Ch 5- bio 151

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which statement accurately describes the digestion of cellulose in the human digestive tract?

Cellulose passes through the digestive tract as soluble fiber.

Humans can digest cellulose due to specific enzymes.

Cellulose is fully digested into glucose.

Cellulose cannot be hydrolyzed by enzymes that digest starch. (correct)

What role do certain microbes play in the digestion of cellulose?

They digest cellulose and provide energy to herbivores. (correct)

They convert cellulose into sugars for herbivore consumption.

They inhibit the digestion of cellulose.

They produce cellulose to aid digestion.

Which of the following correctly identifies the primary components of fats?

Cholesterol and hydrocarbon chains.

Two fatty acids and a triglyceride.

Three fatty acids and a phospholipid.

Glycerol and fatty acids. (correct)

Why do fats separate from water?

Water molecules hydrogen-bond to each other, excluding fats. Signup and view all the answers

What feature distinguishes saturated fatty acids from unsaturated fatty acids?

Saturated fatty acids have maximum hydrogen and no double bonds. Signup and view all the answers

What type of linkage connects fatty acids to glycerol in a fat molecule?

Ester linkage. Signup and view all the answers

Which of the following best describes lipids?

Lipids are a diverse group of hydrophobic molecules. Signup and view all the answers

Chitin is known for its role in which of the following?

Providing structural support in fungi and arthropod exoskeletons. Signup and view all the answers

What determines the primary structure of a protein?

The sequence of amino acids Signup and view all the answers

Which of the following describes secondary structure in proteins?

Hydrogen bonds creating coils and folds Signup and view all the answers

The tertiary structure of a protein is primarily determined by which of the following?

Interactions among various side chains (R groups) Signup and view all the answers

What is a common example of a secondary protein structure?

α helix Signup and view all the answers

Which level of protein structure consists of multiple polypeptide chains?

Quaternary structure Signup and view all the answers

How does the primary structure of a protein relate to its function?

It determines the protein's ability to bind with other molecules Signup and view all the answers

What role do disulfide bridges play in protein structure?

They stabilize tertiary and quaternary structures Signup and view all the answers

Which interactions are involved in stabilizing tertiary structures?

Hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions Signup and view all the answers

What type of protein structure is formed when two or more polypeptide chains come together?

Quaternary structure Signup and view all the answers

Which of the following proteins consists of three polypeptides coiled together?

Collagen Signup and view all the answers

What is the result of a single amino acid substitution in hemoglobin?

Sickle-cell disease Signup and view all the answers

What term describes the process by which a protein loses its native structure and becomes biologically inactive?

Denaturation Signup and view all the answers

Under what circumstances can denaturation of proteins sometimes be reversed?

When the denaturing agent is removed Signup and view all the answers

What factors, aside from primary structure, can influence a protein's structure?

Environmental factors such as pH and temperature Signup and view all the answers

What is a common consequence of misfolded proteins in diseases such as Alzheimer's and Parkinson's?

Development of neurodegenerative conditions Signup and view all the answers

What happens to proteins in the blood at extremely high body temperatures?

They tend to denature Signup and view all the answers

What method does not require protein crystallization?

Nuclear magnetic resonance (NMR) spectroscopy Signup and view all the answers

Which molecule directs the synthesis of messenger RNA (mRNA)?

Deoxyribonucleic acid (DNA) Signup and view all the answers

What is a polynucleotide made of?

Nucleotides Signup and view all the answers

Which nitrogenous bases are classified as purines?

Adenine and guanine Signup and view all the answers

What is the sugar component of RNA?

Ribose Signup and view all the answers

The process of gene expression follows which flow of information?

DNA → RNA → protein Signup and view all the answers

What is the definition of a nucleoside?

Nitrogenous base + sugar Signup and view all the answers

Which of the following is true about the structure of DNA?

DNA is a double helix. Signup and view all the answers

What type of fats are solid at room temperature?

Saturated fats Signup and view all the answers

Which of the following is formed by hydrogenating vegetable oils?

Trans fats Signup and view all the answers

What is the primary function of fats in the body?

Energy storage Signup and view all the answers

What characterizes the structure of phospholipids?

Two fatty acids and a phosphate group Signup and view all the answers

What structural feature do phospholipids form when added to water?

Bilayers Signup and view all the answers

Which type of fat may contribute more to cardiovascular disease than saturated fats?

Trans fats Signup and view all the answers

What is the role of cholesterol in animal cells?

Precursor for steroid synthesis Signup and view all the answers

Which type of fat is typically derived from plants and fish?

Unsaturated fats Signup and view all the answers

What process forms a disaccharide from two monosaccharides?

Dehydration reaction Signup and view all the answers

Which of the following describes the primary function of monosaccharides in cells?

