Biology LibreText

Question 1

2.11

Hydrophilic

Answer 1

having an affinity for water; able to absorb, or be
wetted by water

Question 2

2.11

Hydrophobic

Answer 2

lacking an affinity for water; unable to absorb, or
be wetted by water

Question 3

2.11

Polarity

Answer 3

The intermolecular forces between the slightly positively-charged end of one molecule to the negative end of
another or the same molecule

Question 4

2.12

Describe the difference in desnity between ice and water

Answer 4

Due to ice (solid) being held by hydrogen bonds in a lattice (or crystalline) formation that separates the indvidual water molecules, water (liquid) is denser than ice, given the molecules’ ability to move in close proximity using kinetic energy.

Question 5

2.12

Density

Answer 5

A measure of the amount of matter contained by a given
volume

Question 6

2.13

Heat of vaporization

Answer 6

The energy required to transform a given
quantity of a substance from a liquid into a gas at a given
pressure (often atmospheric pressure).

Question 7

2.14

Heat capacity

Answer 7

The capability of a substance to absorb heat energy. Water has a high beat capacity

Question 8

2.14

Specific heat

Answer 8

the amount of heat, in calories, needed to raise the temperature of 1 gram of water by 1 degree Celsius

Question 9

2.15

Dissociation

Answer 9

The process by which a compound or complex body breaks up into simpler constituents such as atoms or ions,
usually reversibly.

Water dissociates salts by separating the cations and anions and forming new interactions between the water and ions.

Question 10

2.15

Hydration shell

Answer 10

The term given to a solvation shell (a structure composed of a chemical that acts as a solvent and surrounds a solute species) with a water solvent; also referred to as a hydration sphere.

Question 11

2.16

Cohesion

Answer 11

Various intermolecular forces that hold solids and liquids together; attraction between like molecules.

Cohesion holds hydrogen bonds together to create surface tension on water.

Water is transported in plants through both cohesive and adhesive forces; these forces pull water and the dissolved minerals from the roots to the leaves and other parts of the plant.

Question 12

2.16

Adhesion

Answer 12

The ability of a substance to stick to an unlike substance; attraction between unlike molecules.

Since water is attracted to other molecules, adhesive forces pull the water toward other molecules.

Water is transported in plants through both cohesive and adhesive forces; these forces pull water and the dissolved minerals from the roots to the leaves and other parts of the plant.

Question 13

2.17

Calculation needed for pH

Answer 13

pH = – log[H+]

*Hydronium concentration can be used as well

Question 14

2.17

Buffer

Answer 14

a solution composed of a weak acid and its conjugate base that can be used to stabilize the pH of a solution

Question 15

2.18

Describe the structure of carbon

Answer 15

Individual carbon atoms have an incomplete outermost electron
shell. With an atomic number of 6 (six electrons and six protons), the first two electrons fill the inner shell, leaving four in the second shell. Therefore, carbon atoms can form four covalent bonds with other atoms to satisfy the octet rule.

Question 16

2.18

How is carbon vital for cells?

Answer 16

Cells are made of many complex molecules called macromolecules, which include proteins, nucleic acids (RNA and DNA), carbohydrates, and lipids.

The macromolecules are a subset of organic molecules (any carbon-containing liquid, solid, or gas) that are especially important for life. The fundamental component for all of these macromolecules is carbon.

The carbon atom has unique properties that allow it to form covalent bonds to as many as four different atoms, making this versatile element ideal to serve as the
basic structural component, or “backbone,” of the macromolecules.

Question 17

2.18

Carbon cycle

Answer 17

the physical cycle of carbon through the earth’s biosphere, geosphere, hydrosphere, and atmosphere; includes
such processes as photosynthesis, decomposition, respiration and
carbonification

Question 18

2.18

Macromolecule

Answer 18

a very large molecule, especially used in
reference to large biological polymers (e.g., nucleic acids, carbohydrates, lipids and proteins)

Question 19

2.19

Covalent bond

Answer 19

A type of chemical bond where two atoms are connected to each other by the sharing of two or more electrons.

Question 20

2.19

Aliphatic

Answer 20

Of a class of organic compounds in which the carbon atoms are arranged in an open chain.

Question 21

2.19

Aromatic

Answer 21

Having a closed ring of alternate single and double bonds with delocalized electrons.

