Chemistry: Carbon and Hydrocarbons

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Questions and Answers

What defines the primary structure of a protein?

The interaction between multiple polypeptides

The overall three-dimensional shape of the protein

The unique sequence of amino acids in a polypeptide (correct)

The folding of the polypeptide into alpha helices and beta sheets

How does sickle cell anemia illustrate the importance of amino acid sequence?

It shows that all mutations in DNA affect protein function.

A single amino acid change can alter protein structure and function. (correct)

It indicates that proteins do not have a defined structure.

It highlights that proteins are always modified after translation.

Which level of protein structure involves local folding due to hydrogen bonding?

Primary structure

Quaternary structure

Tertiary structure

Secondary structure (correct)

What is the potential consequence of altering the order of amino acids in a protein?

The protein may lose its original function. Signup and view all the answers

What can result from a change in the nucleotide sequence of DNA?

It can change the primary structure of a protein. Signup and view all the answers

What characteristic distinguishes the inner surface of the plasma membrane from the outer surface?

They differ in the types of proteins present. Signup and view all the answers

Which type of transport across the plasma membrane requires energy input?

Active transport Signup and view all the answers

What factor would most likely increase the rate of diffusion of a substance across the plasma membrane?

Increasing the concentration gradient. Signup and view all the answers

Which type of molecules can diffuse directly through biological membranes?

Small non-polar molecules. Signup and view all the answers

What effect does an increase in solvent density have on diffusion rates?

It decreases diffusion rates. Signup and view all the answers

What is the maximum number of different atoms that carbon can form covalent bonds with?

Four Signup and view all the answers

Which of the following best describes the geometry of methane?

Tetrahedral Signup and view all the answers

What happens to the energy stored in covalent bonds of hydrocarbons when they are burned?

It is released as heat and light energy. Signup and view all the answers

Which of the following statements is true about double bonds in hydrocarbons?

Atoms on either side of a double bond are locked in place. Signup and view all the answers

Which of the following is NOT one of the four major classes of macromolecules?

Hydrocarbons Signup and view all the answers

What is the primary structural component of prokaryotic cell walls?

Peptidoglycan Signup and view all the answers

Which of the following best characterizes eukaryotic ribosomes compared to prokaryotic ribosomes?

Eukaryotic ribosomes are slightly larger. Signup and view all the answers

What is the role of the nucleolus within the nucleus?

To assemble ribosomes Signup and view all the answers

How do plant cell walls differ from prokaryotic cell walls?

They are made of cellulose. Signup and view all the answers

What distinguishes centrosomes in animal cells from those in plant cells?

Animal cells have two centrioles. Signup and view all the answers

What are cristae and where are they found?

Folds of the mitochondrion inner membrane Signup and view all the answers

Which statement best describes the endomembrane system in eukaryotic cells?

It modifies, packages, and transports lipids and proteins. Signup and view all the answers

What is the primary function of the central vacuole in plant cells?

Regulation of water concentration Signup and view all the answers

What is the main purpose of the nuclear pores in the nuclear envelope?

To facilitate the flow of molecules between the nucleus and cytoplasm Signup and view all the answers

Why are prokaryotic cells typically smaller than eukaryotic cells?

They have a higher surface area to volume ratio. Signup and view all the answers

What is the primary role of channel proteins in facilitated diffusion?

To allow the movement of ions and polar molecules through the membrane Signup and view all the answers

What characterizes a hypotonic solution?

Lower solute concentration compared to the cytosol Signup and view all the answers

Which type of active transport directly uses ATP as its energy source?

Primary active transport Signup and view all the answers

How do carrier proteins function in facilitated transport?

They bind to a substance, change shape, and move it across the membrane Signup and view all the answers

Which of the following statements is true regarding osmosis?

Water moves from higher water concentration to lower water concentration Signup and view all the answers

What distinguishes phagocytosis from pinocytosis?

