Protein & Enzyme (Protein structure, Role of Protein, Denaturation, Enzymes, Factors affecting Enzymes, Inhibitors) Flashcards
Plasma Membrane
The plasma membrane is a phospholipid bilayer (two layers of phospholipids)
- Keeps the cytoplasm/cytosol of the cell and all the organelles contained;
- Controls the movement of water, ions, gasses, and other substances into and out of the cell.
What does the Plasma Membrane consist of?
Extracellular, Intracellular, Phospholipid bilayer, Hydrophobic tail (water fearing), hydrophilic head (water loving).
The membrane is SEMI-PERMEABLE and SELECTIVELY PERMEABLE. This means that small molecules that pass through the membrane, but others cannot. Protein channels and carrier proteins, help to control which molecules move into and out of the cell.
The plasma membrane includes a lot of different proteins and other molecules.
Plasma membrane also consists of
- Cholesterol,
- Protein channels/pump
- Glycoproteins
- Oligosaccharides
Plasma membrane - Cholesterol
Helps to stabilise the cell membrane, and reduce it’s permeability to water solute molecules
Plasma membrane - Protein channels/pump
These allow the movement of specific molecules in/out of the cell
Plasma Membrane - Glycoproteins
Often these are the receptors for bigger molecules and trigger cellular responses when these molecules are detected
Plasma Membrane - Oligosaccharides
Involved in recognising ‘self’ cells, and signalling between cells
What is 4 differences between Plant cells & Animal cells?
- Plant cells have a cellulose cell wall outside the cell membrane. Animal cells have NO cell wall.
- Plant cells have a CELL MEMBRANE. Animal cells DO NOT have chloroplasts.
- Plant cells have a cytoplasm. Animal cells only have small vacuoles.
- Plant cells have a nucleus
What does the plant cell consist of? (Eight)
Chlorophyll, Vacuole, Grana, Thylakoid, Stroma, Chloroplast, Outer Membrane, Inner Membrane
What is a protein?
They are long chains of amino acid that are then folded into very specific shapes. They are then held in the right shape by chemical bonds between amino acids.
The shape and structure of proteins is VITAL to their correct function.
What is an enzyme?
Enzymes are proteins that help speed up metabolism, or the chemical reactions in our bodies. They build some substances and breaks others down.
Enzymes are proteins that catalyse chemical reactions.
- Enzymes speed up reactions by lowering the activation energy.
- Enzyme is unchanged by the reaction there can be used many times
- They are very specific (one enzyme = one reaction)
Enzyme - Substrate
A substrate is the substance which the enzyme acts on to catalyse a reaction
Enzyme LOCK & KEY MODEL
All enzymes have an active site - a groove or nook in the protein structure that the enzyme’s substrate can fit into.
According to the lock & key model, the substrate must perfectly fit into the enzyme’s active site for the reaction to be catalysed
Substrates are held in place by hydrogen bonds.
The reaction is catalysed and the products are released by the enzyme.
Enzyme - Induced Fit Model
According to the Induced Fit Model, the enzyme’s active site will loosely fit the specific substrate.
When the substrate binds to the enzyme’s active site, the enzyme’s active site changes shape slightly to better fit the substrate and lock it in place. This causes a change in the shape of the substrate too, which makes the reaction more likely to be successful.
Enzyme - Denaturation
Enzyme denaturation occurs when an enzyme loses its native conformation, or three-dimensional structure, rendering it unable to bind to substrate and catalyze product formation. The two main causes for enzyme denaturation are deviations from optimal temperature and pH.
Enzyme - Site Competitive Inhibitors
Site competitive Inhibitors bind to the active site of the enzyme. They block the active site so that the substrate cannot bind.
If the substrate does not bind, the reaction cannot proceed.
May be reversible or irreversible
Enzyme - Non Site Competitive Inhibitors
Non site competitive Inhibitors bind to a location away from the enzyme’s active site.
It causes a change in the shape of the enzyme’s active site so that the substrate does not bind, or binding is impaired.
If the substrate can’t bind securely, the reaction cannot proceed
What are the different types of proteins?
What is a catalyst?
Relationship between Substrates & Active Site
A substrate enters the active site of the enzyme. This forms the enzyme-substrate complex. The reaction then occurs, converting the substrate into products and forming an enzyme products complex. The products then leave the active site of the enzyme.
COMPARE and CONTRAST the INDUCED TO FIT and the LOCK AND KEY Model of enzyme function
Factors affecting enzyme activity/function
Temperature
pH
Concentration of substrates
Inhibitors
How does Temperature affect enzyme activity?
Too cold: Substrate particles are not moving/colliding with the enzyme often
Optimum: Substrate particles are colliding more often and the reaction is catalysed efficiently
Too hot: The enzyme will denature. The enzyme cannot catalyse the reaction.
How does pH affect enzyme activity?
Most enzymes work inside cells, so optimum pH of 7.
Changes in pH (higher or lower) can affect the way the substrate binds to the enzyme, or cause the enzyme to denature.
What are the TWO type of Inhibitors?
Site Competitive Inhibitors
Non site competitive Inhibitors
