Nutrition 9 - 11

Metabolism

the chemical processes that occur within a living organism in order to maintain life.

metabolic pathway

Is A Group of biochemical reactions that occur in A progression

intermediates

Are compounds formed during The steps

anabolic pathways

use small compounds to build larger ones

\-glucose, fatty acids, cholesterol, and amino acids are building blocks

\-requires energy

\

catabolic pathways

break down compounds

* glycogen is broken down to make glucose
* results in The *release* of carbon dioxide,Water, AND ATP
* More prominent during weight loss or wasting diseases

converting food into energy

The series of catabolic reactions that produce energy for cells begins with digestion:

\-Continues when monosaccharides, amino acids, fatty acids, glycerol, and alcohol are sent through metabolic pathways:

\-Captures energy as

adenosine triphosphate

\-Heat, carbon dioxide, and water are also released

3 stages of catabolism

1. digestion: breakdown of complex molecules to their component building blocks
2. conversion of building blocks to acetyl-CoA
3. metabolism of acetyl-CoA to CO2 and formation of ATP

Adenosine Triphosphate (ATP)

Only energy in ATP can be used directly to:

* synthesize New compounds


* contract muscles
* conduct nerve impulses
* pump ions across membranes

made of adenosine bound to 3 phosphate groups

* Bonds contain energy
* hydrolysis release energy

Cells Break High Energy Phosphate Bonds of ATP

* Release energy
* creates ADP AND A phosphate Group

Hydrolysis of ADP

Adenosine monophosphate. (Amp)

Recycling of ATP

ATP is generated by adding phosphate back to AMP and ADP. Cells constantly break down ATP and regenerate it.

A substance is oxidized when it

loses electrons of Hs & gains O2

a substance is reduced when it

gains electrons, loses oxygen

Niacin oxidized

NAD

Niacin Reduced

NADH2

riboflavin oxidized

FAD

riboflavin reduced form

FADH2

lactate dehydrogenase reduces pyruvate to form lactate

NADH + H

lactate can be oxidized back to pyruvate

NAD

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Aerobic

Process that requires oxygen, More efficient, net gain of 30 -32 ATP

Anaerobic

Process that does not require oxygen, net gain of 2 ATP

Glycolysis

Role is TO break down carbohydrates TO generate energy AND produce building blocks FOR other compounds, No oxygen

converts pyruvate to acetyl CoA

Mitochondria, need oxygen, irreversible, produces NADH + H AnD carbon dioxide

citric acid cycle

Completes the breakdown of glucose by oxidizing a derivative of pyruvate to carbon dioxide. Doesn't need oxygen. Produces FADH2 AND NADH+H

electron transport chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.

oxidative phosphorylation

Part of the electron transport chain. A process occurring in the mitochondria that results in the formation of ATP from the flow of electrons across the inner membrane to bind with oxygen.

Importance of Oxygen

Oxygen is needed for every cell in the human body. Without oxygen, cells are unable to create ATP (energy). Without ATP energy, cells die within minutes.

anaerobic metabolism

The metabolism that takes place in the absence of oxygen; the main by-product is lactic acid.

Cori Cycle

The removal and recycling of lactic acid by the liver, Liver converts lactic acid to pyruvic acid, Glucose is released to recharge muscle glycogen reserves

ATP production from fats

lipolysis, fatty acids are carried to mitochondria, fatty acid oxidation, beta-oxidation occurs

adipose tissue

Tissue that stores fat.

fatty acids

Are taken up by cells and shuttled into mitochondria from cytosol by CARNITINE

Carbohydrate Aids Fat Metabolism

The CAF provides other compounds that leave the cycle. Eventually the cycle can slow and not have enough oxaloacetate to combine with the acetyl CA entering hte cycle. Cells can synthesize more oxaloacetate using pyruvate. Carbs are needed to keep enough pyruvate high enough to resupply. the pathway works better when carbohydrates are available.

Ketones

chemical substances that the body produces when it does not have enough insulin in the blood

steps of ketosis

1. Insufficient insulin production
2. Large amounts of fatty acids released by fat cells
3. Fatty acids flood into liver and are broken down into acetyl-CoA
4. High production of acetyl-CoA from beta oxidation slows citric acid cycle
5. High amounts of acetyl-CoA unite in pairs to form ketone bodies

ketosis in diabetes

In type 1 diabetes, too little insulin is produced

• Fat and carbohydrate metabolism are not normal

If insulin is not present:

•Cells cannot use glucose

•Rapid lipolysis occurs

•Ketone bodies are produced in excess

\-Spill into urine with sodium and potassium, leading to ion imbalances

\-Blood becomes acidic because of acid groups on ketone bodies

•Resulting condition is diabetic ketosis

ketosis in fasting or semi-starvation

Glucose AND insulin levels fall

protein metabolism

deaminates amino acids; forms urea; synthesizes plasma proteins; converts certain amino acids into other amino acids ( in liver )

glucogenic amino acids

use carbons from carbon skeleton to form glucose

ketogenic amino acids

use carbons to form acetyl-CoA

Gluconeogenesis

the making of glucose from a noncarbohydrate source such as amino acids or glycerol, in liver and kidney, requires ATP, biotin/ riboflavin, niacin, B6

Fatty acids cannot be turned into glucose

- Make 2 carbon acetyl-coa

Glycerol portion of triglyceride can form glucose

- Enter glycolysis pathway, insignificant amount of glucose made

disposal of excess amino groups

converted ammonia, excreted in urine

Alcohol metabolism

\-ADH and NAD+ remove hydrogen from alcohol--> acetaldehyde

\-Acetaldehyde dehydrogenase (ALDH) removes more H and forms acetate.

