Lecture 8

1. Anaerobic Cellular Respiration & Fermentation 2. Catabolism of Proteins & Fats 3. Nutrition

Aerobic Cellular Respiration

→ Utilizes glycolysis, synthesis of acetyl-CoA, Krebs cycle, and electron transport chain; results in complete breakdown of _________ to carbon dioxide, water and

ATP

The ultimate objective is to make molecules to do cellular work.

ATP

A total of 38 molecules of ATP are formed from one molecule of glucose.

(Again, a currency analogy is useful. If you travel to Europe, you exchange US currency for Euros that you can spend anywhere).

Electron Transport

How do cells get energy if there is no

O 2

available to them?

_______________________

or

______________

_____________________

• Many anaerobic bacteria can make ATP by using something other than oxygen as an electron acceptor

(nitrate, sulfate and carbon dioxide).

• In anaerobic respiration, not all the ETC is used, so less ATP is produced. • When carbon dioxide is used as an electron acceptor, the product is either methane or acetic acid

(depending on the organism).

• Methane produced in our gut, or by cows, or in swamps is produced by this process.

______________

• Fermentation is an alternative system that allows glycolysis to continue without the other steps of respiration. • Essential function: oxidize NADH (onto NAD +) • The electrons and hydrogen ions from the NADH produced by glycolysis are donated to another organic molecule.

• Not as energetically efficient as respiration. • Produces only 2 ATP.

ATP ATP

Glycolysis

Energy Investment & Lysis

Figure 5.14

Glycolysis

Energy Conserving Stage

Figure 5.14

Fermentation

• Two different fermentation pathways: • Yeasts and some bacterial cells are able to get their ATP from glycolysis by using _________________ . Converts pyruvate into ethanol and carbon dioxide. • Animal cells and some bacteria through the process of ___________ ___________ . Here pyruvate • The steps of fermentation do not produce any additional ATP. • The ATP is produced during glycolysis. • Fermentation allows the breakdown of glucose to continue, oxidizing NADH, so that some energy to be recovered in the absence of oxygen.

Fermentation

Figure 5.22

Muscles & Lactic Acid Fermentation

• When you exert yourself, muscles may use up the available oxygen, and must switch to anaerobic

lactic acid fermentation

. • Muscle cells quickly become fatigued (run out of ATP) as their stores of glycogen are used up. • Eventually the muscles lack sufficient ATP to continue contracting, lactic acid builds up.

Muscles & Lactic Acid Fermentation

_____ and ______ Twitch Muscle

• Slow twitch fibers contract and fatigue more slowly than fast twitch muscle fibers. • Most of us have about 50% slow twitch fibers and 50% fast twitch fibers.

• Long-distance runners often have more slow twitch fibers while sprinters or bodybuilders often have

But what is the difference between slow and fast twitch muscle?

Slow and Fast Twitch Muscle

Poultry: white meat & dark meat

• It is dark because it contains an oxygen storing protein called __________. • Slow twitch muscles tend to be wing and leg muscles where long term endurance is required. • Fast twitch muscles more common in the breast where quick response but not necessarily endurance is needed. • Wild animals tend to have more slow twitch muscle than their domestic counterparts.

Fermentation

• Most of the potential energy remains in the bonds of fermentation products.

• Fermentation products are wastes to cells that make them, many are useful to humans (ethanol, acetic acid, and lactic acid).

•

Souring vs. Spoilage

Fermentation of carbohydrates to organic acid products is commonly called

___________

. • Sour cream, cheese, and yogurt are produced by the action of fermenting bacteria. • Lactic-acid bacteria of the genus Lactobacillus are used in the fermentation process. • Bacteria convert lactose to lactic acid, which causes milk to change from liquid to solid curd. •

__________

, or putrification, is when microbes use anaerobic respiration to break down proteins, releasing nitrogen and sulfur containing organic compounds as products.

• Anaerobic respiration of protein often produces foul smelling chemicals such as putrescine, cadaverine & hydrogen sulfide.

How do we metabolize things that aren’t glucose?

• Fats, proteins and carbs can all provide energy for the cell.

• The basic pathways used to extract energy from fat & protein are the same as for carbs: glycolysis, Krebs, ETC but there are extra steps.

Organic Molecules - Proteins

Image:

www.rothamsted.ac.uk/.../courses/guide/aa.htm

Protein Catabolism

Figure 5.25

How do we metabolize protein?

ketogluterate, which enters the Krebs cycle.

How do we metabolize fats?

• Fats and oils are made from two kinds of molecules • Before these fats can be broken down to release energy, they must be converted to smaller units. • The first step is to break the bonds between the glycerol and the fatty acids. • Glycerol is a 3-carbon molecule that is converted into glyceraldehyde-3 phosphate . • Because glyceraldehyde-3-phosphate is involved in one of the steps in glycolysis , it can enter the glycolysis pathway.

Glycolysis

Energy Conserving Stage

Figure 5.14

What about the fatty acid tails?

These long molecules (typically 14 to 20 carbons long) must also be processed before they can be further metabolized. 1. Enter the mitochondrion, where each long chain of carbons that makes up the carbon skeleton is hydrolyzed (split by the addition of a water molecule) into 2-carbon fragments. C C 2. Each of the 2-carbon fragments is converted into acetyl. Coenzyme A is added to the acetyl, and the ____________ goes into _______ ______.

The Krebs Cycle

Figure 5.19

Glycerol and fatty acids

•

Metabolic Processes … Bottom Line

•

Every cell acquires ___________.

•

Energy is ultimately stored in _____.

•

ATP

is used to do cellular work.

