Biology Chapter on Cell Functions

Specialized cells with the same function group together to form tissues.

Different types of tissues work together to form an organ, which performs specific functions.

Organisms are made up of multiple organs that work together to maintain life functions.

The process of unspezialized (stem) cells developing into different types of cells with specific functions.

The special structure of a cell enables it to perform its specific function.

Projections on neurons that allow for communication between cells, facilitating rapid signal transmission in the nervous system.

Specialized cells in leaves responsible for photosynthesis.

Cells in leaves allowing for gas exchange.

Animal cells need to move actively for functions like cell migration and deformation, unlike plant cells which are relatively rigid.

The cytoskeleton is a network of fibers that provides structural support for the cell, allowing it to maintain its shape, resist external forces, and move.

The cytoskeleton forms specialized structures called spindle fibers during cell division. These fibers help separate the chromosomes during mitosis and meiosis.

Fluorescent dyes are used to bind to specific cellular proteins, then illuminated with UV light, causing them to emit visible light. This allows researchers to visualize and study specific cell structures.

The model compares the cell to a bustling festival, with different areas like food stalls and stages representing specialized functions and organelles within the cell.

This model compares the cell to an omelet, where ingredients are mixed and react with each other, analogous to the various molecules and reactions happening inside a cell.

The 'Oktoberfest Model' highlights organization and teamwork in the cell, with different functions being carried out in a coordinated manner.

Both models simplify complex cellular processes, sacrificing detailed molecular interactions and the simultaneous nature of many cellular processes.

The proteasome is a protein complex that acts as a "molecular shredder", breaking down damaged or no longer needed proteins in cells.

It removes damaged or malfunctioning proteins that could be harmful to the cell, ensuring the cell's health.

The proteasome regulates cellular processes by controlling the concentration of certain proteins through targeted degradation. It controls the level of specific proteins needed for different cellular functions.

The proteasome breaks down proteins into smaller peptides, which are used by the immune system for antigen presentation. This helps the body recognize and fight off invaders.

First, a protein destined for degradation is tagged with ubiquitin. Then, the tagged protein is transported to the proteasome. Inside the proteasome, the protein is broken down into smaller peptides. Finally, these fragments might be further used or disposed of.

The endoplasmic reticulum (ER) is a network of membranes that extends throughout the cytoplasm of eukaryotic cells. It plays a crucial role in protein synthesis, processing, and transport.

The rough ER (rER) is studded with ribosomes on its surface, actively involved in protein synthesis. It produces proteins for export or incorporation into membranes. The smooth ER (sER) lacks ribosomes and focuses on synthesizing lipids, phospholipids, and steroids. It also detoxifies substances and stores calcium ions.

Amylase is a digestive enzyme that breaks down starch. Its production involves multiple steps. First, the genetic information for amylase is stored in the nucleus of a salivary gland cell and transcribed into mRNA. Then, the rER translates the mRNA into amylase protein and folds it. The amylase is transported in vesicles from the ER to the Golgi apparatus. The Golgi apparatus modifies and sorts the amylase before it is released from the cell.

Specialized compartments within a cell, separated by biomembranes, allowing for the specialization of cell functions and the parallel execution of different chemical processes without interference.

A double layer of phospholipid molecules forming the structural basis of cell membranes. Each molecule has a hydrophilic head and two hydrophobic tails.

Proteins embedded within the lipid bilayer, spanning the entire membrane. They enable the transport of substances through channels or carrier proteins.

Proteins associated with the surface of the cell membrane, involved in signal transduction or anchoring the cytoskeleton.

An experimental technique where cell membranes are frozen and fractured, revealing an arrangement of proteins embedded in the lipid bilayer, supporting the fluid mosaic model.

The application of fluorescent dyes to label membrane proteins, demonstrating their movement within the cell membrane after cell fusion, supporting the fluidity of the membrane.

A model describing the structure of cell membranes as a fluid bilayer of phospholipids with proteins embedded within, allowing for flexibility and dynamic movement of components.

A model that incorporates the key properties of cell membranes, including the lipid bilayer, embedded proteins, and the fluidity of the membrane.

Gorter and Grendel extracted lipids from red blood cell membranes, spreading them on water to form a film. The film's area was double the cell's surface, suggesting a lipid bilayer with hydrophilic heads facing outward and hydrophobic tails inward.

This technique involves freezing cells, then splitting them along the lipid layer. An electron microscope revealed particles embedded in the membrane, identified as proteins, indicating their integration within the lipid bilayer.

Cells were labeled with fluorescent dyes, then fused. The dyes mixed uniformly within minutes, proving that membrane proteins can move laterally, highlighting the flexible and dynamic fluid mosaic structure.

A model describing the structure of cell membranes, where lipids form a flexible bilayer, with embedded proteins. The proteins can move laterally, contributing to the membrane's fluidity and function.

The movement of molecules from an area of higher concentration to an area of lower concentration, driven by the concentration gradient.

The difference in concentration of a substance between two regions.

A process where molecules move across a membrane from an area of high concentration to an area of low concentration, using a membrane protein as a channel.

Movement of molecules across a membrane against their concentration gradient, requiring energy.

LDL (low-density lipoprotein) particles transport cholesterol in the blood. When they reach the liver, they bind to LDL receptors on the liver cells.

In familial hypercholesterolemia, LDL receptors are either missing or malfunctioning. This prevents LDL particles from being taken up by liver cells, leading to high cholesterol levels in the blood.

Dendrites receive signals from other neurons and transmit them to the cell body (soma) as electrical signals.

The cell body (soma) integrates the signals received from dendrites and determines whether to trigger an action potential.

The axon transmits action potentials (electrical signals) from the cell body to the axon terminals.

Axon terminals (synapses) are the end points of an axon. They release neurotransmitters, which transmit signals to other neurons, muscles, or glands.

Myelin sheaths, formed by Schwann cells, insulate axons, allowing for faster transmission of action potentials.

Neurons have specialized structures like dendrites, axons, and synapses, which are absent in undifferentiated animal cells. These structures enable neurons to communicate efficiently through electrical and chemical signaling.