Chapter 3.3 Exchanging Substances Flashcards
Def do exchange?
Transfer of materials between organisms and their environment
Def of transport?
Distribution of absorbed material round organism’s body
Link the size of organism with the SA:V ratio
Smaller organism have higher SA:V ratios than larger organism
This means that substances are exchanged more quickly (can be + or - for the organism)
Calculation of SA: V ratio
Of cube/cuboid
SA ( 6x Hx L) : V ( Hx Lx W)
Calculation; volume of cylinder
(SA:V ratios)
π x radius^2 x height
Examples of exchanged substance?
O2, CO2, nutrients, excretory products (urea, ammonia, water), heat
{def of }
1) excrete
2) secrete
3) egest
1) excrete -metabolic water removal
2) secrete- useful molecules move out of cells
2) egest - removal of undigested food
Examples of passive and active processes of exchange?
passive Active
- diffusion. - active transport
- osmosis. - co transport
- conduction - bulk transport (exo/endo cytosis)
- convection
-radiation
Substance exchange in single celled organism? + why this method
Simple diffusion occurs fast enough to be sufficient (takes place across membrane)
E.g gas exchange happens this way
+ large SA:V so efficient diffusion
+ steep concentration gradient maintained by substances used/ produced/ stored quickly
Reasons multicellular organism need adaptions for substance exchange ?
Diffusion across outer membrane is too slow
1) some cells are deep within the body - large distance between them and environment
2) decreased SA:V ratio - exchange is less efficient
Process of gas exchange in INSECTS?
Insects have a tracheal system:
- air entres exoskeleton via spiracles - pores on insects skin
- oxygen moves down conc. gradient (diffusion) & travels along tracheae - air filled pipes
- tracheae branches off into smaller tracheoles
- trancheoles terminate in respiring tissues and oxygen diffuses into cells CO2 diffuses out and travels out of spiracles
Adaptions gases exchange organs in insects
TRACHEOLES
- thin permeable walls
- gas exchange with tissue fluids by diffusion down conc. gradient
- terminate within body tissues (short diffusion pathway)
- tracheal fluid/ moisture allows O2 to diffuse into liquid before cells
SPIRACLES
-
TRACHEA
- muscles in trachea can squeeze trachea leading to mass movement of air
Insects can increase/control air flow;
> rhythmic abdominal movements either 🔼or 🔽 abdominal pressure moving air in & out of spiracles
Problems of water loss through spiracles for insects? + how is it prevents
-
+ close their spiracles using muscles (sphincters)
+ waterproof, waxy cuticle all over body & tiny hairs around spiracles both to reduce evaporation
How are fish adapted for gas exchange?
-have gills with pairs of lamella on them
- short diffusion pathway (lamellea)
- excellent blood supply to gills
- counter current exchange system
- one way flow of water over gills
Explain gas exchange system in fish
Counter-current exchange system
1) blood flows through lamella in 1 direction
2) water (entre through mouth) flows in opposite direction over lamella
This means that O2 concentration of the water flowing towards the blood is always higher than the blood flowing towards the water.
Benefits of fish using counter current system
Counter current system ensures a concentration gradient is maintained across the membrane thus maximising uptake of O2.
This is important because lower levels of O2 in water that the air therefore maximising its uptake is critical for a fish to survive
Describe the structure of the gills?
Each gill is made of lots of thin plates gill filaments attached onto a gill arch.
Each of these gill filaments is then covered in tiny structures called lamellae
[singular= lamella, plural = lamellae]
Role of salivary gland
+mouth
- situated near mouth, pass secretion via ducts in mouth
Secretion contains amylase to hydrolyse starch into maltose
+mouth = mechanical digestion to increase SA of particles
And starch digestion due to saliva
Role of stomach
- muscular sac w. inner enzyme producing layer
It stores and digests foods (chemically and mechanically)
mechanical digestion - muscles break down food
chemical digestion - protase in stomach juices
Role of pancreas
-gland situated below stomach, produces secretions (pancreatic juices)
secretes enzymes
Pancreatic juices contain protease, lipase, amylase
Role of ileum
-long muscular tube, food digested here via enzymes produced by its walls & glands.