Diet & Metabolism

Stuff We Need: • Carbohydrates • Proteins • Lipids • Vitamins • Minerals • Water

CARBOHYDRATES - Fiber

• • • Also called “bulk” or “roughage”.

Most are indigestible ___________________.

• There are two main types of fiber with different effects:

insoluble fiber fiber

. and

soluble

• ______________________ improves elimination by increasing stool bulk, preventing constipation and decreasing risk of colon cancer.

Foods high in insoluble fiber

seeds.

: legumes, whole grains, vegetables, fruits, nuts and • • • ___________________ delays gastric emptying, slows absorption of glucose into the bloodstream and inhibits cholesterol absorption.

Good sources of soluble fiber

and seeds. : Fruits, vegetables, oat bran, legumes, barley, nuts The American Dietetic Association recommend 20 to 35 grams of total fiber each day. Most people get FAR LESS than this.

PROTEINS

•

__________ Proteins

= contain all (essential) amino acids necessary for good health •

__________ Proteins

= are missing some of the (essential) amino acids necessary for good health • Essential Amino Acids = can’t be synthesized by the human body • The amount of protein that a person actually requires on a daily basis is quite small (1/4# hamburger, ½ chicken breast).

Animal Protein Versus Vegetable Protein Animal proteins

(meat, fish, poultry, milk, cheese, and eggs) good sources of

complete proteins

.

Vegetable proteins

(grains, legumes, nuts, seeds, and other vegetables) are

incomplete proteins

they are missing, or do not have enough of, one or more of the essential amino acids. because By combining foods from two or more of the following columns you create a self-made complete protein. Foods in one column may be missing amino acids that are present in the foods listed in another column. When eaten in combination at the same meal (or separately throughout the day), your body receives all nine essential amino acids.

Sources of Complementary Proteins

Grains

Barley Bulgur Cornmeal Oats Buckwheat Rice Pasta Rye Wheat

Legumes

Beans Lentils Dried peas Peanuts Chickpeas Soy products

Nuts/Seeds

Sesame seeds Sunflower seeds Walnuts Cashews Pumpkin seeds Other nuts

LIPIDS

• • • • • • • We typically refer to them as “Fats”, but remember, fats are only one of several molecules known as lipids. Phospholipids, steroids and true fats play an important role in human nutrition.

The fats are sometimes referred to as true (neutral) fats, or triglycerides and are an excellent source of energy.

Have ___ kcal of energy per gram (protein or carbs only have __ ).

______________ the amount of energy needed to raise one kilogram of water one degree Celsius.

______________ fatty acids (EFAs) are fats that the body can’t make, but needs to take in from outside sources. There are two families of EFAs: omega-3 and omega-6. Fats from each of these families are essential, as the body can convert one omega-3 to another omega-3, for example, but cannot create an omega-3 from scratch.

Olive oil has both omega 3 and omega 6 EFAs

VITAMINS

• ________________ essential in minute amounts for metabolism. • Do not serve as a source of energy, but some help facilitate many metabolic reactions as _____________.

•

Example

: B vitamins - Eight water-soluble vitamins that play important roles in cell metabolism.

-Once thought to be a single vitamin, referred to as Vitamin B (much like how people refer to Vitamin C or Vitamin D). - Later research showed that they are chemically distinct vitamins that often coexist in the same foods. - Supplements containing all eight B vitamins are generally referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific name of each vitamin (e.g. B1, B2, B3).

VITAMIN - B

12

• • • • • Vitamin B 12 is the largest and most complex of all the vitamins.

B 12 is involved in many aspect of our health.

(See http://lpi.oregonstate.edu/infocenter/vitamins/vitaminB12 for more info.)

10-15% of people are believed to be deficient in this vitamin.

B 12 and Depression

Observational studies have found as many as 30% of patients hospitalized for depression to be deficient in vitamin B 12 . A recent cross-sectional study of 700 community-living, physically disabled women over the age of 65 found that vitamin B 12 deficient women were twice as likely to be severely depressed as non-deficient women. The reasons for the relationship between vitamin B 12 deficiency and depression are not clear. Sources of B12 Only bacteria can synthesize vitamin B yeast 12 . Present in animal products such as meat, poultry, fish (including shellfish), and to a lesser extent milk, but it is not generally present in plant products or

MINERALS

• All minerals are ___________________ nature.

found throughout • Cannot be synthesized by the body.

• Because they are elements, they cannot be broken down or changed by metabolism.

• Important in many metabolic reactions of the cell.

MINERALS - Magnesium

• Magnesium plays a role in the

production

and

transport of energy

. • It is also important for the

contraction

and

muscles

.

relaxation of

• Magnesium is involved in the

synthesis of protein

, and it

assists certain enzymes

in the body.

• Magnesium, a gentle ____________, helps to prevent constipation by relaxing the colon walls and allowing for normal peristaltic action.

• Because magnesium attracts water, more water moves into the colon when one takes magnesium supplements or eats foods high in Mg.

What process is this???

• It’s magnesium, no matter what the “brand”: - 30 Phillips capsules ~$6.00

-150 magnesium supplements of same strength ~$6.00

•

WATER

All chemical reactions of living things take place in water. • Many types of metabolic wastes can only be eliminated from the body when dissolved in water. • The metabolic breakdown of materials requires water. •

What are some reactions that we’ve discussed in which water is necessary?

• You may be able to survive weeks without food, but you wouldn’t last more than a few days without water.

• Human body about 65% water (Even dense tissue like bone is 33% water).

• Food provides about 20% of total water intake. Remaining 80% from intake of water and beverages of all kinds.

• The Institute of Medicine advises that men consume roughly 3.0 liters (about 13 cups) of total beverages a day and women consume 2.2 liters (about 9 cups).