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Biology AS > Gas Exchange > Flashcards

Gas Exchange Flashcards

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1
Q

Single Celled Organisms

A
  • Absorb and release gases by diffusion
  • Through their outer surface
  • They have a large surface area, thin surface and short diffusion pathway (don’t need a gas exchange system)
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2
Q

Multicellular Organisms

A
  • Some cells are too far from the outer environment and deep within the body
  • Large organisms have a low surface area to volume ratio
  • So they need specialised exchange systems to transport substances to and from individual cells via a mass transport
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3
Q

Body Size & Rate Of Heat Loss

A
  • Rate of heat loss depends on surface area
  • Organisms with large volume to surface area ratio (e.g. Hippo) don’t lose body heat easily
  • Organisms with a small volume to surface area ratio (e.g. Mouse) easily lose body heat
  • Small organisms require a high metabolic rate to generate enough heat to stay warm
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4
Q

Body Shape & Environment

A
  • Animals with a compact shape have a small surface area to volume ratio (don’t easily lose heat)
  • Compact shapes are beneficial in colder environments
  • Animals with a less compact shape have a larger surface area to volume ratio (lose heat easily)
  • Less compact shapes are beneficial in hotter environments
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5
Q

Insects Gas Exchange

A
  • Use tracheae (small air-filled pipes)
  • Air moves into the tracheae
  • Through pores on the surface called spiracles
  • Oxygen travels down its concentration gradient towards respiring cells
  • The tracheae branch off into smaller tracheoles (these are thin, have permeable walls and go to individual cells)
  • This allows oxygen to diffuse directly into the respiring cells
  • Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles and is released into the atmosphere
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6
Q

Rhythmic Abdominal Movements

A
  • Rhythmic contractions of abdominal muscles compress the air sacs
  • This helps increase ventilation
  • Insects are then able to maintain a concentration gradient during vigorous activity (e.g. flying)
  • This increases the rate of gas exchange when the insect is more active and has increased metabolic demand
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7
Q

Insects Water Loss

A
  • When they’re losing too much water they close their spiracles using muscles
  • They have a waterproof waxy cuticle over their body
  • They have small hairs around their spiracles
  • These all reduce evaporation
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8
Q

Fish Adaptations For Gas Exchange

A
  • There’s a lower concentration of oxygen in water than air
  • Thin epithelium for a short pathway
  • Large surface area from gill filaments and their lamellae projections
  • Good blood supply to maintain a concentration gradient
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9
Q

Fish Ventilation

A
  • Fish opens it’s mouth and lowers buccal floor
  • This increases the volume and decreased pressure in the mouth
  • Water rushes into the mouth
  • Fish closes its mouth and raises buccal floor
  • This decreases volume and increases pressure in the mouth
  • Water is forced over the gills and out of the operculum
  • Gas exchange happens in the gills
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10
Q

Fish Counter-Current System

A
  • Blood flows through the lamellae in one direction
  • Water flows over the lamellae in the opposite direction
  • This counter-current system maintains a large concentration gradient between the water and blood throughout the length of the gill
  • The blood always passes water with a higher oxygen concentration
  • This means as much oxygen as possible diffuses from the water into the blood
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11
Q

Fish Gas Exchange Structure

A
  • Each gill is made of thin gill filaments
  • These give it a big surface area
  • The gill filaments are covered in lots of tiny structures called lamellae
  • These increase the surface area even more
  • Lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
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12
Q

Waxy Cuticle

A
  • A waxy layer that reduced water loss from the surface of the leaf
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13
Q

Upper Epidermis

A
  • Protects internal tissue from damage and bacterial or fungal invasion
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14
Q

Palisade Mesophyll

A
  • Full of chloroplasts with chlorophyll

- To absorb light for photosynthesis

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15
Q

Spongy Mesophyll

A
  • Large, moist air spaces that are loosely packed

- Help with the gas exchange diffusion

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16
Q

Vascular Bundle

A
  • Has the xylem and phloem transport tubes inside
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17
Q

Xylem

A
  • Carries water and mineral salts upwards
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18
Q

Phloem

A
  • Transports organic substances e.g. glucose in both directions
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19
Q

Stoma

A
  • Pore in the bottom of the leaf
  • Where gases move in and out by diffusion
  • This is made up of two guard cells
20
Q

Guard Cells

A
  • Allow stoma to open and close
21
Q

Lower Epidermis

A
  • Contains stoma/stomata

- Thinner than the upper one

22
Q

Plants Water Loss

A
  • When guard cells are flaccid and lack water the stoma closes
  • When guard cells are turgid and full of water the stoma opens
23
Q

Plants & Potassium Ions

A
  • Potassium pumps using ATP actively transport potassium ions
  • From epidermal cells to guard cells
  • Potassium ions are moved into the guard cells to lower water potential
  • Water can then move into the guard cells
  • Active transport is used; there is the same concentration of these ions in guard cells and epidermal cells
24
Q

Xerophytes & Water Loss Adaptations

A
  • E.g. Mariam grass, live in hot and dry environments
  • Thick waxy water proof cuticles reduce evaporation
  • Layer of hairs on the epidermis trap moist air around the stoma (increases humidity, decreases water potential gradient, less diffusion occurs)
  • Curled leaves with stoma inside reduces area exposed to windy conditions (increases humidity, decreases water potential gradient, less diffusion occurs)
  • Sunken stoma trap moist air (increases humidity, decreases water potential gradient, less diffusion occurs)
25
Q

Humans Gas Exchange System

A
  • Lungs are a pair of lobed structures
  • As you breathe in air enters the trachea (supported by cartilage to prevent it from falling)
  • The trachea splits into two bronchi
  • One bronchus leads to each lung and they have mucus to trap particles and cilia to move it towards the throat
  • Each bronchus branches off into smaller tubes called bronchioles
  • The bronchioles end in smaller air sacs called alveoli (where gas is exchanged)
26
Q