Phagocytosis surrounds solids, while pinocytosis surrounds fluids Signup and view all the answers

Which type of pump is characterized by transporting two different molecules or ions in the same direction?

Symporter Signup and view all the answers

What is the primary reason energy is required for active transport?

To move substances against their concentration gradient Signup and view all the answers

What occurs during exocytosis?

Vesicles fuse with the cell membrane releasing their contents outside Signup and view all the answers

Study Notes

Carbon

Key component of macromolecules
Forms covalent bonds with up to four different atoms
Serves as a "backbone" for the macromolecules
Has four electrons in the outer shell
Forms four covalent bonds to fill the outer shell, allowing it to achieve the "octet rule"

Hydrocarbons

Carbon + Hydrogen (Ex: Methane)
Covalent bonds between atoms store energy, which is released when the molecules are burned
The energy released from hydrocarbons is used to heat homes and power cars

Methane

Binds to four hydrogens to satisfy the octet rule
Has a tetrahedral geometry, with each of the four hydrogen atoms spaced 109.5° apart

Hydrocarbon Chains

Carbon forms single bonds with other atoms, resulting in a tetrahedral shape.
Two carbon atoms form a double bond, resulting in a planar (flat) shape.
Single bonds can rotate, while double bonds cannot.

Hydrocarbon Rings

Carbon can form five and six-membered rings (closed chain)
Single or double bonds connect the carbons in the ring
Nitrogen can substitute for carbon
Benzene is an important hydrocarbon ring used in various molecules, including amino acids, cholesterol, and its derivatives.

Four Major Classes of Macromolecules:

Carbohydrates
Lipids
Proteins
Polypeptides - a chain of amino acids joined together in peptide linkages
Proteins - a polypeptide or multiple polypeptides
- Often combined with non-peptide prosthetic groups
- Have unique structures and functions
- Many proteins are modified following translation (the process of creating a new protein)

Protein Structure

The shape of a protein is crucial for its function
Protein shape is determined by four levels of structure:
- Primary structure
- Secondary structure
- Tertiary structure
- Quaternary structure

Primary Protein Structure

The unique sequence of amino acids in a polypeptide
Protein function can be compromised if the order of amino acids is altered
The amino acid sequence is based on the gene encoding the protein
A change in the nucleotide sequence of DNA can lead to a change in the amino acid sequence, potentially affecting protein structure and function

Sickle Cell Anemia

An example of how a change in one amino acid can impact human health
Normal hemoglobin has glutamic acid at position seven
Sickle cell hemoglobin replaces glutamic acid with valine
This single amino acid change in the 600 amino acids that code for human hemoglobin alters the shape of red blood cells from disc-shaped to crescent shaped.

Secondary Protein Structure

Local folding of the polypeptide
α-helix – formed by hydrogen bonding between oxygen in the carbonyl group and an amino acid four positions down the chain
β- pleated sheet – formed by hydrogen bonding between atoms in the polypeptide backbone (not the side chains)

Tertiary Protein Structure

The three-dimensional structure of a single polypeptide chain
Interactions between R-groups (side chains) of amino acids contribute to the tertiary structure, including:
- Hydrophobic interactions
- Hydrogen bonds
- Ionic bonds
- Disulfide bridges

Quaternary Protein Structure

The arrangement of multiple polypeptide chains (subunits) into a functional protein
Held together by non-covalent interactions

Prokaryotes

Primarily unicellular organisms
Lack internal membrane-bound organelles (nucleus, mitochondria, etc.)
Most have a cell wall containing peptidoglycan
Believed to be much like the first cells
Organisms in the domains Archaea and Bacteria are Prokaryotes

Generalized Structure of a Prokaryotic Cell

Chromosomal DNA is localized in a nucleoid
Ribosomes are in the cytoplasm
The cell membrane is surrounded by a cell wall

Prokaryotic Cells are Smaller than Eukaryotic Cells

The surface area to volume ratio is more favorable for moving material in and out of the cell
They lack modifications found in eukaryotes that aid internal transport

Factors Limiting Cell Size

Surface area-to-volume ratio
As cells get bigger, volume increases faster than surface area

Eukaryotic Plasma Membrane

Phospholipid bilayer with embedded proteins
Provides a selectively permeable barrier, regulating what enters and leaves the cell.

