HISTOLOGY (THE CELL) Flashcards by Josefida Marie Gayte

Q

2 MAJOR components of cells

A

CYTOPLASM AND CELL MEMBRANE

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Q

located outside the nucleus

contains organelles and inclusions

A

Cytoplasm

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Q

fluid surrounding the cytoplasm bathing metabolically active structures
(organelles) which can either be membranous or nonmembranous

A

Cytosol

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Q

contains hundreds of enzymes (eg. is the glycolytic pathway) that produce
building blocks for larger molecules and break down small molecules to liberate
energy

A

Cytosol

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Q

Largest organelle within the cell
Contains the genome (along with enzymes necessary for DNA replication and
RNA transcription)

A

Nucleus

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Q

associated with ribosomes and the site of protein synthesis and modification of
newly synthesized proteins

A

Rough-surfaced endoplasmic reticulum (rER)

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Q

basophilic staining is caused by RNA [portion of cytoplasm that is stained with the basic
dye is referred to as ergastoplasm

A

Rough-surfaced endoplasmic reticulum (rER)

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Q

is highly developed in active secretory cells (cells that synthesize proteins destined to
leave the cells) such as plasma cells, glandular cells, osteoblasts

A

Rough-surfaced endoplasmic reticulum (rER)

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Q

involved in lipid and steroid synthesis but not associated with ribosomes

A

Smooth-surfaced endoplasmic reticulum (sER)/Sarcoplasmic

reticulum

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Q

functions in lipid metabolism

A

Smooth-surfaced endoplasmic reticulum (sER)/Sarcoplasmic

reticulum

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Q

well developed in cells that synthesize and secrete steroids such as adrenocortical cells
and testicular Leydig (interstitial) cells

A

Smooth-surfaced endoplasmic reticulum (sER)/Sarcoplasmic

reticulum

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Q

well-developed in the liver and contains a variety of detoxifying enzymes (they modify
and detoxify hydrophobic compounds such as pesticides and carcinogens by chemically
converting them into water soluble-conjugated products that can be eliminated from the
body)

A

Smooth-surfaced endoplasmic reticulum (sER)/Sarcoplasmic

reticulum

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Q

also involved in:
glycogen metabolism
membrane forming and recycling

A

Smooth-surfaced endoplasmic reticulum (sER)/Sarcoplasmic

reticulum

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Q

responsible for modifying, sorting, and packaging proteins and lipids for intracellular or
extracellular transport
functions in the post-translational modification, sorting, and packaging of proteins

A

Golgi apparatus

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Q

are rich in hydrolytic enzymes (enzymes are synthesized in the rER and sorted in the
Golgi apparatus)
represents a major digestive compartment in the cell

A

Lysosomes

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Q

agent used in the treatment and prevention of malaria, is a lysosomotropic agent
that accumulates in the lysosomes

A

Chloroquine

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Q

raises the pH of the lysosomal content = inactivates lysosomal enzymes
the drug concentrates in the acidic food vacuole of the malaria parasite (P.
falciparum) and interferes with its digestive processes, eventually killing the parasite

A

Chloroquine

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Q

have lysosomes that contain phagocytized bacteria and fragments of damaged cells

A

Macrophages

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Q

azurophilic granules represent lysosomes (in acute inflammation,
lysosomal enzymes are released directly into the extracellular space)

A

Neutrophils

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Q

is a debris-filled vacuole produced by the hydrolytic breakdown of the
contents of lysosomes that may remain for the entire life of the cell.

A

Residual bodies

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Q

in neurons, residual bodies are referred to as

A

age pigment/lipofuscin granules

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Q

absence of certain lysosomal enzymes can cause the pathologic accumulation of
undigested substrate in residual bodies leading to several

A

lysosomal storage

diseases

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Q

absence of beta hexosaminidase that catalyzes a

step in lysosomal breakdown of gangliosides in neurons

A

Tay-sachs disease

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Q

provide most of the energy to the cell by producing adenosine
triphosphate (ATP) in the process of oxidative phosphorylation — major site of ATP
synthesis

A

Mitochondria

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a closed circular molecule that contains 13 enzymes involved in the oxidative phosphorylation pathway, 2 rRNAs, and 22 tRNAs (used in the translation of mitochondrial mRNA)

mitochondrial DNA

mitochondrias are present in all cells except

RBCs and terminal keratinocytes

surrounds a space called the matrix; rich in cardiolipin (makes the cell impermeable to ions) performs 3 important functions: oxidation reactions of the respiratory electron-transport chain synthesizes ATP regulate transport of metabolites into and out of the matrix

Inner mitochondrial membrane

is in close contact with the cytoplasm; contains many voltage-dependent anion channels (are permeable to uncharged molecules as large as 5000 daltons—allows passage of small molecule, ions, and metabolites but cannot penetrate inner membrane)