\-Acetate continues thru metabolic pathways to form energy or is converted to a fatty acid and stored as fat

Regulation of Energy Metabolism

most water soluble vitamins, pass through liver

Fasting

The body fuels itself with glycogen AND fatty acids

feasting

when a person eats in excess of energy needs, the body stores a small amount of glycogen and much larger quantities of fat

inborn errors of metabolism

congenital disabilities preventing normal metabolism, soon after birth

Phenylketonuria (PKU)

a disorder related to a defective recessive gene on chromosome 12 that prevents metabolism of phenylalanine

Galactosemia

recessive genetic disorder; characterized by body's inability to tolerate galactose

Glycogen storage disease

A genetic disorder characterized by the inability to break down glycogen due to the lack of glucose 6-phosphatase.

Trimethylaminuria

Rotting fish odor

energy balance

the relationship between energy intake and energy expenditure

energy equilibrium

When calories consumed matches the amount of energy expended

positive energy balance

energy intake is greater than energy expended, generally resulting in weight gain

negative energy balance

the state in which energy intake is less than energy expended, resulting in weight loss

bomb calorimeter

a constant-volume device used to measure the energy released during a combustion reaction

energy expenditure

the energy the body expends to maintain its basic functions and to perform all levels of movement and activity

basal metabolism

the energy needed to maintain life when a body is at complete digestive, physical, and emotional rest

resting metabolism

the energy requirement to maintain the body's vital processes in the resting state

BMR men

1 cal/kg of body weight per hour

BMR women

0.9 cal/kg of body weight per hour

Factors that increase BMR

\-higher lean body mass

\-greater height

\-younger age

\-elevated levels of thyroid hormone

\-stress, fever, illness

\-male gender

\-pregnancy and lactation

\-certain drugs, such as stimulants, caffeine, and tobacco

Factors that decrease BMR

lower lean body mass, lower height, older age, depressed levels of thyroid hormone, starvation or fasting, female gender

energy for physical activity

\-Increases energy expenditure by as much as 25% to 40%

\-More activity, more energy burned

\-Lack of activity is a major cause of obesity

Thermic Effect of Food (TEF)

additional energy use for digestion; 6-10% of total energy expenditure

thermogenesis

heat production

adaptive thermogenesis

adjustments in energy expenditure related to changes in environment such as extreme cold and to physiological events such as overfeeding, trauma, and changes in hormone status

Measuring Energy Expenditure

direct calorimetry and indirect calorimetry

direct calorimetry

measurement of heat production as an indication of metabolic rate

indirect calorimetry

measurement of oxygen consumption as an estimate of resting metabolic rate

Estimated Energy Requirement (EER)

the average dietary energy intake predicted to maintain energy balance in a healthy adult of a certain age, gender, weight, height, and level of physical activity consistent with good health

hunger

The physical need for food

appetite

desire for food

Hypothalamus

a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion

sympathetic nervous system

fight or flight

satiety process

1. Flavor of food
2. Knowing a meal was just eaten
3. Influence of stomach and intestinal expansion and activity
4. Influence of nutrient use in the liver and related communication with the hypothalamus and other regions of the brain
5. Conscious thinking takes place in the brain's cortex and can overcome hunger or satiety signals

Body Mass Index (BMI)

a ratio that allows you to assess your body size in relation to your height and weight

Underweight BMI

below 18.5

Healthy weight BMI

18.5-24.9

Overweight BMI

25-30

Obese BMI

over 30

desirable amount of body fat for women

21-35%

desirable amounts of body fat FOR men

8-24%

underwater weighing

used in exercise physiology labs; lean mass sinks, fat mass floats; dry weight compared to underwater weight

air displacement

technique to assess body composition by calculating the body volume from the air replaced by an individual sitting inside a small chamber

skinfold thickness

Calipers used to measure fat layer under skin

bioelectrical impedance

a technique for measuring body fatness by measuring the body's electrical conductivity.

dual-energy X-ray absorptiometry (DXA) test

test of bone mineral density (BMD) at the hip and spine

Assessing Body Fat Distribution

\-Upper body (Android; apple shape): increased chronic disease risk, men: waist circumference more than 40 inches, women: waist circumference more than 35 inches

\-Lower body (Gynoid; pear shape)

role of genetics

\-Cognitive strengths and physical abilities are inherited

\-Impact of genetic influence affects gender differences in occupation/career aspirations and choice

\-Social welfare programs that promote equal access to higher education highlight this influence

set point theory

belief that brain mechanisms regulate body weight around a genetically predetermined 'set point'

Roles in the environment

* little change in gene pool over last 50 years, but obesity has drastically increased
* couples and friends tend toward similar weights
* many factors play a role in food intake; cultural, economic, etc.
* genes and environment both matter

Limited fat stores can be caused by

* Marfan syndrome.
* Anorexia nervosa.
* AIDS
* hyperthyroidism
* cancer

obesity can be caused by

Brain tumors, ovarian cysts, hypothyroidism, Prader-Willi syndrome

Weight loss programs should include

food choice changes, exercise, behavior modification, nutrition education, psychological support