Transport Flashcards
What is the average circulatory time?
1 minute
How many cells are reached in circulation?
10¹⁴ cells within minutes
How many oxygen molecules does each haemoglobin molecule bind to?
4
How many times stronger does CO bind to haemoglobin compared to O2?
250 times stronger
What percentage of CO in air leads to unconsciousness?
0.1%
What compounds have similar characteristics to CO?
CN-
H2S
What are steroids and thyroids carried through the blood by? Why?
Plasma carrier proteins
They are very non-polar and don’t dissolve in the blood plasma
What transports steroids?
Transcortin
What transports thyroid hormones?
They bind to thyroxine-binding globin
What type of core does the cell membrane have? What does this mean?
Hydrophobic
Prevents ions, charged molecules, polar molecules and peptides from passing through
What are the three ways molecules can pass through the membrane?
Passive transport
Active transport
Facilitated transport
What is passive transport?
The compound diffuses spontaneously through the membrane from high to low concentration
Does passive transport require energy?
No
What is facilitated transport?
A protein helps transport ions/molecules from high to low concentration
Does facilitated transport require energy?
No
What is active transport?
A protein pumps ions/molecules against a gradient
Does active transport require energy?
Yes
What types of molecules are mainly involved in passive transport?
Gases and small molecules
What is passive transport driven by?
Entropy
What are the 3 factors affecting diffusion rate?
Concentration
Hydrophobicity
Electrochemical gradients
How does concentration affect diffusion rate?
The larger the concentration gradient, the faster the diffusion
What are the three membrane transport proteins?
Channels
Transporters
Pumps
What do channels do?
Transports ions and water down the gradient
Forms a “pore” through the membrane
What do transporters do?
Transports small molecules or ions down the gradient
Binds to the molecule and “moves” it across the membrane
Is there any energy used in a transporter? Why?
No
Transports down a gradient
What do pumps do?
Transport ions or small molecules against the gradient
Do pumps use energy? Why?
Yes
They break an equilibrium which needs energy to do
What type of membrane transport protein does facilitated transport use?
Channels
Transporters
What do most ion channels open in response to?
Specific signals
Eg. Voltage gated
What forms a hydrophilic channel through the membrane?
Alpha-helices
Is there any energy involved in a channel? Why?
No
Molecules and ions move down a gradient
How do transporters work?
The molecule/ion binds to the transporter from the outside which causes a conformational change and causes the transporter to open the other side, releasing the molecule/ion
What are the three types of transporter?
Uniporter
Symporter
Antiporter
What does a uniporter do? eg?
Transports only one molecule down the gradient
glucose transport
What does a symporter do? eg?
Transports two molecules down the gradient in the same direction
Glucose/Na+ transport
What does an antiporter do? eg?
Transports two molecules down the gradient in opposite directions
Na+/H+ transport
What voltage membrane potential do nerve cells need?
-70mV
How is membrane potential -70mV maintained?
Actively pumping positive ions to the outside
What does the synthesis of ATP use?
Reverse ATP-pump
What are the 4 types of ATP-powered pumps?
P-class Maintains membrane potential Aids in muscle relaxation Maintains low pH in stomach
What are the steps of the P-Type ATP powered pump?
Ca2+ and ATP binds Phosphorylation Conformation change where the channel changes direction Ca2+ is released Dephosphorylation Conformation change
What do secretory and endocytic pathways do?
Move large molecules or large amounts of molecules across the cell membrane
