Chapter 24: Metabolism

nutrients

Any substance the body uses for growth, repair, & maintenance

macronutrients

carbohydrates, lipids, proteins

• Make up most of our diet

micronutrients

vitamins and minerals

• Only required in minute amounts!

carbohydrates sources in diet

mostly plants, but also dairy (lactose) and meats (glycogen)

use of carbohydrates

• 1) ATP production** by body
• Monosaccharide molecule glucose used

• 2) Nucleic acid synthesis with pentose sugars

• 3) Glycocalyx formation

can fructose and galactose be used?

yes, but must be converted to glucose

what % of daily caloric intake is recommended?

45-60% of daily caloric intake

Complex carbohydrates:

grains and plant-based sources that are unprocessed, nutrient rich

empty carbohydrates

processed sugars (soda, candy, etc.)

more likely lead to adipose formation

Why are they called “empty” carbs?

they’ve been stripped of all of their nutrients

source of lipids in diet

1. triglycerides

2. cholesterol

types of triglycerides

1. saturated

2. unsaturated

saturated triglycerides

meat, dairy, margarine, etc.

-solid at room temp

bonds are shorter

unsaturated triglycerides

nuts, seeds, olive oil, etc.

-more viscous at room temp

-bonds are longer, atoms have more space

what % of cholesterol is produced by liver regardless of lipid intake

85

what does remaining 15% of cholesterol come from

from meat, eggs, dairy, etc.

uses of lipids

• 1) Used to build adipose tissue

• 2) Phospholipids used for cell membranes

• 3) Bile salt, steroid hormones, & other molecule construction

• 4) Absorbing fat-soluble vitamins

which are fat soluble vitamins

A

D

E

K

what % of total daily nutritional intake should be lipids?

20-35%

which types of fats should you limit intake of?

saturated fat and cholesterol

sources of protein

1. complete proteins

2. incomplete proteins

complete proteins

meet all the body’s amino acid requirements

• Ex: egg, meat, dairy, fish

incomplete proteins

are “short” 1 or more amino acid

• Ex: seeds, nuts, legumes

exception SOYBEANS

uses of protein

• 1) Structural molecules

• Ex: keratin, collagen, elastin, muscle protein

• 2) Functional molecules

ex, enzymes and hormones

nutritional requirements of protein

~0.8 g protein per kg body weight

Nitrogen balance:

when the rate of protein synthesis equals the rate of protein breakdown in the body

Positive nitrogen balance:

when protein synthesis > protein breakdown

examples of positive nitrogen balance

• Ex: growing children, pregnant people, tissue repair

Negative nitrogen balance:

when protein breakdown > protein synthesis

examples of negative nitrogen balance

stress, low protein content or quality in diet, starvation

When are amino acids not used by the body?

• 1) Inadequate dietary intake

• 2) Insufficient amino acid supply:

3) Hormonal control

Inadequate dietary intake

being short of carbohydrates or fats forces the

body to use proteins for energy source (ex: skeletal muscle tissue)

Insufficient amino acid supply:

all amino acids must be present to build a particular protein

all or none rule amino acids

If one or more is missing, or if there is not enough of one type of amino acid, the rest are used for energy

Adrenal glucocorticoids promote??? when it comes to proteins

protein breakdown

anabolic hormones promote ??? when it comes to proteins

protein systhesis and growth

importance of vitamins

Vitamins act as coenzymes: assist enzymes in accomplishing various tasks

how do coenzymes assist enzymes

enzymes as they are catalyzing RXNs cannot hold anything, they can only move things around but coenzymes can hold onto hydrogen

sources of vitamins

• 1) Made by body: vitamin D (in skin), vitamin K & some vitamin B

(bacterial flora)

• 2) Diet**

types of vitamins

1. water soluble vitamins

2. fat soluble vitamins

what are the water soluble vitamins

B & C

What does “water soluble” mean

needs water

what does “fat soluble” mean?

needs fat to take them

primary sources of minerals

legumes, vegetables, dairy

what toxicity can occur from fat soluble vitamins

liver damage, bone pain, kidney problems

what is the primary function of minerals?

structural

• Others bound to organic compounds: creates phospholipids, hormones,

several different proteins

with minerals, balance between ___ and ___ is necessary

uptake and excretion

Like fat-soluble vitamins: toxic overload can occur
• Ex: iron overdose, low iodine intake & goiters, high Na+ intake and fluid

retention

what is iodine necessary for

thyroid hormone

what is Na responsible for

fluid retention

metabolism

the sum of all the chemical reactions occurring in the cells

of the body that is used to provide energy for vital processes and

synthesizing new material

• Metabolic reactions can be either:

1. anabolic

2. catabolic

anabolic

building larger, more complex molecules/structures from their smaller subdivisions

catabolic

: any reaction that breaks down larger molecules into smaller ones

what is a main catabolic reaction

cellular respiration

cellular respiration

a group of reactions that form ATP from the breakdown of food fuels (glucose)

Oxidation-Reduction Reactions (“redox” reactions)

transfer of es from 1 molecule to another

oxidation

the loss of electrons (or gain in O2)

• An oxidized substance always loses electrons

lose hydrogen

reduction

the gain of electrons (lose oxygen)

gain hydrogen

• This process is coupled with oxidationwhen one substance loses an electron, another must gain the electron

Why are Redox reactions important?

most of our metabolic energy comes from these reactions

what are redox reactions catalyzed by

enzymes and coenzymes

Enzymes & coenzymes are specific to the reaction being carried out

Most coenzymes derived from?????

