histology Flashcards
what do cells consist of
cytoplasm enclosed within a lipid sheath
what is cytosol
solution of salts and organic compounds
where does cytoskeleton radiate
from the nucleus outwards to the cell surface
what does lipid bilayer separate
the cell contents from the external environment
what is phospholipid head
water loving = hydrophilic
what is phospholipid tail
water hating = hydrophobic
how are phospholipid arranged
in a bilayer
what can cells absorb
gases or small hydrophobic compounds directly across the plasma membrane
how are anchored proteins anchored to the membrane
by acyl chain
how does solute move through membrane proteins
downhill its electrochemical gradient
example of membrane protein
cystic fibrosis transmembrane regulator
what is the CFTR
chloride channel found on the apical surface of epithelial cells
what does CFTR regulate
the fluidity of the extra-epithelial mucous layer
what does water follow
the efflux of sodium chloride by osmosis
how do transporters work
by binding solute on one side of the membrane (conformational change) that exposes the solute biding site on the other side of the membrane for release
how does passive transport work
without an energy source
which way does passive transport move solute
downhill
does active transport require energy
yes
which way does active transport work
uphill
what are the 2 types of active transport
- primary
- secondary
what is primary active transport
use ATP
how does secondary active pump work
driven by ion gradient
what are the 3 types of receptors
- endocytosis
- anchorage
- signalling
what are the 2 form of receptor mediated endocytosis
- phagocytosis
- pinocytosis
what are specialised phagocytic cells
- macrophages
- neutrophils
what is pinocytosis
phagocytosis on a small scale and occurs continually
example of molecule that is pinocytosed
LDL
what is the endoplasmic reticulum
an array of interconnecting tubules or flattened sacs (cisternae)
what is endoplasmic reticulum contiguouos with
outer nuclear membrane
what are the 2 types of ER
- rough
- smooth
what does RER carry
ribosomes on its cytosolic surface
what does SER do
lipids and sterols are synthesised
steroids and drugs are metabolised
what does SER store
calcium that can be released in to the cytosol
what is the Golgi apparatus
flattened cisternae arranged in a stack
what does the golgi apparatus do
proteins, lipids and sterol from the ER are exported to the Golgi apparatus to complete maturation
what do lysosome mature from
the vesicles that bud from the golgi
what do lysosomes contain
digestive enzymes such as lipase, proteases, nucleases and amylases that work in acidic environments
what does the membrane of a lysosome contain
proton ATPase pump to acidify the lumen of the organelle
what do lysosome fuse with
phagocytosis vesicles to digest their contents
what do peroxisomes contain
enzymes for the catabolism of long chain fatty acids
what is hydrogen peroxide
highly reactive oxidising agent
what can catalase reduce
H2O2 to water
what is mitochondria
engines of the cell
what does mitochondria produce
ATP
where are mitochondria abundant
in cells with high energy demand
e.g. hepatocytes or muscle cells
what does the mitochondria have of its own
genome encoding 13 proteins
what is mitochondria’s membrane like
double membrane
what does central matrix contain
enzymes for the Kreb cycle
what is mitochondria’s inner membrane like
highly folded into cristae
what do Cristae do
increase the surface area
how is ATP moved
using the H+ electrochemical gradient
what are the other roles of mitochondria
- roles in apoptosis
- supply substrates for biosynthesis
- synthesis of porphyrin
what is the most prominent cellular organelle
nucleus
what is nucleus membrane like
double membrane
what does nucleus membrane contain
nuclear pores
are euchromatin active or not
active
where is rRNA transcribed
in the nucleolus
what does the nuclear compartment of the nucleus contain
nucleolus
what is the cytoskeleton
complex network of structural proteins that regulate the shape, strength and movement of the cell
what are the components of cytoskeleton
- microtubules
- intermediate filaments
- microfilament
what makes up microtubules
alpha and beta tubular
what is special about tubular structures
they resist bending and stretching
what are the 2 proteins in microtubule
- kinesin
- dynein
what do intermediate filaments form
a network around the nucleus extending to the periphery of the cell
how do intermediate filaments contact with adjacent cells
via desmosomes
what is function of intermediate filaments
structural integrity
what are microfilaments
polymers of actin
