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Biology Paper 1 Bio notes > Section 3: Gas Exchange + Digestion and Absorption > Flashcards

Section 3: Gas Exchange + Digestion and Absorption Flashcards

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1
Q

What is the relationship between SA:V and metabolic rate?

A
  • Rate of heat loss per unit mass increases as SA: V increases - smaller animals
  • So they need a higher metabolic rate/ faster respiration
  • To generate enough heat to maintain a constant body temp
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2
Q

What is the relationship between the size of the organism and its SA: V?

A
  • Smaller organisms have a high SA:V
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3
Q

What are the adaptations of gas exchange across the body surface of a single-celled organism?

A
  • Thin, flat shape
    • Large SA: V
    • Short diffusion pathway
    • For rapid diffusion e.g oxygen/ carbon dioxide
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4
Q

How does gas exchange occur in an insect?

A
  • Air moves through spiracles on the surface of the insect
  • Air moves through tracheae
  • Gas exchange at tracheoles directly to/from cells
    • Oxygen diffuses down conc. gradient to respiring cells
    • CO2 diffuses down conc gradient from respiring cells
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5
Q

What are the adaptations of the insect’s gas exchange system?

A
  • Lots of thin, branched tracheoles - short diffusion pathway
  • Large surface area - rapid diffusion
  • Abdominal movements - increase the amount of O2 entering - maintains greater conc gradient for diffusion
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6
Q

How does gas exchange occur in a fish?

A
  • Counter current flow
  • Blood flows through lamellae and water flows over lamellae in opposite directions
  • Always a higher conc of O2 near blood - hence a conc gradient is maintained along the whole length of lamellae
  • Maximising diffusion of oxygen
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7
Q

What are the adaptations of the gas exchange of a fish?

A
  • Each gill is made of lots of gill filaments which are covered in many lamellae - provide a large surface area
  • Vast network of capillaries on lamellae - remove oxygen to maintain a conc gradient
  • Thin/flattened epithelium - shorter diffusion pathway between water and blood
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8
Q

What is the process of gas exchange in plants?

A
  • Co2/ oxygen diffuses through the stomata
  • Stomata opened by guard cells
  • CO2 / oxygen diffuse into mesophyll layer into air spaces
  • CO2/ oxygen diffuses down conc gradient
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9
Q

What are the adaptations of the gas exchange system in plants?

A
  • Lots of stomata that are close together
    • Large SA for gas exchange
  • Interconnecting air space in mesophyll layers
  • Mesophyll cells have a large surface area
  • Thin - short diffusion pathway
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10
Q

What are the adaptations in xerophytic plants?

A
  • Thick waxy cuticle - increases diffusion distance
  • Stomata in pits/grooves/ rolled leaves/ hairs - trap water vapour - WP gradient decreased - less evaporation
  • Spindles/ needles - reduces SA:Vol
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11
Q

What is the order of passage in the gas exchange in humans?

A
  • Mouth/ nose
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
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12
Q

How does gas exchange occur in the alveoli with oxygen?

A
  • Oxygen diffuses from alveoli
  • Down its concentration gradient
  • Across the alveolar epithelium
  • Across the capillary endothelium
  • Into the blood
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13
Q

How does gas exchange occur in the alveoli with carbon dioxide?

A
  • Carbon dioxide diffuses from capillary
  • Down its concentration gradient
  • Across the capillary endothelium
  • Across the alveolar epithelium
  • Into the alveoli
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14
Q

Why is ventilation needed?

A
  • Maintains an oxygen gradient
    • Brings in air containing higher concentration of oxygen
    • Removes air with lower concentration of oxygen
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15
Q

What are the essential features of the alveolar epithelium which allows gas exchange to occur?

A
  • Squamous epithelium - 1 cell thick
  • Large surface area to volume ratio
  • Permeable
  • Good blood supply from network of capillaries - maintains conc gradient
  • Elastic tissue - recoil
  • Surfactant
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16
Q

How are the lungs adapted for efficient/ rapid gas exchange?

A
  • Many alveoli/ capillaries
  • Alveoli/ capillary walls are thin
  • Ventilation/ circulation
17
Q

What is the mechanism of breathing in?

A
  • External intercostal muscles contract, internal intercostal muscles relax
  • Ribcage moves up and out
  • Diaphragm muscles contract - move down
  • Increasing volume
  • Decreasing pressure
  • Atmospheric pressure higher than pressure in lungs
  • Air moves down pressure gradient into lungs
18
Q

What is the mechanism of Breathing out?

A
  • Internal intercostal muscles contract, external intercostal muscles relax
  • Moving rib cage down and in
  • Diaphragm relaxes, move upwards
  • Decreasing volume
  • Increasing pressure
  • Atmospheric pressure lower than pressure in lungs
  • Air moves down pressure gradient out of lungs
19
Q

What is tidal volume?

