Part 1: The Cell Membrane

Definition

• Also called Plasma membrane.

• Plasma membrane has a double layer of phospholipid molecules.

• A phospholipid molecule is made up of glycerol which is a phosphate group and two chains of fatty acid.

• Protein molecules are also found embedded in phospholipids.

• The membrane is composed of both protein and phospholipid molecules.    

• Serves as the boundary between the outside environment and the inside of the cell.

• Gives form and shape to the cells.

• Connects one cell to two or more adjacent cells.

Functions

Osmosis

• It is the spontaneous movement of solvent molecules through a semi-permeable (selective of what goes in and out) membrane.

• The region of the higher solute concentration tends to equalize the lower solute concentration.

• Is an essential process by means of which nutrients are delivered to the cells.

Diffusion

• It is the movement of molecules from a region of high concentration to a region of low concentration.

Transporters

• It lets nutrients enter the cell and by–products to leave the cell.

• Sugar to glucose to energy

Endocytosis

• It is the process in which cells absorb molecules by engulfing them.

• The cell creates a small deformation inward called invagination.

Phagocytosis

• Cell eating

Pinocytosis

• Cell drinking

Exocytosis

• It removes undigested residue of a substance brought in by endocytosis.

• It also secretes substances such as hormones and enzymes.

• Pathway

Part 2: Protoplasm and Organelles

Protoplasm

• These are the plasma or mass of jelly-like materials inside the cell.

• A protoplasm can change into a semisolid gel to semiliquid solution.

• protoplasm:

  • proto = first

  • plasm = substance 

• is divided in two forms

  • Liquid  

  • Jelly

Protoplasm is composed of:

• 20% Carbon

• 10% Hydrogen

• 62% Oxygen

• 3% nitrogen

• 5% other elements.

Organelles

Major Organelles

1. Mitochondria

• (singular: Mitochondrion)

• These are the microscopic rod–shaped bodies in the cytoplasm.

• They are the centers of cellular respiration, a process in which it produces energy–rich adenosine triphosphate (ATP)

• ATP is a high – energy compound in cells that functions in energy storage and transfer.

• If there is an absence of nucleus, Mitochondria takes over the place.

Ribosomes

• All throughout the cytoplasm are tiny structures.

• These organelles are composed of nucleic acid.

• Made up of protein.
  Protein is synthesized produce in the ribosome

• It serves as the site of biological protein synthesis or translation.

• Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules.

• Ribonucleic acid

• Translation

  • Is the process in which ribosomes create proteins in the cytoplasm.

  • Ex. Ribosomes produce protein

• Amino acids

  • Elements that are present are carbon, hydrogen, oxygen, and nitrogen.

  • It is important in biosynthesis.

  • It is the final product of protein digestion.

• mRNA

  • It conveys genetic information from DNA

  • Function: delivers genetic information to DNA

3. Endoplasmic Reticulum

• It forms a network of tiny canals throughout the cell.

• Function: transports the proteins and other molecules to other parts of the cell.

  Two types of Endoplasmic Reticulum:

  • Rough Endoplasmic Reticulum

  • Smooth Endoplasmic Reticulum

• Rough Endoplasmic Reticulum

  Function: the rough ER helps the proteins stay organized

• Smooth Endoplasmic Reticulum

  Function: The main function of the smooth ER is synthesizing the lipids used in the cell membrane.

Packaging Counter of the Cell

1. Golgi Bodies

• It is the major collection and dispatch station of protein products received from the endoplasmic reticulum (ER).

• Function: enhance the proteins and lipids, make secrete mucus, package product into vesicles for transport.

• Proteins synthesized in the ER are packaged into vesicles which fuse with the Golgi apparatus.

• The cargo proteins are modified and secreted via exocytosis.

• Same as post office, Golgi Bodies package and label items which it then sends to different parts of the cells.

• Function: move materials within the cell.

• Structure of Golgi Bodies

  • Golgi Apparatus is made up of a series of compartments consisting of two networks:

    • Cis Golgi Network (CGN)

    • Trans Golgi Network (TGN)

• CIS Golgi Network

  • Is a collection of fused, flattened membrane – enclosed cisternae, originating from a vesicular cluster that buds off the endoplasmic reticulum.

  • Entrance of proteins 

• Trans Golgi Network

  • It is the final cisterna structure, from which protein are package into vesicles destined to: Lysosomes, Secretory vesicles, or the cell surface.

• Exit of molecules (proteins).

Storage Tank of the Cell

1. Vacuoles 

• It is a membrane that is present in all plants and fungal cells. 

• They are essentially enclosed compartments that are filled with water containing organic and inorganic molecules.

The functions of the vacuole are:

• Isolating materials that might be harmful or a threat to the cell.

• Containing waste products

• Containing water in plant cells

• Allow plants to support structures such as leaves and flowers.

• Plant Vacuole typically occupies more than 30% of the cell’s volume, and that can occupy as much as 80% of the volume for certain cell types and conditions.

• Function: storage area for water, salts, proteins and carbohydrates.

• A sac like structure.

Structure of a Vacuole

• Tonoplast

  • Also known as vacuolar membrane.

  • A membrane that surrounds the vacuole.

  • It separates the vacuole content from the cytoplasm.

• Cell sap

  • Water like content that fills the vacuole.

Suicide Bag of the Cell

1. Lysosomes 

• It acts as the waste disposal system of the cell by digesting the unwanted materials in the cytoplasm.

