General Biology I: Carbohydrates

Flashcards covering Lecture 5: Carbohydrates, focusing on their structure, types, and roles in biological systems including energy storage, structural support, and cell identity.

What is a carbohydrate?

Molecules with a carbonyl (C=O) and several hydroxyl (-OH) functional groups, along with many carbon-hydrogen (C-H) bonds.

What is the general chemical formula for carbohydrates?

(CH2O)n

What are the monomer units that make up carbohydrates?

Monosaccharides (simple sugars).

What are the polymer forms of monosaccharides called?

Polysaccharides (complex carbohydrates).

What are the four main ways monosaccharides can vary?

1) Location of the carbonyl group, 2) Number of carbon atoms, 3) Spatial arrangement of their atoms, and 4) Linear and alternate ring forms.

What characterizes an aldose sugar?

The carbonyl group is located at the end of the monosaccharide's carbon chain.

What characterizes a ketose sugar?

The carbonyl group is located in the middle of the monosaccharide's carbon chain.

How many carbon atoms does a triose monosaccharide have?

Three carbon atoms.

How many carbon atoms does a pentose monosaccharide have?

Five carbon atoms.

How many carbon atoms does a hexose monosaccharide have?

Six carbon atoms.

In what form do sugars typically exist when in aqueous solutions?

They tend to form ring structures.

What type of reaction links monosaccharide monomers to form polysaccharides?

Condensation reactions between two hydroxyl groups.

What is the name of the covalent bond formed between monosaccharides in a polysaccharide?

A glycosidic linkage.

What are two common types of glycosidic linkages mentioned in the lecture?

α-1,4-glycosidic linkage and β-1,4-glycosidic linkage.

What is a structural difference between chains with β-1,4-glycosidic linkages and α-1,4-glycosidic linkages?

Chains with β-1,4-glycosidic linkages have alternating monosaccharides flipped in orientation.

What is starch, and what is its primary biological role?

It is how plants store sugar, comprised of branched (amylopectin) and unbranched (amylose) α-glucose polymers.

What is glycogen, and what is its primary biological role?

It is how animals store sugar, a highly branched α-glucose polymer.

What is cellulose, and where is it predominantly found?

A structural polymer of β-glucose monomers found in plant cell walls.

What is chitin, and where is it found?

A structural polymer comprised of N-acetylglucosamine (NAG) monomers, found in fungi cell walls, some algae, and many animal exoskeletons.

What is peptidoglycan, and what is its common location?

A structural polymer found in bacterial cell walls, composed of two alternating types of monosaccharides, one with short amino acid chains.

What characteristic makes β-1,4-glycosidic linkages in structural carbohydrates difficult to break down?

Very few enzymes have active sites that can accommodate their geometry or have the necessary reactive groups for hydrolysis.

How do α-1,4-glycosidic linkages in storage carbohydrates differ from β-1,4 linkages in terms of hydrolysis?

α-1,4-glycosidic linkages are readily hydrolyzed.

What are the three major roles carbohydrates play ?

1) Structural support, 2) Cell identity, and 3) Store chemical energy.

Name three structural carbohydrates.

Cellulose, Chitin, and Peptidoglycan.

How do carbohydrates contribute to cell identity?

They display information on the outer surfaces of cells through glycoproteins, which are key in cell-cell recognition and signaling.

What are glycoproteins?

Proteins joined to carbohydrates by covalent bonds, critical for cell-cell recognition and cell-cell signaling.

What process do plants use to store sunlight energy in carbohydrates?

Photosynthesis.

What is the overall chemical equation for photosynthesis?

CO2 + H2O + sunlight → (CH2O)n + O2

How does the energy storage capacity of fats compare to carbohydrates per gram?

Fats store approximately two times (2x) more energy per gram compared to carbohydrates.

How does the structural variability of glycosidic linkages compare to peptide bonds or phosphodiester bonds?

Glycosidic linkages are much more variable in structure compared to peptide bonds (proteins) or phosphodiester bonds (nucleic acids).