2A Flashcards
Structure of cell membrane
Phospholipid bilayer
● Transmembrane proteins- channel proteins and carrier proteins
● Surface proteins and glycoproteins
Fluid mosaic model
Phospholipids can move in the plane, and have a mosaic-like arrangement of proteins.
Structure of phospholipid
One hydrophilic head with two fatty acid tails
What is te función of channel protein
Allow small charged particles/polar molecules to move through the membrane.
What is the function of a carrier protein?
To move large molecules across the membrane by facilitated diffusion or to move any particle against the concentration gradient.
Ósmosis
The movement of free water molecules from an area of high concentration of water (dilute) to an area of low concentration of water (concentrated), across a partially permeable membrane.
Diffusion
The movement of small non-polar, lipid-soluble molecules from an area of high concentration to an area of low concentration.
Active transport
The movement of molecules against a concentration gradient (low to high), meaning energy in the form of ATP is required. Also uses carrier proteins.
Give an example of particle that moves by facilitated diffusion using a carrier protein
Glucose
How are large molecules such as proteins moved across a cell membrane?
Endo or exocytosis
Give three examples of particles that move by facilitated diffusion using channel proteins
Sodium chloride
Endocytosis
Cell membrane forms a vesicle and engulfs the material, which enters the cytoplasm.
Exocytosis
Vesicle formed in the golgi apparatus fuses with cell membrane to release contents from cell.
What evidence led to the fluid mosaic model
● Phospholipids naturally form bilayers in water.
● Microscope images show proteins on membrane surface.
● Lipid-soluble substances pass more easily in and out of cells than water-soluble.
Name three features of an efficient gas exchange surface
Large surface area, e.g. folded membranes in mitochondria.
2. Thin/short diffusion distance, e.g. wall of capillaries.
3. Steep concentration gradient, maintained by blood supply or ventilation, e.g. alveoli.
