Metabolism Flashcards
Macromolecules
The large molecules necessary for life that are built from smaller organic molecules.
4 macromolecules
Carbohydrates, proteins, lipids, nucleic acids
Macromolecules structure
These macromolecules are often complex in nature but really are just polymers
* Long molecules made up of similar building blocks of smaller molecules
* Most of these polymers can be broken
down relatively easily through hydrolysis
(Carbohydrates, Proteins and Nucleic
Acids)
* Lipids are broken down by lipolysis
carbohydrates
- Are saccharides
- They are all built on a C(H2 O)n formula which represents a carbon backbone is attached to a 2:1 hydrogen:oxygen ratio
- This enables a ton of different configurations that are easy to build and break-a-part.
- These can be used as fuel sources or converted to other organic molecules
Types of carbohydrates
- Monosaccharides (1 sugar)
- Disaccharides (2 sugars)
- Polysaccharides (many sugars)
Monosaccharides
- These are the simplest sugars and can not be broken down by hydrolysis into smaller carbohydrate molecules
- They can readily be used as fuel sources in the body
Monosaccharides types
Glucose, Fructose and Galactose all have the same formula (C6 H 12 O6 ) are regarded as dietary monosaccharides since they are readily absorbed by the small intestines.
Glucose
An important source of energy. During cellular respiration, energy is released from glucose and that energy is used to help make adenosine triphosphate (ATP).
fructose
A naturally occurring sugar often found in fruits, fruit juices, honey and some vegetables. It is often used in the body to aid in glycolysis and helps replenish liver glycogen stores
Ribose
- (C5 H10 O5)
- Is the pentose sugar component of the nucleotides of RNA
Deoxyribose
- (C5 H10 O4)
- The sugar component of the nucleotides of DNA
Disaccharides
These form when two monosaccharides are joined together
* One of the monosaccharides is always glucose
Disaccharide types:
Sucrose, lactose, Maltose
Sucrose
- Most common dietary disaccharide and can make up to 25% of the calories
consumed in the USA - Occurs naturally and is in most foods that contain carbohydrates
lactose
- Only natural source is from milk and milk sugar products
- This is not found in plants
- Is the least sweet of the three main dietary disaccharides
Maltose
- Made from two glucose molecules
- Found in beer, breakfast cereals, and germinating seeds
- Only contributes a small amount to the dietary carbohydrate consumption totals
Polysaccharides
A long chain of monosaccharides is known as a polysaccharide (“many”)
* The chain may be branched or unbranched, and it may contain different types of monosaccharides.
Polysaccharides Types
Starch, glycogen, cellulose and chitin
Starch
Is the storage form of carbohydrates within plants.
Starch two main forms:
- Amylose: long, straight chains that are twisted to form helical coils (slow to
breakdown) - Amylopectin: highly branched glucose chains (fast to breakdown)
Glycogen
- Is the storage form of carbohydrates within animals (Muscle and Liver)
- Highly branched (similar to amylopectin and is fast to breakdown)
- Converted to glucose in the body via glycogenolysis
cellulose
- Most abundant naturally occurring polysaccharide
- Found in plant walls and provides the structural support to the cell
- Made of long-straight chains which provide plant cells with their rigidity
- Very hard to breakdown
Chitin
- Found in the exoskeleton of arthropods and provides the structural support to
the cell - Similar to cellulose it is made of long-
straight chains which provide rigidity to
the shells (Also in fungal cell walls) - Can be made into flexible surgical thread that decomposes over time
Proteins
Perform essential functions throughout our systems. These long chains of amino acids are critically important.
Proteins importance
- Catalyzing chemical reactions
- Synthesizing and repairing DNA
- Transporting materials across the cell
- Receiving and sending chemical signals
- Responding to stimuli
- Providing structural suppor
Protein structure
Proteins are made from polymers of specific amino acid sequences that form polypeptide chains
* There are 20 different amino acids required by the body and these are used to make up all of our proteins
* In total there are about 50,000 different proteins in the human body! (all with unique functions)
Protein shape
- The function of each protein will depend on how each protein is shaped.
