Turn on thread page Beta
    • Thread Starter
    Offline

    14
    ReputationRep:
    hi guys could someone kindly explain to me the above topics please?

    thank you!
    • Study Helper
    Offline

    18
    ReputationRep:
    Study Helper
    (Original post by kandykissesxox)
    hi guys could someone kindly explain to me the above topics please?

    thank you!
    Well how about you gives us a starting point and we'll take it from there? What do you know about those two topics already?
    Offline

    11
    ReputationRep:
    I'm an AS student and I'm doing these topics now!

    Active transport is a form of diffusion where energy (in the form of ATP) is required to transport substances. This is in comparison to passive transport, such as osmosis, which uses no extra energy to occur. My textbook defines it as so: "The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using energy and carrier molecules." This makes sense, as regular passive diffusion takes place from HIGH to LOW concentration, like water down a hill. It takes electricity (energy) to pump water back up the hill!

    Proteins called "carrier molecules" are used to transport these substances. These proteins are SELECTIVE as each protein has specific shapes inside of it that hold on to specific substances, similar to how antibodies have specific shapes to fit antigens.

    (does this diagram help?)

    A good example of active transport is the way Epitheleal cells digest food in the small intestine. Active transport plays a part in this by using a concentration gradient that has already been set up by direct active transport (using ATP to directly move molecules). This is known as co-transport, and is used in the small intestine to get the nutrients from food into your bloodstream!

    Facilitated diffusion is a passive process, i.e. it relies on the inbuilt motion (kinetic energy) of the diffusing molecules. No extra energy in the form of ATP is required. It occurs DOWN the concentration gradient, from HIGH to LOW (think of the water running down the hill...). It uses protein channels in the phospholipid bilayer, intrinsic (goes all the way through) proteins to be specific. These protein channels form water-filled channels across the membrane. These allow WATER-SOLUABLE ions and molecules such as glucose and amino acids to pass through.

    The channels are SELECTIVE, each opening only in the presence of a specific molecule. This therefore shows that the cell surface membrane is a barrier, controlling what goes in and out of the cell.

    Facilitated diffusion can also occur via carrier proteins, these span the cell membrane.

    When a particular molecule that is also specific to the protein is present, it binds with the protein. This causes the protein to change shape in such a way that the molecule is released to the inside of the cell.

    Ummm ok that's all my notes on facilitated diffusion and active transport! Hope this helps

    (If I got something wrong or explained it wrong, please tell me so I can change my class/revision notes oo er!)
    Attached Images
     
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by suirrel)
    I'm an AS student and I'm doing these topics now!

    Active transport is a form of diffusion where energy (in the form of ATP) is required to transport substances. This is in comparison to passive transport, such as osmosis, which uses no extra energy to occur. My textbook defines it as so: "The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using energy and carrier molecules." This makes sense, as regular passive diffusion takes place from HIGH to LOW concentration, like water down a hill. It takes electricity (energy) to pump water back up the hill!

    Proteins called "carrier molecules" are used to transport these substances. These proteins are SELECTIVE as each protein has specific shapes inside of it that hold on to specific substances, similar to how antibodies have specific shapes to fit antigens.

    (does this diagram help?)

    A good example of active transport is the way Epitheleal cells digest food in the small intestine. Active transport plays a part in this by using a concentration gradient that has already been set up by direct active transport (using ATP to directly move molecules). This is known as co-transport, and is used in the small intestine to get the nutrients from food into your bloodstream!

    Facilitated diffusion is a passive process, i.e. it relies on the inbuilt motion (kinetic energy) of the diffusing molecules. No extra energy in the form of ATP is required. It occurs DOWN the concentration gradient, from HIGH to LOW (think of the water running down the hill...). It uses protein channels in the phospholipid bilayer, intrinsic (goes all the way through) proteins to be specific. These protein channels form water-filled channels across the membrane. These allow WATER-SOLUABLE ions and molecules such as glucose and amino acids to pass through.

    The channels are SELECTIVE, each opening only in the presence of a specific molecule. This therefore shows that the cell surface membrane is a barrier, controlling what goes in and out of the cell.

    Facilitated diffusion can also occur via carrier proteins, these span the cell membrane.

    When a particular molecule that is also specific to the protein is present, it binds with the protein. This causes the protein to change shape in such a way that the molecule is released to the inside of the cell.

    Ummm ok that's all my notes on facilitated diffusion and active transport! Hope this helps

    (If I got something wrong or explained it wrong, please tell me so I can change my class/revision notes oo er!)

    This helped me so much, thank you!!
    Offline

    11
    ReputationRep:
    No problem! I'm happy I helped, good luck for your lessons this week.
    Offline

    0
    ReputationRep:
    Nice question, I copy and pasted this from another page. It's about transportation and the structure of the cell

    The Fluid Mosaic model states that the Cell/Plasma Membrane is made of an Phospholipid Bilayer that is made of individual strands of hydrophobic tails and hydrophilic heads that is set in rows. The Cell Membranes has an semi-permeable property that allows diffusion of materials like O2 and CO2 quickly to aid respiration. How ever some molecules like C6-H12-O6, charged ions, and large molecules would have an hard time diffusing through cell membranes so the cell surface has protein receptor to detect useful large molecules and also have Glycolipids and Glycoproteins polymers which acts as receptors which help bind some molecules. Intrinsic proteins like Protein Channels and Carrier proteins aid in the process of 'Facilitated Diffusion' where large molecules can pass through the cell membrane. Facilitated diffusion is an form of Passive transport because it does not use energy. Carrier proteins change shape to allow these molecules to go through. Active transport also uses carrier proteins but uses energy to allow small and large molecules to travel against it's concentration gradient. It uses energy in the form of ATP which hydrolyses to become ADP+ (Pi) (An Phosphate Group).
    Cell membranes also do bulk transportation called Endocytosis which involves the cell engulfing the material outside the cell via detection by intrinsic and extrinic cell receptor. An form of Endocytosis is Phycocytosis where some specialized like lymphocytes/White Blood cell engulfs an bacterium and creates an vesicle where it fuses with the membrane of the Lysosome to digest the Microbe. Exocytosis is the opposite. For example, Golgi apparatus create an vesicle which transport material created in the cell to the cell membrane to be expelled.

    Some Sexual hormones are steroids like androgen where the molecules diffuses (with the concentration gradient) across the cell membrane, attach to receptors located in the cytoplasm. Those receptor hormones complex enter the nucleus and triggers gene expression. Very long lasting effect.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 8, 2014

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.