Difference Between Carbohydrates and Lipids

Main Difference – Carbohydrates vs Lipids

Macronutrients are the nutrients required in large amounts in the diet. They can be divided into three categories. They are carbohydrates, proteins and lipids. A carbohydrate consists of carbon (C), hydrogen (H), and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water). Carbohydrates are further divided into three groups including monosaccharides, disaccharides, and polysaccharides. Both monosaccharides and disaccharides are water soluble whereas polysaccharides are not soluble in water. In contrast, lipids are a diverse group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. All these compounds are not soluble in water. This is the main difference between carbohydrates and lipids. Both carbohydrates and lipids act as the main fuels and energy storage compounds of the human body. The biochemical metabolism of carbohydrates and lipids are closely interconnected, but these macronutrients have different purposes. In this article, let’s discuss the difference between carbohydrates and lipids in terms of their intended uses as well as chemical and physical properties.

What are Carbohydrates

A carbohydrate is a macronutrient consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. Similar to a water molecule, it has a hydrogen–oxygen atom ratio of 2:1 and its empirical formula is C_m(H₂O)_n. Carbohydrates are also known as hydrates of carbon, and it mainly exists as polyhydroxy aldehydes and ketones. The glycemic index (GI) and glycemic load concepts have been developed to characterize carbohydrate-rich food behavior during human digestion to identify the speed and extent of their effect on blood glucose levels.

What are Lipids

Lipids are macronutrient mainly consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. It is a hydrophobic or small amphiphilic molecule that is not soluble in water. Biological lipids are from two distinct types of biochemical subunits known as ketoacyl and isoprene groups.

The differences between carbohydrates and lipids can be divided into following categories. They are;

Categories and Examples

Carbohydrates: Carbohydrates are categorized into following subgroups;

Monosaccharides – glucose, fructose, galactose, xylose
Disaccharides – sucrose, lactose, maltose, trehalose
Polyols – sorbitol, mannitol
Oligosaccharides – maltodextrins, raffinose, stachyose, fructo-oligosaccharides
Polysaccharides – amylose, cellulose, amylopectin, modified starches, hemicellulose, pectins, hydrocolloids

Lipid: Lipids are categorized into following subgroups;

Fatty acids – arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid
Glycerolipids
Glycerophospholipids – phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine
Sphingolipids – sphingomyelins, cerebrosides, and gangliosides.
Sterol lipids – testosterone and androsterone
Prenol lipids – quinones and hydroquinones
Saccharolipids
Polyketides – erythromycins, tetracyclines, avermectins

Caloric Content

Carbohydrates: 4 calories of energy per gram of energy is generated in the human cells when metabolizing the carbohydrates.

Lipid: 9 calories of energy per gram of energy is generated in the human cells when metabolizing the lipids. Lipids provide more than twice the number of calories compared to carbohydrates.

Solubility

Carbohydrates: Majority of carbohydrates groups (except polysaccharides) are soluble in water, and they are hydrophilic in nature

Lipid: Lipids are not soluble in water because they are hydrophobic in nature

Digestion and Absorption

Carbohydrates: Digestive enzymes from saliva, pancreas and small intestine act directly on sugars and starches in the foods and break down carbohydrates into simple sugars known as monosaccharides, which are absorbed into the bloodstream for distribution to organs and tissues. Cells absorb the simple sugar with the assistance of the hormone insulin.

Lipid: Lipid has a complex digestive process. The gallbladder releases the bile acid into small intestine after food ingestion and bile contributes to breaking down large lipid globules into microscopic droplets, which are consequently digested by enzymes from the pancreas. Then the lining cells of small intestine absorb the digested fat particles and transported by carrier proteins.

Major Digestive Enzyme

Carbohydrates: The major digestive enzyme is α-amylase.

Lipid: The major digestive enzyme is Lipase.

Primary Functions in the Living Organisms

Carbohydrates: Primary functions of dietary carbohydrates are as follows;

Providing energy for body organs and tissues
Creating structural components in animals and plants (e.g. cellulose in plants and chitin in arthropods)
Synthesis of coenzymes (e.g. ribose in ATP, FAD, and NAD) and the backbone of the genetic molecule known as RNA
Function in immune system, fertilization, preventing pathogenesis and blood clotting
Synthesize of carbohydrates from carbon dioxide and water by photosynthesis in plants

Lipid: Primary functions of dietary lipids are as follows;

Storing energy in the cells
Facilitating the absorption and distribution of fat-soluble vitamins
Providing structural stability for cells and cushioning vital organs like kidney, liver,
Cell signaling mechanisms
Synthesis of reproduction hormones

Primary functions in industry

Carbohydrates: Primary functions of carbohydrates are as follows;

The complex carbohydrate starch used as the main ingredient in bakery products, noodles, and pasta production
Starch is used as a thickening agent in sauces
Simple carbohydrates, such as sugar used in beverages, candy, jams, and desserts production

Lipid: Primary functions of lipids are as follows;

Used for cosmetic production
Wax production
Used as a lubricant in many industrial applications
Used for emulsion production
Cooking oil and spreads production

Natural Food Sources

Carbohydrates:

Wheat, maize, rice, barley contains starch (polysaccharides)
Fruits contain fructose and dietary fiber
Milk contains lactose

Lipids:

Nuts such as peanuts, cashew nuts, almonds, walnut
Fruits such as avocado
Seeds such as sunflower, flax, rapeseed seeds
legumes (soy)
Fish and sea foods

Health Effects

Carbohydrates:

Excess consumption of refined sugars is associated with increased risk of metabolic syndrome, type II diabetes, cancers, cardiovascular diseases and obesity
Consumption of dietary fiber such as cellulose, hemicellulose, pectins, hydrocolloids can reduce the risk of colon cancers, constipation, type II diabetes, and obesity

Lipids:

High amount of saturated fats consumption may increase LDL cholesterol and risk of heart disease, and increase risk of type II diabetes and obesity
Unsaturated fats are associated with various health benefits including the reduction of the risk of cancer development, prevention of cardiovascular disease, platelet aggregation, and hypertension. They have anti-inflammatory properties and lower markers of inflammation in the blood. However, some unsaturated fats have both pro-inflammatory and anti-inflammatory properties.

In conclusion, carbohydrates and lipids are primarily essential macronutrients, and they offer important nutrients to the daily diet. Carbohydrates are considered as a ready source of fuel to cells, whereas lipids can store energy in fat tissue for future use. However, excess consumption of these macronutrients may associate with detrimental health effects.

References

Carbohydrates in human nutrition – Chapter 1 – The role of carbohydrates in nutrition. Food and Agriculture Organization of the United Nations. FAO

Hunt SM, Groff JL, Gropper SA (1995). Advanced Nutrition and Human Metabolism. Belmont, California: West Pub. Co. p. 98. ISBN 978-0-314-04467-9.

Joint WHO/FAO expert consultation (1998), Carbohydrates in human nutrition, chapter 1. ISBN 92-5-104114-8.

Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. pp. 52–59

Vance JE, Vance DE (2002). Biochemistry of Lipids, Lipoproteins and Membranes. Amsterdam: Elsevier. ISBN 978-0-444-51139-3.