Ch. 5 Cell Respiration and Metabolism Flashcards
Metabolism
All of the reactions in the body that require energy transfer.
Anabolism
Catabolism
Anabolism
Requires the input of energy to synthesize large molecules
Building something up
Catabolism
Releases energy by breaking down large molecules into small molecules
Part of glycolysis
Describe how catabolism drives anabolism
The catabolic reactions that break down glucose, fatty acids, and AAs serve as energy sources for the anabolism of ATP.
–gives us energy so we can make ATP
The complete catabolism of glucose requires ____ as the final electron acceptor.
Oxygen
This is called Aerobic Cellular Respiration
Breaking down glucose requires many enzymatically catalyzed spots, the first of which are ____.
Anaerobic
–but to completely break down glucose, oxygen is necessary
Glycolysis
Conversion of glucose into 2 molecules of pyruvic acid
–doesn’t require oxygen
Glycogenesis
Production of glycogen, mostly in skeletal muscles and the liver
Glycogenolysis
Hydrolysis (breakdown) of glycogen
Ketogenesis
Formation of ketone bodies, from fatty acids; occurs in liver
Describe the 3 steps of aerobic respiration of glucose.
1) Glycolysis - occurs in cytoplasm; anaerobic
2) Citric acid (Krebs) cycle - occurs in matrix of mitochondria; aerobic
3) Electron transport - occurs on cristae of mitochondria inner membrane; aerobic
In which step of aerobic respiration of glucose are we going to get the most ATP?
Step 3
[3) Electron transport - occurs on cristae of mitochondria inner membrane; aerobic]
Glycolysis
First step in catabolism of glucose, occurs in cytoplasm of cell
Glucose is split into 2 pyruvic acid molecules
–pyruvic acid is a 3-carbon molecule, and we get 2 of those
There is a loss of 4 hydrogen ions. Those were used to reduce 2 molecules of NAD
Generate 4 ATP, use ATP…net gain of 2 ATP
What do I need to know about glycolysis?
2 pyruvic acid + 2 NADH + 2 ATP
–for balance we reduce NAD to get NADH
Out of glycolysis we get 2 pyruvic acid and 2 ATP
Describe the conversion of pyruvic acid to lactic acid.
When there is no oxygen to complete the breakdown of glucose, NADH has to give its electrons to pyruvic acid. This results in the reformation of NAD and the conversion of pyruvic acid to lactic acid
Lactic Acid Pathway yields a net gain of ____ ATP
2 ATP.
The Lactic Acid Pathway is also known as?
Anaerobic metabolism or Lactic acid fermentation
Muscle cells can survive for awhile without oxygen using what?
Lactic acid fermentation
RBCs can only use lactic acid fermentation because they lack ____.
Mitochondria
The citric acid cycle is step ____.
Step #2
The citric acid cycle is also known as?
Krebs cycle or TCA cycle
Describe the Citric Acid Cycle. Pay close attention to where ATP comes from (for exam).
Acetyl CoA combines with oxaloacetic acid to form citric acid.
–fuel the cell w/ Acetyl CoA that we got from pyruvic acid; can go through cycle twice b/c we have 2 Acetyl CoA
Citric acid starts the citric acid cycle and ‘moves’ through a series of reactions to produce oxaloacetic acid again.
–happens once for every Acetyl CoA
Makes GTP, GTP gives us ADP –> ATP
Citric Acid Cycle: For each glucose, we have ____ NADH, ____ FADH2, ____ ATP, and ____ CO2.
6 NADH
2 FADH2
2 ATP
4 CO2
Electron Transport and Oxidative Phosphorylation
In the [inner membrane] folds or cristae of the mitochondria are molecules that serve as electron transporters.
- -these accept electrons from NADH and FADH2 (from Krebs cycle). The hydrogens are not transported with the electrons.
- -oxidized FAD and NAD are reused
The mitochondria has a double membrane meaning it is ____ ____.
Highly folded
Electron Transport Chain
Electron transport molecules pass the electrons down a chain, with each being reduced then oxidized.
This is an exergonic reaction, and the energy produced is used to make ATP from ADP
–this process is called oxidative phosphorylation
Process is not 100%; difference is released as heat
–inefficient reaction b/c a lot of energy is lost/released as heat
Is oxidative phosphorylation aerobic or anaerobic?
Aerobic
Oxidative Phosphorylation
Intermembrane space of mitochondria folded in cristae increases surface area (SA) to fit large complexes.
Pumping hydrogen from the matrix into intermembrane space.
Hydrogen goes back down concentration gradient which allows for the production of ATP; recycle hydrogen and start pumping it back into intermembrane space again.