Alveoli Adaptations For Gas Exchange (Humans)

A
  • Thin exchange surface (alveolar epithelium is one cell thick; short diffusion pathway)
  • Large surface area (many alveoli present)
  • Good blood supply (surrounded by a network of capillaries)
27
Q

Gas Exchange In The Alveoli (Humans)

A
  • Oxygen from the air moves down the trachea, bronchi and bronchioles into the alveoli
  • Oxygen then diffuses across the alveolar epithelium and capillary endothelium into the haemoglobin in the blood
  • Carbon dioxide diffuses into the alveoli from the blood and is breathed out
  • Alveoli have collagen fibers which are elastic and allow them to return to their original shape after expansion
28
Q

Inspiration (Humans)

A
  • External intercostal and diaphragm muscles contract
  • Ribcage moves upwards and outwards
  • Diaphragm flattens
  • Volume of the thoracic cavity increases (where lungs are) causing air pressure in the lungs to decrease
  • Air flows from trachea (area of higher pressure) to lungs (area of lower pressure)
  • Active process; requires energy
29
Q

Expiration (Humans)

A
  • External intercostal and diaphragm muscles relax
  • Ribcage moves downwards and inwards
  • Diaphragm to becomes curved again
  • Volume of thoracic cavity decreases causing air pressure in the lungs to increase
  • Air is forced down the pressure gradient and out of the lungs
  • Passive process; doesn’t require energy
30
Q

Forced Expiration (Humans)

A
  • E.g. blowing out birthday candles
  • External intercostal muscles relax
  • Internal intercostal muscles contract
  • Ribcage is pulled downwards and inwards
  • Air is forced out of the lungs
  • The movement of the two sets of intercostal muscles is antagonistic (opposing)
31
Q

Pulmonary Ventilation

A
  • Actual volume of air that is moved into the lungs during one minute (dm3min-1)

= Tidal volume X Ventilation rate

32
Q

Tidal Volume

A
  • Volume of air in each breath (dm3)
33
Q

Ventilation Rate

A
  • The number of breaths per minute (min-1)
34
Q

Digestion

A
  • The hydrolysis of large/insoluble substances into smaller soluble substances
35
Q

Digestive process

A
  • Mouth: chemical and mechanical digestion, amylase is released and a bolus of food forms
  • Esophagus: bolus is pushed to stomach by peristalsis tightening and relaxation of muscles
  • Stomach: food is temporarily stored there and broken down by HCL
  • Duodenum: first part of the small intestine food is further broken down by pancreatic enzymes and bile from the liver (stored in gall bladder)
  • Ileum: last part of small intestine, inner walls fold into villi (provide large surface area) to absorb products of digestion into bloodstream
  • Large intestine: absorbs water secreted from digestive glands
  • Rectum: feces are stored before being removed via anus by process called egestion
36
Q

Digestive Enzymes

A
  • Digestive enzymes are used to break down biological molecules in food
  • Via hydrolysis (addition of water to the bond)
37
Q

Carbohydrates & Their Digestive Enzyme

A
  • Amylase
  • Made in salivary glands and pancreas, released into small intestine
  • It catalyses conversion of starch into maltose
  • By hydrolysis of the glycosidic bonds in starch
38
Q

Membrane-bound Disaccharides

A
  • Enzymes
  • Attached to the cell membrane of epithelial lining the ileum
  • Help to breakdown disaccharides into monosaccharides
39
Q

Lipids & Their Digestive Enzyme

A
  • Lipase
  • Made in the pancreas and work in the small intestine
  • It catalyses the breakdown of lipids into glycerides and fatty acids
  • By hydrolysis of ester bonds in lipids
  • Bile salts are produced by the liver and emulsify lipids, forming droplets
  • Monoglycerides and fatty acids stick with bile salts to form tiny structures called micelles
40
Q

Protein Digestion

A
  • Proteins are large molecules hydrolysed by a group of enzymes called peptidases into amino acids
41
Q

Endopeptidases

A
  • Hydrolyse peptide bonds within a protein centre

- Break down bonds from the inside

42
Q

Exopeptidases

A
  • Hydrolyse peptide bonds at the ends of the protein molecule
  • Progressively remove single amino acids
43
Q

Dipeptidases

A
  • A type of exopeptidases
  • Work specifically on dipeptides
  • Act to separate two amino acids
  • By hydrolysing peptide bonds between dipeptides
44
Q

Monosaccharides (Product Of Digestion)

A
  • Glucose is absorbed by active transport with sodium ions via a co-transporter protein
  • Galactose is absorbed by active transport with sodium ions via a co-transporter protein
  • Fructose is absorbed via facilitated diffusion through a transporter protein
45
Q

Amino Acids (Product Of Digestion)

A
  • Sodium are actively transported out of the epithelial cells into the ileum
  • They diffuse back into the epithelial cells through sodium-dependent transporter proteins
  • These proteins are found in the epithelial membranes carrying the amino acids with them
46
Q

Triglycerides (Product Of Digestion)

A
  • Monoglycerides and fatty acids are emulsified by bile salts to from micelles
  • Micelles come into contact with epithelial cells
  • These cells break micelles down to release monoglycerides and fatty acids
  • They enter epithelial cells and are transported to the endoplasmic reticulum to recombine into triglycerides
  • Which move to the Golgi apparatus to associate with cholesterol and lipoproteins (to form chylomicrons)
  • Chylomicrons are special structures adapted for transporting lipids and they move out of the epithelial cells by exocytosis
  • They enter lymphatic capillaries called lacteal and are transported away from the intestine

Biology AS (7 decks)

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