Unit 4 Cell Communication and Cell Cycle

Flashcards about cell communication, cell cycle, feedback mechanisms, and regulation.

Positive feedback

When the output of a system is also the input.

Negative feedback

Counters a process, tries to maintain homeostasis.

Stimulus

Something that triggers a reaction.

Sensor / receptor

Biological structure that detects a stimulus.

Effector

Responds to the stimulus, changes bodily function.

Response

The change that responds to the stimulus.

Insulin

Body releases this after consuming high levels of glucose, negative feedback as allows cells to absorb glucose and lower glucose levels.

Glucagon

Body releases this when low levels of glucose, signals for body to turn stored sugar into glucose, negative feedback.

Set points

The value around which a homeostatic process fluctuates.

Disease

When homeostasis is disrupted.

Cell cycle

How the cell cycle duplicates itself.

Mitosis

Cell division for body cells.

Interphase

Where cells are for most of their lives, growing, DNA replication, and cell functions.

G1

Cell is growing, part of interphase.

S

DNA is replicated, part of interphase.

G2

Cells continue to grow.

Prophase

Nucleus is still present, chromosomes are condensing, spindles start to form.

Metaphase

Nucleus is gone, chromosomes line up in the middle, spindles attach to centromeres.

Anaphase

Chromosomes are pulled to opposite sides of the cell.

Telophase

Chromosomes are on opposite sides of the cell, new nuclei form.

Cytokinesis

Cytoplasm splits between the two nuclei creating 2 new daughter cells.

Centriole / centriole pair

Where the spindle fibers come out of.

Chromosome

Condensed units of DNA (look like Xs).

Replicated chromosome

When chromosomes are replicated during the S phase of the cell cycle, sister chromatids form and each chromosome is doubled.

Histones

The proteins that the DNA is wrapped around.

Pole(s)

The ends of the cell where the spindle fibers pull chromosomes to.

Spindle fiber

Attach to the centromeres of chromosomes during metaphase.

Condense

DNA is usually unbound and loose in the nucleus but for mitosis, it condenses into chromosomes.

Spindle apparatus (mitotic spindle)

Small structures that attach to kinetochores of chromosomes and pull them to each pole.

Midline (equatorial plate)

Where chromosomes line up during metaphase.

Sister chromatid

Each identical half of a chromosome.

Cleavage furrow

When the cytoplasm pinches during cytokinesis to prepare for cytoplasmic division.

Decondense / unwind

After mitosis, the DNA in the daughter cells begins to decondense back into a more loose form.

Kinetochore

Center of a chromosome where the spindles attach.

Centrosome

The structure that contains the spindles and the centrioles.

Checkpoints

Several times throughout the cell cycle, activity stops so that the cell can be examined for errors. This helps prevent erroneous cells from being made.

Cyclin

Internal regulator of the cell cycle, the binding of cyclins and CDKs signals for new phases of the cell cycle to commence and end. They are not always present, their abundance depends on the abundance of CDKs.

CDK (cyclin dependent kinase)

Internal regulator of the cell cycle, their activation helps progress the cell cycle. CDKs are always present.

G0

Phase where cells never divide, like nerve and muscle cells.

G2 checkpoint

After S phase, checks for errors in DNA replication.

M checkpoint

After metaphase, checks all spindles are properly attached.

Contact inhibition

When normal cells touch each other, their replication rate slows until they fill up a certain space. For cancer cells, contact inhibition doesn’t stop them and they continue to grow uncontrollably.

Cancer

Uncontrolled cell growth.

Tumor

A clump of cancer cells.

Malignant

Mass of cancer cells that can leave the tumor site and travel throughout the body.

Benign

Abnormal cells, not considered cancerous yet. These cells are unable to leave the tumor site.

Metastasis

When cells spread throughout the body away from the initial tumor site.

Describe the events that occur in the cell cycle

The cell is in interphase for most of its life: it continues to grow in G1; it replicates DNA in S phase; it continues to grow further in G2; and finally enters mitosis in the M phase.

Explain how mitosis results in the transmission of chromosomes from one generation to the next.

Since DNA is replicated, the replicated chromosomes are split into two areas and the cytoplasm splits, causing two new cells with the same amount of initial DNA as the original parent cell

Identify and describe the main stages of mitosis

Prophase: nucleus is still present, DNA condenses, spindle fibers are present. Metaphase: nucleus is gone, spindle fibers attach to the kinetochore as chromosomes line up at midline. Anaphase: spindle fibers pull chromosomes apart toward each pole. Telophase: nuclei reform, DNA loosens. Cytokinesis: begins with the cleavage furrow, then cytoplasm splits into two new daughter cells

Describe how cytokinesis differs in plants and animals

During telophase, plant cells will begin to build a cell plate between the two forming cells. This cell plate will become the cell wall that separates the two cells.

