Honors Biology Midterm Ritz

List 7 characteristics of life

Order & Organization

Growth & Development

Reproduction & DNA

Ability to Adapt

Energy Processing

Homeostasis

Response to Stimuli

Explain what is meant by "structure dictates/ determines function"

How something is built determines what it can do

What are the Functional Groups

Hydroxyl (–OH)

Carbonyl (C=O)

Carboxyl (–COOH)

Amino (–NH₂)

Phosphate (–PO₄)

Methyl (–CH₃)

Matter

Anything that has mass and takes up space

Example: air, water, a desk, your body

Element

A pure substance made of only one kind of atom

Example: oxygen (O), carbon (C)

Molecule

Two or more atoms bonded together

Example: O₂, H₂O

Compound

A molecule made of two or more different elements bonded together

Example: water (H₂O), carbon dioxide (CO₂)

Which elements make up most living matter (CHNOPS)

C - Carbon: backbone of all organic molecules

H - Hydrogen: part of water and organic molecules

N - Nitrogen: found in proteins and DNA

O - Oxygen: needed for respiration and water

P - Phosphorus: found in DNA, ATP, and membranes

S - Sulfur: found in some proteins

Trace Elements

Trace elements are needed in very small amounts, but are still essential.

Without trace elements, enzymes and proteins cannot function properly.

Examples: iron (Fe), iodine (I), zinc (Zn)

Parts of an Atom

Protons - positive charge, in the nucleus

Neutrons - no charge, in the nucleus

Electrons - negative charge, move around nucleus

Organization

Nucleus: protons + neutrons

Electron cloud: electrons in energy levels (shells)

Bohr Model

Shows electrons in specific energy levels (rings) around the nucleus

Helps visualize how many electrons are in each shell

Lewis Dot Diagram

Shows only valence (outer) electrons as dots around the element symbol

Helps predict bonding behavior

Ion

An atom that has gained or lost electrons

Has a charge

Examples:

Na⁺ (lost an electron → positive)

Cl⁻ (gained an electron → negative)

Important for nerve signals and muscle movement

Isotope

Atoms of the same element with different numbers of neutrons

Same chemical behavior, different mass

Example:

Carbon-12 vs Carbon-14

Some isotopes are radioactive and used in dating fossils

Isomer

Molecules with the same chemical formula but different structures

Different shapes → different properties

Example:

glucose vs fructose

Structure difference = function difference

How does the distribution of electrons determines an atom's chemical properties.

Electrons, especially valence (outer-shell) electrons, determine how an atom behaves chemically.

Atoms are most stable when their outer shell is full.

To become stable, atoms will:

Share electrons

Gain electrons

Lose electrons

The number and arrangement of valence electrons determines:

How many bonds an atom can form

What type of bond it forms

How reactive it is

Example:

Oxygen has 6 valence electrons → forms 2 bonds

Hydrogen has 1 valence electron → forms 1 bond

Nonpolar Covalent Bond

Electrons are shared equally

Occurs when atoms have similar electronegativity

No partial charges

Example:

O₂, N₂, C-H bonds

Polar Covalent Bond

Electrons are shared unequally

One atom is more electronegative

Creates partial charges:

δ⁻ (partial negative)

δ⁺ (partial positive)

Example:

Water (H₂O)

Oxygen pulls electrons closer than hydrogen

Ionic Bonds

Electrons are transferred, not shared

One atom becomes a positive ion

The other becomes a negative ion

Opposite charges attract

Example:

Sodium chloride (NaCl)

Bond formed by electrical attraction

How are hydrogen bonds formed due to polarity

They form between:

A partially positive hydrogen (δ⁺)

A partially negative atom (δ⁻), like oxygen or nitrogen

Extra Note- They are weak bonds

Water Example:

Oxygen is more electronegative → becomes δ⁻

Hydrogen becomes δ⁺

Hydrogen atoms from one water molecule are attracted to oxygen of another

Hydrogen bonding causes

Cohesion

Adhesion

Surface tension

High specific heat

What do chemical reactions involve

Breaking bonds in reactants

Forming new bonds to make products

Breaking bonds...

releases energy

Ex. Cellular respiration breaks bonds to release energy

Forming bonds...

needs energy

Ex.Photosynthesis rearranges atoms to store energy

Reactions convert....

to products

How does hydrogen bonding and its polarity gives water life-supporting properties

Water is polar because oxygen is more electronegative than hydrogen.

This creates partial charges:

Oxygen = δ⁻

Hydrogen = δ⁺

Because of polarity, water molecules form hydrogen bonds with each other.

Hydrogen bonding causes many of water's unique properties.....

