Part of phospholipid that interacts with water in an aqueous solution?
The polar, hydrophilic head region
What bonds connect fatty acids to glycerol in fats
Ester linkages
How many fatty acid tails do most phospholipids have?
2 tails (and one head )
Why are phospholipids heads hydrophilic while tails are hydrophobic
Heads are polar/charged
Tails are non polar hydrocarbons
What term describes molecules with both hydrophilic and hydrophobic regions.
Amphipathic (am-fuh- pathik)
3 types of lipids
Fats
Steroids: 4 fused carbon rings
Phospholipids
Fats (triglycerides) structure
Glycerol backbone bonded to 3 fatty acids with ester linkages.
Fatty acids : long hydrocarbon chains (usually hydrophobic)
Fats store energy sufficiently
Phospholipids structure
Glycerol backbone bonded to 2 fatty acids and one phosphate group (which often bonds further to small polar molecules)
What happens to glycerol when fats are formed?
Glycerol forms ester linkages with fatty acids, releasing water ( dehydration)
Cholesterol’s effect on membrane’s permeability
Reduces permeability (cholesterol gets inserted between phospholipids, making the membrane more tightly packed , restricting the passage of molecules like glycerol , water , ions)
Temperature effect on physical properties of lipids
Influenced fluidity and stability of lipid membranes; higher temp. Increases fluidity while lower temp lead to rigidity
Diffusion
Net movement of solutes from an area of higher concentration to an area of lower concentration.
To achieve equilibrium
Lipid bilayer
Membrane structure composed of two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.
Semi-permeable - selective barrier
Hypertonic
Causes vesicle to shrink and membrane to shrivel due to higher [solutes] outside of vesicle compared to inside
Hypotonic
Lower [solutes] outside compared to inside, leading to water moving inside the vesicle causing it to swell and potentially burst
Osmosis
Movement of water from area of low [solute] to high [solute]
Passive transport
Movement of substance without the need of energy
Channel proteins
These proteins form pores or channels in the membrane that allow specific ions or molecules to pass through
Passive - doesn’t require energy
Carrier protein
Bind to specific molecules and change shape to transport them across the membrane.
Can move down their gradient (passive) and against their gradient (active - requires energy )
Ion channels
A specific type of channel protein that lets ions (charged particles) move across the membrane.
Usually passive, down the electrochemical gradient
Electrochemical gradient
combined force that drives ions across a membrane.
The concentration gradient (ions moving from high to low concentration)
The electrical gradient: Positively charged ions (like Na⁺ or K⁺) are attracted to the negative side, while negatively charged ions (like Cl⁻) are repelled.
