Topic 2.3 - Transport of substances Flashcards
Transports of substances (25 cards)
What is the function of the phospholipid bilayer ?
selectively permeable: only allows small, non-polar, lipid soluble substances through
allows to form vesicles
-> provides fluidity
What is the function of the glycoprotein ?
-> used fro cell recognition and cell signaling
-> different organisms have different glycoproteins and can be used to initiate immune responce
What is the function of glycolipids ?
(Chain of carbohydrates attached to a protein)
-> used for cell recognition and also a source of energy by hydrolysed to release glucose for respiration
What is the function of extrinsic proteins ?
-> receptor site for proteins: detects chemicals released from other cells
What is the function of transport proteins ?
-> two transport proteins: carrier and channels
-> carrier proteins can be used for faciliated diffusion and active transport
-> channel proteins can be used for facilated diffusion
What is the function of cholestrol ?
-> decreases fluidity and increases rigidity
Why is the plasma membrane referred as fluid-mosaic ?
-> molecules within the membrane are able to move
-> mixture of phospholipds, glycoproteins, glycolipids,cholestrol, transportproteins
Define diffusion
It is passive NET movement of substances from an area of high concentration, to an area of low concentration, down a concentration gradient.
Which substances can simply diffuse across the phospholipid bilayer?
Small, non-charged (or non-polar), lipid soluble
Explain why molecules of oxygen and carbon dioxide are able to diffuse across membranes.
-> The hydrophobic fatty acid part of membrane is non-polar
-> Oxygen and carbon dioxide are small non-polar molecules;
-> Oxygen/carbon dioxide can diffuse through the fatty acid layer
-> Down a concentration gradient
Write the equation for Fick’s law
What could limit the rate of facilitated diffusion?
-> The number of transport proteins available in the membrane
-> the concentration gradient
-> the surface area
Define active transport
Active transport is the movement of a substance against its concentration gradient.
This requires the use of a carrier protein that uses energy released from ATP hydrolysis.
How does active transport move substances against their concentration gradient?
Substance binds to a carrier protein
ATP binds to carrier protein
ATP is hydrolysed into ADP and Pi and this releases energy
This causes the carrier protein’s tertiary structure to change (undergoes a conformational change)
The substance is released on the other side of the membrane
What could limit the rate of active transport?
The number of carrier proteins
The amount of oxygen available for respiration. (this affects the amount of ATP available)
Very High temperature – if the temperature is high it could denature enzymes involved in respiration so ATP cannot be produced.
Give two ways in which active transport differs from diffusion?
In active transport ATP is used;
and movement is against a concentration gradient
Contrast the processes of facilitated diffusion and active transport.
Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins;
Facilitated diffusion does not use ATP whereas active transport uses ATP;
Facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient.
Define osmosis
The net movement of water from an area of high water potential to an area of lower water potential through a partially permeable membrane
What does it mean if 2 solutions are isotonic?
They have the same water potential
Vegetables are made of different types of tissue, in an experiment where do you take a cutting from and why?
When taking a cutting you must ensure it’s through one tissue only in order for it to be a fair test. As different tissues may affect water potential differently.
Why are bungs are placed on test tubes when conducting an experiment overnight?
To stop water from evaporating and therefore changing the water potential
Ratio’s or % change in mass are calculated to
allow a valid comparison when the initial length/mass is not the same.
Summarise how the products of carbohydrate digestion or the products of protein digestion are absorbed
Na+/K+ pump moves 3 Na+ ions out of the cell (into the blood) and 2K+ ions into the cell by active transport. This uses ATP.
This creates a lower concentration of Na+ in the epithelial cell than in the lumen of the intestine
Na+ ions move into the epithelial cell by facilitated diffusion. They travel through a symport protein and bring glucose with them. This is called co-transport.
The glucose is moving into the cell cell against its concentration gradient
The glucose concentration in the epithelial cell increases
Glucose moves into the blood from the epithelial cell through a carrier protein by facilitated diffusion.
Adaptations of the epithelial cell
Lots of mitochondria 🡪 Release energy in the form of ATP 🡪 ATP is needed for active transport
Lots of enzymes attached to their membrane 🡪 Breaks down maltose into glucose
Microvilli 🡪 provide a large surface area for maximum absorption
Carrier proteins for active transport
Channel/Carrier proteins for facilitated diffusion
