Metabolic Pathways and their Control 2.1 Flashcards
(33 cards)
What is Cell Metabolism?
Thousands of enzyme controlled reactions that occur within a living cell
What are Metabolic Pathways?
It is the sequence of reactions, controlled by enzymes that change one metabolite into another
What do catabolic pathways do?
Catabolic pathways bring about the breakdown of complex molecules to simpler ones usually releasing energy and often providing building blocks
e.g. Protein -> Amino Acids
Do anabolic and catabolic pathways depend on eachother?
Yes, they are closely integrated and depend on eachother
What do anabolic pathways do?
Anabolic pathways bring about the build up of large molecules from small molecules. This requires energy.
e.g. Amino acids -> proteins
What form is the energy in?
ATP
What are metabolic pathways controlled by?
They are controlled by enzymes and each enzyme catalyses a specific reaction.
Is there only one pathway per reaction?
No, pathways include alternative routes. Pathways may also have reversible and irriversible steps.
What can the plasma membranes structure be described as?
It is selectively permeable
It is made up of a bilayer of proteins which are in constant motion
Proteins are scattered on the surface and embedded within the membrane.
The fluid mosaic model.
What are the roles of the Membrane Proteins?
The proteins on the surface act as enzymes and are involved in cell communication.
Many proteins which span the membrane system as a whole are essential for intracellular and intercellular transport
What do Protein Pores do in transport?
Only allow specific substances to passively move across the membrane (diffusion)
What to Protein pumps do in transport?
Active transport requires ions or molecules to be pumped against the concentration gradient. Energy released from the breakdown of ATP is needed to change the shape of the protein and allow the molecules or ions to transfer across the membrane.
What does the sodium-potassium pump do?
Actively pumps sodium ions out of the cell and potassium ions into the cell both against the concentration gradient.
What factors affect how quickly a protein pump can operate?
Temperature and availability of oxygen and glucose affect the rate of respiration and therefore the rate of active transport (since this requires ATP)
(anything that effects the rate of respiration effects the rate of active transport)
Enzymes in the membrane
Some proteins in the membrane are enzymes which catalyse steps within cellular metabolic processes e.g ATP synthase
Why enzymes?
Energy is required to start a reaction to initially break bonds and this is known as the activation energy
What is the transition state?
When the bonds in a reaction have broken and are unstable.
What does the enzyme do to the activation energy?
It lowers the activation energy so that the reaction can occur at lower temperatures.
What does the enzyme do to substrates?
It brings the substrates closer together to allow a reaction to happen
What is the induced fit model?
The shape of the active site alters slightly to better fit the substrate - initially the shapes are only complementary not an exact fit
Explain the affinity relationships.
Substrates have a high affinity for the active site.
Products have a ow affinity for the active site.
What is affinity?
A chemical attraction
What do active sites do to help a reaction and how? (Clue: starts with o)
When two or more substrates are involved in the reaction the shape change of the active site helps orientate the substrate for the reaction to occur
How can we track enzyme activity?
It can be measured by either the decrease in the substrates or the increase in the products;
- Gas Production
- Changes in pH
- Colour Changes
