Exam 2 Flashcards
1
Q
List the 4 major classes biomolecules
A
- Carbohydrates
- Proteins
- Nucleic Acid
- Lipids
2
Q
Define monomer
A
is a small molecule that can chemically bond with other monomers to form a polymer.
3
Q
Define polymer
A
is a large molecule made up of repeating units (monomers) covalently bonded together.
4
Q
Why is a lipid not a monomer?
A
they are not built from repeating monomers. They are a diverse group of molecules, including fats, phospholipids, and steroids, which do not form long chains
5
Q
Difference between dehydration and hydrolysis reactions
A
Dehydration Reaction: Also known as a condensation reaction, this is a chemical reaction in which two molecules covalently bond with the loss of a water molecule. It is how monomers are joined together to form polymers.
Hydrolysis Reaction: This is the reverse of a dehydration reaction. It involves the breaking of a covalent bond with the addition of a water molecule. It is how polymers are broken down into their monomers.
6
Q
Carbohydrate
A
Atomic Composition: Made of carbon, hydrogen, and oxygen in a 1:2:1 ratio.
Functional Groups: Hydroxyl (-OH) groups.
They are hydrophilic.
Main Functions:
- Provide energy for cellular activities (glucose).
- Serve as structural components (cellulose in plant cell walls).
7
Q
Proteins
A
Atomic Composition: Made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
Functional Groups: Amino (-NH2) and carboxyl (-COOH) groups. Variable R groups define different amino acids. Hydrophilic or hydrophobic depending on the R group.
Main Functions:
- Enzymatic reactions, structural support, transport, signaling, movement, and defense.
8
Q
Nucleic Acid
A
Atomic Composition: Made of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
Functional Groups: Phosphate groups (-PO4) and nitrogenous bases (adenine, guanine, cytosine, thymine/uracil). Hydrophilic.
Main Functions:
DNA stores genetic information, RNA serves in protein synthesis and other cellular functions.
9
Q
Lipids
A
Atomic Composition: Primarily carbon and hydrogen, with some oxygen.
Functional Groups: Varied, but they often include long hydrocarbon chains or rings. Hydrophobic.
Main Functions:
Energy storage, cell membrane structure (phospholipids), insulation, and signaling molecules (steroids).
10
Q
Define/Example of Monosaccharide
A
- Glucose
- Fructose
- The general molecular formula for a monosaccharide is (CH2O)
11
Q
Define/Example of Disaccharide
A
- Sucrose (Glucose + Fructose)
- Lactose (Glucose + Galactose)
- Maltose (Glucose + Glucose)
12
Q
Define/Example of polysaccharide
A
- Starch (found in plants for energy storage)
- Glycogen (found in animals for energy storage)
- Cellulose (found in plant cell walls for structure)
- Chitin (found in the exoskeletons of arthropods and insects).
13
Q
Difference between a ribose sugar and a deoxyribose sugar
A
Ribose sugar has a hydroxyl group (-OH) attached to its 2’ carbon, while deoxyribose lacks this group, hence the name “deoxy.”
14
Q
Carbons in monosaccharides are numbered. Use glucose as an example to number the carbons in the chain &
ring structural formulas.
A
- In the chain form, the carbons are numbered from 1 to 6. Carbon 1 is the carbonyl carbon.
- In the ring form, the anomeric carbon (where the ring is formed) is also carbon 1.
15
Q
Use the ring structural formula to explain the key difference between the α- and β-glucose.
A
- The key difference lies in the orientation of the hydroxyl group attached to the anomeric carbon (carbon 1) in the ring structure.
- In α-glucose, the -OH group is below the ring, while in β-glucose, it is above the ring.
16
Q
Identify the covalent bond that links two monosaccharides together and describe how it is formed.
A
- The covalent bond that links two monosaccharides together is a glycosidic bond. It is formed through a dehydration (condensation) reaction, where a hydroxyl group from one sugar molecule combines with a hydrogen atom from the other, resulting in the release of a water molecule.
