Biology Unit 3 - Life

NA replication/synthesis, organelles/origin of life, cell cycle, cancer

What is senescence?

a cell’s state of permanent inability to replicate due to the disappearance of telomeres because of decreased telomerase activity. Cells that have constant telomerase activity even as they age can become cancerous

What is necrosis and how is it different from apoptosis?

The death of body tissue that is unplanned and damages organelles, while apoptosis is planned cell death in which the organelles can still function

What is metastasis?

The spread of cancer cells from one body part to another

What is the cell theory? (List the three postulates.)

(1) All living things are made of cells, (2) cells come from other cells, and (3) cells are the basic unit of life

What happens during the initiation phase of DNA synthesis?

Helicase breaks the hydrogen bonds in the DNA, creating replication forks and strands

What happens during the elongation phase of DNA sythesis?

RNA primer (created by primase enzyme) allows DNA polymerase III to add free nucleotides to each of the template strands where the RNA is (lagging or leading).

What prevents the two strands of DNA from assuming their double-helical shape?

Proteins that hold the shape apart by breaking the hydrogen bonds between the DNA, lets the strands wrap around each other, and then puts them back together (topoisomerase)

What happens during the termination phase of DNA synthesis?

The RNA primers are separated from the DNA by DNA Pol 1, ligase bonds the Okazaki fragments in the lagging strand, DNA poly II proofreads the DNA, and nucleotides fill the gaps the RNA primer left. It finishes when the DNA ends.

Each copy of DNA at the end of replication is (typically)…

identical to each other

Why is DNA replication also called the Semiconservative Model (and not conservative or dispersive?

It is called semiconservative because the two original strands are separated and used whole in the two new molecules of DNA after replication, rather than being completely broken down (dispersive), or not used in the new molecule (conservative)

What type of bond holds (a) bases together (also broken by helicase) and (b) holds the DNA backbone together?

(a) hydrogen bonds and (b) phosphodiester bonds

Which strand in DNA replication is the leading strand?

The 3’ ended strand (DNA pol 3 starts a strand with the 5’ end and builds towards the helicase)

Which strand in DNA replication is the lagging strand?

The 5’ ended strand (DNA pol 3 starts the strand with the 3’ end and builds away the helicase)

From what direction does DNA build in?

From the 5’ end to the 3’ end

What does DNA polymerase I do?

It takes out the RNA primer

What does DNA polymerase II do?

It proofreads the work that DNA polymerase completed

What does DNA polymerase III do?

It synthesizes the leading strand and the Okazaki fragments

What is the function of the RNA primer? How does it enter DNA synthesis?

It helps DNA poly III initiate DNA synthesis by binding to the template strands of DNA

What are Okazaki fragments?

Short sections of DNA used to make the lagging strand

What does ligase do?

It joins fragments of DNA

What does telomerase do?

What does topoisomerase do?

It reverses the tension on the DNA helicase causes (splits the bonds, then wraps it back up)

How might have life began (according to the cell theory)?

When smaller organisms began working in tandem to do more functions due to their hot, hydrogen rich environment

What is the smallest unit of life?

The cell

What is another name for proto-cells?

coacervates

What is abiogenesis? Is it viable today?

The original evolution of life or living organisms from inorganic or inanimate substances. No, because the conditions (pH, temperature, atmosphere, etc.) are different from the past

What is simple diffusion?

The process by which solutes are moved along a concentration gradient in a solution or across a semipermeable membrane.

How do cells (through their cell wall) use simple diffusion?

By using their plasma membrane; a high concentration of lipid-soluble particles can diffuse through the wall and into the lower concentration cytoplasm in the cell, which stops once the inside of the cell reaches equilibrium with the outside of the cell.

How does a cell allow different types of particles to diffuse?

A cell’s phospholipid bilayer allows lipid-soluble molecules to pass through it, but a cell’s membrane may have other proteins and protein channels to allow bigger molecules to pass through

What limits and how is a cell’s size limited? Why do cells have different shapes and sizes?

A cell’s surface area to volume ratio. Having a larger ratio is better than a smaller one when it is more efficient for the cell to diffuse materials into itself. To maximize cell space or increase efficiency based on the cell’s function.

Why are viruses not living?

They are not made of cells

What are the six criteria for life?

Regulation/Homeostasis, organization, replication, energy processing, growth/development, and response to stimuli.

Describe regulation/homeostasis

All living things have many ways to regulate changes within and their reaction to changes outside of it.

Describe organization

All living things are bound by membranes, made of cells, and can contain DNA

Describe replication

All living things can produce more of themselves

Describe energy processing

All living things can get energy and process it for their own use.

Describe growth/development

All living things can become more complex.

Response to stimuli

All living things can react to their environment/can alter themselves because of it through their DNA.

What do all cells (and living things) have? Why?

(1) DNA: To reproduce

(2) cytoplasm: To contain its cytosol and organelles

(3) a cell membrane: To protect and regulate the cell from its outside environment

(4) ribosomes: to run its internal processes

What are prokaryotes?

Cells that lack membrane-bound organelles (like a nucleus, allways unicellular)

How do some prokaryotes obtain some necessary resources and remove wastes?

Through diffusion; since they lack membrane-bound organelles like vesicles, they can only use diffusion to obtain resources, limiting their size (to keep diffusion efficient)

What are eukaryotes?

Cells that have membrane-bound organelles

List some common eukaryotes

Plants, animals, fungi, protists (can be plant- or animal-like)

What cells are lysosomes found in? What is their function?

