Topic 3B

Cytoplasm: Material between plasma membrane and nucleus.
- Cytosol: Solution where cellular materials are suspended.
- Organelles: Specialized structures within cells with unique functions.
- Inclusions: Chemical substances like stored nutrients, lipid droplets, or pigments.

Membrane-bound organelles:
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Peroxisomes
- Lysosomes
Non-membrane bound organelles:
- Ribosomes
- Cytoskeleton
- Centrioles
Membrane Function: Compartmentalization and maintenance of distinct environments for organelles.

Function: Provide ATP through aerobic cellular respiration (utilizes glucose and oxygen).
Structure:
- Double membrane with cristae (folds within the mitochondria that increase surface area).
- Inner membrane contains proteins; outer membrane is smooth.
- Matrix: Inner section containing enzymes and substrates.
Unique Features:
- Contain own DNA and RNA;
- Resemble bacterial cells (potential evolutionary symbiosis);
- Can increase or decrease in number based on energy needs.

Type: Non-membrane bound organelles.
Function: Site of protein synthesis; contains ribosomal RNA (rRNA).
Two Forms (dictated by proteins being produced):
- Free Ribosomes: Floats around the cell, synthesizes soluble proteins.
- Membrane-bound Ribosomes: Attached to the rough ER, synthesizing proteins for secretion or membrane incorporation.

Structure: Membranous tubes enclosing fluid-filled interiors, continuous with the nuclear envelope.
Types:
- Rough ER: Studded with ribosomes; synthesizes secreted or membrane proteins.
- Smooth ER: Lacks ribosomes; involved in lipid metabolism, detoxification, and calcium ion storage.

Structure: Stacked, flat membranous sacs.
Function: Modifies, concentrates, and packages proteins/lipids received from the rough ER.

Structure: Membranous sacs containing detoxifying substances.
Function: Neutralize toxins such as free radicals; breakdown and synthesis of fatty acids.

Structure: Membranous structures filled with digestive enzymes (acid hydrolases).
Function: Digest ingested bacteria, viruses, and toxins, as well as degrade organelles and facilitate autophagy (self-digestion).
Autophagy: cell digesting itself

Components:
- Includes ER, Golgi apparatus, secretory vesicles, lysosomes, and nuclear/plasma membranes.
Function: Together, these organelles produce, degrade, store, and export biological molecules and eliminate harmful substances.

Description: Complex network of protein rods providing scaffolding for the cell and aiding in movement of cell components.
Types:
- Microfilaments:
  - Thinnest, dynamic actin strands involved in cell motility.
  - Involved in changing cell shape, endocytosis, and exocytosis
  - Strengthens cell surface and helps to resist tension
- Intermediate Filaments:
  - Tough, ropelike fibers providing structural support; stabilizes cell connections.
  - Bigger than microfilaments, smaller that microtubles
  - help cell resist pulling forces
  - can be known as neurofilaments (nerve cells) and keratin filaments (epithelial cells)
- Microtubules:
  - Largest, hollow tubes forming tracks for organelle movement and determining cell shape.
  - Made up of tubulin proteins
  - Help resist compression

Function: Fingerlike extensions increasing surface area for absorption, composed of actin microfilaments.
- Can be found in the intestinal tracts and kidney tubules cells

Centrosome: Microtubule organizing center; contains centrioles.
Function: Anchor microtubules, aid in cell division, and serve as building blocks for cilia and flagella.

Function: Cilia are motile extensions that move substances across cell surfaces; flagella propel whole cells (e.g., sperm).
Structure: Composed of microtubules synthesized by centrioles.

Function: Largest organelle housing genetic information and directing protein synthesis.
Characteristics: Most cells are uninucleate, some are multinucleate or anucleate.

Double membrane separating nucleoplasm; outer layer continuous with rough ER, inner layer lined with nuclear lamina proteins that maintain nuclear shape
Nuclear pores: Allow movement of substances in and out, regulated by nuclear pore complexes.

Function: Site of ribosomal RNA synthesis and assembly of ribosome subunits.

Composition: 30% DNA strands, 60% histone proteins, and 10% RNA. Arranged in fundamental units called nucleosomes
Function: Condensed into chromosomes during cell division for DNA protection.

Process: DNA is transcribed (transcription) into RNA within the nucleus, which is then translated (translation) into proteins.

Apoptosis: Programmed cell death, involving mitochondrial membranes leaking chemicals that activate enzymes called caspases. This process does not use lysosomes
- Capsases cause the degradation of DNA and cytoskeleton
Autophagy (self-eating/organelle recycling): Removal of damaged organelles via autophagosomes that fuse with lysosomes.
Proteasomes(protein recycling): 4 ubiquitins mark unneeded proteins that are disassembled for recycling.

All cells share the same DNA but differ in function through gene expression during development (differentiation).

Cell division is needed for growth
- Needed in adults to replace cells and wounds
Hyperplasia: accelerated growth that increases cell numbers when needed
Atrophy: decrease in size that results from loss of stimulation or use

Aging Mechanisms: Various theories include wear and tear, mitochondrial failure, immune system decline, and genetic programming.
Telomeres: Strings of nucleotides that protect chromosome ends; their shortening (happens when cell divides) relates to aging and cancer.
- Telomerase is responsible for the growth of Telomeres; its found in germ cells of embryo (unborn babies) and present in cancer cells (adults)