- As such, any small change to the form of a protein can greatly alter it’s function and result in the protein becoming dysfunctional (sickle cell anemia)
Enzymes
Are proteins that catalyze biochemical reactions, which otherwise would not take place.
Why are enzymes essential
- Enzymes are essential for chemical processes like digestion and cellular
metabolism. - Without enzymes, most physiological processes would proceed so slowly (or not at all) that life could not exist.
Two types of enzymes
Anabolic and catabolic enzymes
Anabolic enzymes
enzymes that build more complex molecules from their substrate
Catabolic
enzymes that break down their substrate
Enzymes in digestion
breaking larger food molecules down into subunits small enough to diffuse through a
cell membrane and to be used by the cell (Catabolic Enzymes)
Enzymes that help: Amylase, pepsin, lipase, trypsin
Amylase
digestion carbohydrates in the mouth and small intestine
Pepsin
digestion of proteins in the stomach
Lipase
emulsify fats in the small intestine
Trypsin
further digestion of proteins in the small intestine
Hormones
are often proteins that are secreted by endocrine cells and act to control or regulate specific physiological processes:
* Growth
* Development
* Metabolism
* Reproduction
Insulin
A protein hormone that helps to regulate blood glucose levels
Other proteins
- Act as receptors to detect the concentrations of chemicals and send signals to respond.
- Some types of hormones, such as estrogen and testosterone, are lipid steroids, not proteins
Lipids
- Are the fats, oils, waxes and other similar compounds in out bodies
- Lipids are mainly used in the body for energy storage and structure
Lipids structure
- They are mainly made from carbon, hydrogen and oxygen (but in very different ratios than carbohydrates)
- The vast majority of lipids are non-polar, they do not dissolve in water (or blood which is ~90% water)
- Instead they are transported via lipoproteins
Lipid, three main types
- Fats
- Phospholipid
- Steroids
Fats
- Fats are constructed from a single glycerol molecule and three fatty acids
Saturated fatty acids
- have the maximal number of hydrogen atoms that are possible for the structure
- Therefore, no double bonds are present
- Tend to form solids at room temperature (more rigid structures)
Unsaturated fatty acids
- have one or more double bonds present
- Usually of plant origin and contain cis fatty acids
- Tend to form liquids at room temperature (less rigid structures)
Phospholipid
- Are major components of the plasma membrane, the outermost layer of animal cells
Phospholipid structure
- Like fats, they are composed of fatty acid chains attached to a glycerol backbone.
- Unlike fats, which have three fatty acids, phospholipids have two fatty acids and a
phosphate group that help form a diacylglycerol. - The cell membrane consists of two adjacent layers of phospholipids, which form a bilayer.
Phospholipid- Phosphate group
Is negatively charged, making the head polar and hydrophilic, or “water loving”
Phospholipid- fatty acid tails
Are uncharged, non polar, and hydrophobic, or “water fearing”
Phospholipid bilayer
- Acts as a semipermeable membrane
- Only lipophilic solutes can easily pass the bilayer.
- As a result, there are two distinct aqueous compartments on each side of the membrane.
- This separation is essential for many biological functions, including cell communication and metabolism.
Steroids
- Play roles in reproduction, absorption, metabolism regulation, and brain activity
- Unlike phospholipids and fats, steroids have a fused ring structure.
- All steroids have four linked carbon rings
- Although they do not resemble the other lipids, they are grouped with them because they are also hydrophobic and insoluble in water.
Cholesterol
- The most common steroid and is mainly synthesized in the liver; it is the precursor to:
- Vitamin D
- Steroid hormones like estrogen, testosterone, and progesterone
- Plays a role in synthesizing aldosterone, which is used for osmoregulation
- Also contributes to the formation of cortisol, which plays a role in metabolism.
Nucleic acid
Two main types: DNA and RNA
DNA
- the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals.
