydrostatic pressure low and maintaining a gradient.

A-levels (23 decks)

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