Chapter 5-6 Flashcards
Fluid mosaic model
The cell membrane consists of a fluid formed by a bi-layer of phospholipids, with embedded proteins forming a mosaic patchwork of semi permeability.
Receptor proteins
Most are glycoproteins that span the plasma membranes. Messenger molecules such as hormones bind to these initiating a cell response.
Connection proteins function
Anchoring of cell membrane in various ways. Maintain cell shape by linking the membrane with cytoskeleton. Also link adjacent cells.
Diffusion is the process of;
Movement of solutes from high concentration to low concentration.
Facilitated diffusion and three types of transport proteins;
Carrier proteins
Channel proteins
Aquporins
Define osmosis
The diffusion of water across a semi-permeable membrane in response to gradients of concentration, pressure and temp.
Solutions with equal concentrations of solute and thus equal concentrations of water are described as;
Isotonic
When comparing 2 solutions, the hypertonic solution is;
The solution with the higher solute concentration.
Hypotonic is to be;
A less concentrated solution and therefore water content.
When comparing 2 solutions, the hypotonic solution is;
The solution with the lower solute concentration.
Cells maintain concentration gradients by using;
Active transport
Two types of endocytosis
Pinocytosis and phagocytosis
A very small patch of plasma membrane dimples inwards as it takes in a small amount of extra cellular fluid. Virus cells can be taken up by a cell through this process;
Pinocytosis
Large particles, sometimes entire organisms moved into a cell through a large pocket of cell membrane. (Engulfing)
Phagocytosis
Aquaporin
A selective channel for water molecules, (extremely small). Amino acids that line the walls have slight positive charges repelling ions but attracting water molecules.
Adhesive junctions
Specialised groups of proteins that link cells to one another within tissues.
Desmosome
An adhesive junction which join cells in tissues that are repeatedly stretched (skin, intestines and the heart).
Tight junctions
Span the plasma membrane at corresponding sites. As if stitched together.
Gap junction proteins
Consist of protein channels interconnecting the cytosol of adjacent cells. (Plasmodesmata)
Plasmodesmata function
Are gap junctions that link nearly all adjacent plant cells and allow movement of large molecules between them.
Energy
Capacity to do work
Work
The transfer of energy to an object that causes the object to move.
Potential energy
Stored energy, including the elastic energy stored in a compressed spring or a drawn bow.
Chemical energy
A type of potential energy, stored in for example; batteries and biological molecules.
Kinetic energy
Heat or thermal, x-rays or light.
First law of thermodynamics;
Energy can be neither be created nor destroyed by ordinary processes.
The second law of thermodynamics;
When energy is converted from one form to another the amount of useful energy decreases. For example losses in heat.
Entropy
A tendancy toward the loss of complexity, order and useful energy.
Reactants;
A combination of molecules of which are not yet broken down into other forms yet.
Exogernic or exothermic
If there is an overal release of heat in a reaction.
Endergonic or endergonic
If a reaction requires a net input of energy.
Electron carriers
Energy transport mechanisms.
Catalyst
Speed up the rate of a reaction by reducing it’s activation energy. Enzymes are biological catalysts.
Active site
A pocket on an enzyme, location of binding to a molecule (the substrate) to help push it towards a reaction.
Substrate
A molecule that is yet to be reacted with, one of which an enzyme can bind to to push it towards a reaction.
Metabolism of a cell;
Is the sum of all a cells chemical reactions.
Metabolic pathways of cells;
Sequence of reactions of a cells metabolism. From molecule to molecule by different enzymes respectively.
Competitive inhibition
A substance that is not the enzymes normal substrate can also bind to the active site.
noncompetitive inhibition
a molecule binds to a site on the enzyme that is distinct from the active site. This causes the active site to change shape and become una- vailable, making the enzyme unable to catalyze the reaction
allosteric regulation (form of noncompetetive inhibition)
the same enzyme is ei- ther activated or inhibited by molecules binding to an allo- steric site on the enzyme; these sites are always distinct from the active site. Enzymes regulated in this manner are called allosteric enzymes.
feedback inhibition
an important form of allosteric regulation, the activity of an enzyme near the beginning of a metabolic pathway is inhib- ited by the end product.
poisons and drugs can impact:
enzymes and their functions. both non competitive; heavy metals etc. and competetive; nerve gas.
Function of Penecillin
destroys bacteria by competitively inhibiting an enzyme that is needed to syn- thesize bacterial cell walls.
Environmental conditions affect on enzymes
pH, salt concentration, and temperature, can promote or inhibit enzyme function by altering or preserving the enzyme’s three-dimensional structure.