• Function: to destroy any foreign material which enter the cell such as bacteria and virus, to protect the cells from infection

Cell Division

1. Centrosomes

• It is a mass of dense protoplasm with structures called centrioles at the center

• Function: responsible for the regulation of cell division

2. Centrioles

• It is a part of the cytoplasm, duplicated and formed at the center for spindle fiber formation during the cell division.

• Function: help with cell division, microtubules form spindle fibers for nuclear division.

Organelles Peculiar to plant cell

1. Cell Wall

• A structural layer surrounding some types of cells, located outside the cell membrane.

• Provides both structural support and protection, and acts as a filtering mechanism.

Structure of a cell wall

• A cell wall has three layers:

  • Primary Cell Wall

  • Secondary Cell Wall

  • Middle Lamella

Primary Cell Wall

• Generally, a thin, flexible and extensible layer forms while the cell is growing.

Secondary Cell Wall

• A thick layer forms inside the primary cell wall after the cell is fully grown.

Middle Lamella

• A layer rich in pectin.

• This is the outermost layer that forms the interface between adjacent plant cells and glues them together.

2. Pectin

• It makes the cell strong.

• But in fruits, the pectin loosens in the cell that results in softening of the fruit.

3. Plastids

• These are the large membrane – bound organelles found in the cytoplasm of plant cells.

4. Chromoplasts

• These are classified as the colored plastids.

  • Carotenoids

    • Various yellow or orange pigments.

    • These chromoplasts also may give flowers, ripened fruits, and autumn leaves their characteristic yellow or orange color.

  • Rhodoplast

    • Chromoplast with red pigment.

  • Leucoplast

    • These are the colorless plastids that serve as food storehouses in many plant cells.

    • They contain oil, starch grains, and proteins, as well as enzymes necessary to link glucose molecules together and form starch molecules.

5. CHLOROPHYLL

• Is very essential in the manufacture of food by green plants. 

Part 3: The Nucleus

Nucleus

• Latin: Nuculeus – kernel or seed

• Contains most of the cell’s genetic material, organized as multiple long layers of DNA molecules with a large variety of proteins to form chromosomes.

• Function: The nucleus maintains the integrity of genes and controls the activities of the cell by regulating the genes expression.

Gene Expression

• It is the process by which information from a gene is used in synthesis.

• It involves transcription (DNA use as a template to produce RNA)

• Using DNA code to create a protein that control a specific trait in expressing genetic information

Nuclear Envelope

• Is composed of a phospholipid bilayer membrane (outer membrane and inner membrane) that encloses the entire organelle and isolates its contents from the cellular cytoplasm. Also called nucleus 

• The nuclear envelope allows the nucleus to control its contents and separate them from the rest of the cytoplasm.

• Function: Regulates the movement of molecules into and out of the cell.

Nuclear Pores

• Helps to regulate nuclear transport of molecules across the envelope.

• Function: Allows passage between the nucleus and cytoplasm.

Function of the Nucleus

• The nucleus provides a site for genetic transcription.

• Responsible for gene expression

• Cell compartmentalization

• Processing pre-mRNA (mRNA being exported to the cytoplasm)

Cell Function

• All the life processes of a living cell involve transformation of energy and matter. 

A living cell performs the following life processes:

Nutrition

• It is the process by which cells obtain food molecules to support their other activities.

Digestion

• It is the process by which food particles are broken down into smaller soluble units suitable for cell use, with the help of enzymes.

Absorption

• It is the process by which cells absorb water, minerals, and other materials essential to life from their environment.

Movement

• It is the process which includes the locomotion of cells by means of special structures like cilia and flagella.

Irritability

• How cells respond or react to external factors or conditions around them.

• Cells can alter their functions in response to changes in their environment.

Respiration

• It is the process of breaking down food molecules into chemical energy needed by all cells in order to function.

Reproduction

• It is a process by which a cell copies or replicates its DNA and increases its number by cell division. In reproduction, cells give rise to new cells.

Additional Facts

• Ribosomes are the most important organelles

• Remember the size of large virus and bacteria

• Prokaryotes are the simplest cellular organisms

• Flagella (flagellum) is longer that pili (pilus)

• Genetic material is not separated from the cytoplasm

• Cytoskeleton is the framework for cells

• Distinguishing characteristic of eukaryotic cell is the NUCLEUS

• In eukaryotic, each compartment can provide specific conditions favoring a particular process

• Chromatin is found if cell is not dividing

• Chromosomes (the membranes are removed) in cell division

• Golgi complex, Golgi apparatus, Golgi bodies

• Plasma membrane is conceptualized as fluid mosaic model (patches because of proteins)

• Endocrine glands are ductless, hormones pass through blood streams

• Cell service proteins that serve as markers for them to know their target destinations

• Cholesterol affects the fluidity of cells

• Nuclear surface is perforated with nuclear pores for passage between nucleus and cytoplasm

• Ribosomes in the cytoplasm only make proteins for its cell

• Ribosomes from the ER make proteins for its neighboring cells.

• Pathogens are invaders

• Lysosomes are single membrane

• Mitochondria and chloroplasts have double membrane

• Study parts of plant cell from the ppt

• Symbiosis – two organism benefit from each other

• Endosymbiosis – single membraned ancient bacteria enter pre-eukaryotic cell and transform into mitochondria and chloroplast

• Ancient bacteria will have habitat. They will have sugar, lipids, and proteins as their benefit in the symbiosis.

• Meanwhile, pre-eukaryotic cell will benefit from the created mitochondrion and chloroplast 

• Actin filament (microfilament) is the thinnest

• Intermediate filament if the thickest