Flashcards in 8 - Exchange with the environment Deck (37):
What is Fick's Law?
Rate of diffusion is proportional to: Surface area x concentration gradient divided by diffusion distance
How are the alveoli adapted for gas exchange?
- Many alveoli, provide large surface area
- Walls of alveoli 1 cell thick, short diffusion distance
- Walls of capillary are 1 cell thick, short diffusion distance
- Capillary and alevoli walls are flattened cells, short diffusion distance
- Cell membrane permeable to gases
- Many blood capillaries, provide a large surface area and good circulation
Describe breathing in humans?
Inspiration - external intercostal muscles contract, expands ribs up and out, diaphragm flattens; volumes increases, pressure decreases
Expiration - Intercostal muscles relax, volume decreases, pressure increases
During exercise the internal intercostal muscles and abdominal muscles force expiration
Structure of trachea?
C shaped rings of cartilage, creates flexibility. Walls made of muscle and ciliated epithelium and goblet cells.
Structure of bronchi?
Divisions of trachea with cartilage
Structure of Bronchioles?
Walls made of muscles and lined with epithelial cells. Muscles allows control of air in and out.
Structure of alveoli?
Folded walls to increase SA. Single cell thick. Flattened cells. Walls contain elastic fibre and collagen. Elasticity to stretch and recoil to help expel air.
Describe the thorax?
Linned by two pleural membranes which secrete pleural fluid that reduces friction of moving lungs and attaches the lungs to the inside of the ribs by surface tension, so the lungs can move with the ribs.
Total volume of air moved into lungs in a minute
Volume of air taken in in a normal breath
Number of breaths taken in a minute
Pulmonary ventilation rate (dm-3/min)?
Tidal volume (dm-3) x ventilation (min)
Why is gas exchange difficult for fish?
Low oxygen content in water and water has a high density and requires a lot of energy to move across exchange surfaces.
How are gills adapted for gas exchange?
- Filaments and secondary lamellae increase SA
- Thin epithelium decrease diffusion distance
- Counter-current flow maintains concentration gradient along the length of gill, so equilibrium is not reached early.
Describe counter-current flow?
Water flows in opposite direction to blood across lamellae so difference in concentration is maintained so diffusion occurs across the entire length of the lamellae.
Describe inspiration in fish
1. Mouth opens
2. Opercular valve shuts
3. Floor of mouth lowered
4. Increases volume
5. Water enters due to decreased pressure
Expiration in fish
1. Mouth closes
2. Opercular valve opens
3. Floor raised causes decreased volume
4. increased pressure causes water to be forced over gills
How is the trachea adapted in insects for gas exchange?
- Spiracles on underside of insect, openings of exoskeleton
- Low conc of oxygen in tissues, so oxygen diffuses down conc gradient from air
- Tracheoles heavily branched to increase SA
- Tracheoles branch deep into tissue, decreased diffusion distance
- Abdominal beating: contractions forcing air out of air sacs keeps air ventilating
- Spirales not always open to decrease water loss, are controlled by valves and only open when CO2 conc peaks, forcing them open
- Waterproof, waxy cuticle and tiny hairs around their spiracles which reduces water loss by evaporation
How are leaves adapted for gas exchange?
- Mesophyll cells
- Leaves have large SA:V ratio (broad and flat)
- Large numbers of stomata provide large surface area
- Guard cells open stomata
- Leaves are thin, short diffusion distance
How do plants reduce water loss?
- Thick waxy cuticle, increase diffusion distance
- Guard cells can close
- Spines - reduce SA
- Shrunken stomata and hairs, traps moist air increasing humidity and decreasing conc gradient
- Curled leaves, traps moist air increasing humidity and decreasing conc gradient
Inflammation of alveoli attracts phagocytes,
breaks down elastic tissue which reduces conc gradient
Scar tissue, thicker, less elastic, reduces expansion of lungs and therefore tidal volume is decreased
increase in diffusion distance and decrease in conc gradient
Bacteria transmitted by droplets, bacteria will wake and destroy the alveoli, reducing surface area
Tidal volume decreased
Smooth muscle in bronchioles contacts, mucus produced, narrows air way, less oxygen absorbed, less respiration
Digestion in mouth
Salivary amylase released
Chemical digestion - starch to maltose by maltase
Mechanical digestion - chewing
Saliva lubricates food for swallowing
Digestion in osophagus
Food moves down by perisalsis
Digestion in stomach
Larger polypeptide chains broken down into smaller polypeptide chains, hydrolyse reactions
Pepsin is an endopeptidase
Juices secreted are called gastric juices
Low pH kills bacteria and is optimum for pepsin
Digestion in small intestine (duodenum)
Amylase - Starch to maltose
Trypsin - small polypeptide to amino acid
Maltase - maltose to glucose
Lipase - lipids to fatty acids and glycerol
Enzymes in pancreatic juices
NaHCO3 released to neutralise stomach acid
What happens in the ileum?
Absorption of glucose, amino acids, fatty acids and glycerol.
Many villi and micro villi speed it up
- Large protein broken down by pepsin into shorter polypeptides (endopeptidase)(Hydrogen bonds break the chain)(stomach)
- Trypsin breaks down shorter polypeptides into dipeptides (duodenum)(endo and exo peptidase)
- Di-peptides broken down into amino acids in the walls of the duodenum
Large fatty acids and glycerol diffuse across epithelial cells where they combine to form triglycerides, which packaged with phospholipids to make Chylomicrons which are absorbed by the laceal villus
Short fatty acids diffuse straight away
Glucose and Na+ ions co-transported into epithelial cell
Na + ions diffuse into capillary
Glucose actively transported into capillary
Amino Acid digestion
Amino acid diffuses into epithelial cell
Na + ion diffuses into capillary
Amino acid actively transported into capillary
Volume and surface area?
Volume = Height * Length * Width
SA = Area of surface sides
Size and shape?
Size - Smaller sized organisms have a larger surface area to volume ratio and therefore lose heat more quickly - higher metabolic rate due to this
Shape - Compact shape - small surface area to volume ration - minimised heat loss
Bile salts emulsify the lipids to increase their surface area for effective action of lipase - form small droplets
Lipase made in pancreas and secreted into the small intestine
Lipase breaks down lipids into monoglycerides and fatty acids
Monoglycerides and fatty acids combine with bile salts to produce micelles
Bile also helps neutralise stomach acid
Lipids absorbed in illeum