[HEMA-LEC] CELLS

Cells

Cells

Structural units that constitute living organisms.

Plasma Membrane

Separates the cytoplasm and cellular components from the extracellular environment.

Plasma Membrane
Membrane-bound Nucleus
Other unique subcellular structures and organelles

Regardless of shape, size, or function, human cells contain

1. Provides a physical but flexible barrier to contain and protect cell components from the extracellular environment.

2. Regulates and facilitates the interchange of substances with the environment by endocytosis, exocytosis, and selective permeability (using various membrane channels and transporters).

3. Establishes electrochemical gradients between the interior and exterior of the cell.

4. Has receptors that allow the cell to respond to a multitude of signaling molecules through signal transduction pathways.

Functions of Plasma Membrane

Cell surface glycoprotein
Glycolipid molecules

Used for Blood Cell Identity which are located in the Membrane

Flow Cytometry

Antigen-specific monoclonal antibodies enable identification of these antigens using ______.

Cluster of Differentiation (CD System)

International nomenclature in which a number was assigned to each identified blood cell antigen

More than 400 CD

Number of CD antigens identified on blood cells

Resilient
Elastic

The cell membrane has a fluid structure of proteins floating in lipids for it to be ____ and _____.

Phospholipids
Cholesterol

Two lipids that are arranged in two layers

Polar-Charged Hydrophilic

The phosphate end of the phospholipid and the hydroxyl radical of cholesterol

Nonpolar-Charged Hydrophobic

Fatty acid chains of the phospholipids and the steroid nucleus of cholesterol

Transmembrane
Cytoskeletal

Two types of Proteins in the Membrane

Transmembrane Proteins

In Membrane Proteins:

Functions as receptor and adhesion molecules.

It serves as channels and transporters of water, ions, and other molecules between the cytoplasm and the external environment.

Cytoskeletal Proteins

In Membrane Proteins:

Provide structural integrity to the cell and vertical support in linking the membrane to the cytoskeleton.

Glycocalyx

An external protective carbohydrate coating

Cell-to-cell recognition and adhesion

The carbohydrate moieties function in ______ and _______ and provide a negative surface charge to repel adjacent cells in circulation.

Nucleus

The control center of the cell and the largest organelle within the cell.

Site of DNA replication and transcription

Chromatin
Nuclear Envelope
Nucleoli

Composition of the Nucleus

Chromatin

Consists of one long molecule of double- stranded DNA in each chromosome that is tightly folded with histone and nonhistone proteins.

Formation of nucleosomes along the length of the DNA molecule

The first level of folding

11 nm in length

Length of each Nucleosome

150 Base Pairs of DNA

Base pairs of DNA in each Nucleosome

30 nm chromatin fibers

The Nucleosomes are folded into _____.

Heterochromatin
Euchromatin

Two division of Chromatin

Heterochromatin

In Two division of Chromatin:

Has a more darkly stained, condensed clumping pattern

Transcriptionally inactive area of the nucleus.

Euchromatin

In Two division of Chromatin:

Has a diffuse, uncondensed, open chromatin pattern.

Loosely coiled and turns a pale blue when stained with Wright stain.

Pale Blue

Color of Euchromatin when stained with Wright Stain

Nuclear Envelope

Consists of two phospholipid bilayer membranes.

Nucleoli

The site of ribosomal RNA (rRNA) production and assembly into ribosome subunits.

NOTE: Number of nucleoli in the nucleus is proportional to the amount of protein synthesis that occurs in the cell

NOTE: Number of nucleoli in the nucleus is proportional to the amount of protein synthesis that occurs in the cell

Cytosol

The cytoplasmic matrix is a homogeneous, continuous, aqueous solution

Cytoplasm

It is the environment in which the organelles exist and function

Ribosomes

Macromolecular complexes composed of a small and large subunit of rRNA and many accessory ribosomal proteins.

Serve as the site of protein synthesis.

Endoplasmic Reticulum

A membrane-bound, interconnected network of flattened sacs and tubes located adjacent to the nucleus and extending throughout the cytoplasm.

Cisternae

A system of stacked, membrane-bound, flattened sacs

Involved in modifying, sorting, and packaging macromolecules for secretion or delivery to other organelles

Golgi Apparatus

May be observed as an unstained region next to the nucleus in stained bone marrow smears of developing white blood cell precursors

Cis Face

Where Vesicles containing membrane-bound and soluble proteins from the RER enter the Golgi network

Trans Face

Where Vesicles with processed proteins exit the Golgi

Cristae

Internal ridges where oxidative enzymes are attached

Convolution of inner membrane

Increases the surface area to enhance respiratory capability of the cell

Mitochondria

Generate the most of the adenosine triphosphate (ATP) for the cell

Mitochondrial Matrix

The interior of the mitochondrion consists of a homogeneous material

NOTE: Mitochondrial enzymes oxidize pyruvate and fatty acids → Acetyl CoA → Citric Acid oxidizes the Acetyl CoA producing electrons → Electron-Transport Pathway

NOTE: Mitochondrial enzymes oxidize pyruvate and fatty acids → Acetyl CoA → Citric Acid oxidizes the Acetyl CoA producing electrons → Electron-Transport Pathway

Electron-phosphate pathway

Generates ATP through oxidative phosphorylation

NOTE: Number of Mitochondria directly related to the amount of energy required per cell

NOTE: Number of Mitochondria directly related to the amount of energy required per cell

Less than 100 or up to several thousand mitochondria

Amount of Mitochondria per cell

Lysosomes

Contain hydrolytic enzymes bound within a membrane and are involved in the cell’s intracellular digestive process

