B2.1 Flashcards
State that phospholipids naturally form continuous sheet-like bilayers in water
When added to water phospholipids naturally form bilayers
List locations of lipid bilayers in cells
Nucleus, mitochondria, and chloroplast
Outline the location of aqueous solutions in relation to the lipid bilayer
The cytoplasm is located within the lipid bilayer and other aqueous solutions are located outside the lipid bilayer
State the primary function of the cell membrane
Separating the cytoplasm and cell contents from the environment
Explain why the hydrophobic core of a lipid bilayer has low permeability to large molecules and hydrophobic particles
In order to not ruin the internal chemistry of the cell
Describe simple diffusion
the passive transport of particles from a region of high concentration to low concentration
Outline the impact of concentration gradient, particle size and polarity or charge of molecules on the rate of diffusion across a lipid membrane
Higher concentration gradients, smaller particle sizes, and non-polar characteristics promote faster diffusion and vice versa
Outline how the hydrophobic and hydrophilic structures of proteins impact their anchoring to the membrane
The hydrophobic section of the integral protein anchors the protein in the bilayer, whereas the peripheral protein has no hydrophobic part and isnt anchored to the protein
Explain two examples of simple diffusion of molecules into and out of cells
Oxygen moves from an area of higher concentration (such as the external environment or capillaries) to an area of lower concentration (inside the cell).
The higher concentration of carbon dioxide inside the cell creates a concentration gradient, and CO2 molecules move from inside the cell to an area of lower concentration (such as the bloodstream or extracellular space)
Compare the location of integral and peripheral proteins in the membrane
Integral proteins are permanently attached to the plasma membrane, peripheral proteins are temporarily attached to one side of the membrane
List at least four functions (with example) of membrane bound proteins
Transport GLUT2
Cell signalling EGFR
Enzymatic activity ATP
Cell adhesion Cadherin
Define osmosis.
Osmosis is the passive transport of water molecules from a region of low solute to a region of high solute concentration
Outline the structure and function of aquaporin proteins
Aquaporins are integral channel proteins that selectively transport water rapidly through membranes
Describe the structure and function of channel proteins
Channel proteins are specific to the molecule that can pass through them making cell membranes more selective
Define facilitated diffusion
The passive transport of molecules from a region of high concentration to a region of low concentration through channel proteins
Outline the specificity of channel proteins for ions
size, charge, and coordination chemistry
List types of gates on channel proteins
Gated channels open in response to stimuli whereas voltage gated channels open and close based on potential difference across membranes
Describe one example of facilitated diffusion through a protein channel
GLUT1 a transmembrane protein that facilitates the passive transport of glucose molecules across the cell membrane
Explain one example of active transport of molecules into and out of cells through a protein pump
The sodium potassium pump an integral membrane protein that transports three sodium ions out of the cell while also moving 2 potassium ions into the cell
Describe the structure and function of pump proteins, including the role of specificity, conformational change and ATP
Pump proteins are integral membrane proteins that function as active transporters by utilizing energy from ATP to move ions against their concentration gradient with high specificity
Compare active transport using a pump protein to facilitate diffusion using a channel protein
Channel proteins requires no energy, has no conformational change, goes with the concentration gradient and are a lot less selective
Define selective permeability
Allowing certain substances to pass while restricting others from crossing
Outline how channels and pumps in the membrane allow for selective permeability.