17
Q
What is the most common monomer for polysaccharide?
A
Glucose
18
Q
List the four examples of polysaccharides and state
where each would be found
A
Starch: Found in plants for energy storage (e.g., potatoes, grains).
Glycogen: Found in animals for energy storage (stored in liver and muscles).
Cellulose: Found in plant cell walls for structure (dietary fiber in humans).
Chitin: Found in the exoskeletons of arthropods and insects.
19
Q
Compare the structure of starch with that of cellulose. What are the dietary implications of the difference?
A
Starch:
Helical structure.
Digestible by humans due to the α-linkages.
Used for energy storage in plants.
Cellulose:
Straight-chain structure.
Indigestible by humans due to the β-linkages.
Provides structural support in plant cell walls and dietary fiber for humans.
Dietary implication: Humans lack the enzymes needed to break down cellulose, so it provides bulk to our diet (fiber) without contributing calories. Starch, on the other hand, is a source of energy.
20
Q
What is the characteristic used to classify a molecule as a lipid?
A
- Consists of mostly hydrocarbons
- Hydrophobic
21
Q
How do you identify a molecule as a fatty acid?
A
Fatty acids are long hydrocarbon chains with a carboxyl group (-COOH) at one end. They can be identified by this carboxyl group.
22
Q
What is saturated fat acid “saturated” with?
A
A saturated fatty acid is “saturated” with hydrogen atoms. This means there are no double bonds between the carbon atoms in the hydrocarbon chain.
23
Q
Name the components needed to build a triglyceride
A
A triglyceride is formed from three fatty acids and one glycerol molecule through a dehydration (esterification) reaction.
24
Q
Distinguish between a saturated and an unsaturated fat and list some unique emergent properties that are a consequence of these structural differences
A
Saturated Fat:
- Have no double bonds in their hydrocarbon chains.
- Tend to be solid at room temperature.
- Found in animal products and some plant oils (e.g., coconut oil, butter).
Unsaturated Fat:
- Have one or more double bonds in their hydrocarbon chains.
- Tend to be liquid at room temperature.
- Found in seeds, nuts, and fish.
Emergent Properties:
Unsaturated fats have kinks in their structure due to double bonds, which prevent them from packing closely together. This leads to a lower melting point and a liquid state at room temperature.
25
How do triglyceride and phospholipid differ structurally?
Triglyceride:
- Consists of three fatty acids attached to a glycerol molecule.
- Used primarily for energy storage.
Phospholipid:
- Consists of two fatty acids, a glycerol molecule, and a
phosphate group.
- Has a hydrophilic (polar) "head" and two hydrophobic (nonpolar) "tails".
- Forms the basic structure of cell membranes due to its amphipathic nature.
26
What unique property that arises from the phospholipid structure leads to its main function?
Phospholipids can spontaneously form bilayers in aqueous environments, creating a semi-permeable barrier that forms the basis of cellular membranes.
27
How do you identify a molecule as a steroid? Note an example.
- Steroids are characterized by their four interconnected carbon rings. They often have specific functional groups attached.
- An example of a steroid is cholesterol, a crucial molecule in cell membranes and a precursor for various other molecules like hormones.
28
Summarize the functions of nucleic acids.
Nucleic acids, specifically DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are responsible for the storage, transmission, and expression of genetic information in living organisms
29
Identify, with a drawing, the three components found in a nucleotide and explain the differences between the DNA & RNA nucleotide.
A nucleotide is composed of three components:
- A nitrogenous base (either a purine or a pyrimidine).
A five-carbon sugar (deoxyribose in DNA, ribose in RNA).
- A phosphate group.
The key difference between DNA and RNA nucleotides lies in the sugar molecule: deoxyribose in DNA and ribose in RNA.
30
What is the difference between a purine and a pyrimidine?
Purine: Purines are larger, double-ringed nitrogenous bases. The two purines found in nucleic acids are adenine (A) and guanine (G).
Pyrimidine: Pyrimidines are smaller, single-ringed nitrogenous bases. The three pyrimidines found in nucleic acids are cytosine (C), thymine (T) in DNA, and uracil (U) in RNA.