Cohesion

Adhesion

High specific heat

High heat of vaporization

Ice being less dense than liquid water

Cohesion vs. Adhesion

Cohesion

Water molecules stick to other water molecules

Caused by hydrogen bonding

Example: surface tension that lets insects walk on water

Adhesion

Water molecules stick to other substances

Example: water sticking to plant cell walls in xylem

Cohesion and Adhesion both are

important for water transport in plants

How does water moderate temprature

Water has a high specific heat, meaning:

It takes a lot of energy to raise or lower its temperature.

Hydrogen bonds absorb heat when breaking and release heat when forming.

This allows water to:

Keep body temperatures stable

Prevent rapid temperature changes in environments (like oceans and lakes)

Why does ice float

When water freezes:

Hydrogen bonds lock water molecules into a crystal structure

Molecules spread farther apart

Ice becomes less dense than liquid water

Example of Solvent

Water

Example of Solute

Salt or Sugar

Example of Solution

Saltwater

Neutral

Equal H⁺ and OH⁻

pH = 7

Acidic

More H⁺ than OH⁻

pH < 7

Basic (Alkaline)

More OH⁻ than H⁺

pH > 7

Carbons 4 valence electrons allow it to

form 4 covalent bonds and...

Long chains

Branched structures

Rings

Carbon can bond with

C, H, O, N, S, P).

Monomers

A small building-block molecule

Polymer

A large molecule made of many monomers bonded together

Monomer and Polymers

Monomers link together to form polymers.

Examples

Amino acids → proteins

Monosaccharides → polysaccharides

Nucleotides → nucleic acids

Dehydration Synthesis

Builds polymers

Removes a water molecule

Forms a covalent bond between monomers

Hydrolysis

Breaks polymers

Adds water

Breaks covalent bonds between monomers

What are the 6 Chemical groups

1. Hydroxyl (-OH) 2. Carbonyl (C=O) 3. Carboxyl (-COOH) 4. Amino (-NH₂) 5. Phosphate (-PO₄)6. Methyl (-CH₃)

Fuctional groups determine

Polarity

Reactivity

Solubility

Shape

Function

Even small changes in functional groups can drastically change a molecule's behavior

Monosaccharides

One sugar unit (simple sugar)

Cannot be broken down into smaller carbs

Examples: glucose, fructose, galactose

Used for quick energy

Disaccharides

Two monosaccharides bonded together

Formed by dehydration synthesis

Examples:

Sucrose = glucose + fructose

Lactose = glucose + galactose

Polysaccharides

Many monosaccharides linked together

Complex carbohydrates

Examples: starch, glycogen, cellulose, chitin

Used for energy storage or structure

Carbohydrates contain

carbon, hydrogen, and oxygen the ratio is 1 : 2 : 1

Carbohydrates normally have

Rings or short chains

Many hydroxyl (-OH) groups

Lots of Hydroxyl....

increases polarity and makes it more water soluble

Isomers are molecules with

The same chemical formula

Different structures

Ex. Glucose and fructose

Both are C₆H₁₂O₆

Atoms arranged differently

Why do isomers have different properties

Different structures change:

Shape

How enzymes interact with them

Their function in cells

Carbohydrates are used for

Quick energy

Short-term energy storage

Structural support

Cell recognition

What are the 4 major Polysaccharides

Starch, Glycogen, Cellulose, and Chitin

What does Starch do

Energy storage in plants

Made of glucose

Stored in roots and seeds

Humans can digest starch

What does Glycogen do

Energy storage in animals

Stored in liver and muscles

More highly branched than starch

Provides quick access to glucose

What does Cellulose do

Structural support in plant cell walls

Made of glucose

Humans cannot digest it

Provides fiber

What does Chitin do

Structural support

Found in:

Exoskeletons of arthropods

Fungal cell walls

Strong and flexible

What are the three primary elements in lipids

Carbon (C)

Hydrogen (H)

Oxygen (O)

Lipids vs Carbohydrates

Lipids have much more hydrogen and much less oxygen than carbohydrates.

Lipids do NOT have a 1:2:1 ratio of C:H:O.

Lipids are nonpolar and hydrophobic, while carbohydrates are usually polar and water-soluble.

Lipids store more energy

What are the three types of lipids

Fats, Phospholipids, and Steroids

Fats

Used for long-term energy storage, insulation, and cushioning.

Made of glycerol + 3 fatty acids.

Phospholipids

Main component of cell membranes.

Have both hydrophilic and hydrophobic regions.

Steroids

Lipids with a four fused carbon ring structure.

Act as hormones or membrane components.

What makes up a triglyceride structure

1 glycerol molecule

3 fatty acid chains

Fatty acids attach to glycerol by ester bonds.

Shape looks like an "E" or a tuning fork.

What makes up a phospholipid structure

Glycerol backbone

2 fatty acid tails

Hydrophobic (nonpolar)

1 phosphate group

Hydrophilic (polar)

Parts:

Head (phosphate) → hydrophilic

Tails (fatty acids) → hydrophobic

The hydrophobic tails and hydrophilic heads create a

permeable membrane, controlling what enters and exits the cell.

