Chapter 25: Metabolism, Nutrients, Energetics

What are nutrients?

essential elements and molecules

Metabolic activity:

-Organic molecules are broken down to obtain _____

• Energy is stored as _____

-This is then used to construct new organic molecules

(ongoing cycle of breaking down food to get energy and using that energy to build and repair stuff in your body)

energy, ATP

What is energetics?

how the body balances heat gains and losses

What is metabolism?

the sum of all chemical and physical changes that occur in the body tissues

(cycle of breaking things down to get energy and building things up to keep your body running smoothly)

What does metabolism consist of?

1. Catabolism

2. Anabolism

What is the nutrient pool?

all available nutrient molecules distributed in blood

(nutrients in blood, ready to be used by body whenever)

What is catabolism?

converts large molecules into smaller ones

-breakdown of organic substrates releases energy used to synthesize ATP

What is anabolism?

converts small molecules into larger ones

-synthesis of new organic compounds is an “uphill” process that forms new chemical bonds

What is cellular metabolism?

chemical reactions within cells

(process of turning food and nutrients into energy and other essential stuff that keeps your cells)

Cellular metabolism provides energy to maintain _____ and perform essential functions

homeostasis

What are the essential functions of cellular metabolism?

1. Metabolic turnover

   • breaking down old molecules to make new ones

2. Growth and cell division

   • cellular metabolism provides energy for growth and division

3. Special processes

What are the three nutrient reserves?

1. Triglycerides

   • most abundant storage lipids

   • consist primarily of fatty acids

   • when body needs energy, triglycerides broken down into fatty acids to use for fuel

2. Glycogen

   • most abundant storage carbohydrate

   • a branched chain of glucose molecules

   • when you need energy during exercise, body quickly breaks down glycogen into glucose for fuel

3. Proteins

   • most abundant organic components in body

   • perform many vital cellular functions

   • build and repair tissues, help with chemical reactions, can be broken down and used for energy when needed

What is energetics?

study of the flow of energy and this change from one form to another

Which organs are responsible for the digestion of glycogen, triglycerides, and protein?

Glycogen:

• mouth, stomach, small intestine

Triglycerides:

• mouth, small intestine (jejunum)

Protein:

• stomach and small intestine

Which organ(s) are responsible for absorption?

small intestine and large intestine

What are the five metabolic tissues?

1. Liver

2. Adipose tissue

3. Skeletal muscle

4. Neural tissue

5. Other peripheral tissues

This is the focal point of metabolic regulation and control

Liver

The liver has great diversity of enzymes that break down or synthesize _____, ____ and _____

carbohydrates, lipids, amino acids

The liver contains ______

• have an extensive blood supply

• monitor and adjust nutrient composition of circulating blood

(in charge of making sure the levels of different nutrients in your bloodstream are just right)

hepatocytes

The liver has significant energy reserves (_____ deposits). Why?

glycogen

1. glycogen is used as a backup source of energy

   • when blood sugar levels drop (fasting or btw meals), liver breaks down glycogen into glucose to maintain a steady supply of energy to your cells. prevents blood sugar from dropping too low

2. glycogen can be rapidly broken down into glucose when you need quick energy

   • exercise or increased activity

3. if you eat a high carb meal, liver can store excess glucose as glycogen for later use, and during low carb intake liver can break down glycogen to maintain blood glucose levels and provide energy for body

Adipose tissue stores ______, primarily ______

lipids, triglycerides

Adipose tissue contains ____ that are located in many areas. What are they?

adipocytes

• fat cells in body

• when you eat more calories than your body needs, these cells expand to store the extra energy as fat

• when you need energy, they shrink as the fat is broken down and released into your bloodstream to be used by body

Where are adipocytes located?