Granules in white blood cells and platelets

Visualization of Lysosomes in Wright Stain

Gaucher Disease
Tay-Sachs Disease

Examples of Lysosomal lipid storage diseases

Actin Microfilaments

Double stranded, intertwined solid structures approximately 5 to 7 mm in diameter

Associate with myosin

Intermediate Filaments

Diameter of approximately 8 to 10 nm, self-assemble into larger bundles

Most durable element of the cytoskeleton

Keratin
Lamin

Examples of Intermediate Filaments

Microtubules

Hollow cylindrical structures that are approximately 25 nm in diameter and vary in length

Organized from α- and β-tubulin through self-assembly

Tubulin Polypeptide

Forms protofilaments

13 Protofilaments

Amount of Protofilaments in a Microtubule

Tubulins

Rapidly polymerize and form microtubules and then rapidly depolymerize them when no longer needed by the cell

1. Help support the cytoskeleton to maintain the cell’s shape

2. Involved in the movement of some intracellular organelles

3. Form the mitotic spindle fibers during mitosis

4. Major component of centrioles

Functions of Microtubules

Centrosomes

Consists of two cylinder-shaped centrioles that are typically oriented at right angles to each other

Centriole

Consists of nine bundles of three microtubules each

Serve as insertion points for the mitotic spindle fibers during mitosis.

Plasma Membrane

In Summary of Parts and Functions:

Provides physical barrier for cell; Facilitates interchange of substance

Nucleus

In Summary of Parts and Functions:

Controls cell division and functions

Nucleolus

In Summary of Parts and Functions:

Synthesizes ribosomal RNA

Ribosomes

In Summary of Parts and Functions:

Synthesizes proteins

Rough Endoplasmic Reticulum

In Summary of Parts and Functions:

Synthesizes membrane-bound protein

Smooth Endoplasmic Reticulum

In Summary of Parts and Functions:

Synthesizes phospholipids,

Detoxifies drugs,

Stores calcium

Golgi Apparatus

In Summary of Parts and Functions:

Modifies and packages macromolecules

Mitochondria

In Summary of Parts and Functions:

Produces most of the ATP

Lysosomes

In Summary of Parts and Functions:

Degrade unwanted materials

Microfilament

In Summary of Parts and Functions:

Support cytoskeleton

Intermediate Filaments

In Summary of Parts and Functions:

Provide structural support

Microtubules

In Summary of Parts and Functions:

Maintain cell shape

Centrosome

In Summary of Parts and Functions:

Contains centrioles

Hematopoiesis

Occurs predominantly in the bone marrow from the third trimester of fetal life through adulthood

Stromal Cells

A broad term for specialized endothelial cells; reticular adventitial cells (fibroblasts); adipocytes (fat cells); lymphocytes and macrophages; osteoblasts; and osteoclasts

Extracellular Progenitor Cells

Critical for cell growth and for anchoring developing blood cell progenitor in the bone marrow

Hematopoietic Progenitor Cells

Provides a mechanism for attachment to extracellular matrix

Provides an avenue for cell-cell interaction, which is essential for regulated hematopoiesis

Grwoth Factors

Secreted by stromal cells

Required for stem, progenitor, and precursor cell survival

Participate in complex processes to regulate the proliferation and differentiation of progenitor and precursor cells

Erythropoietin

Has a hormone-type stimulation in that it is produced in another location (kidney) and exerts its effect on erythroid progenitors in the bone marrow

Cell Cycle

A biochemical and morphologic four-stage process through which a cell passes when it is stimulated to divide

Replicate DNA once and distribute identical chromosome copies equally to two daughter cells during mitosis

Purpose of Cell Cycle

G1 (gap 1)
G2 (gap 2)
M (mitosis)

Cell Cycle Stages

G0 (Quiescence)

Cell is not actively in the cell cycle

G1 (Gap 1)

A period of cell growth and synthesis of components necessary for replication

10 hours

Time in which G1 lasts for

S Stage

Stage where DNA replication takes place for about 8 hours

G2 (Gap 2)

The tetraploid DNA is checked for proper replication and damage

4 Hours

Time in which G2 lasts for

Mitosis

Involves the division of chromosomes and cytoplasm into two daughter cells

Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis

6 Phases of Mitosis

Prophase

Phase of Mitosis:

Chromosomes condense

Duplicated centrosomes begin to separate

Mitotic spindle fibers appear

Prometaphase

Phase of Mitosis:

Centrosomes move to opposite poles of the cell and serve as a point of origin of the mitotic spindle fibers

Nuclear envelope disassembles

Sister chromatids, or chromosome pairs, attach to the mitotic spindle fibers

Metaphase

Phase of Mitosis:

Sister chromatids align on the mitotic spindle fibers at a location equidistant from the centrosome poles

Anaphase

Phase of Mitosis:

Sister chromatids separate

Move on the mitotic spindles toward the centrosomes on opposite poles

Telophase

Phase of Mitosis:

Nuclear membrane reassembles around on each set of chromosomes

Mitotic spindle fibers disappear

Cytokinesis

Phase of Mitosis:

Cell divides into two identical daughter cells

Regulation of the Cell Cycle

A regulatory mechanism is needed to prevent abnormal or mutated cells from going through the cell cycle and producing an abnormal clone

Restriction Point (Late G1)

In Cell Checkpoints:

Checks for adequate nutrients and appropriate cell volume

G1 Checkpoint

In Cell Checkpoints:

Checks the DNA for damage and makes the cell either wait for DNA repair or initiates apoptosis.

S-Phase Checkpoint

In Cell Checkpoints:

DNA for damage and completion of replication