Unit 3.2 and 3.3: Membrane + traffic Flashcards
What are the three macromolecules that consists the membrane structure?
1) Lipids (usually phospholipids)
2) Sterol lipids
3) Proteins
What are the two parts forming a phospholipid molecule
An hydrophobic tail and an hydrophilic head : form a bilayer
What are sterol lipids in animals? In plants?
In animal: cholesterol
In plant: phytosterol
What is the role of the sterol lipid?
Keeps membrane fluid and provides stability
What are the three type of proteins in the membrane structure?
1) Integral
2) Transmembrane
3) Peripheral (membrane’s surface)
What are the 7 functions of the membrane?
1) define cell - contains and seperates
2) selective transport
3) enzyme activity
4) signal transduction
5) cell adhesion
6) cell recognition
7) attachement to cytoskeleton
From what are due these 6 membrane functions:
selective transport, enzyme activity, signal transduction, cell adhesion, cell recognition, attachement to cytoskeleton
Due to membrane proteins
What are the three types of passive transport?
Diffusion, osmosis and facilitated diffusion
Explain what diffusion is.
Movement of particles down concentration gradient
Give exemples of molecules that can diffuse through membranes
O2, CO2, lipid-soluble molecules
What is the difference between passive and active transport
Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input while active transport requires work/energy (ATP).
Explain what osmosis is.
Transport of water through aquaporin channels through membrane
Explain what is facilitated diffusion
Transport of solutes across membrane down concentration gradient via specific protein channels
What is the goal of osmosis?
From hypotonic to hypertonic until isotonic
Give example of facilitated diffusion
glucose transporter, gated ion channels ( Na+, K+) in membranes neurons
Give exemple of osmosis
Turgor pressure, using salt and sugar as a perservative, water moving into stomach, contractile vacuoles
Describe what is active transport
It move substance cross membrane against concentration gradient.
What does active transport require?
Energy (ATP) and transmembrane protein
Name the 4 types of active transport.
Ions pumps
Co-transport
Exocytosis
Endocytosis
Describe ions pumps transport
It moves ions across membrane against their concentration gradient
What does ions pumps maintain?
Maintain electrochemical gradient (membrane potential) and help maintain osmotic pressure.
Give four exemples of ions pumps
Na+/K+ ions pump
Ca++ pump in sarcoplasmic reticulum
Proton pump
H+/K+ ATPase (in stomach pumps H+ into lumen)
Proton pump’s roles?
In lysosome membranes maintain acid pH
In mitochondria use H+ gradient to make ATP
Describe co-transport.
Movement of 2 ions : one moves down concentration gradient, one moves against concentration gradient. Both move through same transport protein
Give two types of co-transport and one example for each of them.
symport : coupled molecule move in same direction (plant cells uptake of H+/sucrose)
antiport: coupled molecules move in opposite direction (cardiac muscle cells Na+ into cell/Ca++ out of cell)
Describe exocytosis
Vesicles containing molecules are transported from within the cell to the cell membrane.
The vesicle membrane attaches to the cell membrane.
Fusion of the vesicle membrane with the cell membrane releases the vesicle contents outside the cell.
Give examples of exocytosis
secretion of neurotransmitters by neuron
secretion of hormones and enzymes
insertion of plasma membrane
insertion of transmembrane proteins
Describe endocytosis
Uptake of macromolecules by formation of vesicles with plasma membranes to bring it inside cell
What are the three types of endocytosis
1) Phagocytosis = surrounds “stuff” outside cell with cell membrane to create food vacuole
2) Pinocytosis = unspecific uptake of extracellular fluid and dissolved solutes
3) Receptor-mediated endocytosis = specific molecules bind to receptor
