Transport Across Cell Membranes Flashcards
What is meant by diffusion
The net movement of molecules from a HIGH concentration to a LOW concentration across a concentration gradient until an equilibrium is reached
What molecules can slip through the gaps set up by the movement of phospholipid molecules in the membrane
Small, non-polar, lipid-soluble
What is meant by FACILITATED DIFFUSION
Some molecules diffuse across the membrane FASTER than their concentration gradient should allow. Movement is facilitated by proteins in the membrane
What are carrier proteins
Permanently open. Each channel proteins is specific and some do have gates which open and close
Lined with hydrophilic amino acids and water
Insulin binds to gate and changes the enzyme to open the gate to let the glucose through. Hormones open gated channels one way
What is a carrier protein
Helps glucose across the membrane but won’t take water solubility
Complementary shape helps glucose move into a cell
No ATP required
Is REVERSIBLE
What is active transport
Low to high
Requires ATP and carrier proteins
Highly selective by complementary shapes
Needs mitochondria as this is where ATP takes place
Molecules move AGAINST their concentration gradient
What is meant by osmosis
The net movement of after molecules from a region of HIGH WATER POTENTIAL to a region of LOW WATER POTENTIAL across a partially permeable membrane, until an equilibrium is reached, down a water potential gradient
What does co-transport include
Active transport and facilitated diffusion
How can cells be adapted for rapid transport
Surface area of their membrane increased (villi)
Number of ports in channel molecules
Number of protein carrier molecules
Bulk transport
What happened internal ( ENDOCYTOSIS)
Big molecules move to membrane surface
Membrane invaginate and forms a vesicles around the molecule
Vesicles moves into cytoplasm
Bulk transport
What happens external membrane (EXOCYTOSIS)
Vesicles moves towards membrane
Vesicles fuses with membrane
Molecules released to outside cell
What is the structure of the cell-surface membrane
Arrangement and any movement of PHOSPHOLIPID, PROTEINS, GLYCOPROTEIN, GYLCOLIPIDS in the fluid-mosaic model
The plasma membrane=
Serves as a boundary around cells and organelles
It is partially permeable and appears on electron micrograph a as a 3-layered structure
Cholesterol may also be present in cell membrane where it’s restricts the movement of other molecules making up the membrane. Forces holding the molecule together are weak(HYDROGEN BONDS)
