Carbohydrates

What are carbohydrates?

Organic compounds

What atoms do carbohydrates have?

Carbon, hydrogen, and oxygen

What are monomers?

Small, water soluble sugars

What is another name for monomers?

Monosaccharides

What are polymers?

Monomers joined together

What are two different names for polymers?

Disaccharides (2 monosaccharides joined together) or polysaccharides (more than 2 monosaccharides joined together)

Are the hydroxyl (-OH) groups of sugars polar or non-polar?

polar (soluble) and form hydrogen bonds with water

What are the four functions of carbohydrates?

Quick fuel

Energy storage (in the liver and muscles)

Structural roles (bacteria, making the cell wall tough in plants, and forming the exoskeleton in insects)

Cell-to-cell recognition (carbohydrates on cell surfaces to help the immune system recognize invaders)

Are monosaccharides simple or complex sugars?

Simple

How many carbon atoms are usually in the backbone of a monosaccharide?

3-7

What is the general formula of a monosaccharide?

(CH₂O)_n

Where n = number of carbon atoms

How many carbons are in a hexose sugar?

6

How many carbons are in a triose sugar?

3

How many carbons are in a pentose sugar?

5

What is the sugar called in DNA?

deoxyribose

What is the sugar called in RNA?

ribose

How many carbons are in glucose?

6 (glucose is a hexose sugar)

What is the purpose of glucose?

For organisms to degrade as a source of energy during the process of cellular respiration

Cellular respiration:

glucose + oxygen = carbon dioxide + water

When dissolved in water (such as the cytoplasm), what structure does the carbon backbone of a sugar usually form?

A ring

In a glucose molecule, where is the carbonyl group?

Always on carbon #1

The ring always has 5 carbons, with the 6th carbon being attached as a chain

How do you find the chain?

Orient the alone oxygen in the top right corner, then start counting the carbons to the bottom right of the alone oxygen. The branch will be connected to the 5th carbon

What are three common hexoses?

Fructose, glucose, and galactose

What are similar about fructose, glucose, and galactose?

They all occur as ring structures and they all have the same chemical formula (C₆H₁₂O₆), but are arranged in different ways

What happens when monosaccharides are broken down?

Energy is released

What is the process of monosaccharides being linked together called?

Dehydration reaction

Are disaccharides simple or complex carbohydrates?

Simple

How many sugars are in disaccharides?

Two (di=two)

What bond holds two monosaccharides together

A covalent bond, called a glycosidic bond/linkage in this case

What process breaks apart disaccharides?

hydrolysis reaction

Give three examples of disaccharides

Maltose, sucrose, and lactose

What two monosaccharides come together to form maltose?

glucose + glucose = maltose

What enzyme breaks down maltose?

Maltase

What are examples of maltose?

oats, grains, wheat

What two monosaccharides come together to form sucrose?

glucose + fructose = sucrose

What enzyme breaks down sucrose?

Sucrase

What are examples of sucrose?

Fruits and vegetables

What two monosaccharides come together to form lactose?

glucose + galactose = lactose

What enzyme breaks down lactose?

Lactase

What are examples of lactose?

Dairy products

What is released when two monosaccharides join together?

water

mono + mono = di + water

Monosaccharides are joined through a dehydration reaction

What is a polysaccharide?

A polymer made from many monosaccharides

What are four examples of glucose subunit polymers?

Starch, glycogen, cellulose, chitin

What is starch?

A long term storage form of glucose

Where is starh

What is the form of starch?

Long branches chains

Where is glycogen found?

Animals (specifically the liver and muscles)

Is glycogen or starch better for quick release energy?

Glycogen is better because there are more branches. Imagine if you cut glycogen (see picture) with scissors, you would break more bonds than if you cut starch

What do starch and glycogen do in cells that differentiates them from cellulose?

They form granules (clusters) in the cell

What is cellulose?

An insoluble carbohydrate composed of glucose subunits?

Where is cellulose found?

In the cell wall of plants

Why is cellulose in cell walls?

To give plants structure and strength, as cellulose is very strong

Instead of forming granules, what does cellulose do?

It forms long straight chains that link to other chains, forming bundles of cellulose

What bond links chains of cellulose to each other?

Hydrogen bonds

What are bundles of cellulose molecules called?

Microfibrils

What can cellulose be compared to, strength wise?

An equivalent amount of steel

What can the cell wall be compared to and why?

A woven basket

Bundles of microfibrils are laid down in parallel and interwoven bands to form a structure similar to reinforced steel

How are the glucose units in cellulose joined differently than those in starch or glycogen?

In cellulose, every other subunit is inverted (upside down)

What are alpha linkages?

Bonds where everything is the same direction

What are beta bonds?

Where every other bond is inverted

Can humans digest food containing B bonds and why or why not?

We can’t because humans don’t have the enzyme cellulase

What purpose does cellulose have in most animal bodies?

It passes undigested but serves as a fibre that feeds our gut microbes and prevents constipation

What is chitin?

Another polysaccharide made of glucose subunits

Where is chitin found?

In the exoskeletons of various animals (particularly insects)

What differs the glucose subunits of chitin to the glucose subunits of glycogen, starch, and cellulose?

The glucose subunits in chitin have a nitrogen-containing function group instead of one hydroxyl attached to the second carbon (see bottom right of each diagram and notice the different function groups)

What is chitin often made into?

A thread used as a suture material