A
  • Volume of air in each breath
20
Q

What is Ventilation rate?

A
  • Number of breaths per minute
21
Q

What is Forced Expiratory volume (FEV)?

A
  • Maximum volume of air that can be breathed out in 1 second
22
Q

What is Forced Vital capacity (FVC)?

A
  • Maximum volume of air possible to breathe forcefully out of lungs after a deep breath in
23
Q

What is Fibrosis and what is its effect?

A
  • Scar tissue in lungs - scar tissue is thicker and less elastic than normal
  • Diffusion distance increased - rate of diffusion of decreased
  • Lungs can expand and recoil less - can’t hold as much air - reduced tidal volume/ reduced forced vital capacity
24
Q

What is asthma and what is its effect?

A
  • Asthma - inflamed bronchi
  • Asthma attack: smooth muscle lining bronchioles contracts
  • Constriction of airways - narrow diameter - airflow in/ out of lungs reduced - FEV reduced
  • Less oxygen enters alveoli/ blood
25
Q

What happens when there is a reduced rate of gas exchange in the alveoli?

A
  • Less oxygen diffuses into blood
  • Cells receive less oxygen
  • Rate of aerobic reduced
  • Less energy released
  • Fatigue/ weakness
26
Q

Why are a large biological molecules hydrolysed into smaller molecules?

A
  • Large biological molecules in food e.g starch/ proteins too big to be absorbed across cell membranes
  • Digestion breaks them into smaller molecules e.g glucose/ amino acids - absorbed from the gut to the blood
27
Q

How is starch hydrolysed?

A
  • Amylase hydrolyses starch to maltose
    • Amylase produced by salivary glands, released into mouth
    • Amylase produced by pancreas, released into small intestine
  • Membrane bound maltase hydrolyse maltose to glucose by hydrolyses glycosidic bond
28
Q

How are disaccharides digested?

A
  • Membrane bound disaccharides e.g maltose, sucrose, lactase hydrolyse a disaccharide into 2 monosaccharide
  • Maltase - glucose + glucose
  • Sucrase - fructose + glucose
  • Lactase - galactose + glucose
  • Hydrolyses a glycosidic bond
29
Q

How are lipids digested in mammals?

A
  • Bile salts produced by the liver
  • Bile salts emulsify lipid to smaller lipid droplets - increasing surface area of lipids and speeds up action of lipases
  • Lipase made in the pancreas, released to small intestine
  • Lipase hydrolyses lipids - monoglycerides + fatty acids
  • Breaking ester bond
  • Monoglycerides, fatty acids and bile salts stick together to form micelles
30
Q

How are lipids digested in mammals?

A
  • Bile salts produced by the liver
  • Bile salts emulsify lipid to smaller lipid droplets - increasing surface area of lipids and speeds up action of lipases
  • Lipase made in the pancreas, released to small intestine
  • Lipase hydrolyses lipids - monoglycerides + fatty acids
  • Breaking ester bond
  • Monoglycerides, fatty acids and bile salts stick together to form micelles
31
Q

How are proteins digested in mammals?

A
  • Endopeptidases -
    • Hydrolyse peptide bonds within a protein/ between amino acids in the central region. 2 smaller peptides
  • Exopeptidases -
    • Hydrolyse peptide bonds at the ends of the protein molecules. Removing a single amino acid
  • Dipeptidases -
    • Often membrane bound to ileum. Hydrolyse peptide bond between dipeptide.
32
Q

Exam Question: Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own (2)

A
  • Endopeptidases hydrolyse internal peptide bonds OR exopeptidases remove amino acids/ hydrolyse bonds at ends
  • More ends or increased surface area
33
Q

How are glucose and amino acids absorbed?

A
  1. Sodium ions are actively transported out of the epithelial cells lining the ileum, into the blood by the sodium potassium pump
  2. This creates a concentration gradient (higher in the lumen than ileum)
  3. Sodium ions and glucose move by facilitated diffusion using a co-transporter protein
  4. This creates a concentration gradient of glucose - higher in epithelial than blood
  5. Glucose moves out of cell into blood by facilitated diffusion through a protein channel
34
Q

Exam Question: The addition of a respiratory inhibitor stops the absorption of amino acids. Why?

A
  • No/ less ATP produced
  • Sodium ions not moved out of cell
  • No diffusion gradient for sodium to move into cell with amino acid
35
Q

How are lipids absorbed?

A
  • Monoglycerides and fatty acids diffuse out of micelles into epithelial cell - because they are lipid soluble
  • They recombine into triglycerides which aggregate into globules
  • Globules coated with proteins to form chylomicrons
  • Leave via exocytosis and enter lymphatic vessels
  • Return to blood circulation

Biology Paper 1 Bio notes (9 decks)

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