B complex vitamins

2 important coenzymes

• 1) Nicotinamide adenine dinucleotide (NAD+)

• 2) Flavin adenine dinucleotide (FAD)

what is Nicotinamide adenine dinucleotide (NAD+) often called?

niacin

vitamin B3

what is Flavin adenine dinucleotide (FAD) often called?

riboflavin

vitamin B2

All carbohydrates brought into body will eventually be converted to…

glucose

Once inside cell: glucose converted to…

glucose-6-phosphate

why is it necessary glucose is converted to glucose 6 phosphate

everything in body travels with concentration gradient

by converting it, you keep intracellular glucose down, so glucose keeps flowing in

Glucose + ATP glucose-6-PO4 + ADP

Substrate-level phosphorylation:

the direct transfer of a phosphate group to an ADP molecule

net gain of Glycolysis & Citric Acid Cycle:

4 atp

Oxidative phosphorylation:

the transfer of a phosphate group to an ADP molecule by the oxidation of food fuels & transfer of electrons

net gain of Electron Transport Chain:

28 atp

How many ATP can a single glucose molecule yield?

32

glucose oxidation reaction

C6H12O6 + 6O2 yields 6H2O + 6CO2 + 32 ATP + heat

the breakdown of glucose involves 3 sequential pathways

1. glycolysis

2. citric acid cycle

3. electron transport chain (ETC) & oxidative phosphorylation

where does glycolysis occur

cytosol of cell

what type of process is glycolysis?

anaerobic

what goes into glycolysis

glucose

what comes out of glycolysis

• 1) 2 pyruvic acid,

• 2) 2 NADH + H+

• 3) Net gain of 2 ATP

phase 1 highlights glycolysis:

1) Glucose is phosphorylated to produce fructose-1,6-

bisphosphate
2) 2 ATP are used for this conversion

-using energy to produce energy

phase 2 highlights glycolysis

1) Fructose 1,6-bispohosphate is split to form 2 carbon fragments (have H removed)

phase 3 highlights

1) 4 ATP molecules are produced by oxidizing carbon fragments

2 NAD+ pick\ up hydrogen: forms 2 NADH + H+

2) 2 pyruvic acids produced

if O2 is available what happens w pyruvic acid

• If O2 is available: pyruvic acid pumped into the next pathway (Citric Acid Cycle)

if O2 is not available, what happens to pyruvic acid

• If O2 is not available: pyruvic acid converted to lactic acid

• Some lactic acid pumped out of cell & transported to liver for

processing

• Once O2 becomes available again: lactic acid oxidized back to pyruvic acid & used in Citric Acid Cycle

where does critic acid cycle occur

in mitochondrial matrix

which type of process is citric acid cycle

aerobic process

• This reaction DOES NOT directly utilize oxygen, but products from citric

acid cycle are used in ETC

what goes into citric acid cycle

acetyl CoA (derived from pyruvic acid)

what comes out in a single turn of citric acid cycle

• 1) 3 CO2 molecules
• 2) 5 reduced coenzymes: 4 NADH + H+, 1 FADH2

• 3) 1 ATP

key steps of citric acid cycle

Pyruvic acid oxidized to form Acetyl CoA

1 CO2 molecule produced

NAD+ converted to NADH + H+

where does ETC and oxidative phosphorylation occur

inner mitochondrial membrane

which type of process is ETC and oxidative phosphorylation

aerobic

What goes in ETC & oxidative phosphorylation

• 1) NADH + H+ & FADH2 from citric acid cycle

• 2) Oxygen

what comes out ETC and oxidative phosphorylation

• 1) 28 ATP molecules

2) 6 H2O

highlights of ETC

NADH + H+ & FADH2 are relieved of their H+ ions
NAD+ and FAD available again

H+ pumped into intermembrane space to create a proton gradient

• H+ from proton gradient used by Complex V (ATP Synthase) to create ATP molecules

why can’t your body utilize endless amounts of glucose to produce large quantities of ATP

there’s no storage spots for atp in our body, as soon as it is produced, it is used

what does rising intracellular atp inhibit?

glucose breakdown

Three processes allow for glucose storage & access:

1. glycogenesis

2. glycogenolysis

3. gluconeogenesis

Glycogenesis

Glucose is converted to glycogen & stored in animal tissue

glycogen

polysaccharide stored in animal tissue (e.g., muscle tissue

what parts of body are most active in glycogen production and storage?

Skeletal muscle & liver

when does glycogenesis occur?

when glucose levels are high in body