1. Areolar tissue

2. Mesenteries (membrane attached to intestine)

3. Red and yellow bone marrows

4. Epicardium (around heart)

5. Around eyes and kidneys

Skeletal muscle maintains substantial _____ reserves. Why?

glycogen

1. Quick energy source

2. Energy during exercise

3. Metabolic flexibility (can be broken down for immediate energy or stored for later use)

In skeletal muscle, if other nutrients are unavailable

• ______ ______ can be broken down

• _____ ______ can be used as an energy source

contractile proteins, amino acids

• if your body does not have enough of other nutrients, like sugar and fat to use for energy, it has a backup plan

• it can break down the proteins in your muscles into small parts —> amino acids, can be used as an energy source to keep your body going

Nervous tissue does not maintain reserves of ____, ____, and ______

carbohydrates, lipids, proteins

Nervous tissue requires a reliable supply of ______.

• cannot metabolize other molecules

glucose

Nervous tissue in the CNS cannot function in _______ conditions. Why?

low-glucose

• an individual becomes unconcious

• Only uses glucose for energy, not other molecules like fats or proteins, so with no glucose available (especially in CNS), can lead to problems since brain is not getting the energy it needs to function properly

Other peripheral tissues, do not maintain _____ metabolic reserves. Why?

large

• they don’t keep big stores of extra energy (like fat or sugar) saved for later use, instead they rely on a more “pay as you go” system

• they use up energy as they need it and don’t share large amounts for future use

Other peripheral tissues can metabolize ____, _______ and other substances. Why?

glucose, fatty acids

• can use different types of fuel for energy because they’re adaptable

• use whatever energy sources available to keep themselves running smoothly

Other peripheral tissues preferred ____ source varies

• according to instructions from endocrine system

energy

• depending on what your body needs at that moment, the hormones from your endocrine system tell your tissues which energy sources to use

What are the two patterns of daily metabolic activity?

1. Absorptive state

2. Postabsorptive state

What is the absorptive state?

period following a meal when nutrient absorption is under way

• lasts about four hours

when body is actively absorbing and storing nutrients from the food you’ve eaten, glucose is used for energy while excess nutrients stored

What is the postabsorptive state?

normal blood glucose levels are maintained

• body relies on internal energy reserves

• most cells break down lipids or amino acids

  • preserving glucose for use by nervous tissue

-body starts using stored energy reserves because you haven’t eaten recently

-glucose levels drop, your body begins to break down stored glycogen and fat to provide energy

Which state are you in after eating pizza?

absorptive state

How long does the absorptive state last?

about 4 hours

You travel to another country and decide to try some new food that you’ve never had before. Bad idea!! You now have traveler’s diarrhea! Since you can’t eat anything, your body begins to use energy sources other than carbohydrates.

1. What state are you in?

2. What happens to the fats in your body? How?

3. What happens in the liver? How?

4. Would your urine be dilute or concentrated? Why?

1. Post absorptive state

2. With limited food intake, your body shifts to alternative energy sources (fats). Fats stored in adipose tissue are broken down through lipolysis into fatty acids and glycerol, which are then released into the bloodstream

4. Concentrated due to decreased fluid intake and potential dehydration

What is nutrition?

The absorption of nutrients from food

• the body’s requirement for each nutrient varies

absorbing nutrients from food to fuel the body

What is a balanced diet?

all necessary nutrients needed to maintain homeostasis

What is malnutrition?

unhealthy state resulting from nutrient imbalance

when the body lacks essential nutrients, leading to health problems and imbalances

Homeostasis can be maintained only if ______ absorbs enough fluids, organic substrates, minerals, and vitamins to meet cellular demands

digestive tract

when absorption process functions properly, it supports body’s stability and ensures essential requirements are met for cellular functions

What is nitrogen balance?

difference between total nitrogen consumed and the amount excreted in urine and feces

it indicates whether your body is retaining or loosing nitrogen, which is important for assessing protein intake and metabolism

Nitrogen ______ stored in the body

is not

Nitrogen must be obtained from ___ or ________

diet, recycled compounds

must get from food we eat or recycled substances already in body

What is positive nitrogen balance?

individuals actively synthesizing N compounds

• Need to absorb more nitrogen than they excrete

• Example: growing children, athletes, pregnant or lactating women, and people recovering from illness or injury

body is retaining more nitrogen than it is losing

What is negative nitrogen balance?

