The Cell
The Cell
Cellular membranes are fluid mosaics of lipids and proteins
- The plasma membrane is selectively permeable, meaning it allows some substances to cross more easily than others
- FLUID MOSAIC MODEL: membrane represented as a fluid with proteins integrated in the phospholipid bilayer
- PHOSPHLIPIDS: provide a hydrophobic barrier that separates the cell from its liquid environment
-amphipathic
-fluid/ viscous membrane
-saturated fatty acids
-decreases fluidity
-unsaturated fatty acid tails
-increases fluidity
- PROTEINS: acts as transport channels by molecular receptors (ligands:
-integral
-transmembrane
-peripheral
- CARBOHYDRATES: crucial for cell to cell recognition
- CHOLESTEROL: plays a role in membrane fluidity , prevents water soluble molecules from diffusing across
Membrane structure results in selective permeability
- NONPOLAR MOLECULES: able to pass the bilayer easily
- polar and large molecules have to go through transport proteins which it is called facilitated diffusion
- water is special and in order to cross, have to go through aquaporins
Passive transport is diffusion of a substance across a membrane with no energy investment
- PASSIVE DIFFUSION: a substance travels down the concentration gradient and requires no energy
- the diffusion of water across a selectively permeable membrane is osmosis
- ISOTONIC: n net movement of water across the plasma membrane
- HYPERTONIC: the cell will lose water due to its surroundings
- HYPOTONIC: water will enter the cell faster than it leaves
Active transport uses energy to move solutes against their gradients
- ACTIVE TRANSPORT: substances are moved against their concentration gradient, this energy, usually ATP
- SODIUM POTASSIUM PUMP: moves 3 + NA+ out and 2 K+ into the cell to maintain homeostasis
- MEMBRANE POTENTIAL: is the difference in electric charge across a membrane and is expressed in voltage
- the inside of the cells is negatively charged, so positively charges molecules are attracted to the cell. The combination of forces forms an electrochemical gradient
- bulk transport across the plasma membrane occurs by exocytosis and endocytosis
- EXOCYTOSIS: vesicles from the cell's interior fuse with the cell membrane and expel their contents
- ENDOCYTOSIS: essentially the reverse of exocytosis, the cell forms new vesicles from the plasma membrane
The Cell
Cellular membranes are fluid mosaics of lipids and proteins
- The plasma membrane is selectively permeable, meaning it allows some substances to cross more easily than others
- FLUID MOSAIC MODEL: membrane represented as a fluid with proteins integrated in the phospholipid bilayer
- PHOSPHLIPIDS: provide a hydrophobic barrier that separates the cell from its liquid environment
-amphipathic
-fluid/ viscous membrane
-saturated fatty acids
-decreases fluidity
-unsaturated fatty acid tails
-increases fluidity
- PROTEINS: acts as transport channels by molecular receptors (ligands:
-integral
-transmembrane
-peripheral
- CARBOHYDRATES: crucial for cell to cell recognition
- CHOLESTEROL: plays a role in membrane fluidity , prevents water soluble molecules from diffusing across
Membrane structure results in selective permeability
- NONPOLAR MOLECULES: able to pass the bilayer easily
- polar and large molecules have to go through transport proteins which it is called facilitated diffusion
- water is special and in order to cross, have to go through aquaporins
Passive transport is diffusion of a substance across a membrane with no energy investment
- PASSIVE DIFFUSION: a substance travels down the concentration gradient and requires no energy
- the diffusion of water across a selectively permeable membrane is osmosis
- ISOTONIC: n net movement of water across the plasma membrane
- HYPERTONIC: the cell will lose water due to its surroundings
- HYPOTONIC: water will enter the cell faster than it leaves
Active transport uses energy to move solutes against their gradients
- ACTIVE TRANSPORT: substances are moved against their concentration gradient, this energy, usually ATP
- SODIUM POTASSIUM PUMP: moves 3 + NA+ out and 2 K+ into the cell to maintain homeostasis
- MEMBRANE POTENTIAL: is the difference in electric charge across a membrane and is expressed in voltage
- the inside of the cells is negatively charged, so positively charges molecules are attracted to the cell. The combination of forces forms an electrochemical gradient
- bulk transport across the plasma membrane occurs by exocytosis and endocytosis
- EXOCYTOSIS: vesicles from the cell's interior fuse with the cell membrane and expel their contents
- ENDOCYTOSIS: essentially the reverse of exocytosis, the cell forms new vesicles from the plasma membrane