Key Area 3 Flashcards
What is the plasma membrane composed of?
Phospholipids
Proteins
Properties of phospholipids?
The head region of a phospholipid molecule is charged, therefore hydrophilic (attracted to water)
The tail region is uncharged and non-polar, therefore hydrophobic( repelled by water)
What gives the membrane its fluid quality?
The phospholipids constantly changing position.
What are the different functions of proteins found within the membrane?
- active transport proteins
- channel forming proteins
- enzymes
- receptors
- attachment proteins for the cell cytoskeleton
What are the different types of protein in the plasma membrane?
Integral protein
Peripheral protein
What are integral proteins?
These are proteins found within the membrane. Some are transmembrane proteins.
What are transmembrane proteins?
This means they span the entire width of the membrane.
What do integral membrane proteins interact with?
They interact extensively with the hydrophobic region of membrane phospholipids.
What are peripheral proteins?
These proteins are found on the surface of the membrane.
Properties of peripheral membranes?
- they may have hydrophilic R groups on their surface and are bound to the surface of membranes
- they are mainly bound by ionic and hydrogen bond interactions
What are the types of proteins involved in transporting substances?
Channel proteins
Transporter proteins
Protein pumps
What is facilitated diffusion?
It is the passive transport of substances across the membrane through specific transmembrane proteins.
Proteins that use this are channel proteins and transporter proteins.
What are channel proteins?
Channels are multi-subunit proteins with the subunits arranged to form water-filled pores that extend across the membrane.
What are most channel proteins like in animal and plant cells?
Highly selective
What is the stimulus that causes gates channels to open?
Chemical ( ligand-gated)
Electrical (voltage-gated)
What is the stimulus that causes gates channels to open?
Chemical ( ligand-gated)
Electrical (voltage-gated)
Properties of ligand-gated channels?
Always signal
Ligand-gated channels are controlled by the binding of signal molecules (ligands)
When the correct signal molecule binds, the gate opens allowing ions to flow through.
Properties of voltage- gated channels?
Always ion concentration
Voltage-gated channels are controlled by changes in ion concentration
What are transporter proteins?
These are proteins that bind to the specific substance to be transported and undergo a conformational change to transfer the solute across the membrane.
Why do transporter proteins alternate between two conformations?
This is so the binding site for a solute is sequentially exposed on one side of the bilateral than the other.
What are protein pumps?
They are used by active transport to transfer substances across the membrane against their concentration gradient.
What are pumps that mediate active transport?
These are transporters proteins coupled to an energy source.
What is the electrochemical gradient?
The concentration gradient and the electrical potential difference combined.
What does the electrochemical gradient determine?
The transport of the solute. i.e how and where the solute goes
What is the concentration gradient?
The difference in concentration of a solute across the plasma membrane
What is the electrical potential difference?
Also known as the membrane potential. It is created when there is a difference in electrical charge in two sides of the membrane.
Process of the sodium potassium pump?
It transports ions against a steel concentration gradient using energy directly from ATP hydrolysis.
- it actively transports 3 sodium ions out of cells and 2 potassium ions in.
What happens for each ATP hydrolysed?
Three sodium ions are transported out of the cell and two potassium ions are transported into the cell.
What is the function of the sodium potassium pump in the small intestine?
The sodium potassium pump generates a sodium ion gradient across the plasma membrane. This gradient drives the active transport of glucose.
What is the glucose symport?
The glucose transporter responsible for the active transport of glucose
What does the glucose symport transport?
It transports sodium ions and glucose at the same time and in the same direction
