Exam 3 November 23 Lecture Flashcards
How is the keto and the gluco world connected?
by 1 step: pyruvate being converted to acetyl CoA (this step is irreversible so can’t go back to pyruvate) → can’t utilize acetyl CoA to make pyruvate
When we’re hungry, what does the liver do?
makes glucose during gluconeogenesis
What happens when there is plenty of acetyl CoA?
we make fatty acids
What happens when there is a lot of fatty acids?
we break down fatty acids to make acetyl CoA
What do unsaturated fatty acids (aka kinks) do to the melting temperature?
lowers the melting temperature
What does it mean if a fatty acid is essential?
our body needs them but the body is unable to make them so we get them from the foods we eat
What are eicosanoids?
have 20 carbons and are like hormones such as prostaglandins that function in inflammation
What is excess energy stored as?
fat → fatty acids are synthesized from acetyl CoA in which the liver and adipose tissues convert glucose to fatty acids and then to triacylglycerol
How is triacylglycerol released into the bloodstream by the liver?
it is packed in lipoproteins (VLDL) → lipoproteins are not soluble so they can build up and block the bloodstream
What type of cells store triacylglycerol?
adipocytes (fat cells)
What is the difference between white fat cells and brown fat cells?
white fat cells are primarily composed of triacylglycerol and is used for storage like tiny tanks while brown fat cells have lots of mitochondria to help generate heat since these type of cells generate body heat so that when it’s cold, it helps the body maintain its temperature → infants have lots of brown fat cells but we lose them as we age
Why is the transfer of acetyl CoA crucial?
fatty acid synthesis occurs in the cytosol but acetyl CoA is produced in the mitochondria → acetyl CoA is needed to be brought into the cytosol but it has no transporter and is a large molecule → needs to be converted to citrate to be transported to the cytosol
What happens when there is a lot of acetyl CoA in the mitochondria?
the TCA cycle is active to make citrate and citrate is transported to the cytosol so that it can be converted to acetyl CoA to make fatty acids
What is the difference between malonyl CoA and acetyl CoA?
malonyl CoA has 3 carbons but acetyl CoA has 2 carbons
What is the commitment step of fatty acid synthesis?
the conversion of acetyl CoA to malonyl CoA (is also the rate limiting step and is a highly regulated step and requires ATP)
How is the activity of acetyl CoA carboxylase regulated?
activated by citrate and isocitrate
inhibited by acyl CoAs
What is malonyl CoA used for?
as a substrate for fatty acid synthesis → therefore, it inhibits fatty acid oxidation
What happens if there are high levels of malonyl CoA?
we are synthesizing fatty acids which means we should not be breaking down fatty acids → malonyl CoA inhibits fatty acid oxidation
What do high levels of citrate mean?
we have lots of acetyl CoA which signifies we need to make fatty acids
What do high levels of acyl CoA mean?
we don’t need to make fatty acids → we need to break down fatty acids to make energy
What are the steps to fatty acid synthesis?
starts with acetyl CoA adding 2 carbon units at a time → the growing fatty acids are carried by acyl carrier protein (ACP) or fatty acid synthase through a covalent bond (thioester) → carboxyl group of malonyl CoA is released as CO2 during synthesis → final product is released from ACP by hydrolysis
How many NADPH are used for fatty acid synthesis?
two NADPH are used per cycle
Fatty acid synthase is what kind of enzyme?
multifunctional → huge enzyme with multiple subunits
How are the growing fatty acids released?
when the chain grows to be 16 carbons → becomes palmitate and the thioester bond is cut and the molecule is released
