lipids Flashcards
What is the structure of a triglyceride? (2)
Consists of one molecule of glycerol;
With three fatty acids attached
What is the structure of a phospholipid? (2)
Consists of one molecule of glycerol;
With two fatty acids and one phosphate group attached to it
How are triglycerides synthesised? (2)
By the formation of an ester bond;
Between each fatty acid and the glycerol molecule
How is each ester bond in a triglyceride formed? (3)
Formed by a condensation reaction,
Where one molecule of water is released.;
To form one triglyceride, three condensation reactions take place, releasing three molecules of water
Are lipids polymers? Explain your answer. (2)
No;
Polymers consist of repeating units of monomers whereas lipids do not.
What is esterification? (1)
Process by which triglycerides are synthesised
How can triglycerides be broken down? (2)
Hydrolysis of each ester bond;-
To form glycerol and fatty acids as well as water
What is the difference between saturated and unsaturated fatty acids? (2)
Saturated fatty acids do not have any double bonds between their carbon atoms;
Unsaturated fatty acids have at least one double bond between their carbon atoms
What is the primary function of triglycerides in plants and animals? (2)
Function as energy storage molecules in plants and animals;
Some bacteria, such as Mycobacterium tuberculosis, also use triglycerides to store energy and carbon
Why are triglycerides good storage molecules? (3)
Long hydrocarbon tails of the fatty acids contain a lot of chemical energy;
Which is released when they are broken down;
This is why lipids provide twice as much energy per gram as carbohydrates
Why do triglycerides not cause water to enter the cell by osmosis? (3)
Triglycerides are insoluble;
So they do not cause water to enter cells by osmosis;
Preventing cell swelling
How do triglycerides form insoluble droplets in cells? (2)
The fatty acid tails are hydrophobic;
These tails face inward, shielding themselves from water with their glycerol heads
Where are phospholipids found? (1)
In the cell membranes of all eukaryotes and prokaryotes
What structure do phospholipids form in cell membranes? (1)
The phospholipid bilayer
How do phospholipids arrange themselves in the phospholipid bilayer? (3)
They have hydrophilic phosphate heads and hydrophobic fatty acid tails;
So they form a double layer;-
With their heads facing outwards towards the water on either side of the membrane
Why is the centre of the phospholipid bilayer important for cell function? (3)
It is hydrophobic;
Preventing water-soluble substances from passing through it;
Making the membrane a barrier that controls what enters and leaves the cell
Describe the basic structure of cholesterol (2)
Has a hydrocarbon ring structure attached to a hydrocarbon tail;
The ring structure has a polar OH group attached to it
What is the role of cholesterol in eukaryotic cell membranes? (2)
Strengthens the cell membrane;
By interacting with the phospholipid bilayer
How does cholesterol fit into the phospholipid bilayer? (2)
It is small and flattened;
So it can fit between the phospholipid molecules in the membrane
How does cholesterol interact with phospholipids to regulate membrane fluidity? (3)
OH group interacts with phospholipid heads;
Hydrocarbon tail embeds alongside fatty acid tails of phospholipids;
Phospholipids pack closer together, making the membrane less fluid and more rigid
