Chapter 4 Part 2 [Section 4.4-4.6]

Chapter 4 Part 2
Cellular Metabolism
Section 4.4-4.6

4.4 Energy for Metabolic Reactions

​Who remembers what the ability to do work is?

We have already established that metabolic reactions have to have energy.

Energy can come in many forms - heat, light, sound, electrical, mechanical, and chemical.

Which form of energy does most metabolic reactions use?

Release of Chemical Energy

Chemical energy is held in the bonds between the atoms of molecules and is released when these bonds break.

Burning is an example of an intervention that can break bonds of chemicals in the environment (outside the body). Burning begins by applying ____. As the chemical burns, bonds break, and energy escapes as ____ and ____.

Inside the body: Cells "burn" glucose (sugar) molecules in a process called oxidation - the process by which oxygen combines with another chemical.

The energy released from breaking the bonds of glucose powers anabolic reactions of cells that build molecules.

RCE continued

​Burning inside and outside the body are completely different

Burning requires a large input of ____.

In cells, enzymes reduce the _____ _____ required for the oxidation that occurs in the reactions of cellular respiration.

​RCE continued

These reactions release the energy in the bonds of nutrient molecules. Cells capture about 40% (in cellular respiration) of the energy released and transfer it to high-energy electrons that the cell can use to synthesize molecules of ATP (adenosine triphosphate).

The rest of the released energy escapes as heat, which helps maintain body temperature.

​ATP Molecules

Cells use ATP for a variety of functions, including ____ ____ and ____ of various compounds.
ATP has how many chains of phosphates?
When energy is released during cellular respiration the terminal end phosphate captures some of that energy, then the energy is released when that bond breaks becoming ADP.

How many chains of phosphates are we left with?

​Can ADP convert back to ATP?

I'm glad you asked.

​YES IT CAN!!!

BUT HOW??

CAN YOU GIVE ME YOUR EDUCATED GUESS?

​Here's How...

By adding ENERGY and 1 phosphate!!!

Cellular Respiration

Cellular respiration consists of three distinct, yet interconnected, series of reactions: glycolysis, the citric acid cycle (Kerbs cycle), and the electron transport chain.

Glycolysis and electron transport chain are pathways.

​Formula for Cellular Respiration

Glucose and oxygen are required for cellular respiration. Products of these reactions include carbon dioxide, water, and energy.

C₆H₁₂O₆ + 0₂ --> 6CO₂ + 6H₂O + ENERGY

Cellular Respiration cont'd

​Glycolysis

What did we learn that the suffix -lysis mean? What is glyco- the prefix of? So, what is glycolysis? Are we putting in energy or releasing it?

Takes place in the ____ and it _____ require oxygen, so it is in the ____ phase of cellular respiration.

​Pyruvic acid is an intermediate product of carbohydrate oxidation, and its fate depends on oxygen availability. If oxygen is not present - PA enter what pathway? ___ and yields lactic acid and limited energy (2 ATP).​

Anaerobic Respiration

​If oxygen is present in sufficient quantity, the PA generated by glycolysis can enter the more energy-efficient pathway, that of ____ ____ and takes place in the _____.

​

Aerobic Respiration

​Aerobic Respiration

In the mitochondria, each molecule of PA loses a carbon atom and binds with a coenzyme to form a molecule of acetyl ___, which can then combine with a 4-carbon compound to enter the CAC, and then the ETC.

​Why is this pathway called aerobic?

The final acceptor of electrons passed along the ETC is ____.

Because the reactions of the ETC add phosphates to form ATP, they are also known as oxidative phosphorylation.

Aerobic Reactions...

Yield up to 36 ATP molecules per glucose.

For each glucose molecule that is completely broken down, up to 38 molecules of ATP are produced.
Let's see if the math is mathing...

Glycolysis generates ___ ATP molecules
CAC generates ___ ATP molecules
ETC releases ___-___ ATP molecules
Yielding a total of ___-___ depending on the cell type.

Recall: C₆H₁₂O₆ + 0₂ --> 6CO₂ + 6H₂O + ENERGY

About half (40%) of the energy released goes to ATP synthesis (in cellular respiration) while the rest ends up as ____.

Complete oxidation of glucose also produces __ &__.

Carbon dioxide is eventually ____ and water becomes part of the ____ ____.

Why Must We Drink Water?

If water becomes part of the internal environment, why must we drink it?

I'M GLAD YOU ASKED.

In humans, metabolism does not generate enough water to meet our daily needs, so we must drink water to survive.

​Trivia Question: THINK!!!

If we must drink water to survive, why is it that a small desert rodent, the kangaroo, can survive entirely on the water produced by aerobic respiration?

​We have talked about metabolism of glucose, but other macronutrients, like fats and proteins, are also broken down by ____ to ____ energy for ATP synthesis. For all three types of macronutrients, the final process is ____ ____ and the most common entry point is ____ as ____.

DNA (deoxyribonucleic acid)

Enzymes control essential metabolic reactions. Therefore, cells must have the information for producing enzymes.

What is this information?

DNA molecules hold the information to make proteins in the form of a genetic code.