31
Describe how the nucleotides are linked to form a polynucleotide.
Nucleotides are linked together through a phosphodiester bond between the phosphate group of one nucleotide and the sugar of the next. This forms a sugar-phosphate backbone.
The nitrogenous bases extend from this backbone, creating the "rungs" of the DNA or RNA ladder, which are bonded together by hydrogen bonds. Adenine (A) always pairs with thymine (T) in DNA or uracil (U) in RNA, and guanine (G) always pairs with cytosine (C).
32
What are the biologically important functions of Proteins
Proteins have various crucial functions in living organisms, including:
- Enzymatic catalysis.
- Structural support.
- Transport of substances.
- Cell signaling and communication.
- Immune defense.
- Movement (via muscle proteins).
- Regulation of gene expression (transcription factors).
33
Identify, with a drawing, the four components found in an amino acid. What do all amino acids have in
common? How do they differ? Which feature is used to group them into several general categories?
Amino acids have four components:
- A central carbon atom (α-carbon).
- An amino group (-NH2).
- A carboxyl group (-COOH).
- A side chain (R group), which varies among different amino acids.
All amino acids share these common components, but they differ in the structure of their side chains.
The side chain (R group) is the feature used to group amino acids into several general categories (e.g., nonpolar, polar, charged).
34
Identify the bond that links two amino acids together and explain how it is formed.
A peptide bond forms between the carboxyl group of one amino acid and the amino group of another. This is a dehydration (condensation) reaction, where a water molecule is released.
35
How is a protein different from a polypeptide? Are these two terms interchangeable?
A protein is a functional biological molecule composed of one or more polypeptides.
A polypeptide is a polymer chain of amino acids linked together by peptide bonds.
While they are closely related, the two terms are not entirely interchangeable. A polypeptide may or may not have biological activity, whereas a protein is a functional biomolecule.
36
Describe the four levels of organization possible in a protein, and explain what forces are involved at
each level.
Primary Structure: The linear sequence of amino acids. Held together by covalent peptide bonds.
Secondary Structure: Localized folding patterns (e.g., α-helices, β-sheets) stabilized by hydrogen bonds between amino acids.
Tertiary Structure: Overall three-dimensional folding of a polypeptide, determined by interactions between side chains (R groups) like hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bridges.
Quaternary Structure (if applicable): Only present in proteins with multiple polypeptide chains. It involves the arrangement and interaction of these subunits.
37
What determines the primary structure?
The primary structure of a protein is determined by the sequence of amino acids coded for by the DNA.
38
Describe the two types of secondary protein structure.
α-Helix: A coiled structure stabilized by hydrogen bonds along the backbone.
β-Sheet: A pleated sheet-like structure stabilized by hydrogen bonds between adjacent segments.
39
What must a protein have in order to have a quaternary structure?
A protein must have multiple polypeptide chains (subunits) to have quaternary structure. It involves the interaction and arrangement of these subunits.
40
What does the cell theory state?
- All living organisms are composed of cells.
- The cell is the basic unit of life.
- All cells come from pre-existing cells.
41
Define denaturation and explain how proteins may be denatured
Denaturation is the disruption of a protein's structure without breaking peptide bonds. It leads to loss of function. This can be caused by heat, extreme pH, or chemical agents.
42
Explain why cells are generally quite small. State the importance of surface area to volume ratios in living
systems. What happens to the relationship between surface and volume when a cell doubles in size?
Cells are generally small due to the importance of surface area to volume ratios. As a cell grows, its volume increases faster than its surface area, making it less efficient in exchanging materials with the environment.
Small cells have a greater surface area relative to volume
• As a cell increases in size, volume increases faster than surface area
43
What are the common features shared by all cells?
- Plasma membrane
- cytoplasm
- DNA (genetic material)
- ribosomes (for protein synthesis).