Saturated Fats

No double bonds between carbons

Fatty acid chains are straight

Pack tightly → solid at room temperature

Examples: butter, animal fats

Unsaturated Fats

One or more double bonds

Chains are bent (kinked)

Pack loosely → liquid at room temperature

Examples: olive oil, plant oils

Cholesterol is a

steroid

Cholesterols functions are

Precursor to steroid hormones

Component of cell membranes

Helps maintain membrane fluidity

How does a structure relate to a function

A protein's specific 3D shape allows it to do its job.

The shape creates active sites or binding regions.

If the shape changes, the protein may no longer work.

Structure determines function = how a protein is shaped determines what it can do.

Denaturation is caused by

Heat

pH changes

Salts or chemicals

Amino acids

The monomers (building blocks) of proteins

Polypeptide

A chain of amino acids linked by peptide bonds

Protein

One or more folded polypeptides that are functional

All Amino Acids Have

Amino group (-NH₂)

Carboxyl group (-COOH)

Hydrogen atom

R group (side chain)

The R group determines

Polarity

Charge

Interactions with other amino acids

Describe the 1° structure of proteins

Sequence of amino acids

Determined by DNA

Describe the 2° structure of proteins

Local folding due to hydrogen bonds

Forms:

Alpha helices

Beta pleated sheets

Describe the 3° structure of proteins

Overall 3D shape of one polypeptide

Caused by R group interactions:

Hydrogen bonds

Ionic bonds

Disulfide bridges

Describe the 4° structure of proteins

Multiple polypeptide chains working together

Not all proteins have this level

Example: hemoglobin

Identify the major functions of proteins and what they do

Enzymes - speed up chemical reactions

Structural proteins - support (collagen, keratin)

Transport proteins - carry substances (hemoglobin)

Defense proteins - antibodies

Signaling proteins - hormones and receptors

Movement proteins - muscle contraction (actin, myosin)

What do Nucleic Acids do

Nucleic acids store and transmit genetic information.

DNA stores instructions for making proteins.

RNA uses DNA's instructions to help build proteins.

Without nucleic acids, cells would not know how to function or reproduce.

Compare the structure of DNA and RNA nucleotides

Both DNA and RNA are made of nucleotides.

Each Nucleotide Has 3 Parts:

1.Phosphate group

2.Pentose (5-carbon) sugar

3.Nitrogenous base

DNA Bases

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

RNA Bases

Adenine (A)

Uracil (U) (replaces thymine)

Cytosine (C)

Guanine (G)

Identify a nucleotide based on its structure

To identify a nucleotide, look for:

Phosphate group (PO₄)

Pentose sugar (5-carbon ring)

Nitrogenous base (ring structure with nitrogen)

If all three are present → it's a nucleotide.

Phospholipids functions

forms a barrier and gives the membrane fluidity.

Proteins functions

Integral proteins: go through the membrane; help transport and signal.

Peripheral proteins: on the surface; help with structure and enzymes.

Cholesterol functions

between tails; keeps membrane flexible.

Carbohydrates

attached to proteins/lipids on outside; help with cell recognition and communication.

Explain the hydrophilic and hydrophobic nature of the phospholipid bilayer - explain how these properties affect the structure of the membrane.

Heads face water, tails face each other (away from water).

This makes a bilayer that controls what enters/exits the cell and keeps the cell flexible.

Prokaryote vs. Eukaryote

prokaryote lack nucleus, eukaryote contain a nucleus and complex organelles

prokaryote single cell organism vs eukaryote multi or single cell organism

prokaryote has no membrane-bound organelles vs eukaryote have membrane-bound organelles

Identify structures unique to eukaryotic cells.

Nucleus - stores DNA and controls cell activities

Mitochondria - produce energy (ATP)

Endoplasmic Reticulum (ER) - makes proteins (rough) and lipids (smooth)

Golgi Apparatus - packages and ships proteins

Lysosomes - digest waste

Chloroplasts (in plants) - do photosynthesis

Cytoskeleton - supports cell shape and movement

Explain the endosymbiosis theory

Explains how mitochondria and chloroplasts evolved.

Idea: a long time ago, a larger cell "ate" a smaller cell that could make energy (mitochondria) or perform photosynthesis (chloroplast).

Instead of being digested, the smaller cell lived inside the larger cell, benefiting both.

Evidence: mitochondria and chloroplasts have their own DNA and ribosomes, and they reproduce like bacteria.

Explain how the nucleus and ribosomes carry out genetic control of the cell.

Nucleus: stores DNA; controls all cell activities by giving instructions for making proteins.

Ribosomes: read DNA instructions (from mRNA) to build proteins.

Together, the nucleus and ribosomes control what the cell does.