Chapter 4-Cell Metabolism

Joe Pistack MS/ED

MetabolismMetabolism-series of chemical reactions necessary for the use of raw materials.

The cell is like a factory, must bring in and use raw materials.

Raw materials come from the food we eat: carbohydrates, proteins and fat.

MetabolismTwo parts: Anabolism-includes reactions that build larger, more complex substances from simpler ones. Eg. Building of a large protein from individual amino acids. Anabolic reactions generally require

an input of energy in the form of ATP.

MetabolismCatabolism-reactions that break

down larger, more complex substances into simpler substances.

Eg. Breakdown of a large protein into individual amino acids.

Catabolism releases energy that is eventually converted to ATP.

CarbohydratesSugars and starchy foods:BreadPotatoesPasta Candy

Carbohydrates are organic compounds composed of, Carbon (C), hydrogen (H),

and oxygen (O).

CarbohydratesMonosaccharides-single sugar

compounds.Single=mono (saccharide)

compound

Disaccharides-double sugarDouble=di sugars

Polysaccharides=many sugars

MonosaccharidesSugars that contain three to six

carbons.

The six-carbon simple sugars include: glucose fructose galactose

Glucose is the most important, it is used for immediate energy.

PolysaccharidesMany glucose molecules linked together.

Glycogen-form in which humans store glucose.

Glycogen is stored primarily in the liver and skeletal muscle.

Glycogen is converted to glucose and released into the blood to restore low blood sugar to normal.

PolysaccharidesCellulose is a polysaccharide

found in plants, unable to digest but provides a source of fiber in our diets.

GlucoseGlucose is used by the body in three ways: 1. It can be burned immediately as fuel for energy.

2. It can be stored as glycogen and burned as fuel at a later time.

3. It can be stored as fat and burned as fuel at a later time.

GlucoseGlucose is broken down under the

following conditions: 1. anaerobic catabolism-absence of

oxygen.

2. aerobic catabolism-presence of oxygen.

Glycosis- anaerobic process where glucose is broken down by a series of chemical reactions into pyuric acid and lactic acid, occurs in the cytoplasm.

Aerobic CatabolismThree important points: 1. Chemical reactions occurring

in the mitochondria require O2. If the cells are deprived of O2,

they cannot perform their function.

Ex. Need to breathe continuously to ensure a continuous supply of O2.

Aerobic Catabolism

2. Glucose is broken down completely to

carbon dioxide and water, stored energy

is released as ATP or heat.

3. If O2 is not available to the cell, there is a build-up of pyruvic acid lactic acid

lack of O2 lactic acidosis.

GlucoseGlyconeogenesis-making of glucose from

nonglucose sources, especially protein.

Glyconeogenesis is an important mechanism in the regulation of blood sugar.

If blood sugar drops, protein is converted to glucose in the liver and released into the blood, restoring the blood sugar to normal.

GlucoseDiabetes-lack of the insulin hormone

affects glucose metabolism.

Insulin is needed to transport glucose into the cell, a lack of insulin deprives the cell of glucose and the energy that glucose provides.

Lack of insulin causes body protein to be broken down and converted into glucose.

GlucoseDiabetic cells cannot utilize glucose, it

accumulates in the blood and causes the person to become hyperglycemic.

Glucose ends up in the blood and not in the cell where it is needed for energy.

Drugs to treat diabetes-increase glucose uptake and supress gluconeogenesis by the liver. (Lower blood sugar)

LipidsOrganic compounds.

Commonly called fats and oils.

Solid at room temperature.

Eaten as fatty meats, egg yolks and dairy products.

Lipids

LipidsLipids found in the body: - triglycerides -phospholipids -steroids

Building blocks of lipids-fatty acids and glycerol.

Phospholipids are important components of the cell membrane.

LipidsSteroid-type of lipid.

Cholesterol-most important steroid in the body.

Consumed as meat, eggs and cheese.

Cholesterol is found in all cell membranes, necessary for synthesis of vitamin D and used in the ovaries and testes in synthesis of sex hormones.

LipidsNeeded by the body for: 1. source of energy. 2. component of cell

membranes and coverings of nerve cells. 3. synthesis of steroids.

Metabolism of LipidsFatty acids and glycerol can be

broken down to release stored energy.

Fatty acids are long structures, need to be chopped into tiny units before they enter the mitochondria.

When chopped into units they enter into the Krebs cycle.

Metabolism of LipidsKrebs Cycle-series of reactions

which occur in the mitochondria that results in

the formation of ATP.

Making Fat

Excess calories are consumed

Fat enzymes are stimulated

Fat is deposited in adipose tissue

Fats

ProteinsMost abundant organic matter in

the body.◦Organic material always contains a

carbon moleculeParticipate in every body

function.

Most hormones are proteins.

Amino AcidsBuilding blocks of proteins.

Takes about 20 amino acids to build body protein.

Amino acids come from foods: -lean meat - milk - eggs

Amino AcidsMost amino acids are synthesized

by the body.

Some amino acids cannot be synthesized and must be obtained from dietary sources.

Dietary intake of amino acids is essential.

Amino AcidsTwo types:

Essential amino acids-dietary intake of these amino acids is important since the body does NOT make them.

Nonessential amino acids-synthesized by the liver, not necessary to obtain from diet.

ProteinsUsed in three ways:

1. Plays a key role in physiological function.

2. Protein can be broken down and used as fuel as a source of energy for ATP.

3. Protein can be broken down and converted to glucose.

UreaNitrogen released by the

breakdown of amino acids is converted to urea by the liver.

Urea is a nitrogenous waste.

Blood carries urea from the liver to the kidneys, then eliminates it into the urine.

UreaUnder normal conditions the liver

extracts ammonia from the blood and converts it to urea.

Liver failure-extraction of ammonia from the blood is diminished, blood levels of ammonia rise.

Hepatic encephalopathy-toxic effects of ammonia on the brain.

UreaBUN :

Blood Urea Nitrogen

Laboratory testMeasures the amount of urea in the

blood.Poor kidney function results in an

elevated BUN.

Protein SynthesisGenetic Code:

Protein-synthesizing code is stored in the DNA in the nucleus.

When there is a need for protein synthesis, the code is transferred to the ribosome.

AgingAs we age:Number of mitochondria and

organelles decrease.Metabolism slows down, secondary

to a decrease in hormonal secretion.Rate of protein synthesis decreases.Decrease in metabolism causes,

intolerance to cold, tendency to gain weight, decreased efficiency in using glucose.

Aging