Chapter 3 CMB Cell Membrane Flashcards
What are the 3 functions of proteins?
-Enzyme activity
-Signal transduction
-Transport
What are the 3 membrane proteins?
-Transmembrane proteins
-Integral proteins
-Peripheral proteins
What is a mosaic model of membrane structure?
Mixed composition of different kinds of macromolecules such as integral proteins, peripheral proteins, glycoproteins, phospholipids, glycolipids, etc.
What is a fluid model of membrane structure?
because of its (flexible) hydrophobic integral components such as lipids and membrane proteins move laterally or sideways throughout the membrane
What are the 2 types of transports of proteins?
Passive and active
What is the function of transport protein?
Transport molecules across plasma membrane
What is passive transport?
-Movement is from higher concentration to lower concentration
-No energy (ATP) required
What is active transport?
-Movement is from lower to higher concentration
(against concentration gradient)
-Energy ATP required
Examples of passive transport?
O2 and CO2
Examples of active transport?
Sodium-potassium pump
Function of enzymes?
Enzymes attached to interior surface of membrane help to catalyse chemical reactions
Function of receptors?
-For chemical messages from other cells
-The binding of a messenger to a receptor may trigger signal transduction
Function of structural protein?
Supports shape of membranes
Example of structural protein?
Biconcave shape of red blood cell is due to scaffold of proteins linking membrane with cytoskeleton
Function of cell adhesion proteins?
Special proteins that glue cells to one another
What are glycolipids and state its function
-Cell surface markers
Tissue recognition by lipid/carbohydrate chain shape characteristic to tissue
What are glycoproteins and state its function
-Cell surface markers
“Self”- recognition with protein/carbohydrate chain shape unique to individual
Example of glycoproteins?
major histocompatibility complex protein (MHC) in organ transplant
Example of glycolipids?
ABO blood group markers
Function of plasma membrane?
-Plasma membrane keeps essential substances inside the cell
-Regulates passage of materials between cell and its environment
Function of phospholipid bilayer?
Phospholipid bilayer acts primarily as a barrier
What do proteins on the plasma membranes act as?
Protein act as selective gates (protein channels/ transport proteins)
selectively permeable membrane
State the 3 passive processes
Diffusion
Facilitated diffusion
Osmosis (liquid only)
State the 3 active processes
Active transport
Endocytosis
Exocytosis
What is passive diffusion?
-Substances diffuse through membranes without work by the cell
-Substances move from areas of high concentration to areas of lower concentration
State examples of passive diffusion
-Oxygen (needed for metabolism) enters red blood cells from lungs
-Carbon dioxide (metabolic waste) passed out of red blood cells to lungs
-Oxygen & Carbon dioxide are small non-polar molecules.
What is facilitated diffusion?
-Polar molecules (Ions) cannot easily cross without assistance
-A form ofpassive transport, like diffusion, and thereforedoes not require any energy input.
-Movement of substancesfrom higher to lower concentration
What is facilitated diffusion facilitated by?
channel or transport proteins.
Example of facilitated diffusion?
glucose transport
What is osmosis?
-Passive transport of water across a membrane
-water travels from an area of lower solute concentration (high water) to an area of higher solute concentration
What are hypotonic solution and cell?
Lower solute and more water concentrations than cell cytoplasm
What happens when water enters a hypotonic cell?
It swells
What are hypertonic solution and cell?
higher solute and lower water concentration than the cell cytoplasm
What happens when water leaves a hypertonic cell?
It shrinks
What is an isotonic solution and cell?
Solute and water concentrations are same inside and outside of the cell
Does the volume in isotonic solution and cell change?
No net movement of water. Hence, volume of the cell remains the same
What are active transports?
-Transport proteins can move solutes across a membrane against a concentration gradient
-Active transport requires ATP
-The transport / channel protein changes its structure in order the move the substances
What are the 4 steps of active transport? SPTP
- Solute binding
- Phosphorylation
- Transport
- Protein reversion
Examples of active transport across a membrane?
-sodium-potassium pump
proteins transport sodium ions out of cells and potassium ions into cells, both against steep concentration gradients
-nerve cells have internal potassium concentrations 30x greater than the extra-cellular fluid due to the pumping activity of the proteins. These ionic gradients are utilised in transmission of nerve impulses
What is exocytosis?
To move large molecules or particles out of cells through plasma membrane
A vesicle containing molecules or particles fuse with the membrane and expel its contents
Examples of exocytosis?
E.g. Removal waste from cells
-Secretion of mucus from cells lining stomach wall
-Salty solution containing proteins from cells in tear glands
-Insulin from pancreatic cells into the bloodstream
What is endocytosis?
Uptake of materials too large to penetrate the membrane.
Explain the process of endocytosis
- The membrane fold inward, trapping material from the outside.
- Materials are enclosed within invaginations (vesicles) of the plasma membrane which subsequently pinched off to form cytoplasmic vesicles.
What are the 3 types of endocytosis?
- Phagocytosis
- Pinocytosis
- Receptor-mediated endocytosis
What is phagocytosis?
Ingestion of large solid particles
Example of phagocytosis?
Cell (e.g. white blood cell) ingest large particles e.g. bacteria / pathogens
What is pinocytosis?
Cell ingests liquid, dissolved solutes and small suspended particles
What is Receptor-mediated endocytosis
Plasma membrane indents to form a pit lined with receptor proteins that have picked up particular molecules. Pit will close to form vesicle, carrying the molecules into cytoplasm.
What are the 3 types of cell junctions?
- Tight junctions
- Anchoring junctions
- Communicating junctions
What are tight junctions?
Bind cells together to form a leak proof sheet
Example of tight junctions?
Eg sheet of tissues line the digestive tract preventing contents from leaking into surrounding tissues
What are anchoring junctions?
Attach adjacent cells to one another
What are communicating junctions?
- Allow water and small molecules to flow between neighbouring cells
- Allow passage of small moecules from cell to cell in a tissue.
