Cell Structure

Lecture 5

The Cell

the smallest basic unit of life that makes up all living things and carries out the processes needed for survival

Prokaryotes

smaller single-celled organisms that do NOT have a nucleus or other membrane-bound parts inside their cells

Nucleoid

region where DNA is kept (only in Prokaryotes)

Ribosomes

tiny cellular structures in cytoplasm made of RNA and proteins that build proteins for the cell

Eukaryotes

bigger living organisms whose cells contain a distinct, membrane-bound nucleus and other specialized, membrane-bound structures called organelles (more complex than prokaryotes)

common features for all cells

1. Surrounded by plasma membrane

2. Unique internal environment

3. Store, replicate, transmit genetic information

4. Divide/reproduce

5. Metabolism

6. Interact with/respond to external environment

7. (Generally) limited in size

Nucleus

the membrane-enclosed control center in a cell that stores genetic material and directs cellular activities (has most DNA)

Nuclear envelope

a double-membrane barrier that surrounds and protects the genetic material inside the nucleus of eukaryotic cells (separates nucleoplasm from cytoplasm)…Passage via nuclear pores

mitochondria and chloroplast

Organelles acquired via endosymbiosis (big cell eats small cell but instead of being digested, the small cell becomes apart of the larger cell)

mitochondria

membrane-bound (outer and inner membrane) cellular structures known as the "powerhouses of the cell" because they convert nutrients into usable chemical energy (aerobic respiration)

chloroplasts

specialized plant and algal cell organelles that conduct photosynthesis by converting sunlight into chemical energy (divided into Outer membrane, inner membrane, innermost/thylakoid membrane)

endosymbiosis evidence

1. Double membranes

2. Similar size, morphology, enzymes, ribosomes to bacteria

3. DNA, sequences very similar to living bacteria

4. Divide via binary fission (how bacterial cells divide - origin for prokaryotic cells)

endomembrane system

an internal network of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins- Divides cell into compartments → membrane-bound organelles 

membrane

a thin, soft, flexible sheet or layer of phospholipids that acts as a selective barrier, allowing some substances to pass through while blocking others

Membrane Communication

the process by which cells receive, process, and transmit chemical and physical signals across their cell membrane to coordinate bodily functions and maintain homeostasis (1 space…like a nyc subway system)

vesicular transport

an active cellular process where substances are moved into, out of, or within a cell packaged inside small, membrane-bound sacs called vesicles

Components of Endomembrane System

Endoplasmic Reticulum (ER), Rough ER (RER), Smooth ER (SER), Golgi Apparatus, Vacuoles, Lysosomes

Endoplasmic Reticulum (ER)

a continuous network of membrane-enclosed sacs and tubes found inside the cytoplasm of eukaryotic cells, single continuous lumen (internal space), connected to outer membrane of nuclear envelope

Rough ER (RER)

a cell organelle that looks bumpy because millions of tiny protein-making particles called ribosomes are attached to its outer surface.

Transports the polypeptide into lumen —> proteins made

Smooth ER (SER)

a network of membrane-bound tubes inside eukaryotic cells that lacks ribosomes

Golgi Apparatus

a membrane-bound cell organelle that modifies, sorts, and packages proteins and lipids for transport (via vesicle)

Vacuoles

Large vesicles derived from endomembrane system that store water, nutrients, and waste materials

Lysosomes

a membrane-bound cell organelle (compartment) made in RER that contains digestive/hydrolytic enzymes to break down waste, old cell parts, and foreign invaders