DENT Fun. I - Cell Structure & Organelles

Non-Membrane Bound Organelles

- Ribosomes

- Proteasomes

- Cytoskeleton

- Centrioles/Basal Bodies

- Cilia/Flagella

Membrane-Bound Organelles

- Plasma Membrane

- Nucleus

- ER

- Golgi

- Lysosomes

- Endosomes

- Peroxisomes

- Mitochondria

Functions of Cell Membranes

- Structural Integrity

- Selective Permeability

- Regulates Cell-Cell Interactions

- Carries Receptors

- Transduces Extracellular signals into Intracellular Events

Composition of Cell Membranes

Lipids

- Phospholipids

- Glycolipids

- Cholesterol

Proteins

- Integral Proteins: Transmembrane

- Peripheral Proteins: Located on one side of the membrane

Lipids are ____.

amphipathic; have hydrophilic and hydrophobic components

What are the 4 Membrane Proteins?

- Channel

- Pumps/Carriers

- Surface Receptors

- Linkers/Structural

Channel Proteins

Allow passage of a specific ion

- Voltage-Gated

- Ligand-Gated

- Mechanical

Pump/Carrier Proteins

Bind and transport molecules/ions

- Na/K Pump

- Glc Transporter

Surface Receptors

Bind extracellular ligands to elicit a cellular response

- Receptor-Mediated Endocytosis

- G-Proteins

Linkers/Structural Proteins

- Involved in cell-cell and cell-matrix attachment

- Serve as scaffolds for cytoskeleton

Major Proteins in the Nucleus

- Histones

- Ribosomal Proteins

- Replication/Transcription Factors

The nucleus during interphase contains both ____ and ____.

heterochromatin/euchromatin

The nucleus has a ____ nuclear envelope.

double-membrane

it is still continuous with the cell membrane

Nuclear Envelope

Double-membrane system that separates the genetic material from the cytoplasm

- Inner Membrane is associated with the Nuclear Lamina

- Outer Membrane is contiguous with the ER

Nuclear Pores

Structures in the nuclear envelope that allow passage of smaller molecules between the cell nucleus and the cytoplasm

Larger molecules require a ____ to enter the nucleus.

nuclear localization signal

Amino acid sequence

RNA is transported through Nuclear Pore Complexes as ____.

ribonucleoproteins

Nucleolus

Site of rRNA synthesis and ribosome assembly

Nucleosome

- Functional unit of Euchromatin

- Consists of a core of Histone Proteins

Cell Cycle

(1) G1: Interphase

(2) S: Synthesis

(3) G2

(4) M: Mitosis

Mitosis

(1) Prophase

(2) Metaphase

(3) Anaphase

(4) Telophase

Apoptosis

Programmed cell death via caspases that are activated within the cell

What's the difference between Apoptosis and Necrosis?

Apoptosis is an active process while necrosis results from acute injury

Ribosomes

- Creates proteins from mRNA and tRNA

- Consists of a small and large subunit

As many as 11-15 ribosomes can be on one mRNA, creating a ____.

polyribosome

ER Signal Sequence

A short amino acid sequence that marks a polypeptide for transport to the ER, where synthesis of the polypeptide chain is completed

Where can proteins made in the cytosol go to?

- Cytosol

- Mitochondria

- Peroxisomes

- Nucleus

Where can proteins made in the ER go to?

- Cell Membrane

- Secreted from Cell

- Lysosomes

Any protein made in the ER will be involved in the ____ pathway.

secretory

Anterograde Trafficking

Movement of substances away from the center of the cell

Retrograde Trafficking

Movement of substances to the center of the cell

Rough ER

Site of synthesis for membrane and secretory proteins

Smooth ER

Site of lipid synthesis

The Rough and Smooth ER are separate structures (T/F)

False; they are contiguous

____ concentration is kept high in the ER.

Ca2+

5' Cap

A modified form of guanine nucleotide added onto the 5' end of a pre-mRNA molecule

Poly-A Tail

Modified end of the 3' end of an mRNA molecule consisting of the addition of 50-250 adenine nucleotides