44
Differentiate between prokaryotic and eukaryotic cells; animal & plant cells
Prokaryotic vs. Eukaryotic Cells:
Prokaryotic cells lack a nucleus and membrane-bound organelles. Eukaryotic cells have a nucleus and membrane-bound organelles.
Animal vs. Plant Cells:
Plant cells have a cell wall, chloroplasts, and a large central vacuole, which animal cells lack.
45
Describe the structure and function of the nuclear envelope, including the role of the pore complex
Structure: The nuclear envelope consists of two phospholipid bilayers, forming an outer membrane and an inner membrane, with a space in between known as the perinuclear space. It is studded with nuclear pores.
Function: It encloses the nucleus, separating the nuclear contents from the cytoplasm. It regulates the passage of molecules in and out of the nucleus.
46
Briefly explain how the nucleus controls protein synthesis in the cytoplasm.
The nucleus controls protein synthesis by transcribing DNA into mRNA (transcription) and then exporting this mRNA to the cytoplasm. In the cytoplasm, ribosomes read the mRNA and synthesize proteins (translation) based on the genetic information.
47
Explain the role of the nucleolus in protein synthesis.
The nucleolus is a distinct region within the nucleus. It is involved in the production of ribosomal RNA (rRNA) and the assembly of ribosomes.
48
Distinguish between free and bound ribosomes in terms of location and function.
Location:
Free ribosomes float freely in the cytoplasm.
Bound ribosomes are attached to the surface of the endoplasmic reticulum (ER).
Function:
Free ribosomes synthesize proteins that function in the cytoplasm.
Bound ribosomes synthesize proteins that are destined for membranes, export from the cell, or inclusion within lysosomes.
49
Describe the structure and function of a eukaryotic ribosome
Structure: Eukaryotic ribosomes consist of two subunits (large and small) made up of ribosomal RNA (rRNA) and protein molecules. They have a complex three-dimensional structure.
Function: Ribosomes are the cellular machinery responsible for protein synthesis, catalyzing the formation of peptide bonds between amino acids.
50
list the components of the endomembrane system
- Endoplasmic reticulum
- Golgi apparatus
- lysosomes
- vesicles
- nuclear envelope
- plasma membrane.
51
Distinguish between Rough ER & Smooth ER in terms of their structure & function
Rough ER:
Structure: Studded with ribosomes on its surface.
Function: Involved in protein synthesis and modification.
Smooth ER:
Structure: Lacks ribosomes.
Function: Involved in lipid synthesis, detoxification, and calcium storage.
52
Use a secretory protein as an example to explain that members of endomembrane system are structurally and functionally connected
Example: Secretory Protein
The endomembrane system works together to produce and transport secretory proteins. The rough ER synthesizes the protein, the Golgi apparatus modifies and sorts it, and vesicles transport it to the cell membrane for secretion.
53
From where do lysosomes arise?
Golgi Apparatus
54
Why are lysosomes described as cell's digestive compartment?
Lysosomes are described as the cell's digestive compartment because they contain enzymes that break down various biomolecules, including proteins, lipids, carbohydrates, and nucleic acids.
55
what is unique about lysosome?
lysosomes have an acidic interior due to the presence of acid hydrolases. This low pH is crucial for the enzymatic digestion of cellular materials.
56
Use lysosome as an example to explain why compartmentalization is important in eukaryotic cells
Compartmentalization in eukaryotic cells, exemplified by lysosomes, prevents the enzymes within lysosomes from prematurely digesting cellular structures. This segregation ensures controlled and efficient cellular processes.
57
What are the main functions of the central vacuole? Is it the equivalent of a lysosome in animal cell?
Main Functions:
- Storage of water, ions, and nutrients.
- Maintenance of turgor pressure in plant cells.
- Detoxification of harmful compounds.
Comparison to Lysosomes:
- While central vacuoles share some functions with lysosomes, they are not equivalent. Lysosomes in animal cells are primarily responsible for intracellular digestion, whereas central vacuoles in plant cells have broader roles in storage, structural support, and waste management.