Question 22

2.20

Fatty acid

Answer 22

Any of a class of aliphatic carboxylic acids, of general formula CnH2n+1COOH, that occur combined with glycerol as animal or vegetable oils and fats

Question 23

2.20

Isomer

Answer 23

Any of two or more compounds with the same molecular formula but with different structure.

Question 24

2.23

What are the four major classes of biological macromolecules?

Answer 24

1. carbohydrates
2. lipids
3. proteins
4. nucleic acids

Question 25

# 2.23 Polymer

Answer 25

A relatively large molecule consisting of a chain or network of many identical or similar monomers chemically bonded to each other.

Question 26

# 2.23 Monomer

Answer 26

A relatively small molecule that can form covalent bonds with other molecules of this type to form a polymer

Question 27

# 2.24 What occurs during dehydration synthesis (also known as condensation reactions)?

Answer 27

During dehydration synthesis, either the hydrogen of one monomer combines with the hydroxyl group of another monomer releasing a molecule of water, or two hydrogens from one monomer combine with one oxygen from the other monomer releasing a molecule of water. The monomers that are joined via dehydration synthesis reactions share electrons and form covalent bonds with each other. As additional monomers join via multiple dehydration synthesis reactions, this chain of repeating monomers begins to form a polymer. Complex carbohydrates, nucleic acids, and proteins are all examples of polymers that are formed by dehydration synthesis.

Question 28

# 2.25 Enzyme

Answer 28

A globular protein that catalyses a biological chemical reaction. Proteins are broken down by the enzymes trypsin, pepsin, peptidase and others. Lipids are broken down by lipases. Once the smaller metabolites that result from these hydrolytic enzymezes are absorbed by cells in the body, they are further broken down by other enzymes.

Question 29

# 2.25 Hydrolysis

Answer 29

A chemical process of decomposition involving the splitting of a bond by the addition of water. Hydrolysis reactions break bonds and release energy. Biological macromolecules are ingested and hydrolyzed in the digestive tract to form smaller molecules that can be absorbed by cells and then further broken down to release energy.

Question 30

# 2.25 What happens if the components are ionized after the split during hydrolysis?

Answer 30

If the components are ionized after the split, one part gains two hydrogen atoms and a positive charge, the other part gains an oxygen atom and a negative charge. This is what happens when amino acids are released from protein chains via hydrolysis.

Question 31

# 3.1 Carbohydrates formula

Answer 31

(CH2O)n

Question 32

# 3.1 What are the classified subtypes of carbohydrates?

Answer 32

1. monosaccharides 2. disaccharides 3. polysaccharides

Question 33

# 3.1 Describe monosaccharides

Answer 33

* Simple sugars * Carbons range from 3-7 * If it has an aldehyde group, called an aldose * If it has a ketone group, called a ketose * May be called trioses (3 carbons), pentoses (5 C) and hexoses (6 C) * Can exist as a linear chain or ring-shaped molecule; it's often ring-shaped in aqueous solutions * Examples: glucose, galactose and fructose (same chemical formula)

Question 34

# 3.1 Glycosidic bond (or glycosidic linkage)

Answer 34

A covalent bond formed between a carbohydrate molecule and another molecule (in the case of disaccharides, between two monosaccharides). They can be of the alpha (facing downwards OR below the ring plane) or the beta type (facing upwards or above the ring plane).

Question 35

# 3.1 List three examples of disaccharides

Answer 35

1. Lactose (glucose + galactose) 2. Maltose (glucose + glucose) 3. Sucrose (glucose + fructose)

Question 36

# 3.1 List four examples of polysaccharides

Answer 36

1. starch 2. glycogen 3. cellulose 4. chitin

Question 37

# 3.1 Compare the use of polysaccharides in plants and animals

Answer 37

Plants are able to synthesize glucose, and the excess glucose is stored as **starch** in different plant parts (mainly amyloplasts vacuoles), including roots and seeds. Starch is the stored form of sugars in plants and is made up of glucose monomers that are joined by α1-4 or 1-6 glycosidic bonds. The starch in the seeds provides food for the embryo as it germinates while the starch that is consumed by humans is broken down by enzymes into smaller molecules, such as maltose and glucose. The cells can then absorb the glucose. **Glycogen** is the storage form of glucose in humans and other vertebrates. It is made up of monomers of glucose. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis. **Cellulose** is the most abundant natural biopolymer. The cell wall of plants is mostly made of cellulose and provides structural support to the cell. Cellulose is made up of glucose monomers that are linked by β 1-4 glycosidic bonds. Every other glucose monomer in cellulose is flipped over, and the monomers are packed tightly as extended long chains. This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Arthropods have an outer skeleton, the exoskeleton, which protects their internal body parts. This exoskeleton is made of **chitin**, which is a polysaccharide-containing nitrogen. Chitin is also a major component of fungal cell walls.