Outer mitochondrial membrane

``` (part of mitochondria) space between the two membranes contains specific enzymes that use the ATP generated in the inner membrane such as: creatine kinase adenylate kinase cytochrome c (important in apoptosis) contains enzymes for β-oxidation of fatty acids and the citric acid (Krebs) cycle ```

Intermembrane space

small organelles involved in the production and degradation of H2O2 and degradation of fatty acids

Peroxisomes

form the cytoskeleton (together with actin and intermediate filaments)

Microtubules

the continuous elongation (by adding tubulin dimers) and | shortening (by removing tubulin dimers)—constant remodeling process

dynamic instability

create a system of connections within the cell

Microtubules

Molecular motor proteins - participate in the movement of organelles and other cytoplasmic structures; includes

Dyneins and Kinesins

Are part of the cytoskeleton; classified into actin filaments, myosin, intermediate filaments

Filaments

are flexible chains of actin molecules; present virtually in all cell types

Actin filaments

free actin molecules

G-actin (globular actin)

polymerized actin

F-actin (filamentous actin)

(filaments) changes in length and interactions with binding proteins regulate cytoplasmic viscosity and movement

Actin filaments

bind and move along actin filaments, carrying vesicles or producing cytoplasmic movement

Myosin (Myofilaments)

in muscle cells, 2 types of myofilaments are present:

thin filaments and thick | filaments

- contained by nonmuscle cells (melanocytes, kidney and intestinal absorptive cells, nerve growth cones, and inner ear hair cells

Myosin I

predominant protein in muscle cells

Myosin II

most stable cytoskeletal component, conferring strong mechanical stability to cells

Intermediate filaments

most widely distributed intermediate filament protein in the body

vimentin

- form a network-like structure that is associated with the nuclear envelope

lamins

contain intermediate filament proteins that are | expressed mostly in axons of nerve cells

neurofilament proteins

most diverse groups of intermediate filaments; are especially important in epithelial cells

keratins

``` structures essential for protein synthesis and composed of ribosomal RNA (rRNA) and ribosomal proteins (including proteins attached to membranes of the rER and proteins free in the cytoplasm) ```

Ribosomes

where translation occurs (coded message contained in the mRNA is read by ribosomal complexes to form a polyribosome complex/polysome—produces simultaneously many copies of a particular protein

Ribosomes

reside within the cytoplasm; are not associated with any intracellular membranes

free ribosomes

formed from metabolic products

Inclusions

accumulate as a result of cell senescence (aging); seen in nondividing cells such as neurons and skeletal and cardiac muscle cells

Lipofuscin (wear-and-tear pigment) -

- formed by the indigestible residues of | hemoglobin; most seen in spleen (where aged RBCs are phagocytosed)

Hemosiderin (iron-storage complex)

a highly branched polymer used as a storage material for glucose; mostly seen in liver and striated muscle cells

Glycogen

- provide energy for cellular metabolism; in adipocytes, compressing the other formed organelles into a thin rim at the margin of the cell

Lipid inclusions (fat droplets)

lipid droplets may accumulate in abnormal locations or in | abnormal amounts

lipid storage diseases

refers to the molecular organization of the plasma membrane made of phospholipids, cholesterol, proteins, and oligosaccharide chains covalently linked to phospholipid and protein molecules

Modified fluid-mosaic model

refers to the formation of lipid molecules with an amphipathic character (both hydrophobic and hydrophilic) — position of lipids makes it more stable

Lipid Bilayer

hydrophobic (having no affinity for water)

inner portion of membrane

- hydrophilic (have an affinity for water); charged polar head

surface of membrane

are embedded within the plasma membrane; constitute approx. half of the total membrane mass

Protein Molecules

carbohydrates attached to lipids

Glycolipids

Glycoproteins + Glycolipids

Cell Coat (Glycocalyx)

constitute a layer at the surface of the cell

Cell Coat (Glycocalyx)

control the movement and distribution of proteins within the lipid bilayer have higher concentrations of cholesterol and saturated fatty acids which reduce lipid fluidity

Lipid Rafts

contains DNA in the form of linear arrays of genes

nucleus

determine most of an organism’s characteristics

Genes

are discrete collections of genes and nuclear proteins.

Chromosomes

consists of 46 chromosomes

entire human karyotype,

is a selectively permeable membranous barrier that separates the nuclear compartment and the cytoplasm

Nuclear envelope

perforate the nuclear membranes; mediate the active transport of proteins, ribonucleoproteins, and RNAs between the nucleus and cytoplasm

Nuclear pores

is an internal meshwork composed of lamins (intermediate filament subunits) residing underneath the nuclear membrane; is essential in many nuclear activities such as DNA replication, transcription, and gene regulation

Nuclear lamina

is a combination of DNA and its associated proteins

Chromatin

is the further folding of chromatin (such as that occurring in mitosis)

Chromosomes

complexes of basic proteins on which DNA molecules wrap around to form nucleosomes

Histones

2 forms of chromatin

Euchromatin, Heterochromatin

stains lightly; DNA active in transcription [chromatin is stretched out so that the genetic information in the DNA can be read and transcribed]; prominent in metabolically active cells such as neurons and liver cells

Euchromatin

- stains darkly; inactive chromatin; predominant in metabolically inactive cells such as small circulating lymphocytes and sperm or in cells that produce one major product such as plasma cells

Heterochromatin

found in both euchromatin and heterochromatin and in chromosomes formed from the coiling of the DNA molecule around a protein core (shortens DNA by approx. sevenfold relative to the unfolded DNA molecule) Under the TEM, appear as 'beads on a string'

Nucleosomes

is the site of ribosomal RNA (rRNA) synthesis and initial ribosomal assembly

Nucleolus