3.3 Organisms exchange substances with their environment Flashcards
(112 cards)
1
Q
Surface area to volume ratio
A
- The surface area of an organism divided by its volume
- the larger the organism, the smaller the ratio
2
Q
Factors affecting gas exchange
A
- diffusion distance
- surface area
- concentration gradient
- temperature
3
Q
Ventilation
A
- Inhaling and exhaling in humans
- controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
4
Q
Inspiration
A
- External intercostal muscles contract and internal relax
- pushing ribs up and out
- diaphragm contracts and flattens
- air pressure in lungs drops below atmospheric pressure as lung volume increases
- air moves in down pressure gradient
5
Q
Expiration
A
- External intercostal muscles relax and internal contract
- pulling ribs down and in
- diaphragm relaxes and domes
- air pressure in lungs increases above atmospheric pressure as lung volume decreases
- air forced out down pressure gradient
6
Q
Passage of gas exchange
A
- Mouth/nose → trachea → bronchi → bronchioles → alveoli
- crosses alveolar epithelium into capillary endothelium
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7
Q
Alveoli structure
A
- Tiny air sacs
- highly abundant in each lung – 300 million
- surrounded by the capillary network
- epithelium 1 cell thick
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8
Q
Why large organisms need specialised exchange surface?
A
- They have a small surface area to volume ratio
- higher metabolic rate – demands efficient gas exchange
- specialised organs e.g. lungs/gills designed for exchange
9
Q
Fish gill anatomy
A
- Fish gills are stacks of gill filaments
- each filament is covered with gill lamellae at right angles
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10
Q
How fish gas exchange surface provides large surface area?
A
- Many gill filaments covered in many gill lamellae are positioned at right angles
- creates a large surface area for efficient diffusion
11
Q
Countercurrent flow
A
- When water flows over gills in opposite direction to flow of blood in capillaries
- equilibrium not reached
- diffusion gradient maintained across entire length of gill lamellae
12
Q
Name three structures in tracheal system
A
- Involves trachea, tracheoles, spiracles
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13
Q
How tracheal system provides large surface area?
A
- Highly branched tracheoles
- large number of tracheoles
- filled in ends of tracheoles moves into tissues during exercise:
- so larger surface area for gas exchange
14
Q
Fluid-filled tracheole ends
A
- Adaptation to increase movement of gases
- when insect flies and muscles respire anaerobically – lactate produced
- water potential of cells lowered, so water moves from tracholes to cells by osmosis
- gases diffuse faster in air
15
Q
How do insects limit water loss?
A
- Small surface area to volume ratio
- waterproof exoskeleton
- spiracles can open and close to reduce water loss
- thick waxy cuticle – increases diffusion distance so less evaporation
16
Q
Dicotyledonous plants leaf tissues
A
- Key structures involved are mesophyll layers
- (palisade and spongy mesophyll)
- stomata created by guard cells
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17
Q
Gas exchange in plants
A
- Palisade mesophyll is site of photosynthesis
- oxygen produced and carbon dioxide used creates a concentration gradient
- oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
18
Q
Role of guard cells
A
- swell – open stomata
- shrink – closed stomata
- at night they shrink, reducing water loss by evaporation
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19
Q
Xerophytic plants
A
- Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
- structural features for efficient gas exchange but limiting water loss
20
Q
Adaptations of xerophyte
A
- Adaptations to trap moisture to increase humidity → lowers water potential inside plant so less water lost via osmosis:
- sunken stomata
- curled leaves
- hairs
– - thick cuticle reduces loss by evaporation
- longer root network
21
Q
Digestion
A
- Process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
- so they can be absorbed across cell membranes
22
Q
Locations of carbohydrate digestion
A
- Mouth → duodenum → ileum
23
Q
Locations of protein digestion
A
- Stomach → duodenum → ileum
24
Q
Endopeptidases
A
- Break peptide bonds between amino acids in the middle of the chain
- creates more ends for exopeptidases for efficient hydrolysis
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Exopeptidases
* Break **peptide bonds** between amino acids at the **ends** of polymer chain
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26
Membrane-bound dipeptidases
* Break **peptide bond** between two **amino acids**
27
Digestion of lipids
* Digestion by **lipase** (chemical)
* emulsified by **bile salts** (physical)
* lipase produced in **pancreas**
* bile salts produced in **liver** and stored in **gall bladder**
28
Lipase
* Produced in pancreas
* Breaks **ester bonds** in triglycerides to form:
* **monoglycerides**
* **glycerol**
* **fatty acids**
29
Role of bile salts
* **Emulsify** lipids to form tiny droplets and **micelles**
* **increases surface area** for lipase action – **faster hydrolysis**
30
Micelles
* **Water soluble vesicles** formed from fatty acids, glycerol, monoglycerides and bile salts
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Lipid absorption
* **Micelles** deliver **fatty acids**, **glycerol** and **monoglycerides** to **epithelial cells** of ileum for absorption
* cross via **simple diffusion** as lipid-soluble and non-polar
32
Lipid modification
* **Smooth ER** reforms monoglycerides/fatty acids into **tryglycerides**
* **golgi apparatus** combines tryglycerides with proteins to form vesicles called **chylomicrons**
33
How lipids enter blood after modification?
