bio cells :(

Cell

The basic structural and functional unit of all living organisms capable of performing essential life processes independently

Cell Theory

Proposed by Schleiden and Schwann later modified by Virchow states that all living organisms are composed of cells the cell is the basic unit of life and all cells arise from pre-existing cells

Historical Aspects of Cell Theory

The discovery of cells by Robert Hooke in 1665 Schleiden and Schwann's cell theory and Virchow’s contribution that all cells arise from pre-existing cells

Size and Shape of Cells

Varies depending on function smallest cell is Mycoplasma largest single cell is an ostrich egg cells may be spherical elongated spindle-shaped or irregular

Prokaryotic Cell

A simple unicellular organism without a well-defined nucleus and membrane-bound organelles with DNA present in a nucleoid example Bacteria and Archaea

Structure of Prokaryotic Cell

Consists of a cell envelope plasma membrane cell wall and glycocalyx cytoplasm ribosomes plasmids and flagella

Differences between Prokaryotic and Eukaryotic Cells

Prokaryotic cells lack a nucleus have circular DNA no membrane-bound organelles and smaller ribosomes while eukaryotic cells have a true nucleus linear DNA and membrane-bound organelles

Eukaryotic Cell

A complex cell with a well-defined nucleus and membrane-bound organelles found in plants animals fungi and protists

Differences between Plant and Animal Cells

Plant cells have a cell wall plastids and large central vacuoles while animal cells lack a cell wall have centrioles and small vacuoles

Cell Envelope

The outermost covering of prokaryotic cells consisting of glycocalyx cell wall and plasma membrane

Plasma Membrane

A selectively permeable membrane made of a phospholipid bilayer with embedded proteins controlling the entry and exit of substances

Fluid Mosaic Model

Proposed by Singer and Nicolson describes the plasma membrane as a dynamic structure where proteins are embedded within a fluid phospholipid bilayer

Functions of Plasma Membrane

Selective permeability transport of molecules cell signaling enzymatic activity and structural support

Active and Passive Transport

Active transport requires ATP example sodium-potassium pump while passive transport does not require energy example diffusion and osmosis

Facilitated Diffusion

Passive transport assisted by membrane proteins includes uniport single molecule movement symport two molecules moving together and antiport two molecules moving in opposite directions

Cell Wall

A rigid outer layer found in plant cells fungi and bacteria providing shape protection and preventing excessive water uptake

Composition of Cell Wall

Made of cellulose in plants chitin in fungi and peptidoglycan in bacteria

Plasmodesmata

Cytoplasmic channels between adjacent plant cells that allow transport and communication

Mitochondria

The powerhouse of the cell responsible for ATP production through aerobic respiration

Structure of Mitochondria

Contains an outer membrane an inner membrane with cristae which are folds an intermembrane space and a matrix with circular DNA and ribosomes

Nucleus

The control center of the cell containing genetic material DNA that regulates all cellular functions

Nuclear Membrane

A double membrane surrounding the nucleus with nuclear pores allowing exchange of materials between the nucleus and cytoplasm

Chromatin

A network of DNA and proteins called histones that condenses to form chromosomes during cell division

Nucleolus

A dense spherical structure inside the nucleus responsible for the synthesis of ribosomal RNA rRNA and assembly of ribosomal subunits

Structure of Chromosomes

Composed of chromatin DNA and proteins with a centromere dividing it into arms

Types of Chromosomes based on Centromere Position

Metacentric centromere in the middle submetacentric centromere slightly off-center acrocentric centromere near one end and telocentric centromere at the terminal end

Satellite Chromosomes

Chromosomes with secondary constrictions involved in ribosomal RNA synthesis

Plastids

Double-membrane organelles in plant cells classified into chloroplasts chromoplasts and leucoplasts

Chloroplasts

Green plastids containing chlorophyll responsible for photosynthesis

Structure of Chloroplasts

Contains an outer membrane an inner membrane stroma thylakoids stacked into grana and circular DNA

Chromoplasts

Contain carotenoid pigments that provide red yellow and orange colors in flowers and fruits

Leucoplasts

Colorless plastids involved in the storage of starch called amyloplasts proteins called proteinoplasts and lipids called elaioplasts

Endomembrane System

A network of membranes that includes endoplasmic reticulum Golgi complex lysosomes and vacuoles

Endoplasmic Reticulum ER

A network of interconnected tubules involved in protein and lipid synthesis classified as rough ER RER and smooth ER SER

Rough Endoplasmic Reticulum RER

Has ribosomes attached to its surface and is involved in the synthesis and transport of proteins

Smooth Endoplasmic Reticulum SER

Lacks ribosomes and is involved in lipid synthesis detoxification of drugs and calcium ion storage

Golgi Complex

A stack of flattened membranes responsible for modifying packaging and sorting proteins and lipids for secretion or transport within the cell

Lysosomes

Membrane-bound vesicles containing hydrolytic enzymes that digest cellular waste and foreign substances

Vacuoles

Membrane-bound sacs involved in storage of water ions and waste materials larger in plant cells than animal cells

Ribosomes

Non-membrane bound organelles made of RNA and proteins involved in protein synthesis found freely in cytoplasm or attached to RER

Microbodies

Small single-membrane organelles like peroxisomes and glyoxysomes involved in various metabolic reactions

Peroxisomes

Contain enzymes that break down hydrogen peroxide into water and oxygen

Glyoxysomes

Found in germinating seeds involved in lipid metabolism

Cytoskeleton

A network of protein filaments providing structural support movement and intracellular transport

Microfilaments

Actin-based structures responsible for cell movement cytokinesis and cytoplasmic streaming

Microtubules

Hollow tubulin-based structures involved in maintaining cell shape intracellular transport and spindle fiber formation

Intermediate Filaments

Provide mechanical strength and stability to the cell

Cilia

Short hair-like projections that aid in locomotion and movement of substances over the cell surface

Flagella

Long whip-like structures that aid in locomotion found in sperm cells and some microorganisms

Centrioles

Cylindrical structures made of microtubules arranged in a nine plus zero pattern playing a role in cell division