Biology Chapter 1: What is Life?

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Questions and Answers

What are the common characteristics of living things?

Made up of a common set of chemicals, cells enclosed by a plasma membrane, molecules from environment create new biomolecules, energy from environment is used for biological work, universal genetic code specifies proteins, similar fundamental set of genes that replicate, exist in populations that evolve, self regulate internal environment.

How do we know all living things are genetically related?

Life has a common ancestry, all organisms descended from a common origin, and similarities exist across gene sequences.

How do you correctly assign electrons to their electron shells?

Atomic number equals the number of protons and electrons; the first shell holds 2 electrons; the second holds 8.

Define isotopes and their significance.

Isotopes are forms of an element with different numbers of neutrons, leading to different mass numbers; they are used to find the weighted average mass. Signup and view all the answers

What is the octet rule?

The tendency of atoms to form stable molecules with 8 electrons in their outermost shell. Signup and view all the answers

Which types of covalent bonds are there?

Polar covalent bonds Signup and view all the answers

What is an ion?

Atoms or molecules that have gained or lost electrons, resulting in a net electrical charge. Signup and view all the answers

How is an ionic bond formed?

An ionic bond is formed through the electrical attraction between ions bearing opposite charges. Signup and view all the answers

Explain why salt dissolves in water.

The polar water interacts with the positive and negative ions in salt, breaking the ionic bonds. Signup and view all the answers

What are hydrogen bonds?

Hydrogen bonds form between a hydrogen atom covalently bonded to a highly electronegative atom and another electronegative atom nearby. Signup and view all the answers

Compare the relative strengths of covalent bonds, ionic bonds, hydrogen bonds, and van der Waals forces.

Covalent bonds are the strongest, followed by ionic bonds, hydrogen bonds, and finally van der Waals forces. Signup and view all the answers

Define hydrophilic.

Hydrophilic substances are water 'loving' molecules that often have polar covalent bonds. Signup and view all the answers

Define hydrophobic.

Hydrophobic molecules are water 'fearing' and show greater attraction to one another than to water. Signup and view all the answers

What are hydrophobic interactions?

Hydrophobic interactions occur when water forces hydrophobic groups together. Signup and view all the answers

List properties of water due to hydrogen bonds.

High heat of vaporization, surface tension, cohesion. Signup and view all the answers

Explain why ice floats.

Ice floats due to hydrogen bonds creating lower density compared to liquid water. Signup and view all the answers

What does the pH scale measure?

The pH scale measures the acidity or basicity of a solution. Signup and view all the answers

Study Notes

Common Characteristics of Living Things

Comprised of proteins, lipids, carbohydrates, and nucleic acids.
Cells are enclosed by a plasma membrane.
Utilize environmental molecules to form new biomolecules.
Obtain energy from the environment to perform biological work, such as photosynthesis.
Genetic code is universal, dictating protein production.
Similar fundamental gene sets exist across all life forms, facilitating replication.
Organisms exist in evolving populations.
Maintain homeostasis through self-regulation of internal environment.

Genetic Relationships Among Living Things

All life shares a common ancestry, derived from a singular origin.
Striking genetic similarities manifest across diverse organisms, suggesting common descent.

Atomic Structure and Bonding

Electrons equal protons in neutral atoms, determining atomic number found in the top left corner.
Mass number, reflected in decimal form, indicates total number of protons and neutrons.
Neutron count is calculated by subtracting the atomic number from the mass number.
Electron shells: the first shell holds 2 electrons, while the second holds 8.

Isotopes and Their Significance

Isotopes are variations of an element that differ in neutron count, leading to different mass numbers.
Useful in determining the weighted average atomic mass.

Covalent Bonding and the Octet Rule

Atoms typically form bonds to achieve 8 electrons in their outermost shell, promoting stability.
Octet rule explains the tendency to create stable molecular structures through shared electrons.

Polar vs. Nonpolar Covalent Bonds

Covalent bonds involve sharing of electron pairs, crucial for atom stability.
Nonpolar bonds: equal sharing between atoms of the same element or similar electronegativity.
Polar bonds: unequal sharing due to differences in electronegativity (e.g., water).

Ions: Formation and Recognition

Ions are electrically charged atoms/molecules due to the loss or gain of electrons.
Cations carry a positive charge by losing electrons (e.g., Na⁺).
Anions carry a negative charge by gaining electrons (e.g., Cl⁻).

Ionic Bonds Formation

Ionic bonds form through electrostatic attraction between oppositely charged ions (e.g., metal + nonmetal).
Generally weaker than covalent bonds and commonly observed among elements.

Salt Dissolving in Water

Polar water molecules interact with ionic compounds, disrupting ionic bonds and leading to dissolution.

Hydrogen Bonds

Formed between hydrogen atoms covalently bonded to electronegative atoms (F, O, N) and other electronegative atoms.
Weaker than ionic bonds, these interactions are crucial for many biological processes.

Relative Strengths of Bonds

Strength hierarchy: covalent > ionic > hydrogen > van der Waals forces.

Hydrophilic and Hydrophobic Molecules

Hydrophilic: "water-loving" molecules with polar covalent bonds; they interact well with water.
Hydrophobic: "water-fearing" molecules with nonpolar covalent bonds that prefer interactions with similar molecules over water.

Hydrophobic Interactions

Occur when water molecules force hydrophobic groups to cluster together due to unfavorable interactions with water.

Water Chemistry and Properties

High heat of vaporization allows cooling through the evaporation of sweat.
Surface tension allows organisms to avoid sinking due to cohesive water molecule behavior.
Cohesion aids in water transport in plants from roots to leaves.

Ice Floats and Its Ecological Benefits

Ice's lower density compared to liquid water arises from hydrogen bonding arrangements, providing insulation for aquatic life.

pH Scale

Measures the concentration of hydrogen ions in a solution, indicating acidity or alkalinity.

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Description

Explore the fundamental characteristics that define living organisms in this quiz. From the cellular structure to the biochemical processes, uncover how life is sustained and regulated. Understand the role of genetic codes and evolution in shaping life as we know it.