Question 38

# 3.1 Biopolymer

Answer 38

Any macromolecule of a living organism that is formed from the polymerization of smaller entities; a polymer that occurs in a living organism or results from life.

Question 39

# 3.1 Dehydration reaction

Answer 39

A chemical reaction in which two molecules are covalently linked in a reaction that generates H2O as a second product.

Question 40

# 3.2 Describe fibre and its benefits

Answer 40

Carbohydrates contain soluble and insoluble elements; the insoluble part is known as fiber, which is mostly cellulose. Fiber has many uses: * it promotes regular bowel movement by adding bulk * it regulates the rate of consumption of blood glucose * it also helps to remove excess cholesterol from the body. Fiber binds and attaches to the cholesterol in the small intestine and prevents the cholesterol particles from entering the bloodstream. Then cholesterol exits the body via the feces. * it has a protective role against the development of colon cancer

Question 41

# 3.2 Carbohydrate

Answer 41

A sugar, starch, or cellulose that is a food source of energy for an animal or plant; a saccharide

Question 42

# 3.2 Glucose

Answer 42

a simple monosaccharide (sugar) with a molecular formula of C6H12O6; it is a principal source of energy for cellular metabolism

Question 43

# 3.2 ATP

Answer 43

A nucleotide that occurs in muscle tissue, and is used as a source of energy in cellular reactions, and in the synthesis of nucleic acids. ATP is the abbreviation for adenosine triphosphate

Question 44

# 3.5 Amphipathic

Answer 44

Describing a molecule, such as a detergent, which has both hydrophobic and hydrophilic groups.

Question 45

# 3.5 What is the main cause behind cell membranes' fluidity?

Answer 45

Biological membranes remain fluid because of the unsaturated hydrophobic tails, which prevent phospholipid molecules from packing together and forming a solid.

Question 46

# 3.5 Describe the phospholipid bilayer

Answer 46

Phospholipids consist of a glycerol molecule, two fatty acids, and a phosphate group that is modified by an alcohol. The phosphate group is the negatively-charged polar head, which is hydrophilic. The fatty acid chains are the uncharged, nonpolar tails, which are hydrophobic. Since the tails are hydrophobic, they face the inside, away from the water and meet in the inner region of the membrane. Since the heads are hydrophilic, they face outward and are attracted to the intracellular and extracellular fluid. If phospholipids are placed in water, they form into micelles, which are lipid molecules that arrange themselves in a spherical form in aqueous solutions.

Question 47

# 3.7 State some of the functions of proteins

Answer 47

* catalyzing chemical reactions * synthesizing and repairing DNA * transporting materials across the cell * receiving and sending chemical signals * responding to stimuli * providing structural support

Question 48

# 3.7 Distinguish between fibrous and globular proteins

Answer 48

Fibrous proteins are long, strand-like proteins that are insoluble in water, weak acids, and weak bases, whereas globular proteins have a spherical shape and are soluble in water, acids, and bases.

Question 49

# 3.7 Distinguish between catabolic and anabolic enzymes

Answer 49

Catabolic enzymes: enzymes that break down their substrate Anabolic enzymes: enzymes that build more complex molecules from their substrates

Question 50

# 3.7 Amino acid

Answer 50

Any of 20 naturally occurring α-amino acids (having the amino, and carboxylic acid groups on the same carbon atom), and a variety of side chains, that combine, via peptide bonds, to form proteins.

Question 51

# 3.7 Polypeptide

Answer 51

Any polymer of (same or different) amino acids joined via peptide bonds.

Question 52

# 3.7 Catalyze

Answer 52

To accelerate a process.

Question 53

# 3.8 Distinguish between the N-terminal and the C-terminal in an amino acid

Answer 53

N-terminal --> the amino terminal (where the amino group is situated) C-terminal --> the carboxyl terminal **It is conventional to use the N-to-C structure with a.a. diagrams

Question 54

# 3.8 R-group

Answer 54

The R group is a side chain specific to each amino acid that confers particular chemical properties to that amino acid.