58
Describe the structure and function of peroxisomes
Structure: Peroxisomes are membrane-bound organelles containing enzymes involved in various metabolic reactions, particularly those related to lipid metabolism and detoxification.
Function:
- Involved in the breakdown of fatty acids.
- Participate in detoxification processes, particularly in the liver.
- Produce and decompose hydrogen peroxide as a byproduct.
59
Compare the structure of mitochondria and chloroplasts by drawing & labeling the schematic diagrams of mitochondrion and chloroplast
Mitochondria:
Have an outer membrane and inner membrane (cristae).
Site of cellular respiration, generating ATP.
Contains their own DNA and ribosomes.
Chloroplasts:
Have an outer membrane, inner membrane, and thylakoid membranes.
Site of photosynthesis, producing glucose and oxygen.
Contain chlorophyll for capturing light energy.
60
What do mitochondria & chloroplasts have in common with nucleus?
Both mitochondria and chloroplasts have their own DNA and ribosomes, allowing them to partially self-replicate and carry out protein synthesis.
61
What is the cytoskeleton made of?
Describe the subunits and structures of the three types of cytoskeletal fibers and list their functions
Composition: The cytoskeleton is made of protein filaments: microtubules, microfilaments (actin filaments), and intermediate filaments.
Functions:
Microtubules: Provide structural support, act as tracks for organelle movement.
Microfilaments: Involved in cell motility, support, and muscle contraction.
Intermediate Filaments: Provide structural stability.
62
What are three functions of the cell wall? Distinguish between primary cell wall, middle lamella, and secondary cell wall. Be able to label the structures on a sketch of plant cell wall.
Functions:
- Provides structural support and protection to the cell.
Helps maintain cell shape.
Prevents excessive water uptake.
Differences in Cell Wall Layers:
Primary Cell Wall: The first layer, flexible and thin.
Middle Lamella: A pectin-rich layer between adjacent primary walls, holding adjacent cells together.
Secondary Cell Wall: A rigid, thick layer formed inside the primary cell wall.
63
Animal cells don't have a cell wall, what do they have outside the cell membrane? Its functions?
Animal cells lack a cell wall. Instead, they have an extracellular matrix (ECM) made of glycoproteins like collagen. The ECM provides structural support, regulates cell behavior, and is involved in cell signaling.
64
Describe the properties of phospholipids, their arrangement in cellular membranes, and the important properties of such arrangement.
Properties:
- Phospholipids have a hydrophilic "head" (phosphate group) and hydrophobic "tails" (fatty acid chains).
- They are amphipathic, meaning they have both hydrophilic and hydrophobic regions.
Arrangement:
In cellular membranes, phospholipids arrange in a bilayer, with hydrophilic heads facing outward towards the aqueous environment and hydrophobic tails facing inward, away from water.
Important Properties:
This arrangement provides a stable barrier between the internal and external environments of the cell, maintaining compartmentalization.
65
Describe how proteins and carbohydrates are spatially arranged in cell membranes. What do they contribute to membrane's specific functions
Proteins:
Proteins can be integral (spanning the membrane) or peripheral (attached to the surface).
They contribute to various functions including transport, cell signaling, and structural support.
Carbohydrates:
Carbohydrates are often found attached to proteins (glycoproteins) or lipids (glycolipids) on the extracellular surface.
They play roles in cell recognition, signaling, and adhesion.
66
What do the terms "fluid" and "mosaic" refer to in the fluid mosaic model?
Fluid - refers to the dynamic, flexible nature of the lipid bilayer. Molecules can move within the membrane.
Mosaic - indicates the diverse composition of the membrane, including lipids, proteins, and carbohydrates
67
Use animal cell as an example to explain how membrane fluidity is influenced by temperature and membrane composition.
Higher Temperature:
High temperature increases fluidity as phospholipids move more rapidly, creating spaces in the membrane.
Lower Temperature:
Low temperature decreases fluidity as phospholipids move more slowly and may pack more closely together.
Membrane Composition:
Unsaturated fatty acids increase fluidity due to kinks in their tails. Saturated fatty acids decrease fluidity
68
How do cell membranes adapt to cold temperatures?
