Flashcards for AQA A Level Biology Chapter 4- Transport Across Cell Membranes
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Chapter 4- Transport Across Membranes
Institution
AQA
Contain all you need to know for this chapter of the course. Are detailed and concise, and work best with Anki, but can be used with quizlet. They are in the form of a txt document that can be imported into anki or quizlet. Some images are missing due to the format, so these images will have to be ...
What are the types of molecules that make up the plasma membrane?
Phospholipids <div>Proteins</div><div>Glycolipids</div><div>Glycoproteins</
div><div>Cholesterol </div>
What is the purpose of the phospholipid bilayer? To act as a selectively
permeable membrane that allows lipid soluble substances that are small enough to
enter and leave the cell<div>To prevent hydrophilic substances from entering and
leaving the cell</div><div>To be flexible and self sealing</div>
How does the phospholipid bilayer work? Phospholipids have hydrophobic tails and
hydrophilic tails<div>So when they are placed in solution, they form a bilayer,
with the heads facing outwards towards the water, and the tails inside the bilayer,
away from the water.</div><div>Since a substance has to go through the
<i>whole</i> bilayer to enter the cell, they bilayer acts as a hydrophobic
barrier</div>
What are the functions of proteins in the cell membrane? Provide structural
support<div>Act as channels to transport hydrophilic substances across the
membrane</div><div>Allow active transport across the membrane using carrier
proteins</div><div>Form cell surface receptors to identify cells
with</div><div>Help cells adhere together</div><div>Act as receptors for things
like hormones</div>
What are the two kinds of protein in cell membranes? """One that span the whole
bilayer<div>Ones that are only on the surface and don't extend across the
bilayer</div>"""
What does cholesterol do in the cell membrane? They limit the movement of
phospholipids, making the membrane more rigid and stronger, and so less fluid at
high temperatures<div>They are also very hydrophobic (in 2021?!?!?!?) and so
prevent leakage of water and dissolved ions from the cell</div>
What do glycolipids do? Act as recognition sites<div>Help cells attach to each
other</div><div>Allow cells to recognise one another</div>
What do glycoproteins do? Act as recognition sites<div>Help cells attach to
each other</div> <div>Help maintain the stability of the membrane</div>
What does the fluid mosaic model of the cell membrane describe? Fluid- the
individual phospholipids can move around freely, which gives the cell membrane a
constantly changing shape<div>Mosaic- the proteins embedded in the membrane are all
varied in size, shape and function, like in a mosaic</div>
What is facilitated diffusion? A <b><u>passive</u></b> process where
substances move down a concentration gradient through the cell membrane with the
assistance of channel or carrier proteins as they are hydrophilic and cannot pass
through the cell membrane without assistance
What is osmosis? The movement of water from a region where there is a less
negative water potential to a region where there is a more negative water potential
via a cell membrane
What is water potential always? Negative
Why can water pass through the cell membrane despite being charged? It is so
small
What happens to a water potential when you make a solution more concentrated?
It becomes more negative
What is active transport? The movement of molecules or ions into or out of a
cell against a concentration gradient using ATP
What are the two modes of active transport? Using only ATP to directly
move molecules through carrier proteins<div>Co-transport, where a concentration
gradient has already been set up by active transport </div>
How does a carrier protein work in active transport? """The molecule binds to the
carrier protein<div>On the inside of the cell, the ATP binds to the carrier
protein, and is hydrolysed, changing the carrier protein's shape</div><div>The
molecule is then released into the cell and the carrier protein returns to its
original shape</div>"""
What are the two differences between active transport and facilitated diffusion?
Active transport requires energy whereas facilitated diffusion occurs simply
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