Cytoplasm

Region between the plasma membrane and the nuclear envelope
Contains organelles suspended in a gel-like cytoskeleton plus the cytoskeleton itself
Composed of 70-80% water, but its semi-solid consistency is due to the proteins within it.

Nucleus

Usually only one per cell
Usually the largest organelle
Larger than most prokaryotic cells

Nuclear Envelope

A double membrane that separates DNA from the cytoplasm and separates transcription from translation
Nuclear pores perforate this membrane, connecting the nucleoplasm to the cytoplasm
These pores regulate the flow of molecules back and forth; large molecules require a nuclear localization signal (NLS) to pass.

Nucleolus

A region inside the nucleus where ribosomes are assembled from RNA and proteins

Ribosomes

Made of two different-sized subunits; slightly larger in eukaryotes
Composed of special RNA (rRNA) and proteins
During protein synthesis, ribosomes assemble amino acids into proteins

Mitochondrion

Site for conversion of stored energy (macromolecule molecular bonds) to a more useful form (ATP)
Inner membrane is folded, with folds called cristae
The area enclosed is the mitochondrial matrix

Peroxisomes

Reactions that break down fatty acids and amino acids occur here.
May detoxify poisons

Contrasting Animal and Plant Cells

Both have microtubule organizing centers (MTOCs), but animal cells have centrioles associated with the MTOC; this complex is called the centrosome
Animal cells have lysosomes, plant cells do not
Plant cells have a cell wall, chloroplasts, other specialized plastids, and a large central vacuole; animal cells do not

Animal Cells Include:

Intermediate filament
Ribosomes
Rough endoplasmic reticulum
Nucleus
Nucleolus
Chromatin
Golgi apparatus
Golgi vesicle
Cytoplasm
Vacuole
Peroxisome
Secretory vesicle
Smooth endoplasmic reticulum
Lysosomes
Microfilament
Centrosomes
Microtubule
Plasma membrane
Mitochondria

Plant Cells Include:

Plasmodesmata
Cell wall
Plasma membrane
Cytoplasm
Central vacuole
Cytoskeleton
Chloroplast
Plastid
Peroxisome
Golgi apparatus
Mitochondria
Ribosomes
Nucleus
Rough and smooth endoplasmic reticulum

Centrosome

Consists of two centrioles that lie at right angles to each other
Each centriole is a cylinder made up of nine triplets of microtubules
Nontubulin proteins hold the microtubule triplets together

Plant Cell Walls

A rigid protective structure external to the plasma membrane
Differ from prokaryotes as they are made up of cellulose rather than peptidoglycan

Chloroplasts

Double-membrane organelles; have their own ribosomes and DNA, similar to mitochondria
The inner membrane encloses an aqueous fluid (stroma), which contains a set of interconnected and stacked fluid-filled membrane sacs called thylakoids. Each stack of thylakoids is a granum (plural = grana).

The Central Vacuole

Plant cells have a large vacuole that occupies most of the area of the cell
Helps regulate water concentration under changing environmental conditions and contributes to cell expansion

The Endomembrane System

Consists of internal membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins
Includes:
- Nuclear envelope
- Lysosomes
- Vesicles
- Endoplasmic reticulum
- Golgi apparatus
- The plasma membrane

Plasma Membranes

Asymmetric
Inner surface differs from outer surface
Interior proteins anchor fibers of the cytoskeleton to the membrane
Exterior proteins bind to the extracellular matrix (outside of the cell)
Glycoproteins bind to substances the cell needs to import

Transport

The plasma membrane is selectively permeable, allowing some molecules to pass through, but not others
This allows cytosol solutions (inside the cell) to differ from extracellular fluids
Transport across a membrane can be passive (requiring no energy) or active (requiring energy (ATP))