Describe the role of checkpoints in regulating the cell cycle

They ensure only good cells are able to reproduce, and errors are either corrected or erroneous cells are killed.

Describe how the cell cycle is regulated by cyclins and CDKs

The abundance and activation of these progresses the cell cycle.

Describe the effects of disruptions to the cell cycle on the cell or organism

Cancer can develop.

Explain how cancer is an example of an inability to maintain homeostasis

Cancer’s uncontrollable nature leads to several imbalances throughout the body and other abnormalities

Predict what will happen to a cell if it does not pass the G1 checkpoint

This checkpoint checks for cell size and DNA damage. If it passes, it completes the rest of the cycle. If it fails to pass, the cell enters G0 and never replicates.

Describe what G0 is and the types of cells in G0

G0 is a phase where cells don’t replicate. Nerve cells and muscle cells are examples of these, as well as all cells that don't pass the G1 checkpoint

Predict what will happen to a cell if it does not pass the G2 checkpoint

This checkpoint checks for completion of DNA replication and potential DNA damage. If it passes, the cell continues to mitosis. If it fails, the cell will attempt to fix its errors, but ultimately will undergo apoptosis if nothing can be fixed

List the three types of external cell regulators

Growth factors, contact inhibition, anchorage dependence. Growth factors are hormones that stimulate cell growth, contact inhibition stops reproduction when cells are too close to each other, and anchorage dependence is when cells need to be grounded or attached to something to divide, reducing infinite division.

Describe at least two ways a cancer cell differs from a normal cell

It doesn’t have checkpoints, it divides infinitely, and it evades apoptosis

Direct contact

When there’s a direct connection between two cells where molecules can pass between. Aka Juxtacrine signaling

Local signaling

When ligands are secreted between close-by cells. Aka Paracrine signaling

Long-distance signaling

When hormones are secreted to travel far throughout the organism. Aka Endocrine signaling

Cell junction

Channels, like gap junctions or plasmodesmata that allow molecules to pass through

Gap junction

Channels connecting cells that allow ligands and other molecules to pass through

Plasmodesmata

Junctions between plant cells

Antigen

Foreign cells that trigger immune responses

Antigen presenting cell

When special immune cells bind to antigens and flag them as threats so that T cells can destroy the cell

T cell

Cells that regulate immune responses by destroying antigens

Autocrine signaling

Self-signaling, secretion of hormone or ligand that binds to receptors on that same cell

Juxtacrine signaling

Direct cell-to-cell signaling, ligands flow between attached cells

Paracrine signaling

Secretion of ligands to nearby cells

Synaptic signaling

Type of paracrine signaling where nerve cells communicate

Endocrine signaling

Long distance signaling, uses circulatory system in animals, and the xylem and phloem in plants

Neuron

Brain cells

Synapse

Junction through which neurons communicate

Neurotransmitter

Neurons’ signal molecules that carry messages between neurons

Hormone

Ligand that travels long distance

Reception

First stage of cell signaling, ligand binds to receptor

Ligand

Signaling molecules

Receptor

Where ligands bind, highly specific to ligands

Transduction signal

Second stage of cell signaling, signal is carried throughout the cell

Conversion

When binding is converted into an intracellular signal

Response

The result of signaling

Conformational change

The physical change in the receptor when a ligand binds. This initiates the signaling pathway

GPCR (G protein coupled receptor)

Membrane-embedded proteins that respond to extracellular signals and create intracellular response, can be dormant or active

GTP, GDP

Low energy forms of ATP

Ligand-gated ion channel

Channels that ions pass through that are regulated by ligand-receptor activity

Plasma membrane receptor

Where polar ligands bind

Intracellular receptor

Where nonpolar ligands bind

Protein kinase

Phosphorylates different parts of the signaling pathway

Protein phosphatase

Dephosphorylates different parts of the signaling pathway

Secondary messenger

Relays the signals from reception

cAMP (cyclic AMP)

A secondary messenger

Amplify

Signal is carried throughout the cell

Differentiation

When cells become specialized

Compare and contrast the three main ways cells communicate

Direct signaling is between two cells, local signaling is between neighboring cells, and long-distance signaling is between cells far apart from one another

Compare and contrast direct communication in animal and plant cells

Animal cells use gap junctions, where as plant cells use plasmodesmata

Compare and contrast long-distance signaling in plants and animals

Signals will travel through the circulatory system in animals, and they’ll travel through the xylem and phloem in plants

Identify and describe what happens during the 3 stages of signal transduction

The ligand will bind to a receptor, which will trigger a physical change of the binding site. This will cause a cascading effect of signaling throughout the cell, and will result in a cellular response