AP Bio Unit 4 Complete Student Notes Flashcards

Cell Communication

Cell Communication

Essential for multicellular organisms, achieved mainly through chemical means or protein contact between cells.

Direct Communication Between Cells

Involves physical contact between cells or organisms. Normally through the binding of specific membrane proteins.

Local Communication Between Cells

Cells near each other communicate through chemical messengers.

Long Distance Communication Between Cells

Signaling between cells far apart or different organisms. Normally occurs through hormones.

Autocrine Signaling

Cell signaling where a cell responds to signaling molecules it produces itself, affecting its own activity.

Paracrine Signaling

In biology, a type of cell communication where signaling molecules act on nearby target cells. The signaling molecules don't travel long distances.

Endocrine Signaling

Communication between cells using hormones released into the bloodstream to target distant cells with specific receptors.

Signal Transduction Pathways

Steps of cell signaling process.Occurs after contact between the ligand and the protein receptor occurs. Normally results in amplification of a certain reaction.

Internal Receptors

Also known as intracellular receptors, are located in the cytoplasm and respond to hydrophobic ligands. These receptors bind to proteins that regulate mRNA synthesis, affecting gene expression by binding to DNA and initiating transcription directly.

Cell Surface Receptors

Also known as transmembrane receptors, they are integral proteins on cell membranes that bind external ligands. They facilitate signal transduction, converting extracellular signals to intracellular ones. These receptors are specific to cell types and have three main components: ligand-binding domain, membrane-spanning region, and intracellular domain. They play a crucial role in signaling in multicellular organisms and fall into three categories: ion channel-linked, G-protein-linked, and enzyme-linked receptors.

Ion Channel-Linked Receptors

These bind ligands, opening a channel for specific ions to pass through the membrane. They have hydrophobic amino acids in the membrane-spanning region and hydrophilic amino acids inside the channel, allowing ions like sodium, calcium, magnesium, and hydrogen to pass through upon ligand binding.

G-Protein Linked Receptors

G-protein-linked receptors bind ligands, activating G-proteins that interact with ion channels or enzymes. They have seven transmembrane domains and unique extracellular domains. Signaling involves G-protein activation by ligand binding, GTP exchange, and subsequent deactivation.

Enzyme-Linked Receptors

These are cell-surface receptors with intracellular domains associated with enzymes. They transmit signals upon ligand binding, activating enzymes that trigger cellular responses. An example is the tyrosine kinase receptor, which phosphorylates tyrosine molecules to propagate signals.

Feedback Loops

Mechanisms that regulate processes based on output.

Introduction to the Cell Cycle

Overview of stages in cell division.

Stages of the Cell Cycle/Cell Cycle Regulation

The cell cycle consists of interphase (G1, S, G2) and mitotic phase (mitosis, cytokinesis). In mitosis, the cell divides its nucleus into two genetically identical daughter nuclei. It includes prophase (chromosomes condense), metaphase (chromosomes align at the metaphase plate), anaphase (sister chromatids separate and move to opposite poles), and telophase (chromosomes decondense). Cytokinesis follows, dividing the cytoplasm to form two daughter cells.

The Cell Cycle and Cancer

Cancer normally mutates something that would normally stop cell division. This causes unhindered cell division, which in turn leads to tumor and cancer growth.

Morphogens

Signaling molecules that control cell differentiation and tissue patterning during development by forming concentration gradients.

Quorum Sensing in Bacteria

A communication system where bacteria release signaling molecules to coordinate group behaviors based on population density.

Hormones

Chemical messengers released into the bloodstream to target specific cells.

Pheromones

Chemicals impacting behavior or physiology outside the secreting individual's body.

Steroid Hormones

Lipid-based hormones that can pass through cell membranes to affect gene expression.

Ligand

A signaling molecule that binds to a receptor protein on the cell membrane or inside the cell, causing a conformational change in the receptor to initiate a signal transduction pathway.

Reception

The initial step in cell signaling where a signaling molecule binds to a receptor, leading to a conformational change in the receptor and the transduction of the signal into the cell.

Transduction

The process in cell signaling where a multi-step pathway transmits and amplifies a signal through the addition or removal of phosphate groups, often involving protein kinases and phosphatases.

