Macronutrients: Processing and Disorders Flashcards by Juliette St-Onge

Define metabolism

Sum of all chemical reactions essential to life

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Define catabolism

Catabolic reactions:
-Breakdown
-Energy-producing

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Define anabolism

Anabolic reactions:
-Biosynthesis
-Energy-requiring (store)

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True of false: carbohydrates are the most common source of body fuel

True
-key = glucose

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What are the steps of cellular respiration?

-Glycolysis
-Pyruvate –> acetly CoA
-Krebs cycle
-Oxidative phosphorylation

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What is glycolysis?

-Cytoplasm
-1 glucose becomes 2 pyruvates
-Net ATP production: 2 ATP

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What is pyruvate –> acetyl CoA?

-Mitochondria
-Preliminary step to Krebs cycle

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What is the Krebs cycle?

-Mitochondria
-In presence of oxygen
-Little ATP, but high energy molecules (NADH, FADH2)

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What is oxidative phosphorylation?

-Mitochondria
-34 ATP produced

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How many ATP does one glucose molecule produce?

36 ATP

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Why is a lack of glucose problematic?

-Glucose level must be stable for cells
-Brain works better on glucose (its favorite)

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What metabolic reaction occurs when glucose is lacking?

-Gluconeogenesis

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What is gluconeogenesis?

-Synthesis of new glucose
-Occurs during fasting, starvation or low-carb diets
-Performed in the liver
-From non-sugar molecules (pyruvate, glycerol, some amino acids)

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What metabolic reaction occurs when glucose is in excess?

Surplus is stored:
-Glycogen (skeletal muscles and liver)
-Triglycerides in adipose tissue (adipocytes)

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What are the pancreatic hormones and by what cells are they produced?

-Insulin produced by beta cells
-Glucagon produced by alpha cells

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What insulin does in a state of hyperglycemia?

Lowers blood glucose level by:
1. glucose enters the cells
2. increases glycogen storage
3. inhibits gluconeogenesis and glycogenolysis

What glucagon does in a state of hypoglycemia?

Increases blood glucose levels by:
1. Glucose stops entering cells
2. Increases glycogen breakdown (glycogenolysis)
3. Stimulates gluconeogenesis

What are the 3 types of diabetes mellitus?

Type I, II, and III

What is type I diabetes mellitus?

-High glycemia in blood, not cells
-Insulin deficient (genetic or acquired)
-Pancreas does not produce insulin or not enough
-Treatment: diet + insulin injections

What is type II diabetes mellitus?

-Constant hyperglycemia
-Environmental factors in cause (obesity)
-Starts with insulin resistance
-Treatment: diet + exercises can be enough, insulin sometimes required

What is type III diabetes mellitus?

-In pregnant woman (disappears after child delivery)

Explain lipid absorption

-Fatty acids absorbed in small intestine:
1. Triglycerides reform inside intestinal cells
-Packaged inside chylomicrons (lipoproteins)
-Chylomicrons: layer phospholipids + triglycerides + cholesterol + proteins
2. Chylomicrons circulate in aqueous environment
-Lymphatic and blood vessels
3. Aim for the liver or adipocytes

What are lipoproteins?

-Mix of proteins and lipids
-Lipid transporters
-Hydrophobic inside and hydrophilic outside

What are the 4 types of lipoproteins?

Lipids and proteins proportions vary:
-Chylomicrons
-VLDL: very low density lipoproteins
-LDL: low density lipoproteins
-HDL: high density lipoproteins

What are VLDL?

-VLDL carry triglycerides (from liver to other tissues) -In blood vessels, lipoprotein lipase slowly digests triglycerdies into fatty acids that are used by nearby cells -As they lose triglycerides, VLDLs transform into LDLs

What are LDL?

-LDLs transport cholesterol to cells needing it -Bind on cellular receptors and enter cells -LDL are often termed "bad" cholesterol

What are HDL?

-HDL are produced by the liver as "empty pockets" -HDLs find, absorb and transport excess circulating cholesterol back to liver (component of bile) -HDLs are often termed "good" cholesterol

What is measured in blood cholesterol?

LDL and HDL: -Lots of LDL = high risk of coronary heart diseases -Lots of HDL = healthy

How can we limit cholesterol synthesis?

-Limit ingestion of saturated fats and trans fat -Increase ingestion of unsaturated fats -Ingestion of cholesterol is not a main issue

What is lipogenesis?

Synthesis of lipids: -Adipocytes and hepatocytes -Anabolic process for long-term energy storage -Excess glucose = too much acetyl CoA -Converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts

What is lypolysis?

Breakdown of lipids: -Results = fatty acids + glycerol -Fatty acids go through B-oxidation that produces acetyl CoA that enters Krebs cycle -Glycerol enters glycolysis directly -Yield a lot of energy through aerobic respiration -Can help rising low blood glucose level (Acetyl CoA and glycerol serves for gluconeogenesis)

What is ketogenesis?

-Accumulation of acetyl CoA (too much for Krebs cycle) -Conversion to ketone bodies -Ketones are potential fuel source; prolonged starvation and uncontrolled diabetes

What is ketone body oxidation?

-Overproduction of ketone bodies, at one point, yields CO2 and acetone: -Alcohol smelling breath (acetone) -Ketoacidosis (blood acidification by CO2)

What happens with excess proteins?

-Proteins are never stored: Amino acids --> blood circulation --> liver and other body cells In excess: -Become glucose or ketones -Decomposition = nitrogenous wastes (ammonium); enters into urea cycle, urea eliminated by kidneys

How can the body obtain energy from proteins?

Source of energy (starvation): -Can enter Krebs cycle and produce energy -Can enter gluconeogenesis and produce glucose

What is a disorder linked with proteins consumption?

Cardiovascular disease: -High-protein diets include a lot of meat, which can be high in saturated fats -These fats can raise LDL ("bad") cholesterol levels contributing to the development of heart disease