Major fuel for cells Signup and view all the answers

Which type of polysaccharide is primarily responsible for energy storage in animal cells?

Glycogen Signup and view all the answers

What distinguishes the glycosidic linkages in starch from those in cellulose?

Configuration of glucose ring forms Signup and view all the answers

Which of the following best describes cellulose?

A structural component in plant cells Signup and view all the answers

Which storage polysaccharide is simplest and primarily composed of glucose monomers?

Amylose Signup and view all the answers

What happens to glycogen when there is increased demand for sugar in animal cells?

It undergoes hydrolysis to release glucose Signup and view all the answers

Which characteristic of cellulose allows it to form hydrogen bonds with parallel molecules?

Hydroxyl groups on monomers Signup and view all the answers

Study Notes

Large Biological Molecules

Macromolecules are large polymers composed of monomers
Polymers are long molecules consisting of many similar building blocks
Monomers are repeating units that serve as building blocks
Carbohydrates, proteins, and nucleic acids are polymers
Lipids are not polymers or macromolecules

Synthesis and Breakdown of Polymers

Enzymes are specialized macromolecules that speed up chemical reactions like making or breaking down polymers
Dehydration reactions occur when two monomers bond together through the loss of a water molecule, forming a new bond
Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of a dehydration reaction.

The Diversity of Polymers

A cell has thousands of different macromolecules
Macromolecules vary among cells within an organism
Macromolecules vary more within a species
Macromolecules vary even more between species
A huge variety of polymers can be built from a small set of monomers

Carbohydrates

Carbohydrates include sugars and polymers of sugars
Monosaccharides are simple sugars
Carbohydrate macromolecules are polysaccharides
Polysaccharides are polymers composed of many sugar building blocks

Sugars

Monosaccharides have molecular formulas that are typically multiples of CH2O
Glucose (C6H12O6) is the most common monosaccharide
Monosaccharides are classified by
- the location of the carbonyl group (as aldose or ketose)
- the number of carbons in the carbon skeleton

Structures of Monosaccharides

Though often drawn as linear skeletons, in aqueous solutions many sugars form rings
Monosaccharides serve as a major fuel for cells and as raw material for building molecules

Disaccharides

A disaccharide is formed when a dehydration reaction joins two monosaccharides
The covalent bond between two monosaccharides is called a glycosidic linkage

Polysaccharides

Polysaccharides, the polymers of sugars, have storage and structural roles
The architecture and function of a polysaccharide are determined by its sugar monomers and the positions of its glycosidic linkages

Storage Polysaccharides

Starch, a storage polysaccharide of plants, consists of glucose monomers
Plants store surplus starch as granules within chloroplasts and other plastids
The simplest form of starch is amylose
Glycogen is a storage polysaccharide in animals
Glycogen is stored mainly in liver and muscle cells
Hydrolysis of glycogen in these cells releases glucose when the demand for sugar increases

Structural Polysaccharides

The polysaccharide cellulose is a major component of the tough wall of plant cells
Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ
The difference is based on two ring forms for glucose: alpha (α) and beta (β)
Cellulose molecules are straight and unbranched
Some hydroxyl groups on the monomers of cellulose can hydrogen-bond with hydroxyls of parallel cellulose molecules

Chitin

Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods.
Chitin also provides structural support for the cell walls of many fungi

Lipids

Lipids are the one class of large biological molecules that does not include true polymers
Lipids mix poorly, if at all, with water
Lipids consist mostly of hydrocarbon regions
The most biologically important lipids are fats, phospholipids, and steroids

Fats

Fats are constructed from two types of smaller molecules: glycerol and fatty acids
Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon
A fatty acid consists of a carboxyl group attached to a long carbon skeleton
Fats separate from water because water molecules hydrogen-bond to each other, thus excluding fats
In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride
The fatty acids in a fat can be all the same, or of two or three different kinds

Fatty acids

Fatty acids vary in length (number of carbons) and in the number and locations of double bonds
Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds
Unsaturated fatty acids have one or more double bonds
Fats made from saturated fatty acids are called saturated fats and are solid at room temperature
Most animal fats are saturated.
Fats made from unsaturated fatty acids are called unsaturated fats or oils and are liquid at room temperature.
Plant fats and fish fats are usually unsaturated

Functions of Fats

The major function of fats is energy storage
Humans and other mammals store their long-term food reserves in adipose cells
Adipose tissue also cushions vital organs and insulates the body

Phospholipids

In a phospholipid, two fatty acids and a phosphate group are attached to glycerol
The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
When phospholipids are added to water, they self-assemble into double-layered sheets called bilayers
At the surface of a cell, phospholipids are also arranged in a bilayer, with the hydrophobic tails pointing toward the interior
The phospholipid bilayer forms a boundary between the cell and its external environment

