Section 3: Gas Exchange + Digestion and Absorption Flashcards
(35 cards)
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
2
Q
What is the relationship between the size of the organism and its SA: V?
A
- Smaller organisms have a high SA:V
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
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
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
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
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
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
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
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
11
Q
What is the order of passage in the gas exchange in humans?
A
- Mouth/ nose
- Trachea
- Bronchi
- Bronchioles
- Alveoli
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
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
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
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
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
What happens when there is a reduced rate of gas exchange in the alveoli?
* Less oxygen diffuses into blood
* Cells receive less oxygen
* Rate of aerobic reduced
* Less energy released
* Fatigue/ weakness
26
Why are a large biological molecules hydrolysed into smaller molecules?
* 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
How is starch hydrolysed?
* 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
How are disaccharides digested?
* 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
How are lipids digested in mammals?
* 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
How are lipids digested in mammals?
* 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
How are proteins digested in mammals?
* 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
Exam Question: Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own (2)
* Endopeptidases hydrolyse internal peptide bonds OR exopeptidases remove amino acids/ hydrolyse bonds at ends
* More ends or increased surface area
33
How are glucose and amino acids absorbed?
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
Exam Question: The addition of a respiratory inhibitor stops the absorption of amino acids. Why?
* No/ less ATP produced
* Sodium ions not moved out of cell
* No diffusion gradient for sodium to move into cell with amino acid
35
How are lipids absorbed?
* 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