- inner walls folded into villi- ^SA also microvilli on epithelial cells
Role of large intestine
Absorb water
(Water has come from secretion of digestive glands)
Role of rectum
Store faeces before removed by anus in process called egestion
Def of Micelles
Tiny droplets of broken up lipids
Process of carb digestion in humans
1) saliva contains amylase that hydrolyses starch > maltose
2) food swallowed and enters stomach which acidic conditions denature amylase preventing further hydrolysis
3) in small intestines mixed with pancreatic juices that contain amylase and maintain optimum conditions
4) muscles in intestine push food along ileum. epithelial lining produces maltase on cell surface hydrolysing maltose > glucose
(lactose and sucrose also hydrolysed in this way by membrane bound enzymes)
5) Glucose absorbed by epithelial cell (see transport topic)
Process of lipid digestion in human
1) lipids broken up in tiny droplets (micelles) by bile salts from liver.
This process called emulsification and ^ SA to speed up action of lipase.
2) micelles travel to ileum on contact to lipase on surface they are hydrolysed-> monoglyceride and fatty acids.
3) monoglyceride and fatty acids diffuse into epithelial cell
4) then transported to ER where recombine -> triglycerides
5) move to Golgi -triglycerides associated with cholesterol & lipoproteins to form chylomicrons (special partial adapted for lipid transport)
6) chylomicron moves out of epithelial cell by exocytosis
7) then enter lymphatic capillary found in each villus
8) lymph then passes them to blood stream
Process of protein digestion in humans.
Digestion of proteins takes place in stomach and duodenum of small intestine.
▸ *the stomach contains enzyme of protease which begins to break down peptide bonds in polypeptide chains into smaller chains
In small intestine on the membrane
▸ Endopeptidases break the peptide bond in the middle of the peptide chain.
▸ Exopeptidases acts at the end of the peptide chain and helps in releasing the last
amino acid.
Def of absorption
Transport of products of digestion across epithelial cells into the bloodstream
Def of assimilation
To become part of an organism
(When Soluble food molecules are used to build new parts of cells)
Role of oesophagus
Move food to stomach
Peristalsis- contraction of muscles
Role of the liver
To produce bile that neutralises stomach acid and emulsifies lipids
Adaptions of small intestine for absorption
1) long, folded to increase surface area
2) villi (finger like projections on inner layer) ^ SA and is lined with single layer of epithelial cells =short diffusion pathway
3) microvilli (smaller projections on villi) ^ SA and is site of some enzymes like maltase are found
Describe the structure of an intrinsic transmembrane protein that acts as an aquaporin?
(9 marks)
- primary structure specific sequence of amino acids
- amino acids are joined together by peptide bonds
- secondary structure of alpha coil helix
- H bonds between Amine and carboxyl group
- tertiary/quaternary structure create 3D shape
- bonds between R groups e.g ionic, hydrophilic, disulfate, H
- hydrophobic amino acids embedded in section that interact with fatty acid in bilayer
- hydrophilic amino acids in the inner and outer phosphate groups of bilayer
Def of digestion
The process of breaking down large insoluble molecules by enzymes during hydrolysis with the addition of a water molecule into smaller soluble molecules that can be absorbed and assimilated.
Where do endopeptidases work?
+ what are the products of hydrolysis
Hydrolyse peptide bonds in the middle region of proteins
+ smaller polypeptide chains
Where do exopeptidases work?
+what are products from hydrolysis reaction
Hydrolyse peptide bonds on terminal amino acids
+ single amino acid + dipeptides
Substrate and products of membrane bound dipeptidases in small intestine?
Hydrolyse dipeptides into single amino acids
Structure of human gas exchange system
See diagram
- trachea (windpipe held open by rings of cartilage)
- bronchus (smaller pipes that lead to right/left lung)
- bronchioles (smaller tubes in the lungs)
- alveoli (air sacs)