Passive Transport

The simplest type is diffusion
Diffusion: occurs when a substance from an area of high concentration moves down its concentration gradient
Only small non-polar molecules (O2, CO2, lipid hormones) can diffuse through biological membranes

Factors That Affect Diffusion Rates

Concentration gradient - greater difference, faster diffusion
Mass of the molecules - smaller molecules diffuse more quickly
Temperature - molecules move faster (more fluid) at higher temperatures
Solvent Density - dehydration increases the density of the cytoplasm, which reduces diffusion rates
Solubility - more non-polar (lipid-soluble) materials diffuse faster
Surface area - increase in surface area speeds up diffusion rates
Distance traveled - the greater the distance, the slower the rate; important factor affecting the upper limit of cell size
Pressure - in some cells (i.e., kidney cells), blood pressure forces solutions through membranes, speeding up diffusion rates

Facilitated Passive Transport

Facilitated transport (a.k.a. facilitated diffusion) moves substances down their concentration gradient through transmembrane integral membrane proteins
Two types of facilitated transport proteins:
- Channel proteins
- Carrier proteins

Channel Proteins

The top, bottom, and inner core are composed of hydrophilic amino acids, attracting ions &/or polar molecules
Some are always open
Others are gated, only opening when a signal is received
Important examples:
- Aquaporins - specific to H2O
- Muscle cells have gated ion channels that allow muscle contraction when opened.

Carrier Proteins

Specific to a single substance
They bind to that substance, change shape, and “carry it” to the other side
Many allow movement in either direction, as concentration gradients change

Osmosis

The diffusion of water across the membrane
Water always moves from an area of higher water concentration to a lower water concentration
Differences in water concentration occur when a solute cannot pass through the selectively permeable membrane

Osmolarity

Describes the total solute concentration (salt, sugar, etc.)
Low osmolarity - less solute, more water
Hypotonic: extracellular fluid has lower osmolarity (less solute, more water outside the cell) than the cytosol - water enters the cell
Isotonic: extracellular fluid has the same osmolarity (equal solute and water inside and outside of the cell) than the cytosol - water does not move
Hypertonic: extracellular fluid has higher osmolarity (high solute, less water outside the cell) than the cytosol - water leaves the cell

Active Transport

Used anytime an ion or molecule (like glucose) is transported through a membrane protein
Against its concentration gradient (from low to high concentration) or against its electrochemical gradient
Energy is always required for active transport
Two types of active transport:
- Primary - where ATP provides the energy
- Secondary - where an electrochemical gradient provides the energy
Occurs through transmembrane, integral carrier proteins called pumps
There are 3 types of pumps:
- Uniporter: carries one molecule or ion
- Symporter: carries two different molecules or ions in the same direction
- Antiporter: carries two different molecules or ions in different directions

Electrochemical Gradient

Arise from the combined effects of concentration gradients and electrical gradients

Primary Active Transport

Moves an ion or molecule up its concentration gradient, using energy from ATP hydrolysis

Secondary Active Transport

Uses an electrochemical gradient, created by primary active transport to move a different substance against its concentration gradient

Bulk Transport

Used when cells need to import or export molecules/particles that are too large to pass through a transport protein
A type of active transport requiring energy
Importing by bulk transport is called endocytosis (into the cell); exporting is called exocytosis (outside of the cell)
Two types of endocytosis:
- Phagocytosis - (cellular eating), the cell membrane surrounds a particle and engulfs it
- Pinocytosis - (cellular drinking), the cell membrane invaginates, surrounds a small volume of fluid, and pinches off

Exocytosis

Vesicles containing substances fuse with the plasma membrane
The contents are then released to the exterior of the cell

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Description

Explore the fascinating world of carbon and hydrocarbons through this quiz. Learn about the properties of carbon, the structure of hydrocarbons, and the significance of covalent bonds. Test your understanding of hydrocarbon chains and rings as well.