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Biology > TOPIC 3 exchange of substances > Flashcards

TOPIC 3 exchange of substances Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

How does an organisms size relate to their surface area to volume ratio

A

the larger the organism, the lower the surface area to volume ratio

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2
Q

how does an organisms surface area to volume ratio relate to their metabolic rate

A

the smaller the surface area to volume ratio, the higher the metabolic rate

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3
Q

how might a large organism adapt to compensate for its small surface area to volume ratio

A

changes that increase surface area:
• folding
• body parts become larger e.g elephants ears

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4
Q

why do multicellular organisms require specialised gas exchange surfaces

A

their smaller surface area to volume ratio means the distance that needs to be crossed is larger and substances cannot easily enter the cells as in a single celled organism

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5
Q

name 3 features of an efficient gas exchange surface

A
  1. large surface area
  2. thin/ short diffusion distance
  3. steep concentration gradient, maintained by blood supply or ventilation
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6
Q

why cants insects use their bodies as an exchange surface

A

they have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water

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7
Q

name and describe 3 main parts of an insects gas transport system

A
  1. spiracles = holes on the body’s surface which may be opened or closed by a valve for gas or water exchange
  2. trachea = large tubes extending through all body tissues, supported by rings to prevent collapse
  3. tracheoles = smaller branches dividing off the tracheae
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8
Q

explain the process of gas exchange in insects

A

• gases move in and out of the tracheae through the spiracles

• a diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out

• contraction of muscles in the tracheae allows mass movement of air in and out

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9
Q

why cant fish use their bodies as an exchange surface

A

they have a waterproof , impermeable outer membrane and a small surface area to volume
ratio

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10
Q

name and describe 2 main features of a fishes gas transport system

A
  1. gills = located within the body, supported by arches which are multiple projections of gill filaments
  2. lamellae = at right angles to the gill filaments
    give an increased surface area
    blood and water flow across them in opposite directions (countercurrent exchange systems)
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11
Q

explain the process of gas exchange in a fish

A

• the fish opens its mouth to enable water to flow in, then closes its mouth to increase pressure

• the water passes over the lamellae, and the oxygen diffuses into the blood stream

• waste CO2 diffuses into the water and flows back out of the gills

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12
Q

how does the countercurrent exchange system maximise oxygen absorption by the fish

A

maintains a steep concentration gradient , as water is always next to blood of a lower oxygen concentration

keeps rate of diffusion constant along whole length of of gill enabling 80% of available oxygen to be absorbed

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13
Q

name and describe 3 adaptations of a leaf that allow efficient gas exchange

A
  1. thin and flat to provide short diffusion pathway and larger surface area to volume ratio
  2. many minute pores in the underside of the leaf (stomata) allow gases to easily enter
  3. air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis
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14
Q

how do plants limit their water loss while still allowing gases to be exchanged

A

stomata regulated by guard cells which allow them to open and close as needed

most stay closed to prevent water loss while some open to let oxygen in

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15
Q

describe the pathway taken by air as it enters the mammalian gas exchange system

A

nasal cavity —> trachea —> bronchi -> bronchioles —> alveoli

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16
Q

describe the function of the nasal cavity in the mammalian gas exchange system

A

a good blood supply warms and moistens the air entering the lungs

goblet cells in the membrane secrete mucus which traps dust and bacteria

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17
Q

describe the trachea and its function in the mammalian gas exchange system

A

• wide tube supported by C shaped cartilage to keep the air passage open during pressure changes

• lined by ciliated epithelium cells which move mucus towards the throat to be swallowed,
preventing lung infections

• carries air to the bronchi

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18
Q

describe the bronchi and their function in the mammalian gas exchange system

A
  • like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells
  • however they are narrower and there are 2 of them, one for each lung
  • allow passage of air into the bronchioles
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19
Q

describe the bronchioles and their function in the mammalian gas exchange system

A
  • narrower than the bronchi
  • do not need to be kept open by cartilage, therefore mostly only have muscle and elastic fibres so that they can contract and relax easily during ventilation
  • allow passage of air into alveoli
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20
Q

describe the alveoli and their function in the mammalian gas exchange system

A
  • mini air sacs , lines with epithelium cells, sites of gas exchange
  • walls only one cell thick, covered with a network of capillaries, 300 million in each lung, all of which facilitates gas diffusion
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21
Q

explain the process of expiration and the changes that occur throughout the thorax