Question 55

# 3.9 Antiparallel

Answer 55

The nature of the opposite orientations of the two strands of DNA or two beta strands that comprise a protein’s secondary structure

Question 56

# 3.9 Disulfide bond

Answer 56

A bond, consisting of a covalent bond between two sulfur atoms, formed by the reaction of two thiol groups, especially between the thiol groups of two proteins

Question 57

# 3.9 Beta-pleated sheets

Answer 57

Secondary structure of proteins where N-H groups in the backbone of one fully-extended strand establish hydrogen bonds with C=O groups in the backbone of an adjacent fully-extended strand

Question 58

# 3.9 Alpha-helix

Answer 58

Secondary structure of proteins where every backbone N-H creates a hydrogen bond with the C=O group of the amino acid four residues earlier in the same helix

Question 59

# 3.10 Chaperonin

Answer 59

proteins that provide favorable conditions for the correct folding of other proteins, thus preventing aggregation

Question 60

# 3.10 Denaturation

Answer 60

The change of folding structure of a protein (and thus of physical properties) caused by heating, changes in pH, or exposure to certain chemicals

Question 61

# 3.11 Describe how a phosphodiester linkage is formed

Answer 61

The phosphate residue is attached to the hydroxyl group of the 5′ carbon of one sugar and the hydroxyl group of the 3′ carbon of the sugar of the next nucleotide, which forms a 5′3′ phosphodiester linkage.

Question 62

# 3.11 Nucleotide

Answer 62

The monomer comprising DNA or RNA molecules; consists of a nitrogenous heterocyclic base that can be a purine or pyrimidine, a five-carbon pentose sugar, and a phosphate group

Question 63

# 3.11 Genome

Answer 63

the cell’s complete genetic information packaged as a double-stranded DNA molecule

Question 63

# 3.12 Mutation

Answer 63

Any error in base pairing during the replication of DNA

Question 64

# 3.12 Sugar-phosphate backbone

Answer 64

The outer support of the ladder, forming strong covalent bonds between monomers of DNA.

Question 65

# 3.12 Base pairing

Answer 65

The specific way in which bases of DNA line up and bond to one another; A always with T and G always with C

Question 66

# 3.13 Compare the DNA packing in eukaryotes and prokaryotes

Answer 66

In eukaryotic cells, DNA and RNA synthesis occur in a different location than protein synthesis; in prokaryotic cells, both these processes occur together. DNA is “supercoiled” in prokaryotic cells, meaning that the DNA is either under-wound or over-wound from its normal relaxed state. In eukaryotic cells, DNA is wrapped around proteins known as histones to form structures called nucleosomes.

Question 67

# 3.13 Nucleosomes

Answer 67

The fundamental subunit of chromatin, composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones.

Question 68

# 3.13 Histone

Answer 68

The chief protein components of chromatin, which act as spools around which DNA winds.

Question 69

# 3.14 Codon

Answer 69

a sequence of three adjacent nucleotides, which encode for a specific amino acid during protein synthesis or translation

Question 70

# 3.14 Transcription

Answer 70

the synthesis of RNA under the direction of DNA

Question 71

# 4.1 Prokaryotes

Answer 71

Small cells in the domains Bacteria and Archaea that do not contain a membrane-bound nucleus or other membrane-bound organelles.

Question 72

# 4.1 Eukaryotes

Answer 72

Having complex cells in which the genetic material is contained within membrane-bound nuclei.

Question 73

# 4.1 Cell

Answer 73

The basic unit of a living organism, consisting of a quantity of protoplasm surrounded by a cell membrane, which is able to synthesize proteins and replicate itself.

Question 74

# 4.2 Describe light miscroscopes

Answer 74

Light microscopes allow for magnification of an object approximately up to 400-1000 times depending on whether the high power or oil immersion objective is used. Light microscopes use visible light which passes and bends through the lens system.

Question 75

# 4.2 Describe an electron miscroscope

Answer 75

Electron microscopes use a beam of electrons, opposed to visible light, for magnification. Electron microscopes allow for higher magnification in comparison to a light microscope thus, allowing for visualization of cell internal structures.