Cells in cold environments may increase the proportion of unsaturated fatty acids in their phospholipids to maintain membrane fluidity.
69
Membrane is described to exhibit selective permeability, what does it mean?
It means that the membrane allows certain substances to pass through while restricting the passage of others. This is crucial for maintaining cellular homeostasis.
70
How does membrane's structure determine its selective permeability?
What types of substances are selected for by the lipid membrane?
What types of substances are selected against by the lipid membrane?
Permeability:
The lipid bilayer prevents the passage of charged and large polar molecules. Small non-polar molecules (like oxygen) can pass freely. Proteins in the membrane act as channels, carriers, or receptors, contributing to selective transport.
Selected For:
Small non-polar molecules, certain ions, specific polar molecules.
Selected Against:
Large polar molecules, charged ions (without transport proteins).
71
Define diffusion
Diffusion is the movement of particles (such as molecules or ions) from an area of higher concentration to an area of lower concentration. It is a passive process.
72
Describe passive transport
Passive transport is the movement of substances across a cell membrane without the expenditure of energy by the cell. It occurs along the concentration gradient (from high to low concentration).
73
What is the difference between simple diffusion and diffusion?
Simple Diffusion:
- Molecules move directly through the lipid bilayer.
No specific transport proteins are involved.
Facilitated Diffusion:
- Molecules are assisted by specific transport proteins (channel or carrier proteins) that provide a pathway through the membrane.
This is used for larger, polar, or charged molecules.
74
Define Osmosis
Osmosis is the passive movement of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.
75
Define Hypotonic
- Lower solute concentration outside the cell.
- Water moves into the cell, potentially causing it to swell or burst.
76
Define Hypertonic
- Higher solute concentration outside the cell.
- Water moves out of the cell, potentially causing it to shrink or shrivel.
77
Define Isotonic
- Equal solute concentration inside and outside the cell.
- There is no net movement of water.
78
Describe active transport.
Active transport is the movement of molecules or ions across a membrane against their concentration gradient, which requires energy (usually in the form of ATP) and the involvement of specific transport proteins.
79
What is the key difference between passive and active transport?
Passive Transport:
- Does not require energy.
- Moves along the concentration gradient.
Active Transport:
- Requires energy.
- Moves against the concentration gradient.
80
Use Na*/K+ pump as an example to explain how ATP is used and what type of transport protein is involved
The sodium-potassium pump (Na+/K+ pump) is an active transport protein that pumps three sodium ions out of the cell and two potassium ions into the cell, utilizing ATP.
81
What is membrane potential?
In general, which side of the membrane is positive? What are the main electrogenic pumps used in plants and animals?
Membrane potential is the voltage or electrical potential difference across a cell membrane. In general, the inside of the cell is negative relative to the outside.
Electrogenic Pumps:
Plants: Proton pumps (H+ pumps).
Animals: Sodium-potassium pump (Na+/K+ pump).
82
Concentration Gradient:
This is the difference in concentration of ions between the extracellular and intracellular environments. Ions will naturally move from an area of higher concentration to an area of lower concentration.
Electrochemical Gradient:
This gradient takes into account both the concentration difference and the electrical charge of ions. Ions with opposite charges will be attracted to areas of opposite charge.
The combination of these forces is called the electrochemical gradient. It represents the overall driving force for the movement of ions across a membrane during facilitated diffusio
83
Describe cotransport. Is it a passive or active process? How is it useful to cells?
Cotransport is the coupling of the transport of one substance to the transport of another against its concentration gradient. It can be active or passive depending on the specific system.
84
Describe different types of bulk transport
• Is bulk transport active or passive?
• Does bulk transport use transport proteins?
Bulk transport is the movement of large molecules or particles into or out of a cell using vesicles. It is an active process.
Use of Transport Proteins in Bulk Transport:
Yes, bulk transport involves transport proteins in the form of vesicle membrane proteins that assist in the formation and fusion of vesicles.