* Chylomicrons move out of cell via **exocytosis** and enter **lacteal**
* **lymphatic vessels** carry chylomicrons and deposit them in bloodstream
34
How are glucose and amino acids absorbed?
* Via co-transport in the ileum
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Haemoglobin (Hb)
* **Quaternary structure** protein:
* 2 alpha chains
* 2 beta chains
* with 4 associated haem groups in each chain containing Fe2+
–
* transports oxygen
36
Affinity of haemoglobin
* The ability of haemoglobin to **attract**/**bind to** oxygen
37
Saturation of haemoglobin
* When haemoglobin is holding the **maximum amount of oxygen** it can hold
38
Loading/unloading of haemoglobin
* **Binding/detachment** of oxygen to haemoglobin
* also known as **association** and **disassociation**
39
Oxyhaemoglobin dissociation curve
* oxygen is **loaded** in regions with **high partial pressures** (alveoli)
* unloaded in regions of low partial pressure (respiring tissue)
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Oxyhaemoglobin dissociation curve shifting left
* Hb would have a **higher affinity** for oxygen
* **load more** at the same partial pressure
* becomes **more saturated**
* adaptation in **low-oxygen environments**
* e.g. llamas/in foetuses
41
Cooperative binding
* Hb's **affinity** for oxygen increases as more oxygen molecules are associated with it
* when one binds, Hb **changes shape** meaning others bind more easily
* explaining S shape of curve
42
How carbon dioxide affects haemoglobin?
* When carbon dioxide **dissolves** in liquid, **carbonic acid** forms
* **decreases pH** causing Hb to change shape
* **affinity decreases** at respiring tissues
* more oxygen is unloaded
43
Bohr effect
* **High carbon dioxide partial pressure**
* causes oxyhaemoglobin curve to **shift to the right**
44
Oxyhaemoglobin dissociation curve shifting right
* Hb has **lower affinity** for oxygen
* **unloads more** at the same partial pressures
* **less saturated**
* present in animals with **faster metabolisms** that need more oxygen for respiration
* e.g. birds/rodents
45
Closed circulatory system
* Blood **remains within blood vessels**
46
Name different types of blood vessels
* **Arteries**, **arterioles**, **capillaries**, **venules** and **veins**
47
Structure of arteries
* Thick **muscular** layer
* thick **elastic** layer
* thick **outer layer**
* small lumen
* no valves
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Capillary endothelium
* Extremely thin
* one cell thick
* contains small gaps for small molecules to pass through (e.g. glucose, oxygen)
49
Capillaries
* Form **capillary beds**
* **narrow diameter** (1 cell thick) to slow blood flow
* red blood cells squashed against walls **shortens diffusion pathway**
* **small gaps** for liquid/small molecules to be forced out
50
Arterioles
* Branch off arteries
* **thickest muscle layer** to restrict blood flow
* **thinner elastic layer** and outer layer than arteries as pressure lower
51
Tissue fluid
* Liquid bathing all cells
* contains water, glucose, amino acids, fatty acids, ions and oxygen
* enables **delivery** of **useful molecules** to cells and **removal of waste**
52
Tissue fluid formation
* At arteriole end, the smaller diameter results in **high hydrostatic pressure**
* small molecules forced out (**ultrafiltration**)
* red blood cells/large proteins too big to fit through capillary gaps so remain
53
Reabsorption of tissue fluid
* Large molecules remaining in capillary **lower** its **water potential**
* towards **venule end** there is **lower hydrostatic pressure** due to loss of liquid
* water **reabsorbed** back into capillaries by **osmosis**
54
Role of the lymph in tissue fluid reabsorption
* Not all liquid will be reabsorbed by osmosis as **equilibrium** will be reached
* **excess tissue fluid** **(lymph)** is absorbed into **lymphatic system** and drains back into bloodstream and deposited near heart
55
Cardiac muscle
* Walls of heart having **thick muscular layer**
* unique because it is:
* **myogenic** – can contract and relax without nervous or hormonal stimulation
* **never fatigues** so long as adequate oxygen supply
56
Coronary arteries
* Blood vessels supplying cardiac muscle with **oxygenated blood**
* branch off from aorta
* if blocked, cardiac muscle will not be able to respire, leading to **myocardial infarction** (heart attack)
57
Structure of the heart
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58
Adaptation of left ventricle
* Has a **thick muscular wall** in comparison to right ventricle
* enables **larger contractions** of muscle to create higher pressure
* ensures blood reaches all body cells
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Veins connect to the heart
* **Vena cava** – carries deoxygenated blood from body to right atrium
* **Pulmonary vein** – carries oxygenated blood from lungs to left atrium
60
Arteries connected to the heart
* **Pulmonary artery** – carries deoxygenated blood from right ventricle to lungs
* **Aorta** – carries oxygenated blood from left ventricle to rest of the body
61
Valves within the heart
* Ensure **unidirectional** blood flow
* **semilunar valves** are located in aorta and pulmonary artery near the ventricles
* **atrioventricular valves** between atria and ventricles
62
Opening and closing of valves
* Valves open if the **pressure** is higher behind them compared to in front of them.