A sac filled with digestive enzymes present only in animal cells, lysosomes digest waste and cell invaders

What is the cytoplasm?

The cell fluid (cytosol) and the cell’s skeleton (cytoskeleton) that contains all the cell’s organelles

What is the mitochondria?

A structure that converts nutrients to energy/site of cellular respiration present in plant and animal cells

What is the centrosome?

A structure that produces spindle fibers that aid in aligning the chromosomes

What is the Endoplasmic Reticulum (E.R., rough and smooth)?

Modifies proteins (rough) and synthesizes lipids/carbs (smooth) (like the lipids in the phospholipid bilayer of the cell)

What are vacuoles?

A sac that stores water, nutrients, or waste products

What is the cell membrane?

A cell’s selective (phospholipid bilayer) barrier that controls what enters and exits the cell (small particles can pass through, larger particles use integral proteins to pass, consists of phospholipids, carbs, and proteins)

What is the nucleus?

An organelle directs cell activity and contains genetic material (DNA), making it the site of DNA synthesis and RNA transcription

What is the cytoskeleton?

Structure made of microtubules, actin filaments, and intermediate filaments that holds the cell shape and anchors the cell’s internal structure

What are ribosomes?

Small structures located on the ER or the cytosol that manufacture proteins and are made of rRNA

What is the nuclear membrane/envelope?

The membrane that surrounds and protects the nucleus

What are the Golgi Bodies? (apparatus, cis Golgi network, cisternae, trans Golgi network)

The stack of membranes that processes, sorts, and packages proteins

What are vesicles?

A package created by the Golgi apparatus that stores of materials for movement around or outside the cell

What is the nucleolus

A structure that manufactures ribosomes

What is a plastid?

A strucutre that stores food or pigments found only in plant cells

What is a cell wall?

A structure similar to a cell membrane that gives the plant cell its structure through its rigid formation

What is a chloroplast?

An organelle that converts sunlight to chemical energy

How do vacuoles differ between plant and animal cells?

Vacuoles in plant cells are much bigger than those in animal cells because they help the plant hold its shape

What do cells do during cellular respiration?

They use glucose from food to produce ATP and produce carbon dioxide. Plants only produce carbon dioxide at night because they cannot undergo photosynthesis (use of CO2)

What is endosymbiosis? Why do endosymbionts have double membranes?

The theory that the mitochondria (or other cells with DNA foreign to the cell) originated from the infection of another cell, leading it to incorporate the infection and the host cell to envelop it in another membrane

List the order of the hierarchy of life.

Atoms, molecules, organelles, cells, tissues, organs, organ systems, organism, population, community, ecosystem, biosphere

What are single-stranded proteins, and what is their function?

They are proteins that bind to the DNA near the replication fork, preventing the separated strands from coming together

What are the main phases of the cell cycle?

Interphase (G1, S, G2, the cell spends most of its time here) and the Miotic phase/mitosis (karyokinesis (prophase, anaphase, metaphase, telophase) and cytokinesis. Through these phases, the cell can maintain chromosomal ploidy

What happens in G1? Why are organelles replicated in this phase?

The cell grows, replicates its organelles, builds energy and protein stores and checks them and the DNA so it can begin S phase. To ensure that that replication process does not interfere with the DNA one

Where are the three cell cycle checkpoints and what happens at them?

They are before and after S and M. The pre-S checkpoint checks for DNA damage, adequate reserves, and cell size. The post-S checkpoint checks for the same thing the pre-S does, but the DNA after replication. The M checkpoint checks for proper attachment of sister chromatids to the spindle

What happens in S?

The new chromosomes are synthesized

What happens in G2?

The cell grows again, checks the new chromosomes for errors, and prepares for miotic division

What happens in prophase?

Chromatin condenses into chromosomes, spindle fibers form in the centrioles, and the nucleic membrane dissolves

What happens in metaphase?

The spindle fibers move the chromosomes into a line

What happens in anaphase?

The chromosome (made of sister chromatids) centromeres split and are pulled in opposite directions (so both new cells will have homogelous chromosomes)

What happens in telophase?

The nuclear membrane reforms around the chromosomes at the poles, and the chromosomes unravel

What happens in cytokinesis?

The cell divides its cytoplasm (cleavage furrow in AC and cell plate in PC) and organelles to create two daughter cells.

Why do chromosomes condense in (whatever) phase?

How does the cell ensure that the DNA is a faithful copy of the OG?

Through a semi-conservative replication structure, DNA pol with the ability to check itself, and proteins that fix any mistakes that occurred in DNA synthesis

What are three reasons a cell might undergo apoptosis?

When the cell is not needed, its DNA is mutated and can’t be repaired, or if the DNA that was copied cannot be repaired.

What are the five phases of malignant tumor growth (as opposed to noncancerous/benign tumors)

Growth, survival, angiogenesis (vascular creation), invasion, and inflammation

What do oncogenes (protooncogenes) do?

Protooncogenes regulate the signal for a cell to replicate. A single mutation event can turn them into oncogenes, which keeps the replication signal on permanently, leading to overgrowth.

What do tumor suppressor genes do?

They signal the cell to stop moving if they detect an irregularity in the DNA. When mutated twice, the cell will have decreased apoptosis and stimulate cell proliferation (creation of new cells)

What is carcinogenesis?

When environmental agents damage DNA and somatic cells suffer mutations that result in a tumor (becomes malignant when the proteins become abnormal)

What is cyclin?

A protein that binds and activates cyclin-dependent kinase enzymes that regulate the cell cycle