Golgi Apparatus

A system of membranes that modifies and packages proteins for export by the cell

Proteins are terminally ____ in the Golgi Apparatus.

glycosylated

Produces glycoproteins that are placed in the cell membrane

Constitutive Secretory Pathway

Proteins sent in vesicles from Golgi immediately to cell surface with no regulation

Regulated Secretory Pathway

Secretory pathway in which large amounts of proteins, stored in secretory vesicles, are released from the cell in response to the appropriate signals

ie. Neurotransmitters

Lysosome

An organelle containing digestive enzymes

- pH = 4-5 maintained by proton pumps

Proteins destined for the lysosome contain a recognition site consisting of a ____.

phosphorylated mannose (M6P)

These proteins are transferred to the lysosome via vesicular transport

What are the 3 types of Endocytosis?

- Phagocytosis

- Pinocytosis

- Receptor-Mediated Endocytosis

Phagocytosis

Involves extension of pseudopodia to intake larger molecules

Pinocytosis

Cell invaginates to take in small molecules

General Receptor-Mediated Endocytosis

(1) Binding via Plasma Membrane Receptor

(2) Endocytosis

(3) Uncoating

(4) Endosome Fusion

(5) Return of Receptors to Plasma Membrane

What are the 4 Fates of Endocytic Cargo?

- Receptor Recycled/Ligand Degraded

- Receptor Recycled/Ligand Recycled

- Receptor Degraded/Ligand Degraded

- Receptor Transported/Ligand Transported

Slide 39

Peroxisomes

Membrane-Bound Organelles containing enzymes that participate in oxidative reactions

Peroxisomal proteins are synthesized in the ____.

cytoplasm

Peroxisomal proteins are transported to the peroxisome via a specialized targeting ____.

amino acid sequence

Catalase

Breaks down hydrogen peroxide, a product of lysosomes

Mitochondria

Double-Membraned Organelle that synthesizes ATP from nutrients

Mitochondria contain ____ and can make ____.

their own DNA/their own proteins

Mitochondria divide synchronously with cell division (T/F)

False

Proteasome

Second major compartment for proteolysis

- Abnormal and misfolded proteins are tagged by ubiquitin, which directs the proteasome to break them down

Cytoskeleton

A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement

What are the 3 components of the Cytoskeleton?

- Actin Filaments (Microfilaments)

- Intermediate Filaments

- Microtubules

All of these structures are held together by noncovalent bonds

Functions of Cytoskeletal System

- Pulls chromosomes during division

- Intracellular traffic

- Supports plasma membrane/Cell Shape

- Flagella movement

Actin Filaments

Smallest filament composed of polymerized cross-linked G-Actin

- Acts as the "muscle" of cells

- Creates plasma membrane projections

- Aids in movement of proteins along microtubules

Polymerized G-Actin creates ____.

F-Actin

Plus End

The rapidly growing end of an actin filament/microtubule

Minus End

The less active end of an actin filament/microtubule

Intermediate Filaments

Made up of fibrous keratin-like subunits

- Reinforce the nuclear envelope

Microtubules

Largest cytoskeletal element composed of polymerized dimeric tubulin

- Direct motor proteins in "traffic"

- Form spindle fibers

- Major component of cilia/flagella

Tubulin Dimer Composition

- alpha-Tubulin

- Beta-Tubulin

MTOCs

Microtubule Organizing Centers

- Organized around centrioles/basal bodies

Actin Filaments and Microtubules are more ____.

stiff/rigid

Intermediate Filaments are ____ and ____.

strong/flexible

What are the 4 major tissue types?

- Epithelial

- Connective

- Muscle

- Nerve

Immunohistochemistry detecting components of the electron transport chain would stain very definitively the ____.

inner mitochondrial membrane

Proteins destined for the lysosome via the secretory pathway will contain which modification for proper transport?

Phosphomannose

A patient taking cancer medicine that specifically acts by disrupting tubulin formation will consequently arrest the cell in which stage of the cell cycle?

Mitosis