when excretion exceeds ingestion

body loses more nitrogen than it takes in

• someone not getting enough protein or during periods of illness or injury

What are minerals?

inorganic ions released through the dissociation of electrolytes

released when certain substances (salts) dissolve into ions in water

What are vitamins? What are the two groups?

essential organic nutrients that function as coenzymes in vital enzymatic reactions

1. Fat-soluble vitamins

2. Water-soluble vitamins

are important nutrients that help enzymes work properly in body

What are fat-soluble vitamins?

Vitamins A, D, E, K

vitamins that dissolve in fat rather than water

Fat-soluble vitamins are primarily from ________ tract along with lipids of _____

digestive, micelles

absorbed into body from digestive tract along with fats through micelles

In fat-soluble vitamins, skin synthesizes small amounts of vitamin ___ when exposed to sunlight and intestinal bacteria produce some vitamin ___

D, K

Vitamin A:

• maintains _____

• required for synthesis of ____ pigments

epithelia, visual

keeps skin and other surface tissues healthy and helps you see in dim light

Vitamin D:

• converted to _____

• required for normal ___ growth

calcitriol, bone

helps body use calcium and phosphorus to build strong bones and teeth, made when sunlight hits skin or from food

Vitamin E:

• prevents breakdown of vitamin ___ and ____ ____

A, fatty acids

protects the body’s cells from damage and helps keep the immune system strong, makes sure Vitamin A and fatty acids do not break down too quickly

Vitamin K:

• essential for synthesis of ____ factor

clotting

makes proteins that help your blood clot, important for stopping bleeding when you get a cut or injury

Water soluble vitamins are components of _____

• rapidly exchanged between the ____ in the digestive tract and circulating _____

coenzymes, fluid, blood

• Dissolve in water rather than fat

• Necessary for functioning enzymes

• Move quick between fluid and blood, and extra is removed through urine

What are the two classes of vitamins?

Fat-soluble vitamins and Water-soluble vitamins

-The energy required to raise 1g of water 1 degree Celcius is a ____ (cal)

-The energy required to raise 1 kilogram of water 1 degree Celcius is a _____ (Cal) - _____ (kcal)

calorie, Calorie, kilocalorie

What is the energy content of lipids, carbs, and protein?

Lipids: 9.46 kcal/g

Carbohydrates: 4.18 kcal/g

Protein: 4.32 kcal/g

Metabolic rate is the sum of all ____ and ____ processes in the body

• changes according to _____

anabolic, catabolic, activity

Measures how fast all the building up and breaking down processes are happening inside you

• if you move around a lot, your metabolic rate goes up; if you’re resting, it goes down

What is basal metabolic rate (BMR)?

minimum amount of energy your body uses while resting

energy the body uses at complete rest. minimum amount of energy your body needs to stay alive when you are wake and alert, not physical activity

• breathing, pumping blood, maintaining body temperature

Measuring BMR involves monitoring _____ activity

respiratory

Energy use is _____ to oxygen consumption in resting individuals

proportional

• measured by O2 breathed in and CO2 breathed out (energy your body uses related to how much O2 you consume)

Enzymes operate in a limited ______ range

temperature

What is thermoregulation? give an example

homeostatic mechanisms that keep your body temperature within acceptable limits

(when you are hot your body sweats to cool you down, and when you are cold you shiver to generate heat)

helps keep your temperature just right no matter if it is hot or cold outside

• enzymes work best in limited temp range

The body produces _____ as a by-product of metabolism

heat

Increased physical or metabolic activity generates more _____

• _____ is retained by _____ in body

When you are moving around or digesting food your body produces heat, and to keep your temperature just right, your body holds onto some of this heat with the help of water

heat, heat, water

For body temperature to remain constant, heat must be ____ to environment

lost

To keep you from overheating, your body also needs to let heat escape

Body controls heat gains and losses to maintain ________

homeostasis