Chapter 2 - Nutrients: Ingestion to Energy Metabolism

What is digestion? Where does it start?

process of breaking down ingested foods into their basic units, starts in the mouth with mastication

What is absorption?

food being taken in to the body, substances are outside the body until absorbed into blood or lymph

What is the order for which ingested materials travel?

mouth (oral cavity), esophagus, stomach, small intestine, large intestine, rectum

What are the salivary glands and what do they do?

parotid, sublingual, submandibular, secrete saliva to moisten food and began enzymatic breakdown of CHOs and fats

What happens in the stomach?

major secretions of hydrochloric acid, musuc - protects lining of stomach, digestive enzymes, little absorption of

What occurs in the small intestine and what is unique about it?

absorption, convoluted interior to increase surface area to increase surface area

What happens in the large intestine?

bacteria breakdown of dietary fibers and other undigested carbs, absorbs water and minerals from feces for excretion

What is passive diffusion?

substances move easily through wall, other use protein channels

What is facilitated diffusion?

substances that can’t easily pass through wall, assistant from transmembrane proteins

What is active transport?

lots of support to pass through membrane, energy is needed and usually goes against concentration gradient

What is endocytosis?

use cell membrane to engulf particle, separates inside of cell from particle

What does carbohydrate digestion look like?

mastication - amylase breakdown of starchy foods

stomach - hydrochloric acids, breakdown continues

small intestine - sugar enzymes (maltase, sucrase, lactase)

What are the forms of CHO?

polysaccharides - 11+ simple sugars

oligosaccharides - 3-10 simple sugars

disaccharides - 2 simple sugars

monosaccharides - 1 simple sugar (glucose, fructose, galactose)

Where does most absorption occur?

small intestine

What happens to carbs after absorption?

mechanism - facilitated diffusion

cellular uptake - insulin, glucose uptake

fates - storage (muscle glycogen, blood glucose, liver glucose)

energy

How are fats digested?

mastication - lingual lipase

stomach - gastric lipase secreted

small intestine - bile, pancreatic lipase (neutralizes acid to prevent denature of protein enzyme), micelle formation (microscopic bubbles)

What happens to fats when they’re absorbed?

mechanism - passive diffusion

transport - lymph system (filter and clean)

chylomicrons - triglyceride wrapped in proteins to muscle and blood

cellular uptake - lipoprotein lipase separates glycerol and FA

fates = storage and energy

What does a longer fatty acid chain mean?

more ATP

How are proteins digested?

mastication

stomach - churning, acid denaturation

small intestine - protease: enzyme breakdown proteins (amino acids), peptidases: smaller peptides

What happens to proteins when they’re absorbed?

mechanism - facilitated diffusion, active transport (majority)

transport - blood, become part of amino acid pool

fates - body proteins, conversion (glucose, fat but not easy), energy

What are the protein recommendations?

person - 0.8g/kg bw

athlete - 1-2g/kg bw

Why is it important for vegetarians to track their protein intake?

because it’s hard to get complete, essential amino acids in diet

What is energy?

to perform work

ATP, myosin binds ratchet and release = 1 ATP

What is the body’s main source of energy?

adenosine triphosphate (ATP)

What is negative feedback and what does this have to do with energy?

end product of reduces stimulus of same process

need more ATP, enzymes released to increase it

enough ATP, enzymes released to inhibit ATP enzymes

How many energy bonds does ATP have?

2 high energy bonds

What is the relationship between Creatine Phosphate (CP) and ATP?

when CP runs out, so does ATP

CP donates its P to make ADP to ATP

What happens in the mitochondria?

aerobic energy, production of O2

What are the 3 energy systems?

Phosphagen (ATP/PC)

Anaerobic (Glycolysis)

Aerobic (Oxidation)

What is the phosphagen system?

immediate energy system

substrate - creatine phosphate

rate - high

O2 - anaerobic

Capacity - low ~15sec

What is the anaerobic system?

involved only carbs

substrate - CHO (glucose/glycogen)

rate - mod

O2 - anaerobic/aerobic

capacity - mod ~2min

What is the aerobic energy system?

involved all macronutrients

requires O2

also known as oxidative system

substrate - CHO, fat, protein

rate - low

O2 - aerobic

capacity - unlimited

What are the 4 precursors of gluconegenisis?

1. pyruvate - glu/gly

2. lactate - glu/gly

3. glycerol - fat (TG)

4. alanine - protein (AA)

How does carbohydrate intake affect protein metabolism?

carbs main energy source

low intake = muscle protein breakdown, loss of muscle mass

How do the systems work together?

they are constantly feeding into each other and over lapping

one isn’t doing all the work, maybe dominating but supported by others

What is steady state exercise?

working at a constant workload until physiological responses level off, if above lactate threshold can’t steady state

What foes epinephrine do?

breaks FA off of triglycerides

What does insulin do?

inhibits FA breakdown

When glu/gly breaksdown into pyruvate and there is O2 present, what happens?

slow glycolysis

it turns into acetyl CoA and starts the kreb cycle

When glu/gly breaksdown into pyruvate and there isn’t O2 present, what happens?

fast glycolysis

turns into lactate