A
  • external intercostal muscles relax, bringing the ribs down and in
  • diaphragm relaxes and domes upwards
  • volume of the thorax decreases
  • air pressure inside the lungs is therefore higher than the air pressure outside, so air moves out to rebalance
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22
Q

define tidal volume

A

the volume of air we breathe in and out during each breath at rest

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23
Q

define breathing rate

A

the number of breaths we take per minute

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24
Q

how do you calculate pulmonary ventilation rate

A

tidal volume x breathing rate

measured using a spirometer

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25
Q

define digestion

A

the hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes

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26
Q

which enzymes are involved in carbohydrate digestion and where are they found

A
  • amylase in mouth
  • maltase, sucrase , lactase in membrane of small intestine
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27
Q

what are the substrates and products of the carbohydrate digestive enzymes

A

amalyse –> starch into smaller polysaccharides

maltase –> maltose into 2x glucose

sucrase –> sucrose into glucose and fructose

lactase –> lactose into glucose and galactose

28
Q

where are lipids digested

A

small intestine

29
Q

what needs to happen before lipids can be digested

A

they must be emulsified by bile salts produced by the liver

this breaks down large fat molecules into smaller, soluble molecules called micelles, increasing surface area

30
Q

how are lipids digested

A

lipase hydrolyses ester bond between the monoglycerides and fatty acids

31
Q

which enzymes are involved in protein digestion and what are their roles

A
  • endopeptidases = break between specific amino acids in the middle of a polypeptide
  • exopeptidases = break between specific amino acids at the end of a polypeptide
  • dipeptidases = break dipeptides into amino acids
32
Q

how are certain molecules absorbed into the ileum despite a negative concentration gradient

A

through co- transport

33
Q

which molecules require co-transport

A

amino acids + monosaccharides

34
Q

explain how sodium ions are involved in co-transport

A
  • sodium ions are actively transported out of the cell intp the lumen, creating a diffusion gradient
  • nutrients are then taken up into the cells along with sodium ions
35
Q

why do fatty acids and monoglycerides no require co-transport

A

the molecules are non polar

meaning they can easily diffuse across the membrane of epithelial cells

36
Q

describe the structure of haemoglobin

A

globular, water soluble

consists of 4 polypeptide chains

each carrying a haem group (quaternary structure)

37
Q

describe the role of haemoglobin

A

present in red blood cells

oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues

38
Q

names 3 factors affecting oxygen-haemoglobin binding

A
  1. partial pressure/ concentration of oxygen
  2. partial pressure/ concentration of carbon dioxide
  3. saturation of haemoglobin with oxygen
39
Q

how does partial pressure of oxygen affect oxygen-haemoglobin binding

A

as partial pressure of oxygen increases , the affinity of haemoglobin for oxygen also increases - so oxygen binds tightly to haemoglobin

when partial pressure is low, oxygen is release from haemoglobin

40
Q

how does partial pressure of carbon dioxide affect oxygen- haemoglobin binding

A

as pp of co2 increases, conditions become acidic causing haemoglobin to change shape

the affinity of haemoglobin for oxygen decreases

so oxygen is released from haemoglobin

known as the BOHR effect

41
Q

how does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding

A

it is hard for the first oxygen molecule to bind
- once it does, it changes the shape to make it easier for the 2nd and 3rd molecules to bind (positive cooperativity)