- Deoxyribose
- Deoxyribonucleic acid
- Nucleotide: phosphate, sugar and base
- Double stranded
- Bases: guanine, cytosine, adenine, thymine
- A double bond T, C triple bond G
- Long strands
RNA
- mostly involved in protein synthesis
- Ribose
- Ribonucleic acid
- Nucleotides: phosphate, sugar and base
- Single stranded
- Bases: guanine, cytosine, adenine, uracil
- A double bond U, C triple bond G
- Short strands
- Messenger RNA
- Ribosomal RNA
- Transfer RNA
Energy balance
In biological terms, energy balance can be represented by the following equation:
Energy intake = Internal heat produced
+ External work
+ Internal work
+ Energy storage
Law of thermodynamics
Energy cannot be created or destroyed, therefore there is balance between energy input and output
Energy input
- Energy in ingested food
- Cells capture portion in high-energy bonds of ATP
- Energy output
Energy output
- External work
– Energy expended when skeletal muscles are contracted to move external objects or to move body in relation to the environment - Energy from nutrients that is not used to perform work
– Transformed into thermal energy or heat - Only about 25 percent of chemical energy in food is harnessed to do biological work.
- Remainder is converted to heat (a lot is used to maintain body temperatures)
Energy storage
- Internal work
– All other forms of biological energy expenditure that do not accomplish mechanical work outside the body - Skeletal muscle activity used for purposes other than external work (postural
maintenance contractions, shivering) - All the energy-expending activities that go on continuously just to sustain life
Neutral energy balance
- Energy input = Energy output
- Body weight remains constant.
Positive energy balance
- Energy input is greater than energy output.
- Energy not used is stored primarily as adipose.
- Body weight increases.
Negative energy balance
- Energy input is less than energy output.
- The body must use stored energy to supply energy needs.
- Body weight decreases.
Metabolic rate
the total amount of energy we need to expend (both internal and external work) in
order to perform a given task
MR= energy expenditure/ unit of time
Basal metabolic rate (BMR)
the minimal internal energy expenditure we need to maintain in order to meet the basic physiological functions in our body
Calorimetry assessment conditions:
- Person should be at physical rest
- Person should be at mental rest
- Done at a comfortable room temperature
- No food consumed within 12 hours
Influencing metabolic rate:
- Thyroid hormone levels (Primary determinant of BMR)
- Sympathetic stimulation: epinephrine/ norepinephrine
- Exercise
- Daily activities
- Sex/gender
- Age
Metabolism
the set of life-sustaining chemical processes that enables organisms transform the chemical energy stored in molecules into energy that can be used for cellular processes.
Energy in the body
Every task performed by our bodies require energy
* Energy is needed to perform heavy labor and exercise
* Energy is used while thinking and even sleeping
* For every action that requires energy, many chemical reactions take place to provide chemical energy to the systems of the body, including muscles, nerves, heart, lungs, and brain
Exothermic
Release energy
Endothermic
require energy to proceed
Cellular metabolism
All of the chemical reactions that take place inside cells are part of this
Metabolic processes
break down organic molecules to release the energy for an organism to grow and survive
Activation energy
- Our body requires a certain amount of energy to get started
- We can use enzymes to act as catalysts and lower the activation energy required for a certain chemical reaction to occur, which in turn greatly increases the reaction rate
- each enzyme are able to control a single type of chemical reaction, if one enzyme is not active, whole pathway stops working.
Competitive inhibition
- an inhibitor molecule is similar enough to a
substrate that it can bind to the enzyme’s active site to stop it from binding to the substrate. - It “competes” with the substrate to bind
to the enzyme.
Non-competitive inhibition
- an inhibitor molecule binds to the enzyme at a location other than the active site (allosteric site)
- The substrate can still bind to the enzyme,
but the inhibitor changes the shape of the
enzyme, so it is no longer in optimal position to catalyze the reaction
Allosteric inhibitors
- Allosteric activators can increase
reaction rates. - They bind to an allosteric site which induces a conformational change that increases the affinity of the enzyme’s active site for its substrate.
- This increases the reaction rate.
Cofactors and coenzymes (on/off switch)
- Many enzymes only work if bound to non-protein helper molecules.