Steroids

Steroids are lipids characterized by a carbon skeleton consisting of four fused rings
Cholesterol, a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized
A high level of cholesterol in the blood may contribute to cardiovascular disease

Proteins

Proteins account for more than 50% of the dry mass of most cells
Some proteins speed up chemical reactions
Other protein functions include defence, storage, transport, cellular communication, movement, and structural support
Enzymes are proteins that act as catalysts to speed up chemical reactions
Proteins are all constructed from the same set of 20 amino acids
Polypeptides are unbranched polymers built from these amino acids
The bond between amino acids is a peptide bond
A protein is a biologically functional molecule that consists of one or more polypeptides
Amino acids are organic molecules with amino and carboxyl groups
Amino acids differ in their properties due to differing side chains, called R groups

Polypeptides

Amino acids are linked by covalent bonds called peptide bonds
A polypeptide is a polymer of amino acids
Polypeptides range in length from a few to more than 1,000 monomers
Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (N-terminus)

Protein Structure and Function

The specific activities of proteins result from their intricate three-dimensional architecture
A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape
The sequence of amino acids determines a protein's three-dimensional structure
A protein's structure determines how it works
The function of a protein usually depends on its ability to recognize and bind to some other molecule

Levels of Protein Structure

The primary structure of a protein is its unique sequence of amino acids
Secondary structure consists of coils and folds in the polypeptide chain
Tertiary structure is determined by interactions among various side chains (R groups)
Quaternary structure results when a protein consists of multiple polypeptide chains

Protein Folding

It is hard to predict a protein's structure from its primary structure
Most proteins probably go through several stages on their way to a stable structure
Diseases such as Alzheimer's, Parkinson's, and mad cow disease are associated with misfolded proteins

###Determining Protein Structure

Scientists use X-ray crystallography to determine a protein's structure
Another method is nuclear magnetic resonance (NMR) spectroscopy, which does not require protein crystallization
Bioinformatics is another approach to prediction of protein structure from amino acid sequences

Nucleic Acids

The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene
Genes consist of DNA, a nucleic acid made of monomers called nucleotides
There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
DNA provides directions for its own replication
DNA directs synthesis of messenger RNA (mRNA)
Through mRNA, DNA controls protein synthesis
This process is called gene expression
Each gene along a DNA molecule directs synthesis of a messenger RNA (mRNA)
The mRNA molecule interacts with the cell's protein-synthesizing machinery to direct production of a polypeptide
The flow of genetic information can be summarized as DNA → RNA → protein

Components of Nucleic Acids

Nucleic acids are polymers called polynucleotides
Each polynucleotide is made of monomers called nucleotides
Each nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups
The portion of a nucleotide without the phosphate group is called a nucleoside
There are two families of nitrogenous bases: pyrimidines (cytosine, thymine, and uracil); and purines (adenine and guanine)
In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose
Nucleotide = nucleoside + phosphate group

Nucleotide Polymers

Nucleotides are linked together by a phosphodiester linkage to build a polynucleotide
A phosphodiester linkage consists of a phosphate group that links the sugars of two nucleotides
These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages
The sequence of bases along a DNA or mRNA polymer is unique for each gene

Structures of DNA and RNA Molecules

DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix
The backbones run in opposite 5' → 3' directions from each other; an arrangement referred to as antiparallel
One DNA molecule includes many genes
Only certain bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
This feature of DNA structure makes it possible to generate two identical copies of each DNA molecule in a cell preparing to divide
RNA, in contrast to DNA, is single-stranded
Complementary pairing can also occur between two RNA molecules or between parts of the same molecule
In RNA, thymine is replaced by uracil (U), so A and U pair

Genomics and Proteomics

Once the structure of DNA and its relationship to amino acid sequence was understood, biologists sought to "decode" genes by learning their base sequences
The first chemical techniques for DNA sequencing were developed in the 1970s and refined over the next 20 years
It is enlightening to sequence the full complement of DNA in an organism's genome
The rapid development of faster and less expensive methods of sequencing was a side effect of the Human Genome Project
Many genomes have been sequenced, generating large sets of data
Bioinformatics uses computer software and other computational tools to deal with the data resulting from sequencing many genomes
Analyzing large sets of genes or even comparing whole genomes of different species is called genomics
A similar analysis of large sets of proteins, including their sequences, is called proteomics

DNA and Proteins as Tape Measures of Evolution

Sequences of genes and their protein products document the hereditary background of an organism
Linear sequences of DNA molecules are passed from parents to offspring
We can extend the concept of "molecular genealogy" to relationships between species
Molecular biology has added a new measure to the toolkit of evolutionary biology

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.