Cell, CELL MEMBRANE and INTERCELLULAR JUNCTION Bakare, A. A.

-Cell is the basic functional and structural unit of life -Smallest unit capable of maintaining independent life

BASICA STRUCTURE Organelles are suspended in the cytosol which is embounded by cell membrane

Cell Cell membrane Cytoplasm Organelles Membranous Non-membranous STRUCTURAL COMPONET Cell Cell membrane Cytoplasm Organelles Membranous Non-membranous

Cell membrane Cell membrane or plasma membrane or cytoplasmic membrane It is a biological membrane that form cell boundary or surrounds the cell

FunctionS -Separates cell from external environment - Protects the cell from invasion or attack -Controls in the movement of molecules across the cell -Involves in a variety of cellular processes such as cell adhesion, ion channel conductance and cell signaling

Structure Phospholipd bilayer Each phospholipids has a head (hydrophilic) and tail (hydrophobic) region arranged with the heads at ends

Transmembrane Proteins Proteins are imbedded within the membrane They are permanently attached to the membrane passing from one side of a membrane to the other side of the membrane providing a channel through which molecules and ions can pass into the cell.

Cytoplasm: cytosol +organelles - It is enclosed by the cell membrane. The cytoplasm includes all of the material inside the cell or outside of the nucleus within the cell (nucleoplasm). It is made-up of ; 1. CYTOSOL 2. ORGANELLES

cytosol Jelly-like and colourless substance It is mainly composed ; water (80%) Salts Proteins.

FUNCTIONS of cytosol -Cytosol holds the internal components of cells in place - Maintain cell shape -Create cell Volume, because without it, organelles might collide against each other, resulting in damage -Material transport -Storage, liquid space such as vacuoles are form and act as storage until these materials are actually needed. -Medium for biochemical reactions

CELL ORGANELLES Specialized subunit within the cell with specific function. The basic principle is that organelle are to cell as what an organ is to the body They vary in terms of number and presence depending on the function and location of the cell

Membranous organelles Nucleus Endoplasmic reticulum Golgi apparatus Mitochondria Lysosome Vacuoles They are bound by unit membranes similar to the cell membrane They are more than the none-membranous organelles

Nucleus Largest membrane-bound organelle Usually located at the center of most cells. The viscous liquid within it is called nucleoplasm NB: Most cell have a single nucleus (eukaryotic), but a few cell types have no nuclei (anucleated) and a few others have many (multinucleated).

FUNCTIONS OF THE NUCLEUS Houses the genetic material thru its chromosome deposit Control protein synthesis thru ribosome production

STRUCTURE OF THE NUCLEUS The nucleus is surrounded by nuclear envelope/ membrane which form circular openings called nuclear pores The nuclear envelope consists of two membranes; -Inner membrane -Outer membrane, arranged parallel to one another. The nuclear envelope completely encloses the nucleus and separates the cell's genetic material from the surrounding cytoplasm, serving as a barrier to prevent macromolecules from diffusing freely between the nucleoplasm and the cytoplasm and otherwise if need be. The outer nuclear membrane is continuous with the membrane of the rough endoplasmic reticulum studded with ribosome

Substances that pass through the nuclear pore are: 1. Proteins 2. RNA (required for gene expression and the maintenance of chromosomes) Structures found within the nuclear space are: 1. Chromosomes (thread-like structures made of protein and a single molecule of deoxyribonucleic acid (DNA) that passes genetic information from parent to offsprings 2. Nucleolus

Nucleolus is the largest structure in the nucleus. It assembles ribosomal subunits to form ribosome (protein units of the cell) After being produced, the ribosome are exported to the cytoplasm.

Endoplasmic reticulum -It is a continuous network of highly branching tubular membranes within the cytoplasm. -It can either be *Rough ER *Smooth ER

Rough/Granular endoplasmic reticulum is studded with ribosome closely apposed to the nucleus It provides a pathway for the distribution of nuclear material into the cytoplasm. It involves in the none-membranous packaging of proteins/ribosome produced by the nucleolus. Being highly coiled in nature, it provides an increased surface area for various mechanical and enzymatic processes. It forms an internal supporting framework for the cell.

