Carbohydrates & lipids - phospholipids Flashcards
What forms the basic structure of the cell membrane?
Phospholipids
Phospholipids create the phospholipid bilayer that constitutes the cell membrane.
What type of structure do cell membranes have?
Phospholipid bilayers
Cell membranes are specifically organized into two layers of phospholipids.
What are the two regions of a phospholipid?
Hydrophilic phosphate head and hydrophobic hydrocarbon tails
The hydrophilic head interacts with water while the hydrophobic tails do not.
What property does the phosphate head of a phospholipid exhibit?
Polar and hydrophilic
This polarity allows the phosphate head to be soluble in water.
What characteristic do the fatty acid tails of a phospholipid have?
Nonpolar and hydrophobic
This nonpolarity makes the tails insoluble in water.
What term describes molecules with both polar and non-polar regions?
Amphipathic
Amphipathic molecules have both hydrophilic and hydrophobic properties.
What happens to phospholipids when placed in water?
They form a phospholipid monolayer
The hydrophilic heads orient towards water while the hydrophobic tails orient away.
What structure is formed when phospholipids are mixed with water?
Phospholipid bilayers
This structure is essential for forming the cell membrane.
What is the function of the phospholipid bilayer regarding water-soluble substances?
Acts as a barrier
The bilayer prevents most water-soluble substances from crossing.
What type of molecules can pass through phospholipid bilayers easily?
Small, nonpolar molecules
Examples include O2 and CO2, which can diffuse quickly across the membrane.
Do small, nonpolar molecules require proteins for transport across cell membranes?
No
These molecules can diffuse across the bilayer without assistance.
What type of molecules can also enter the cell across the lipid bilayer?
Larger, non-polar molecules
An example of such molecules includes steroid hormones.
What type of lipid is contained in steroid hormones?
Cholesterol
Cholesterol’s non-polar hydrocarbon region allows it to cross lipid bilayers.
Name two steroid hormones formed from cholesterol.
Oestradiol and testosterone
These hormones are produced by gonadal tissues in the reproductive organs.
What is the effect of steroid hormones inside the nucleus?
They alter and direct the process of transcription
This process is crucial for gene expression regulation.
