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Biology > TOPIC 3 exchange of substances > Flashcards

TOPIC 3 exchange of substances 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
define digestion
the hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes
26
which enzymes are involved in carbohydrate digestion and where are they found
- amylase in mouth - maltase, sucrase , lactase in membrane of small intestine
27
what are the substrates and products of the carbohydrate digestive enzymes
amalyse --> starch into smaller polysaccharides maltase --> maltose into 2x glucose sucrase --> sucrose into glucose and fructose lactase --> lactose into glucose and galactose
28
where are lipids digested
small intestine
29
what needs to happen before lipids can be digested
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
how are lipids digested
lipase hydrolyses ester bond between the monoglycerides and fatty acids
31
which enzymes are involved in protein digestion and what are their roles
- 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
how are certain molecules absorbed into the ileum despite a negative concentration gradient
through co- transport
33
which molecules require co-transport
amino acids + monosaccharides
34
explain how sodium ions are involved in co-transport
- 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
why do fatty acids and monoglycerides no require co-transport
the molecules are non polar meaning they can easily diffuse across the membrane of epithelial cells
36
describe the structure of haemoglobin
globular, water soluble consists of 4 polypeptide chains each carrying a haem group (quaternary structure)
37
describe the role of haemoglobin
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
names 3 factors affecting oxygen-haemoglobin binding
1. partial pressure/ concentration of oxygen 2. partial pressure/ concentration of carbon dioxide 3. saturation of haemoglobin with oxygen
39
how does partial pressure of oxygen affect oxygen-haemoglobin binding
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
how does partial pressure of carbon dioxide affect oxygen- haemoglobin binding
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
how does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding
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
explain why oxygen binds to haemoglobin in the lungs
- partial pressure of oxygen is high - low concentration of co2 in the lungs to affinity is high - positive cooperativity
43
explain why oxygen is released from haemoglobin in respiring tissue
- partial pressure of oxygen is low - high concentration of carbon dioxide in respiring tissues, so affinity decreases
44
what do oxyhaemoglobin dissociation curves show
curves further to the left show the haemoglobin has a higher affinity for oxygen
45
how does co2 affect the position of an oxyhaemoglobin curve
curve shifts to the right because haemoglobins affinity for oxygen has decreased
46
name some common features of a mammalian circulatory system
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
relate the structures of the heart chambers to their function
- 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
relate the structure of the vessels to their function
- 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
why are 2 pumps needed instead of 1
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
what happens during cardiac diastole
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
what happens during atrial systole
the atria contracts, pushing any remaining blood into the ventricles
52
what happens during ventricular systole
the ventricles contract the pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves blood flows into the arteries
53
names the nodes involved in heart contraction and where they are situated
- Sinoatrial node = wall of right atrium - atrioventricular node = in between the 2 atria
54
define myogenic
the hearts contraction is initiated from within the muscle itself, rather than by nerve impulses
55
explain how the heart contracts
-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
why does the impulse need to be delayed
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
how is the structure of capillaries suited to their function
- 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
define tissue fluid
a watery substance containing glucose, amino acids, oxygen and other nutrients it supplies these to the cells, while also removing any waste material
59
how is tissue fluid formed
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
how is water transported in plants
through xylem vessels ; long, continuous columns that also provide structural support to the stem
61
explain cohesion- tension theory
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
what are the 3 components of the phloem vessel
- 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
name the process where organic materials are transported around the plant
translocation
64
how does sucrose in the leaf move into the phloem
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

Biology (6 decks)

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