A site of lipid and carbohydrate synthesis Smooth / Agranular endoplasmic reticulum lacks ribosome. A site of lipid and carbohydrate synthesis Being highly coiled in nature, it provides an increased surface area for various mechanical and enzymatic processes. It forms an internal supporting framework for the cell.

Golgi apparatus -It is a flattened, layered, sac-like organelle. -The apparatus is usually located close to the nucleus and ER (where synthesis of protein, lipids and carbohydrate occurs). -It has two surfaces; CIS and TRANS -The Golgi body further packages/stores proteins and carbohydrates into membrane-bound vesicles for "export". -The Golgi apparatus gathers simple molecules from the nucleus and ER, packages them in vesicles to either stores them for later use or export them out of the cell. It is also responsible for building up lysosomes (cell digestion machines).

Mitochondria - Most important cell organelle -Site of energy production (ATP) for cellular processes. NB: Some cell lack mitochondria (red blood cells have no mitochondria), whereas some can have more than 2000 (liver cells) -It is made up of two membranes; *Outer membrane is smooth *Inner membrane is folded into tubular structures called cristae. -The matrix is the space enclosed by the inner membrane which contain enzymes

Lysosomes Are membrane bound cell organelle in the cytoplasm containing degradative or digestive enzymes (highly acidic fluid). The lysosome membrane ruptures releasing the enzymes to destroy bacteria and cell debris. It also brings about digestion of useful organic substances present in the cell (intracellular digestion). NB: Its membranous property is necessary because the lysosomal enzymes are capable of destroying the entire cell, membrane are ruptured when need arise hence commonly described as suicide bags or time bombs of the cell.

Vacuoles Are membrane bound storage medium of cell. They may store food or any variety of nutrients a cell need to survive or waste products so the rest of the cell is protected from contamination.

Non-membranous organelles These are cell organelles that are not membrane bound found closely within the cytoplasm Ribosome Cytoskeleton

Ribosome -Assemble proteins from RNA codes. -They are found free floating in the cytoplasm throughout the cell or attached to the rough endoplasmic reticulum

cytoskeleton Is a filamentous network to maintain /change cell shape and produce movements. -Microfilaments are the thinnest and most abundant of the cytoskeleton proteins. -Intermediate filaments are slightly larger -Microtubules are hollow tubes composed of a protein called tubulin (biggest).

NOTE!!! Surface extension of Cell Microvilli -Hair-like motile extensions on the surface of some cells. -It increases surface area for cellular processes

A flagellum is a longer lash-like attachment that protrudes from the cell membrane primarily for locomotion. It is found in bacteria and sperm cell

These are cell to cell contact or relationship Cell to cell junctions These are cell to cell contact or relationship

- Tight junction / occluding junctions / zonula occludens are closely associated areas of two cells whose cell/ plasma membranes join together on their lateral surfaces. This forms a virtually impermeable barrier to fluid serving as barriers of diffusion of molecules across the cells.

Gap junction is a specialized intercellular connection with aggregates of intercellular protein channels within the space across the intercellular space. Allows the exchange of nutrients, ions, signals between adjacent cells and are also able to communicate and coordinate their activity.

Desmosome/ macula adheren are very wide intercellular space with proteins embedded within it. The junctional complexes contain channels which permit ion flows and other passages.

Hemidesmosome are very small complexes located on the inner basal surface of cell connecting cell to basement membrane

APPLIED ANATOMY Cell culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. Plant tissue culture, fungal culture, and microbiological culture of microbes are important in getting best yield on plants and providing solution and treatment measures on microbes.

Cell death Clinical Anatomy Necrosis is sudden cell death which can occur as a result of infection, injury or radiation. Necrosis is detrimental and can be fatal Apoptosis is programmed cell death which often provides beneficial effects to the organism. It usually occurs during embryonic development.

Cancerous cell grow and divide uncontrollable to form lump (tumour) that grows in size. Cancerous cells are malignant which grow faster and spread to the surrounding tissues Causes; genetic factors, lifestyle factors such as; tobacco use, diet and physical activity, infections and environmental exposures to different types of chemicals and radiation. Treatment; chemotherapy, radiation, surgery ….