* AV valves open when **pressure in atria > pressure in ventricles**
* SL valves open when **pressure in ventricles > pressure in arteries**
63
The Septum
* **Muscle** that runs down the middle of the heart
* separates oxygenated and deoxygenated blood
* maintains **high concentration** of **oxygen** in oxygenated blood
* maintaining **concentration gradient** to enable **diffusion** to respiring cells
64
Cardiac output
* **Volume of blood** which leaves **one ventricle** in **one minute**.
* heart rate = beats per minute
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Stroke volume
* **Volume of blood** that leaves the heart **each beat**
* measured in dm^3
## Footnote
[CHECK UN/ADDITION OF FORMULA]
66
Cardiac cycle
* Consists of **diastole**, **atrial systole** and **ventricular systole**
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Diastole
* **Atria** and **ventricular muscles** are **relaxed**
* when blood enters atria via vena cava and pulmonary vein
* increasing pressure in atria
68
Atrial systole
* Atria muscular walls **contract**, **increasing pressure** further.
* pressure atria > pressure ventricles
* **atrioventricular valves open** and blood flows into ventricles
* ventricular muscle relaxed
69
Ventricular systole
* After a short delay (so ventricles fill), **ventricular muscular walls contract**
* **pressure ventricle > atria pressure and artery pressure**
* atrioventricular valves close and **semi-lunar valves open**
* blood pushed into artery
70
Transpiration
* Loss of water vapour from stomata by **evaporation**
* affected by:
* light intensity
* temperature
* humidity
* wind
–
* can be measured in a lab using a **potometer**
71
How light intensity affects transpiration?
* As light intensity increases, rate of transpiration increases
* more light means more **stomata open**
* **larger surface area** for evaporation
72
How temperature affects transpiration?
* As temperature increases, rate of transpiration increases
* the more heat there is, the more **kinetic energy** molecules have
* **faster** moving molecules increases evaporation
73
How humidity affects transpiration?
* As humidity increases, transpiration decreases
* the more water vapour in the air, the **greater** the **water potential** outside the leaf
* **reduces water potential gradient** and evaporation
74
How wind affects transpiration?
* As wind increases, rate of transpiration increases
* the more air movement, the more **humid areas** are **blown away**
* maintains **water potential gradient**, increasing evaporation
75
Cohesion in plant transport
* Because of the dipolar nature of water, **hydrogen bonds** can form – **cohesion**
* water can travel up **xylem** as a **continuous column**
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Adhesion in plant transport
* Water can stick to other molecules **(xylem walls)** by forming **H-bonds**
* helps hold water column up **against gravity**
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Root pressure in plant transport
* As water moves into roots by osmosis, the **volume of liquid inside the root increases**
* ∴ the **pressure inside the root increases**
* this forces water upwards
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Cohesion-tension theory
* As water **evaporates** out the stomata, this **lowers pressure**
* water is **pulled up xylem** (due to negative pressure)
* **cohesive** water molecules creates a **column of water**
* water molecules **adhere** to walls of xylem pulling it upwards
* this column creates **tension**, **pulling xylem inwards**
79
Translocation
* Occurs in **phloem**
* explained by **mass flow hypothesis**
* transport of organic substances through plant
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Sieve tube elements
* Living cells
* contain **no nucleus**
* few organelles
* this makes cell **hollow**
* allowing **reduced resistance** to flow of sugars
81
Companion cell
* Provide **ATP** required for **active transport** of organic substances
* contains many **mitochondria**
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Mass flow hypothesis
* Organic substances, sucrose, move **in solution** from leaves (after photosynthesis) to respiring cells
* **source → sink** direction
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How is pressure generated for translocation?