What kind of poison is cyanide?
Mitochondria poison
Oxygen
Final electron acceptor
Citric acid cycle and electron transport require oxygen to continue.
Water is formed
ATP
Direct (substrate-level) phosphorylation in glycolysis and the citric acid cycle yields 4 ATP.
Theoretical ATP yield is 36-38 per glucose, but actual yield is 30-32 per glucose (energy needed to move ATP from mitochondria to cytoplasm)
–we get 2 ATP from pyruvic acid
What happens (in terms of ATP) if the body is deprived of oxygen?
Pyruvic acid and lactic acid converted to ATP
What happens (in terms of ATP) if the body has plenty of oxygen?
Pyruvic acid converted to Acetyl CoA
What is the actual yield of ATP from oxidative phosphorylation?
26 or 28 ATP (theoretical yield is 32 or 34)
Why can’t cells store much glucose?
Cells can’t store much glucose because it will pull water into the cell via osmosis
Glycogenesis
Glucose is stored as larger molecule called glycogen (a polysaccharide) in the liver, skeletal muscles, and cardiac muscles.
Storing glucose as glycogen reduces the osmotic pull.
Glycogen is formed from glucose via ____.
Glycogenesis
Glycogenolysis
When the cell needs glucose, it breaks glycogen down.
Produces glucose 1-phosphate.
What is the catalyst in glycogenolysis?
Glycogen phosphorylase
When glucose from glycogen is in the form of glucose 1-phosphate, where does/can it go?
NOWHERE
It cannot leave muscles or heart cells (trapped there)
How is glucose 1-phosphate finally able to move?
The LIVER has an enzyme called glucose 6-phosphate that removes the phosphate so glucose can reenter the bloodstream.
What are liver cells called?
Hepatocytes
Why is the liver important in glycogenolysis (besides having glucose 6-phosphate)?
The liver brings in glucose and stores some for itself, in addition to the excess glucose it also stores.
When the body needs glucose, the liver sends the excess glucose back out into the bloodstream for other organs to use.
In the Cori Cycle, what is being recycled and where is it being recycled?
Lactic acid is being recycled; only being recycled in the liver.
That lactic acid then gets changed to pyruvic acid in order to help release glucose
____ and ____ can also be used for energy via the same pathways used for the metabolism of pyruvic acid.
Lipids and Proteins
When more food energy is taken into the body than is needed to meet energy demands, are we able to store ATP for later?
No
–we make ATP as we need it…it’s not a great storage form
Because we can’t store ATP, what happens to glucose (in terms of lipid and protein metabolism)?
Glucose is converted to glycogen and fat, and ATP production is inhibited
Lipid Metabolism
Glucose doesn’t complete glycolysis to form pyruvic acid, and Acetyl CoA (already formed) is joined together to produce a variety of lipids, including cholesterol, ketone bodies, and fatty acids.
Lipogenesis
Fatty acids combine with glycerol to form triglycerides in the adipose tissue and liver
–making fatty acids, stored in fat tissue, in times of excess energy consumption
Beta-oxidation
Enzymes remove acetic acid molecules from fatty acids to form Acetyl CoA
–break it down when needed
For every 2 carbons on the fatty acid chain, 1 Acetyl CoA is formed
Each Acetyl CoA yields 10 ATP
[This is how we use fatty acids as energy source]
Why are steroids (come from cholesterol) important?
Important in endocrine (hormone) signaling
Fatty acids (including triglycerides and phospholipids) are important in?
Membrane creation
Proteins provide ____ for the body.
Nitrogen
Amino Acid Metabolism
AA from dietary proteins are needed to replace proteins in the body.
If more AA are consumed than are needed, the excess AA can be used for energy or converted into CHO or fat
How many AA can our body make?
Our bodies can make 12 out of 20 AA from other molecules.
Eight of them (9 in children) must come from the diet and are called Essential AA
Where do AA enter the citric acid cycle?
AA enter at different points throughout the cycle
Do AA enter the citric acid cycle during glycolysis?
No
Glucose and ketone bodies come from the ____.
Liver
Fatty acids come from ____ ____.
Adipose tissue
Lactic acid and AA come from ____.
Muscle
What can we do with lactic acid?
Send it back to liver by Cori Cycle to change it to pyruvic acid
Glycolysis: Glycogen –> ____ ____.
Acetyl CoA
Does the brain store glucose well?
No, that’s why regulation of glucose levels is so important
Where does anaerobic metabolism predominantly occur?
In skeletal muscle
What are the 3 main organs/tissues that energy sources are stored in?
Liver, Adipose tissue, [Skeletal] Muscle