  • it is then slightly harder for the 4th oxygen molecule to bind because there is a low chance at finding a binding site
42
Q

explain why oxygen binds to haemoglobin in the lungs

A
  • partial pressure of oxygen is high
  • low concentration of co2 in the lungs to affinity is high
  • positive cooperativity
43
Q

explain why oxygen is released from haemoglobin in respiring tissue

A
  • partial pressure of oxygen is low
  • high concentration of carbon dioxide in respiring tissues, so affinity decreases
44
Q

what do oxyhaemoglobin dissociation curves show

A

curves further to the left show the haemoglobin has a higher affinity for oxygen

45
Q

how does co2 affect the position of an oxyhaemoglobin curve

A

curve shifts to the right because haemoglobins affinity for oxygen has decreased

46
Q

name some common features of a mammalian circulatory system

A
  1. suitable medium for transport
  2. means of moving the medium and maintaining pressure throughout the body
  3. means of controlling flow so it remains unidirectional, such as valves
47
Q

relate the structures of the heart chambers to their function

A
  • atria = thin walled and elastic, so they can stretch when filled with blood
  • ventricles = thick muscular wall pump blood under high pressure.
    the left ventricle is thicker than the right because it has to pump blood all the way around the body
48
Q

relate the structure of the vessels to their function

A
  • arteries = thick walls to handle high pressure w/o tearing
    muscular and elastic to control blood flow
  • veins = thin walls due to lower pressure
    valves so blood doesnt flow backwards
    less muscular and elastic tissue as they do not have to control blood flow
49
Q

why are 2 pumps needed instead of 1

A

to maintain blood pressure around the whole body.

when blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body.

therefore it is returned to the heart to increase the pressure

50
Q

what happens during cardiac diastole

A

the heart is relaxed

blood enters the atria, increasing the pressure and pushing open the atrioventricular valves

this allows blood to flow into the ventricles

pressure in the heat is lower than in the arteries, so semilunar valves remain closed

51
Q

what happens during atrial systole

A

the atria contracts, pushing any remaining blood into the ventricles

52
Q

what happens during ventricular systole

A

the ventricles contract

the pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves

blood flows into the arteries

53
Q

names the nodes involved in heart contraction and where they are situated

A
  • Sinoatrial node = wall of right atrium
  • atrioventricular node = in between the 2 atria
54
Q

define myogenic

A

the hearts contraction is initiated from within the muscle itself, rather than by nerve impulses

55
Q

explain how the heart contracts

A

-sinoatrial node initiates and spreads impulses across the atria so they contract

  • atrioventricular node receives, delays and then conveys the impulse down the bundle of his
  • impulse travels into the purkinje fibres which branch across the ventricles, so they contract from the bottom up
56
Q

why does the impulse need to be delayed

A

if the impulse spread straight from the atria into the ventricles, there would not be enough time for all of the blood to pass through and for the valves to close

57
Q

how is the structure of capillaries suited to their function

A
  • walls are only 1 cell thick; short diffusion pathway
  • very narrow, so can permeate tissues and red blood cells can lie flat against the wall , effectively delivering oxygen to tissues
  • numerous and highly branched , providing a large surface area
58
Q

define tissue fluid

A

a watery substance containing glucose, amino acids, oxygen and other nutrients

it supplies these to the cells, while also removing any waste material

59
Q

how is tissue fluid formed

A

as blood is pumped through increasingly small vessels, this creates hydrostatic pressure which forces fluid out of the capillaries.

it bathes the cells, and then returns to the capillaries when the hydrostatic pressure is low enough

60
Q

how is water transported in plants

A

through xylem vessels ; long, continuous columns that also provide structural support to the stem

61
Q

explain cohesion- tension theory

A

water molecules from hydrogen bonds with each other , causing them to stick together

the surface tension of the water also creates this sticking effect.
therefore, as water is lost through transpiration, more can be drawn up the stem

62
Q

what are the 3 components of the phloem vessel

A
  • sieve tube elements = form a tube to transport sucrose in the dissolved from of sap
  • companion cells = involved in ATP production for active loading of sucrose into sieve tubes
  • plasmodesmata = gaps between cell walls where the cytoplasm links, allowing substances to flow
63
Q

name the process where organic materials are transported around the plant

A

translocation

64
Q

how does sucrose in the leaf move into the phloem

A

sucrose enters companion cells of the phloem vessels by active loading, which uses ATP and a diffusion gradient of hydrogen ions

sucrose then diffuses from companion cells into the sieve tube elements through the plasmodesmata

65
Q
A

Biology (6 decks)

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