- Binding to these molecules promotes optimal conformation and function for their respective enzymes
- The most common coenzymes are dietary vitamins.
Metabolic regulation
- Feedback inhibition is when a reaction product is used to regulate its own further production.
- Cells have evolved to use feedback inhibition to regulate enzyme activity in metabolism, by using the products of the
enzymatic reactions to inhibit further enzyme activity. - Metabolic reactions, such as anabolic and catabolic processes, must proceed according to cellular demands
- In order to maintain chemical equilibrium and meet the needs of the cell, some metabolic products inhibit the enzymes in the chemical pathway while some reactants activate them.
ATP
- Anytime we are either building or breakdown something through a reaction in the body we require this
- drives all bodily functions, such as contracting muscles, maintaining the
electrical potential of nerve cells, and absorbing food in the gastrointestinal tract.
ATP process
Are processed by digestion, carbohydrates are considered the most common source of energy to fuel the body
Sugar catabolism
- breaks polysaccharides down into their
individual monosaccharides - Among the monosaccharides, glucose is the most common fuel for ATP production via cellular respiration Therefore, there are a number of endocrine control mechanisms to regulate glucose concentration in the bloodstream.
β-oxidation
- Tryglycerides are most often used for energy via this metabolic process
- About 1/2 of the excess fat is stored in adipocytes that accumulate in the subcutaneous tissue under the skin
- The rest is stored in adipocytes in other tissues and organs
Amino acids
- can be used as building blocks of new
proteins or brokendown further for the production of ATP. - When one is chronically starving, this use of amino acids for energy production can lead to a wasting away of the body, as more and more proteins are broken down.
Energy shuttle
ATP-ADP cycle acts as this for our bodies and enables our cells to functions
ADP- released spring, no more stored energy
ATP- compressed spring, with stored energy
Oxidation-reduction reactions
are one category of reactions important in energy transfer
* Some of the energy released during oxidation reactions is captured when ATP is formed
* A phosphate group is added to ADP (phosphorylation) along with energy to form ATP
Three main phases to cellular respiration:
- Glycolysis
- Kreb’s or TCA (the citric acid) cycle
- Electron transport chain
Glycolysis
- Glucose is the body’s most readily available source of energy
+ After digestive processes, monosaccharides (Glucose, Fructose) are transported across the wall of the small intestine and into the circulatory system, which transports them to the liver. - Glycolysis is the breakdown of glucose into pyruvate
+ In the liver, hepatocytes either pass the glucose on through the circulatory system or store excess glucose as glycogen
- Glycogenolysis is the breakdown of glycogen into glucose
Where does glycoysis occur?
In the cytosol of the cell
Glycolysis Process
Through the process of glycolysis two ATP and two NAD+ are used to covert one glucose molecule into two
pyruvate molecules, 4 ATP and 2 NADH
Most important step in the glycolysis pathway
Several steps in glycolysis are regulated, but the most important control point is the third step of the pathway, which is catalyzed by phosphofructokinase (PFK).
* This reaction is the first committed step, making PFK a central target for allosteric regulation of the entire glycolysis pathway
Up regulation
- AMP
- When a cell is very low on ATP, it will start squeezing more ATP out of ADP molecules by converting them to ATP and AMP.
- Therefore, high levels of AMP mean that the cell is very low on energy, and that glycolysis must engaged quickly to replenish these stores.
Down regulation:
- ATP is a negative regulator of PFK (if there is already plenty of ATP in the cell, glycolysis does not need to make more)
- Citrate building up (first product of the citric acid cycle), is a sign that glycolysis can slow down, because the citric acid cycle is
backed up and doesn’t need more fuel.
What happens if the cell cannot catabolize the pyruvate molecule further?
It will have a net gain of two ATP molecules through this anaerobic pathway from one molecule of glucose
Aerobic respiration
- the process in which organisms convert energy in the presence of oxygen— and glycolysis is their sole source of ATP.
- Mature mammalian red blood cells are not capable of this
What if glycolysis is interrupted?
these cells lose their ability to maintain
their sodium-potassium pumps, and eventually, they die.
Krebs/TCA cycle
