Biological Organization

Organelles: Specialized Cellular Unit

Specialized, membrane-bound or non-membrane-bound subunits within a biological cell.

They compartmentalize tasks, maintain homeostasis, produce energy, and synthesize proteins to keep the cell alive.



Cell Wall

  • The cell wall is a characteristic feature of a plant cell.

  • It comprises the outermost layer of the cell.

  • The cell wall is made up of cellulose, hemicellulose, and pectin.

  • It protects the plasma membrane.

  • It is a rigid and immovable structure enclosing the cell membrane.

  • It protects the cells from mechanical shocks and damage while providing them 

with form and support.

  • Animal cells do not have a cell wall



Cell Membrane

  • A cell membrane surrounds the cell.

  • It protects a cell's integrity and regulates the flow of materials into and out of the cell. Additionally, the cell membrane is involved in communication between cells through receptor proteins that can interact with external signals.

  • The cell membrane proteins provide structural support, facilitate material transport, 

and act as receptor sites for substances and transport substances across the membrane.



Cytoplasm

  • The gel-like substance that fills a cell is called cytoplasm.

  • Cytoplasm functions as the site where various cellular processes occur, including metabolism, protein synthesis, and intracellular transport.

  • The cytoplasm of a cell performs every task necessary for cell division, growth

  • and replication.



Nucleus and Nucleolus

  • The nucleus is a specialized structure occurring in most cells and separated from the rest of the cell by a double layer,  called the nuclear membrane. 

  • The nuclear membrane surrounding the cell acts as a barrier, separating the nucleus from other cell parts.

  • Within the nucleus, the nucleolus stands out as a distinct region responsible for ribosome assembly.

  • It contains ribosomal RNA (rRNA) and combines with proteins to form ribosomes,

essential for protein synthesis


The nucleus and nucleolus play vital roles in controlling cellular activities, maintaining genetic integrity, and regulating gene expression.


Chromosomes

  • Thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of DNA that carries the genetic instructions used in the growth, development, and functioning of all living organisms.

  • They are a key part of the process that ensures DNA is accurately copied and distributed in the vast majority of cell divisions.


Endoplasmic Reticulum (ER)

  • Network of membranous tubules and sacs; rough ER has ribosomes attached, 

while smooth ER does not

  • Involved in protein and lipid synthesis and the transportation of molecules within the cell.

  • facilitates the transportation of molecules within the cell, ensuring proper cellular function and organization.


Golgi Bodies

  • Stack of flattened membrane-bound sacs (cisternae) with associated vesicles

  • Modify, sort, and package proteins and lipids for transportation or secretion.



Ribosomes

  • Made of ribosomal proteins and ribosomal RNA (rRNA) 

  • Occur both as free particles in prokaryotic and eukaryotic cells and as particles attached to the membranes of the ER in eukaryotic cells.

  • Serves as a site for protein synthesis  



Mitochondria

  • A double membrane-bound organelle with inner cristae folds; containing mitochondrial DNA (mtDNA)

  • Generates most of the chemical energy needed to power the cell's biochemical reactions ; also known as the "powerhouse" of the cell. 

  • Chemical energy produced by the mitochondria is stored in ATP, then generated through cellular respiration



Chloroplasts

  • Double membrane-bound organelles with internal thylakoid membranes

  • Site of photosynthesis in plant cells that contains chlorophyll for capturing light energy.



Vacuoles

  • Membrane-bound sacs filled with fluid or sap; larger in plant cells

  • Store water, nutrients, and waste; maintain turgor pressure in plant cells.



Lysosomes

  • Membrane-bound vesicles containing digestive enzymes

  • It breaks down waste materials, worn-out organelles, and foreign invaders.




Cell:The Fundamental Unit of Life

The cells are the fundamental structural,functional, and biological units of all living organisms. They contain the genetic material, convert nutrients into energy, and replicate independently.


Tissues

An organized group of similar cells and their surrounding extracellular matrix

that work together to perform a specific function.


Organ System

A group of anatomical organs that work together to perform a specific bodily function

and ensure the survival of an organism. It represents a higher level of biological organization, bridging individual organs to the whole living organism.


Organism

is any individual living thing that functions as a single system. To be classified as 

an organism, it must exhibit the fundamental characteristics of life: organized structure, metabolism, growth, adaptation, response to stimuli, and the ability to reproduce.


Population

refers to a group of individuals of the same species living in the same area at the same time. Members of a population interact with one another, compete for resources, and reproduce more of their own kinds.


Community

Consists of all the different populations living and interacting within a particular area. 

A community includes organisms of various species that depend on one another

through relationships such as predation, competition, mutualism, and parasitism.


Ecosystem

An ecosystem is formed when a community of living organisms interacts with the nonliving components of its environment.These nonliving, or abiotic, factors include sunlight, water, air, soil, temperature, and nutrients.


Biosphere

which encompasses all living organisms and all ecosystems on Earth. The biosphere represents the global ecological system in which all living things interact with one another and with the Earth's atmosphere, hydrosphere, and lithosphere.