Biology Unit 2 Study Guide: Basic Building Blocks of Life

Biology Unit 2 Study Guide: Basic Building Blocks of Life

 What are biomolecules?

 Biomolecules are large molecules made of many smaller repeating units.  Therefore they are also considered polymers because they are made of many monomers.


What helps molecules stick together?

Complete the table about types of chemical bonds.

Type of Bond

Formed When…


Covalent Bond

electrons are shared between atoms




Ionic Bond

electrons are transferred from one atom to another and the two atoms are held together by the attraction of opposite charges



Hydrogen Bond

attraction between hydrogen atom on one water molecule and oxygen atom on another water molecule – not as strong as covalent or ionic bond


Role of Lipids

Lipids have many roles within the cell and body and the function depends on the type of lipid.  What are the functions of the following lipids?

Type of Lipid



insulation, cushion organs, stores energy (longer term)




makes up cell membrane


(ex. testosterone, cholesterol)

hormones, cholesterol provides stability in cell membranes


One physical trait of a lipid that can affect how it behaves is the presence of double bonds between the carbons in the fatty acids.  Complete the table below:


Type of Bonds Found


Solid or Liquid at

Room Temperature



single bond


butter, animal fats


contains one or more double bond


peanut oil, vegetable oil

Role of Carbohydrates

Carbohydrates are best known for their ability to provide organisms with ENERGY.  The cells of autotrophs contain chloroplasts (organelle), which has the ability to capture energy from the sun and produce the monomer glucose through the process of photosynthesisheterotrophs must eat other organisms to get this monomer.  BOTH animals and plants break down glucose through the process of cellular respiration in order to get energy in the form of ATP – this is done by the mitochondria (organelle).

Complete the table about carbohydrates.

Found in …


Monosaccharide or Polysaccharide?





quick energy

glycogen (animal starch)


store energy




store energy



structure: gives strength and rigidity in cell walls

Complete the table for testing the presence of carbohydrates.


What carbohydrate does this test positive for?

What does a positive result look like?

Benedict’s Solution



Lugol’s Solution


black/dark blue

Role of Nucleic Acids

The two types of nucleic acids are DNA and RNA.  In a eukaryotic cell, DNA is found in the nucleus (organelle).  DNA has the ability to “control” the cell because it codes for the production of the biomolecule protein.

Role of Proteins

Proteins have many, many different functions and in a sense, are really what controls what happens in a cell and even an organism.  Complete the following chart on protein functions:

Type of Protein


Protein channel

Allows large polar molecules and ions in and out of the cell membrane.


Speeds up rate of reactions to break apart or make molecules


Helps fight diseases.

Microtubules and filaments

Builds the cytoskeleton, gives cell support and allows movement of motor proteins

Motor proteins

Transports materials inside cell along cytoskeleton


Allows cells to communicate with other cells.

download (1)

Importance of the Role of Enzymes

Enzymes are critical for allowing biological reactions to occur.  Without them, many important reactions (putting together molecules or breaking them apart) simply would not happen.

Describe how the words in the following set are related:      (catalyst, enzyme, activation energy, substrate)

A catalyst lowers the activation energy.  An enzyme is an example of a catalyst.  It works by attaching to the substrate to create a larger molecule or break it apart.

Why are the active site and substrates in an enzyme-catalyzed reaction often compared to a lock and key?

The fit of the substrate to the active site is very precise, therefore they generally only catalyze one reaction.

How do the parts of the cell work together to help the cell function?

A cell can be a living unit all by itself!  All the organelles that help a cell function use various biomolecules to perform their jobs.  Because it is a living thing, the cell must perform various tasks using organelles just to stay alive.  Complete the chart below showing what a cell must do to survive and the role biomolecules play within the organelle.



Responsible Cell Part or Organelle

Break down glucose for energy


Digest old materials and get rid of wastes using enzymes


Store materials such as water, lipids, carbohydrates, and proteins for later use


Contains DNA which “controls” cell activities by coding for the production of protein


Maintain homeostasis by controlling what enters and leaves the cell through the lipid bilayer

cell membrane / plasma membrane

Fills the inside of the cell and allows movement of materials within the cell


Provides structure within the cell through microtubules and filaments made of protein


Plant cells have two more organelles that animal cells do not so they can do two more functions, which are:


Responsible Cell Part or Organelle

Capture energy from the sun to produce glucose


Provide structure and strength to the outside of a cell through the use of cellulose

cell wall

And finally, cells must have a method of building structures and enabling reactions.  Ribosomes do this by making PROTEINS.              

How do cells regulate their interactions with their environment?

Cells regulate their interactions with the environment through the CELL MEMBRANE, also known as the PLASMA MEMBRANE.  Because not everything can pass into or out of the cell, the cell membrane is selectively permeable.

How does the structure of the plasma membrane allow it to be selectively permeable?

Complete the following explanation of the structure of the plasma membrane.

The plasma membrane is composed of a lipid bilayer.  Each layer is composed of small molecules called (a) phospholipids.  These small molecules have a phosphate head which is polar and a non-polar tail comprised of  two (b) fatty acids.  The (c) cholesterol molecules dispersed throughout each layer provide stability to the membrane.  Other structures called (d) membrane proteins/protein channels are present in the membrane and help substances like glucose enter the cell.

What is the importance of polarity?

Because fatty acids are non-polar, only non-polar molecules can easily pass through the membrane.  Large molecules, molecules with a charge, and polar molecules (except for water), need help from a protein channel. 


What is polarity and what causes polarity in a water molecule?

Polarity occurs when electrons are not shared equally within a covalent bond.  Polarity occurs w/in a water molecule because the electrons spend more time around the oxygen instead of the hydrogens, leaving oxygen with a slightly negative charge and hydrogens with a slightly positive charge.

Other Properties of Water

Complete the table about the different properties of water.

Water Property




attraction between molecules of different substances

capillary action – ability of water to “climb” up vessels in plants


attraction between molecules of same substances

water beads on waterproof material, ability of some insects to walk on water


able to dissolve ionic compounds and other polar molecules

sugar dissolves in water

Complete the table about acids and bases.


Type of ions formed in water

Location on the pH scale


H+: hydrogen ions

below 7


OH-: hydroxide ions

above 7

How do cells transport substances through the cell membrane?

When molecules move from a high concentration to a low concentration WITHOUT a membrane, this is called simple diffusion.  Water can go into or out of the plasma membrane easily.  The movement of water molecules across the membrane from high to low concentration is called osmosis.  Sometimes larger molecules need the help of a protein channel to move across the membrane.  When substances move from high to low WITH the help of a protein, this is called facilitated diffusion.  When molecules move across the membrane from a LOW concentration to a HIGH concentration with the help of a protein, this is called active transport.  If a cell takes in water or food by wrapping its membrane around it and taking it into the cell, this is known as endocytosis.

Osmosis is the movement of water particles across a selectively permeable membrane from a high concentration to a low concentration.  Because water can easily pass through a cell membrane, it’s important for a cell to be surrounded by a solution with the same water concentration.  Otherwise, the movement of water can increase or decrease the size of the cell to the point of causing damage.


How do you measure the size of a cell?

Practice Problem

  1. Looking at a cell under high power (25x) the cell diameter takes up 30% of the field of view.  If the field of view at low power (5x) is 4.5 mm, what is the diameter of the cell?

4.5 x 1000 = 4,500 mm(micrometers)           

4,500 x 5/25 = 900mm (high power f.o.v)   


Thanks for reading, and have a wonderful day!

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