Because they only allow specific particles to pass or transport through
State the simple diffusion is not selective and depends only on the concentration gradient, particle size and polarity or charge of molecules
Simple diffusion is not selective and depends only on concentration gradient, particle size and polarity or charge of molecules
Outline the structure of glycoproteins and glycolipids
Glycoproteins are membrane proteins with a carbohydrate chain attached
Glycolipids are phospholipids with a carbohydrate chain attached
Describe the role of glycoproteins and glycolipids in cell adhesion and cell recognition
glycoproteins are sometimes responsible for direct attachment between neighboring cells. The carbohydrates of glycoproteins and glycolipids can form an extracellular matrix with their neighboring cells, leading to stable cell adhesion
The carbohydrate chains that form on glycoproteins and glycolipids have specific shapes allowing the immune system to recognise the cells as self. Glycoproteins and glycolipids act as antigens if the carbohydrate chain isn’t recognized
Compare and contrast the structure, melting point and relative fluidity of saturated and unsaturated fatty acids in lipid bilayers
Saturated fatty acids have no C-C double bonds resulting in a straight and close packing of phospholipids, with a higher melting point and a higher viscosity. Unsaturated fatty acids have C-C double bonds, resulting in kinks in the fatty acid tails, with lower melting points and lower viscosity
Outline an example of adaptation in membrane composition in relation to habitat
As the temperature decreases steelhead trout have a higher concentration of unsaturated fatty acid
Describe the structural placement of cholesterol within the cell membrane
Cholesterol is located between fatty acid tails of phospholipids in cell membranes
Outline how temperature affects cell membrane fluidity
Higher the temperature the less fluid the cholesterol is and vice versa
Describe the function of cholesterol as a modulator of membrane fluidity
It allows for the stability of the membrane as at higher temperatures it increases the melting point and at lower temperatures it maintains the fluidity
Outline the structure and function of vesicles in cells
Vesicles are small membrane bound structures involved in the transport of materials within cells
Describe the formation of a vesicle via endocytosis
The large particle is entering the cell and is surrounded by the plasma membrane, which buds off inside the cell to form a vesicle
State that the fluid properties of the cell membrane allow for the formation of vesicles
The fluid properties of the cell membrane allows the formation of vesicles
Outline the formation of a vesicle within the cell
Through the enclosing of materials required to be transported or stored
Describe the transport of materials within a cell using vesicles
Proteins to be secreted are synthesized by ribosomoes and attached to the RER
The RER forms a vesiclle containing protein and sends it to the Golgi Apparatus
The vesicle then fuses with the Golgi Apparatus and the Golgii modifies the protein, it packages the protein in a secretory vesicle which moves towards the plasma membrane, where it fuses with plasma membrane releasing it outside of the cell.
Outline two examples of materials brought into the cell via endocytosis
bacteria and viruses to eat and destroy
Outline two examples of materials released from a cell via exocytosis
Neurotransmitters released from neurons for intercellular communication.
Hormones released from endocrine cells to regulate body functions
Describe the release of materials from cells via exocytosis.
Exocytosis involves the fusion of a vesicle with the plasma membrane releasing content outside of the cell
State the effect of endocytosis and exocytosis on the area of the cell membrane
Endocytosis increases, exocytosis decreases the cell membrane area
Contrast secretion with excretion
Secretion is the release of specific substances synthesized by cells into body fluids or external environment, whereas excretion is the elimination of waste products or excess substances from the body.
Outline the structure, function and specificity of voltage-gated channels
Integral proteins allowing specific ions to pass through facilitated diffusion in response to changes in membrane potential difference
Describe the function of the voltage-gated potassium channel
A voltage gated channel located along the neurons
Outline the structure, function and specificity of ligand-gated channels
Integral proteins allowing specific ions to pass through facilitated diffusion in response to a ligand attached to the channel
Describe the function of the ligand-gated sodium channel in the postsynaptic cell membrane (AKA the nicotinic acetylcholine receptor)
It allows sodium ions to enter a neuron
State the function of an exchange-transporter proteins
To facilitate silmutaneous movement of 2 different molecules or ions across a membrane in opposite directions
Describe the structure and function of the sodium-potassium pump
An integral membrane protein which allows 3 sodium ions out of the cell and 2 into the cell against their respective concentration gradients
Outline the role of the sodium-potassium pump in maintaining neuronal resting potential
By contributing to the negative charge inside the cell and the positive charge outsidem which is crucial for proper electrical signalling in neurons
Outline the function of cotransporters in indirect active transport
They facilitate the transport of molecules across cell membranes by harnessing the energy stored in the electrochemical gradient of one molecule to drive the transport of another molecule against it’s concentration gradient
Describe the role of glucose cotransport proteins in the small intestine and kidney nephron
SGLT1 in the small intestine and SGLT2 in the kidney nephron play a vital role in contributing to the homeostatis of glucose in the body
Outline the role of CAMs in the formation of tissues
They mediate cell-cell adhesion and cell-matrix interactions. They also regulate tissue dvelopment, differentiation and maintenanc of tissue architecture
State that the loss of CAM function can lead to metastasis of cancer cells.
the loss of CAM function can lead to metastasis of cancer cells
