[RAP0 21LAB] PRELIM: Lesson 2 Cell Level

Cell Level

Cell levels

• It refers to the structure, types, and functions of ___, which are the basic building blocks of life.

• Each type of ___ in the human body has unique functions tailored to its role within tissues, organs, and systems.

Plasma Membrane; Cytoplasm; Nucleus; Organelles

4 Composition of Cells

Plasma Membrane

• Maintains structure and regulates the flow of substances.

• It is primarily composed of a phospholipid bilayer interspersed with proteins, carbohydrates, and cholesterol

Phospholipids

• These have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails, forming a bilayer.

• These were first identified in the human brain by Uauquelin in 1812 and isolated from egg yolks by Gobley in 1844.

• In 1850, Gobley named them lecithin, derived from the Greek word “lekithos,” meaning yolk.

Proteins

Embedded in the membrane, they act as channels, carriers, receptors, and enzymes.

Cholesterol

Provides stability and fluidity to the membrane.

Carbohydrates

Often attached to proteins (glycoproteins) or lipids (glycolipids), they play a role in cell recognition and signaling.

5 Functions of Plasma Membrane

1. Selective Permeability

2. Communication

3. Transport

4. Cell Recognition

5. Structural Support

Selective Permeability

• Functions of Plasma Membrane

• The plasma membrane regulates what enters and exits the cell, maintaining homeostasis.

Communication

• Functions of Plasma Membrane

• Contains receptors that allow cells to receive and respond to signals (e.g., hormones, neurotransmitters).

Transport

• Functions of Plasma Membrane

• Passive and Active Transport

Passive transport

• Functions of Plasma Membrane

• Transport

• Movement of molecules without energy (e.g., diffusion, osmosis).

Active transport

• Functions of Plasma Membrane

• Transport

• Movement of molecules against their gradient using energy (ATP).

Cell Recognition

• Functions of Plasma Membrane

• Glycoproteins and glycolipids enable the immune system to recognize the body's own cells.

Structural Support

• Functions of Plasma Membrane

• Anchors cytoskeletal elements, providing shape and stability to the cell.

Fluid Mosaic Model

• The plasma membrane is described as a ___, meaning:

  • The phospholipid bilayer is fluid, allowing movement of its components.

  • Proteins are dispersed throughout the membrane, forming a mosaic pattern.

Fluid Mosaic

• The phospholipid bilayer is fluid, allowing movement of its components.

• Proteins are dispersed throughout the membrane, forming a mosaic pattern.

Cytoplasm

• It is a fundamental component of cells in human anatomy, found within the plasma membrane but outside the nucleus.

• It is a gel-like substance that houses the cellular organelles and provides the environment for many biochemical processes essential for cell survival.

Cytosols; Organelles; Cytoskeleton

3 Structures of Cytoplasm

Cytosol

• The liquid part of the cytoplasm, a water-based solution containing ions, enzymes, nutrients, and waste products.

• It is the medium through which molecules move within the cell.

• It is a gel-like substance primarily composed of water, dissolved ions, small molecules, and soluble macromolecules like proteins.

• It serves as the medium where various cellular processes occur, such as signal transduction, metabolic pathways, and protein synthesis.

Organelles

• They are specialized structures within cells that perform distinct functions, similar to organs in the body but at the cellular level.

• They are essential for maintaining the life and functionality of cells.

Nucleus

• Function: Acts as the control center of the cell; stores the cell's genetic material (DNA) and coordinates activities like growth, metabolism, and reproduction.

• Contains the nucleolus (where ribosomes are made).

Mitochondria

• Function: Known as the powerhouse of the cell; produces energy in the form of ATP through cellular respiration.

• Has its own DNA and a double membrane.

Ribosomes

• Function: Synthesizes proteins by translating mRNA.

• Found floating in the cytoplasm or attached to the rough endoplasmic reticulum.

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes; synthesizes and transports proteins.

• Smooth ER: Synthesizes lipids, detoxifies chemicals, and stores calcium ions.

Rough ER

• Type of Endoplasmic Reticulum (ER)

• Studded with ribosomes; synthesizes and transports proteins

Smooth ER

• Type of Endoplasmic Reticulum (ER)

• Synthesizes lipids, detoxifies chemicals, and stores calcium ions.

Golgi Apparatus

Function: Modifies, sorts, and packages proteins and lipids for transport or secretion.

Lysosomes (in animal cells)

• Function: Contains enzymes that break down waste materials and cellular debris.

• Acts as the cell’s recycling center.

Peroxisomes

Function: Breaks down fatty acids and detoxifies harmful substances like hydrogen peroxide.

Plasma Membrane

• Function: Controls what enters and exits the cell; provides protection and structural support.

• Composed of a phospholipid bilayer with embedded proteins.

Cytoskeleton

• Function: Provides structural support, facilitates movement, and helps transport materials within the cell.

• Components: Microfilaments, intermediate filaments, and microtubules.

Chloroplasts (in plant cells)

• Function: Site of photosynthesis; converts sunlight into energy stored in glucose.

• Contains chlorophyll and its own DNA.

Vacuoles

• Function: Stores nutrients, waste products, and water; maintains cell turgor pressure.

• Large central ___ in plant cells; smaller ones in animal cells.

5 Functions of the Cytoplasm

1. Supports Organelles

2. Site of Metabolic Activity

3. Intracellular Transport

4. Maintains Cell Shape

5. Stores Molecules

Supports Organelles

• Functions of the Cytoplasm

• Provides a medium to suspend and stabilize the cell’s organelles.

Site of Metabolic Activity

• Functions of the Cytoplasm

• Many vital processes occur in the cytoplasm, such as glycolysis and protein synthesis.

Intracellular Transport

• Functions of the Cytoplasm

• Facilitates the movement of materials (e.g., organelles, vesicles, and molecules) within the cell.

Maintains Cell Shape

• Functions of the Cytoplasm

• The cytoskeleton within the cytoplasm helps maintain the cell’s structural integrity.

Stores Molecules

• Functions of the Cytoplasm

• Reserves nutrients and ions needed for cellular functions.

Cytoplasm in Specialized Cells

In some human cells, the cytoplasm is tailored for specific functions

Muscle cells; Neurons; Red blood cells

Functions of Cytoplasm in Specialized Cells

Muscle cells

• Functions of Cytoplasm in Specialized Cells

• Contain abundant mitochondria in the cytoplasm to meet high energy demands.

Neurons

• Functions of Cytoplasm in Specialized Cells

• Cytoplasm extends into axons and dendrites, aiding in signal transmission.

Red blood cells

• Functions of Cytoplasm in Specialized Cells

• Lack a nucleus and most organelles, with the cytoplasm primarily housing hemoglobin.