​Genetic Information

How are DNA molecules passed to offspring?

When is DNA transferred from the chromosomes to new cells...what stage of the cell cycle?

A complete set of genetic instructions make up the genome. All cells except ____ cells contain two copies of the genome, one from each parent.

​Genetic Information cont'd

Segments of the genome that is responsible for proteins are called genes.

Only 1.5% of the human genome encodes proteins and it's called the exome.

​DNA Molecules

In a DNA molecule, the nitrogenous bases project from the backbone and weakly bind to the bases of the other strand - looking like a ladder.

DNA base may be one of four types:
A-adenine, T-thymine, C-cytosine, G-guanine

The nitrogenous bases of DNA pair in specific ways: A only to T and C only to G

​A gene is a sequence of nucleotide bases along one DNA strand that specifies a particular protein's amino acid sequence.

​The long DNA molecule forms a double helix. It folds tightly to fit inside a cell's nucleus.

A molecule of DNA is typically millions of base pairs long.

If unwound, DNA in a single cell it would stretch to about ____.

​DNA Replication:

When a cell divides, each newly formed cell must have a copy of the original cell's genetic information (DNA). Why? So that it will be able to synthesize the proteins to build cellular parts and metabolize.

​What helps make replication possible?

As replication (copying) begins, bonds break between complementary base pairs in each DNA molecule.

What causes the bonds to break? Enzymes known as Helicases.

​So, the double helix starts to unwind and pull apart exposing the nitrogenous bases. Then an enzyme called DNA polymerase brings in new DNA nucleotides, and they form complementary pairs with the exposed bases

​Other enzymes bring the backbone together.
A new strand of nucleotides forms along each of the old strands. This replication process produces 2 complete DNA molecules, each with one old strand and one new strand. (One from mom and one from dad)

​During what phase of the cell cycle does two DNA molecules pass to each of the new cells?


If there is an error in DNA replication that changes the sequence, it is called a ____?

​Why must DNA molecules replicate?

What is the difference b/w gene and genome?

Review Questions

​List the steps of DNA replication -->

Gene - is a segment of the genome that encodes protein; genome - is the complete set of genetic information

So that each new cell receives a full complement of DNA

​1. Bond breaks
2. Double helix unwinds and pulls apart
3. DNA polymerase brings in DNA nucleotides - forming new complementary pairs
4. Produces 2 complete DNA molecules

Protein Synthesis

​The Genetic Code - instructions for making proteins

Each of the 20 types of amino acids in a biological protein is presented in a DNA molecule by a particular sequence of 3 nucleotides.

The DNA sequence GGT represents one type of amino acid GCA represents another, TTA another.

​The sequence of nucleotides in a DNA molecule indicates the order of amino acids, as well as where to start or stop protein synthesis.

​Transcription - the writing

DNA molecules stay in the nucleus, but protein synthesis occurs in the cytoplasm.

The genetic information reaches the cytoplasm by being copied into molecules of RNA.

How can they exit the nucleus?

I'm glad you asked.

​
Because...

RNA is much shorter than DNA and they are single-stranded

The process of synthesizing RNA is transcription.

Messenger RNA (mRNA) is the type of RNA that carries a gene's message out of the nucleus. Other types of RNA also help to build proteins.

​Like DNA, RNA also has 4 nitrogenous bases - Adenine, Uracil, Cytosine, and Guanine.
In place of Thymine that is only found in DNA, Uracil is in its place in RNA.

The enzyme RNA polymerase synthesizes mRNA following the rules of complementary base pairs.

For example, the DNA sequence A, T, G, C, G specifies the complementary mRNA bases U, A, C, G, C.

RNA polymerase also recognizes DNA sequences that indicate where the gene begins, where it stops, and the correct direction to read the DNA, just like a sentence.

When the RNA polymerase reaches the end of the gene, it releases the newly formed mRNA. Transcription is complete.

Translation

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Happy teaching!

Translation - the interpreter

Amino acids are specified by 3 contiguous bases in DNA sequence - in the correct order it's a codon in mRNA.

The sequence AUG represents the "start" of a gene, and three other mRNA base sequences indicate "stop".
To help you remember the sequence that represents "start" -- think about when you "start" school -- in what month?

To guide protein synthesis, a mRNA molecule must leave the nucleus and associate with a ribosome in the cytoplasm - this is where the codons are translated into the correct language - Translation -->
A ribosome binds to a mRNA molecule, another RNA molecule, tRNA (transfer RNA), correctly aligns amino acids, which are then linked by enzymatic actons to form proteins.

Amino acids released from tRNA molecules join and form a protein molecule that folds into a unique shape.

Correct protein folding is essential to health. In cells, misfolded proteins are threaded through spool-shaped structures called proteasomes. They are either refolded into a functional shape or they destroyed if they are too abnormal.

Proteasomes - focuse on unfit PROTEINS -- let words help you

A gene that is transcribed and translated into a protein is said to be expressed.

Gene expression is the basis for cell differentiation.

​YOU NOW HAVE ALL THE NOTES FOR THE SECOND TEST AND FOR YOUR STUDY GUIDE.

NO EXCUSES! GET IT DONE!