Question 76

# 4.3 Describe Cell Theory

Answer 76

1. The cell is the fundamental unit of structure and function in living things. 2. All organisms are made up of one or more cells. 3. Cells arise from other cells through cellular division The expanded version may also include: * Cells carry genetic material passed to daughter cells during cellular division * All cells are essentially the same in chemical composition * Energy flow (metabolism and biochemistry) occurs within cells

Question 77

# 4.5 Describe the main common features to all cells

Answer 77

1. **a plasma membrane:** an outer covering that separates the cell’s interior from its surrounding environment. 2. **cytoplasm:** a jelly-like cytosol within the cell in which other cellular components are found 3. **DNA:** the genetic material of the cell 4. **ribosomes:** where protein synthesis occurs

Question 78

# 4.5 Explain the unique features of prokaryotic cells

Answer 78

* ** Peptidoglycan cell wall:** acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration * **Capsule: ** enables the cell to attach to surfaces in its environment * **Flagella:** used for locomotion * **Pili: ** used to exchange genetic material during a type of reproduction called conjugation * **Fimbriae: ** used by bacteria to attach to a host cell

Question 79

# 4.5 Compare the size of prokaryotic and eukaryotic cells

Answer 79

At 0.1 to 5.0 μm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10 to 100 μm. The small size of prokaryotes allows ions and organic molecules that enter them to quickly diffuse to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly diffuse out. This is not the case in eukaryotic cells, which have developed different structural adaptations to enhance intracellular transport.

Question 80

# 4.5 Nucleoid

Answer 80

the irregularly-shaped region within a prokaryote cell where the genetic material is localized

Question 81

# 4.6 What is the difference between vesicles and vacuoles?

Answer 81

While both function in storage and transport, the membranes of vesicles can fuse with either the plasma membrane or other membrane systems within the cell.

Question 82

# 4.6 What are two features found in animal cells, yet absent in plant cells?

Answer 82

Animal cells have a centrosome and lysosomes, whereas plant cells do not. The centrosome is a microtubule-organizing center found near the nuclei of animal cells while lysosomes take care of the cell’s digestive process. The centrosome is the primary microtubule-organizing centre (MTOC) in animal cells, and so it regulates cell motility, adhesion and polarity in interphase, and facilitates the organization of the spindle poles during mitosis.

Question 83

# 4.6 Organelle

Answer 83

A specialized structure found inside cells that carries out a specific life process (e.g. ribosomes, vacuoles).

Question 84

# 4.7 Describe the process of osmosis

Answer 84

Osmosis is the diffusion of water through a semi-permeable membrane down its concentration gradient. It occurs when there is an imbalance of solutes outside of a cell versus inside the cell. The solution that has the higher concentration of solutes is said to be hypertonic and the solution that has the lower concentration of solutes is said to be hypotonic. Water molecules will diffuse out of the hypotonic solution and into the hypertonic solution (unless acted upon by hydrostatic forces).

Question 85

# 4.7 Endocytosis

Answer 85

where a cell envelopes extracellular materials using its cell membrane

Question 86

# 4.7 Exocytosis

Answer 86

where a cell exports material using vesicular transport

Question 87

# 4.7 Hypertonic

Answer 87

having a greater osmotic pressure than another

Question 88

# 4.7 Hypotonic

Answer 88

Having a lower osmotic pressure than another; a cell in this environment causes water to enter the cell, causing it to swell.

Question 89

# 4.9 What is the name of the prokaryote hypothesized to be the endosymbiont for mitochondria?

Answer 89

alpha-proteobacteria (or "purple bacteria")

Question 90

# 4.9 Describe and support the endosymbiotic origin of mitochondria

Answer 90

The endosymbiotic hypothesis suggests mitochondria were originally prokaryotic cells, capable of implementing oxidative mechanisms. These prokaryotic cells may have been engulfed by a eukaryote and became endosymbionts living inside the eukaryote. Mitochondria have their own (usually) circular DNA chromosome that is stabilized by attachments to the inner membrane and carries genes similar to genes expressed by alpha-proteobacteria. Mitochondria also have special ribosomes and transfer RNAs that resemble these components in prokaryotes. These features all support the hypothesis that mitochondria were once free-living prokaryotes.

Question 91

# 4.11 Describe how vesicles are formed

Answer 91

Vesicles form naturally during the processes of secretion (exocytosis), uptake (phagocytosis) and transport of materials within the cytoplasm. Alternatively, they may be prepared artificially, in which case they are called liposomes.