Cell communication and cell cycle concepts

Short-distance communication example

Nerve cells release neurotransmitters, which attach immediately to the target cell

Long-distance communication example

Endocrine glands release hormones, which travel to the target cells through the bloodstream

Three stages of cell signaling

Reception, signal transduction, and response

How G-protein coupled receptors work

The ligand binds to the receptor protein, which activates a G-protein, which interacts with an ion channels or enzyme in the membrane

How ligand-gated channels work

The ligand binds to the receptor, which changes shape, letting ions through

Common parts of signal transduction pathways

Protein modification and phosphorylation cascades

Common second messengers

Cyclic AMP/cAMP and Ca+ ions

Cellular response examples

Growth and division, secretion of molecules, gene expression, protein synthesis, change in metabolism, cell death

Result of gene expression response

Transcription and translation are turned on or off

Cellular metabolism response example

Release of adrenaline causes the breakdown of glycogen into glucose for use in “fight or flight” response

Origin of most signals for cell division

Other cells

Signals for apoptosis examples

Damaged DNA and movement of a cell away from the extracellular matrix

Causes of changes in signal transduction pathways

Mutations, chemicals, change in structure of any signaling molecule

Negative feedback examples

Body temperature, water levels, glucose levels

Positive feedback examples

Blood clotting, contractions during childbirth

Why cells are small

Larger cells have a smaller surface area-to-volume ratio, so they have more difficulty getting nutrients in and waste out, placing more demands on its DNA and organelles

Stages of interphase

G1, S, G2

Longest and shortest stages of the cell cycle

Interphase and mitosis

Longest and shortest stages of mitosis

Prophase and metaphase

What happens in G1

Cells grow

What happens in synthesis

Cells replicate DNA

What happens in G2

Cells grow more and prepare for division by making organelles and molecules needed for mitosis

Stages of mitosis

Prophase, metaphase, anaphase, telophase

What happens in prophase

Centrosomes move to opposite sides of the cell, microtubules that will form spindle extend, chromatin condenses into chromosomes, and nuclear envelope breaks down

What happens in metaphase

Chromosomes line up across the equatorial plate, each sister chromatid develops kinetochores, which the spindle attaches to

What happens in anaphase

Sister chromatids are pulled apart by the shortening spindle and become individual chromosomes, which continue to separate until they reach opposite poles

What happens in telophase

Chromosomes group at opposite ends of the cell and unravel into chromatin, new nuclear envelope forms, spindle breaks apart and goes away

What happens in cytokinesis

Cytoplasm pinches in half, forming two daughter cells

Purpose of the cell cycle

Growth of a multicellular organism to adult size, replacement of worn-out or damaged cells, asexual reproduction

Duration of the cell cycle

As short as eight minutes or as long as a year, with most cells taking about twelve to twenty-four hours

Advantages of asexual reproduction

Faster, more efficient, requires only one organism, offspring is an identical copy of the parent

Locations of three major checkpoints

G1, G2, M

What happens at the G1 checkpoint

Cell is checked for size and DNA damage before it commits to the cell division process. External influences such as growth factors play a large role in helping the cell pass.

What happens at the G2 checkpoint

Checks for size and that all chromosomes have been replicated without damage

What happens at the M checkpoint

Determines whether all the sister chromatids are correctly attached to the spindle

How the concentration of cyclins and Cdks changes

It increases as the cell prepares to move to the next phase

Example of density-dependent inhibition

When you get a cut, skin cells stop dividing when they fill the gap and touch each other

Mutagen examples

Infections, radiation exposure, tobacco use, chemicals

Relationship between cancer cells and cell cycle control

Cancer cells do not heed normal cell cycle signals, such as density-dependent inhibition and checkpoints

Common tumor-surppressor proteins

Rb, p53, p21

Treatments for tumors

Surgery, radiation, chemotherapy

Side effects of chemotherapy due to targeting of rapidly dividing cells

Nausea, hair loss, susceptibility to infection

Examples of how chemotherapy works

Freezing the spindle, preventing the spindle from forming at all

Apoptosis example

When hands and feet develop, apoptosis prevents webbing

Notation for diploid human cells

2N = 46

Notation for haploid human cells

N = 23

Sequence of growth following fertilization

Zygote, embryo, fetus, baby

Difference between meiosis metaphase I and mitosis metaphase

In meiosis, homologous chromosomes line up across the middle of the cell, whereas in mitosis sister chromatids do

Why meiosis daughter cells are genetically different

Crossing over and independent assortment

Female daughter cells of meisosis

One egg and three polar bodies

How meiosis provides genetic variation

Genetically different daughter cells and random combination of gametes during fertilization