Response

The cellular action or regulation initiated by a signal transduction pathway, which can include ion channel opening, substance breakdown, gene expression, gene regulation, or cell growth/reproduction.

Receptor Tyrosine Kinase (RTK)

A cell surface receptor that initiates cell signaling pathways by phosphorylating tyrosine residues on target proteins.

Negative Feedback Loop

A regulatory mechanism in biology where the product of a reaction leads to a decrease in that reaction, helping maintain stability or homeostasis by reversing changes away from a set point.

Positive Feedback Loop

A regulatory mechanism where the product of a reaction leads to an increase in that reaction, amplifying effects and moving a system further from equilibrium, often occurring when rapid responses are needed.

Positive Feedback Loop for Childbirth

A process where the stretching of the cervix during childbirth stimulates the release of oxytocin, leading to stronger contractions and further stretching.

Ethylene Gas in Fruit Ripening

Another example of a positive feedback loop. Hormones released by ripening fruits stimulate neighboring fruits to ripen, creating a chain reaction.

Binary Fission

A type of asexual reproduction in prokaryotes where DNA replication leads to the formation of two identical cells.

Sister Chromatids

Halves of a duplicated chromosome held together at the centromere, normally forming an "X" shape during cell division.

G1 Phase

The first stage of the cell cycle is where cells grow and prepare for DNA replication. It is a crucial checkpoint before entering the S phase.

S Phase

The stage in the cell cycle where DNA is replicated occurs between G1 and G2 phases. Ensures each daughter cell receives a complete set of genetic information.

G2 Phase

A stage in the cell cycle where the cell prepares for division after DNA replication in the S phase. It precedes the M phase (mitosis).

Mitosis

Cell division process resulting in two genetically identical daughter cells, crucial for growth, repair, and asexual reproduction.

Meiosis

Cell division process forming haploid gametes from diploid germ cells, leading to genetic variation.

Interphase

Cell cycle phase where cells grow, replicate organelles, and DNA before entering mitosis.

Prophase

First stage of mitosis where chromatin condenses into chromosomes, nuclear envelope breaks down, and spindle fibers begin to form.

Metaphase

Stage of mitosis where chromosomes align in the middle of the cell, ready to be separated into two daughter cells during anaphase.

Anaphase

the stage in mitosis or meiosis where sister chromatids separate and move towards opposite poles of the cell.

Telophase

the final stage of mitosis, where the chromosomes arrive at opposite poles and a new nuclear membrane forms around each set.

Spindle Apparatus

Network of protein filaments aiding in chromosome movement during cell division, crucial for proper segregation.

G0 Phase

The cell cycle phase is where cells are non-dividing, either in a quiescent stage or a post-mitotic state. Where the cell is functioning.

Regulation of the Cell Cycle

The control mechanism that is crucial for normal growth and development, varying from cell type to cell type.

Cyclins

Protein-based cell signals crucial for regulating the cell cycle, increasing in concentration from S phase until Anaphase.

Checkpoints

Key control points in the cell cycle that regulate progression and ensure proper division.

Maturation Promoting Factor (MPF)

An active enzyme formed by the combination of Cyclins with Cyclin dependent Kinase (CdK), initiating mitosis.

Telomerase

An enzyme present in cancer cells that prevents telomeres from shortening, allowing cells to evade apoptosis and become “immortal”. Also occurs whilst humans are in development but stops after birth.

Angiogenesis

The process of creating new blood vessels to supply nutrients to tumors in cancerous cells.

Transformation

The process where the DNA in a cell is altered, often leading to the initiation of cancer, such as the activation of telomerase.

Kinase

The enzyme that adds phosphate groups to molecules, often proteins, to regulate cell processes like growth and metabolism.

Signal Cascade

A series of molecular events triggered by a signaling molecule binding to a receptor, leading to a cellular response.

Secondary Messangers

Signaling molecules are produced in response to the activation of cell surface receptors, amplifying and transmitting the signal inside the cell.

cAMP

A signaling molecule that regulates various cellular processes by activating protein kinase Secondary messenger in most cells.

CA2+

CA2+ is a crucial ion in biology involved in muscle contraction, cell signaling, and bone formation. It plays a key role in processes like neurotransmitter release and enzyme activation. Secondary messenger.