AP Unit 4 Cell Communication Study Guide

Saturated vs. Unsaturated Lipids in Membranes

Saturated lipids pack tightly and decrease membrane fluidity, while unsaturated lipids have kinks that increase fluidity and cold-adaptation.

Role of Aquaporins

Specialized membrane proteins that facilitate the rapid transport of water across the cell membrane.

Three Steps of Signal Transduction

Reception, transduction, and response.

Second Messengers in Signaling

Small, non-protein molecules like cyclic AMP (cAMP) that amplify and relay signals inside the cell.

Disruption of Signaling Pathways

Mutations or inhibitors can block receptors or proteins, disrupting signaling pathways and cellular responses.

Hormonal Regulation and Homeostasis

Hormones like insulin regulate physiological processes (e.g., lowering blood glucose) to maintain homeostasis.

Negative vs. Positive Feedback Loops

Negative feedback counteracts changes to maintain stability, whereas positive feedback amplifies changes away from a set point.

Cyclins and CDKs

Cyclins and cyclin-dependent kinases are key regulatory proteins that control progression through the cell cycle.

Cell Cycle Checkpoints

G1, G2, and M checkpoints monitor DNA integrity, cell size, and proper chromosome attachment before division.

Consequences of Abnormal Cell Regulation

Failure of regulation can lead to uncontrolled division (cancer), cell cycle arrest, failed division, or apoptosis.

Phases of Interphase and Mitosis

Interphase (G1, S, G2) involves growth and DNA replication, followed by M phase (mitosis) and cytokinesis.

Kinetochores and Microtubules

Kinetochores are protein structures where mitotic spindle microtubules attach to ensure proper chromosome segregation.

Motor Proteins and Actin in Cell Division

Kinesin and dynein move chromosomes along microtubules, while actin filaments form the contractile ring during cytokinesis.

Cellular Specialization and Differentiation

Cells differentiate in response to environmental signals (like nitrogen fixation in cyanobacteria) to form specialized tissues.

Synaptic Signaling

Involves neurotransmitter release at synapses, regulated by proteins and enzymes to control neural responses.

Enzyme Active Site Specificity

Enzymes recognize specific substrates through a precise active site shape and chemical environment.

Competitive Inhibition

Inhibitors bind to the active site, competing with substrates; relative concentrations of substrate and inhibitor determine activity.

Endosymbiotic Theory

Theory that organelles like mitochondria and chloroplasts originated from prokaryotes, supported by prokaryotic-like DNA.

Plasmodesmata

Channels between plant cells that allow direct intercellular communication and molecular transport.

Apoptosis

Programmed cell death controlled by specific signals and cellular processes to eliminate damaged cells.

Experimental Design in Cell Signaling

Using gene mutations, drug treatments, and data interpretation to reveal mechanisms of cell signaling and regulation.

Paracrine how it works

It happens between local cells, where a cell will secrete signaling molecules that diffuse to nearby target cells.

synaptic

It happens between local cells where a axon terminal releases neurotransmitters by exocytosis. They cross the synaptic cleft and bind receptors on a target neuron.

Plasma membrane receptors function

Receives hydrophilic or polar ligands because these molecules cannot easily cross the

phospholipid bilayer

Intracellular receptors function and place

They are in cytoplasm or nucleus and receive hydrophobic or nonpolar ligands that can cross the

membrane, including steroid hormones such as estrogen and testosterone

GPCR ligand binding

A ligand binds to the extracellular side of a G protein-coupled receptor (GPCR

G protein activation

The receptor activates an associated G protein by causing GDP to be replaced with GTP. The G protein is active when bound to GTP

Effector enzyme activation

The activated G protein can activate an effector enzyme, such as adenylyl cyclase.

Protein kinases and phosphatases

Protein kinases add phosphate groups to target proteins and often activate them, while protein phosphatases remove phosphate groups and often deactivate them.

nucleosomes

DNA associates with and wraps around proteins known as histones

how does dna shift in mitosis

nucleosomes—>Chromatin—> chromosome—>sister chromatids—>chromosomes

How do sister chromatids form

Chromosomes are joined together by a centromere and proteins called Kinetochore attach to the centromere, allowing the sister chromatids to be pulled apart during cell division.

Stimulus

A variable or environmental change that triggers a physiological reaction.

Receptor (Sensor)

A specialized cell, organ, or structure that detects an environmental change and transmits this information to a control center (such as the brain).

Effector

A muscle, gland, or organ that executes an action instructed by the control center.

Response

The physiological action that modifies conditions by decreasing or increasing the effect of the initial stimulus.

Prophase

● Chromatin condenses

● Nucleoli disappear

● Duplicated chromosomes appear as sister chromatids

● Mitotic spindle begins to form

● Centrosomes move away from each other

Prometaphase

● Nuclear envelope fragments

● Microtubules enter nuclear area and some attach to kinetochores

Metaphase

● Centrosomes are at opposite poles

● Chromosomes line up at the metaphase plate

● Microtubules are attached to each kinetochore

Anaphase

● Sister chromatids separate and move to opposite ends of the cell due to the microtubules shortening

● Cell elongates

Telophase and Cytokinesis

● Two daughter nuclei form

● Nucleoli reappear

● Chromosomes become less condensed

Cytokinesis in animals

a cleavage furrow appears due to a contractile ring of actin filaments

Cytokinesis in plants

Vesicles produced by the Golgi travel to the middle of

the cell and form a cell plate

How many chromsomes & chromatids are in each phase in mitosis

P-46, 92
M-46,92
A-92,92
T-92,92
C-46,46