* Photosynthesising cells produce glucose which **diffuses** into companion cell
* companion cell **actively transports** glucose into phloem
* this **lowers water potential** of phloem so water moves in **from xylem** via **osmosis**
* **hydrostatic pressure gradient generated**
84
What happens to sucrose after translocation?
* Used in **respiration** at the sink
* stored as insoluble **starch**
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Investigating translocation
* Can be investigated using **tracer** and **ringing experiments**
* proves phloem transports sugars not xylem
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Tracing
* Involves **radioactively labelling carbon** – used in photosynthesis
* create sugars with this carbon
* **thin slices** from **stems** are **cut** and placed on **X-ray film** which turns black when exposed to radioactive material
* **stems will turn black** as that is where phloem are
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Ringing experiments
* **Ring of bark** (and phloem) is **peeled** and **removed off a trunk**
* consequently, the trunk **swells** above the removed section
* analysis will show it **contains sugar**
* when phloem removed, sugar **cannot be transported**
88
How do small organisms exchange gases?
* Simple **diffusion**
* across their surface
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Why don't small organisms need breathing systems?
* They have a **large surface area to volume ratio**
* no cells far from the surface
90
How alveoli structure relates to its function?
* Round shape & large number in – **large surface area** for gas exchange (diffusion)
* epithelial cells are flat and very thin to **minimise diffusion distance**
* capillary network maintains **concentration gradient**
91
How fish gas exchange surface provides a short diffusion distance?
* **Thin lamellae epithelium** means short distance between water and blood
* **capillary** network in every lamella
92
How fish gas exchange surface maintains diffusion gradient?
* **Counter-current flow mechanism**
* circulation replaces blood saturated with oxygen
* Ventilation replaces water with oxygen removed
93
Name of gas exchange system in terrestrial insects
* Tracheal system
94
Describe structure of spiracles
* **Round, valve-like openings**
* running along the length of the abdomen
95
Describe trachea & tracheoles structure
* Network of **internal tubes**
* have rings of cartilage adding strength and keeping them open
* trachea branch into smaller tubes – **tracheoles**
* tracheoles extend through all tissues delivering oxygen
96
How tracheal system provides short diffusion distance?
* Tracheoles have **thin walls so** short diffusion distance to cells
97
How tracheal system maintains concentration gradient?
* Body can be moved by muscles to move air – **ventilation**
* Use of oxygen in respiration and production of CO2 sets up steep concentration gradients
98
Amylase
* Produced in pancreas & salivary gland
* hydrolyses starch into maltose
99
Membrane-bound disaccharidases
* Maltase/sucrase/lactase
* hydrolyse disaccharides into monosaccharides
100
Enzymes involved in protein digestion
* endopeptidases
* exopeptidases
* membrane-bound dipeptidases
101
Products of protein digestion
* Large polymer proteins are hydrolysed to **amino acids**
102
Double circulatory system
* Blood passes through heart twice
* **pulmonary circuit** delivers blood to/from lungs
* **systemic circuit** delivers blood to the rest of the body
103
Coronary arteries
* Supply **cardiac muscle with oxygenated blood**
* for continued respiration and energy production for contraction
104
Blood vessels entering/exiting the kidney
* **Renal artery** carries oxygenated blood to kidney
* **renal vein** carries deoxygenated blood to heart
105
Blood vessels entering/exiting the lung
* **Pulmonary artery** carries deoxygenated blood to lung
* **pulmonary vein** carries oxygenated blood to heart
106
Blood vessels entering/exiting the heart
* **Vena cava** carries deoxygenated blood to heart (right atrium)
* **aorta** carries oxygenated blood to body
* **pulmonary artery** – carries blood from the heart to the lungs
* **pulmonary vein** – carries blood from the lungs into the heart
107
Describe then structure of veins
* Thin muscular layer
* thin elastic layer
* thin walls
* valves
108
Explain role of elastic layer in arteries
* Thick elastic layer
* to help maintain blood pressure
* by stretching and recoiling
109
Describe the elastic layer in veins
* **Thin** elastic layer as **pressure lower**
* cannot control the flow of blood
110
Explain the role of valves in veins
* Due to low pressure in veins
* skeletal muscle usually used to flatten walls of veins for blood flow
* **valves prevent the backflow of blood**
* unidirectional flow
111
What causes the AV valves to open?
* Higher pressure in the atria than in the ventricles
112
What causes the semi-lunar valves to open?
* Higher pressure in the ventricles than in the arteries
