bio 170 molecular and cellular biology

exam 3 and 4

What is the structure of DNA?

It looks like a twisted ladder, with sides made of sugar and phosphate, and steps made of pairs of molecules.

What are purines and pyrimidines?

They are two types of molecules in DNA. One is bigger (A and G), and the other is smaller (C and T).

What holds the bases together?

They are connected by hydrogen bonds. A pairs with T (2 bonds), and C pairs with G (3 bonds).

What is the central dogma of biology?

It describes how instructions are passed to make proteins: DNA → RNA → Protein.

What enzyme is responsible for DNA replication?

DNA polymerase

What does helicase do?

It unzips the twisted structure so it can be copied.

What’s the difference between the leading and lagging strands?

One is copied smoothly, while the other is copied in small pieces.

What are Okazaki fragments?

They are short pieces made during the copying of one side.

What does RNA primase do?

It starts the copying process by adding a short piece of RNA.

What is transcription?

It’s when the instructions are copied from DNA to make RNA.

What does mRNA do?

It carries the instructions to the part of the cell that makes proteins.

What is translation?

It’s when the cell reads the instructions to build a protein.

What are the main steps of translation?

There are three steps: starting, building, and stopping the protein.

What are codons?

They are groups of three letters that tell the cell which building blocks to use for a protein.

What is a mutation?

It’s a change in the genetic instructions.

What are types of mutations?

They can be small changes, added pieces, missing pieces, or shifted instructions.

What is the difference between silent and missense mutations?

One doesn’t change the protein, while the other changes one part of it.

What does tRNA do?

It brings building blocks to the protein-making part of the cell.

What is the job of a ribosome?

It’s the factory that builds proteins.

What is DNA replication?

It’s the process of making a copy of genetic instructions.

What are the stages of the cell cycle?

Cells grow, copy their instructions, and divide into two.

What happens in the S phase?

The genetic instructions are copied during this phase.

What does DNA ligase do?

It glues pieces together during replication.

What are telomeres?

They are protective caps on the ends of genetic material.

What does telomerase do?

It adds to the protective caps to keep them from getting too short.

What is an operon?

It’s a group of genes that work together in bacteria.

What is the lac operon?

It helps bacteria break down milk sugar for food.

What does RNA polymerase do?

It makes RNA by copying the instructions.

What is a promoter?

It’s the starting spot where RNA copying begins.

How is transcription different in prokaryotes and eukaryotes?

In one, it happens in the cytoplasm. In the other, it happens in the nucleus and gets edited.

What is RNA splicing?

It’s when extra parts are removed and useful parts are connected in RNA.

What is a spliceosome?

It’s a tool in the cell that helps with editing RNA.

What is a poly-A tail?

It’s a string of A’s added to the end of RNA to protect it.

What is a 5’ cap?

It’s a tag added to the start of RNA to keep it safe and help it work.

Which statement is true for a cell with mitochondria?

They produce ATP and are not found in prokaryotes

Which structure is found in ALL cells?

Ribosomes and cell membranes

Combining lye and lard to make soap demonstrates which big idea?

Emergent Properties.

Example of a structure-function relationship.

Webbed feet allow ducks to swim well in water.

How do we represent electron distribution

They can contain up to 2 electrons in each orbital

How many bonds will oxygen form in a molecule? Why?

Two, because it has two unpaired valence electrons.

What does it mean if Mg²⁺ and Cl⁻ form an ionic bond?

Magnesium and chlorine are extremely different in electronegativity.

Characteristic of orbitals in an atom.

They can contain up to 2 electrons.

Type of bond with unequal sharing of electrons.

Polar covalent bond.

What property is shown when water sticks to glass?

Adhesion.

When water dissolves something, what forms around it?

A hydration shell.

Rules for hydrogen bonding between molecules (pick 2):

Hydrogen bonds form between positive and negative parts of polar molecules; Hydrogen bonds are always the same length.

Carbon is a great element for building molecules because...

It has four unpaired valence electrons.

Two ways to change a carbon backbone to create new organic molecules.

Add new bonds (double or triple); Form a ring shape.

What property does hydroxyl have

Adds polarity.

What molecules would you recommend for dye that won't wash off in water?

Molecules made with only carbon and hydrogen because they are not dissolvable and nonpolar

What are the coiled structures in proteins called?

Alpha helices.

What level of protein structure is formed by folding helices into 3D shapes?

Tertiary structure.

What monomers make up polypeptides?

Amino acids.

What reaction breaks down polypeptides?

Hydrolysis reaction.

How does ATP add energy to molecules?

ATP adds a phosphate group to a molecule.

What property do all lipids have in common?

They are hydrophobic

How do saturated and unsaturated fatty acids differ?

Their shape. Saturated fatty acids are tightly packed; unsaturated fatty acids have kinks from double bonds.

What effect does cholesterol have on membrane fluidity?

It makes the membrane more fluid because it would break the tightly packed phospholipids

What type of protein spans the membrane?

Trans membranes protein.

What allows phospholipids to form bilayers?

They are amphipathic.

How does osmosis work in a hypertonic vesicle?

Water moves into the vesicle.

What type of transport protein is a Na⁺-Glucose co-transporter?

Symport.

Is the Na⁺-Glucose co-transporter active or passive transport?

Active, because glucose moves towards higher concentration.

When is receptor-mediated endocytosis used?

A liver cell selectively removing iron from the bloodstream.

What do we call a molecule that activates a receptor?

A ligand.

What are two events in receptor tyrosine kinase activation?

Two receptors dimerize; Autophosphorylation of receptors.

What are two ways signal transduction cascades affect cells?

Amplify signals; Specify cellular responses.

Which of the following describes facilitated diffusion?

Needs transmembrane proteins.

What forms the bilayer in vesicles?

Phospholipids.