what does the actin microfilaments control
- cell shape
- presents cellular deformation
- involved in cell-cell and cell-matrix adhesion
what does the cytoskeleton determine
cell shape and surface structures
what is the apical surface of some epithelium covered in
tiny microvilli
what does microvilli form
brush border
what do microvilli look like
finger-like projections
what do microvilli do
increase surface area for uptake
what is at the core of microvilli
20-30 cross linked actin microfilaments
what do cilia do in respiratory tract
moving and clearing the mucus that is used to trap dust
what happens to cilia in people that smoke
become paralysed
what is special about motile cilia
are longer
what is at the core of motile cilia
axoneme
what is flagella like
related to cilia but longer
when is cell motility essential
development
what is cell motility essential for in adults
- macrophages migrate to site of infection
- keratinocytes migrate to close wound
- osteoblast tunnel into a remodel bone
- fibroblast migrate to site of injury to repair extracellular matrix
what is filopodia
actin remodelling in one dimension
what is lamelliopodia
remodelling in 2 dimension
what is pseudopodia
3 dimensional projections
what is thrombocytopenia
platelet deficiency
what are the 4 major tissue types
- epithelium
- connective tissue
- muscle
- neural tissue
how are epithelium held tightly together
by intercellular junction
how is epithelium separated from extracellular matrix
basal lamina
what does epithelium cover
surfaces and line passageways
what does epithelium do
protection and regulate absorption and secretion
what does connective tissue do
support other tissues and give organs shape
example of connective tissue
collagen
example of bone cells
osteoblast
cartilage cells
chondrocytes
what is the extracellular matrix
gel matrix outside the cell
what does extracellular matrix determine
tissue properties
what is ECM in bone
calcified
what is ECM in tendons
tough and rope like
what is ECM in neural tissue
absent
what does ECM determine
- cell shape
- migration
- cell-cell communication
- signalling
- proliferation
- survival
what is the gel of ECM made from
polysaccharides
example of polysaccharide
- glycosaminoglycans
- GAGs
what are hyaluronan
large hydrated GAG
where is hyaluronan secreted into
joint space in synovial joints
what does hyaluronan do
lubricate and help reduce compressive forces
what are aggrecan
large proteoglycan
what does aggrecan form
part of the articular cartilage of koitns
what is decorin
small proteoglycan
what does collagen produce
tensile strength
what does elastin do
elasticity
how can ECM be degraded and remodelled
by proteins of the matrix metalloproteins
what is basal lamina
basement membrane
another name for basement membrane
lamina propria
what des basement membrane do
separate cells from underlying tissue
what does breach of basal lamina mean
cancer cells
carcinoma-in-situ
examples of immunoglobulin-like cell adhesion
iCAM
vCAM
what do selections interact with
carbohydrate ligand
what are integrins
membrane glycoproteins with alpha and beta subunits
another name for tight junction
zonula occludens
where do tight junction form
the top (apical) side of the epithelial cells in intestine, skin and kidney
what do gap junction allow
low-molecular- weight substances to pass directly between cells
what are the channel in gap junction regulated by
intracellular calcium, pH and voltage
what are adherent junction
multi protein intercellular adhesive structure prominent in epithelial tissues such as fascia adherens
what do adherent junction attach to
actin microfilaments inside the cell
what do desmosome provide
strong attachment between cells and are prominent in tissue
how to cells adhere to non basal lamina ECM
via secreted proteins such as fibronectin and collagen
what kind of signals can cell receive
- chemical
- mechanical
- electrical
what are examples of chemical signals
- hormones
- neurotransmitters
what are examples of mechanical signals
biomechanical
what do kinases do
phosphorylate
what is signal transduction from the receptor to the site of action in a cell mediated by
small signalling molecules called second messengers
what are examples of second messengers
- cAMP
- IP3
- diacylglycerol
what does IP3 do
mobilise calcium from intracellular stores
when are G proteins active
when GTP bound
when are G protein inactive
when GDP bound
what does kinase do
phosphorylates
what does phosphatase do
de-phosphorylate
what does somatic mutation in BRAF cause
malignant melanoma
what is mutation in malignant melanoma
V600E
what is each strand of DNA made up of
- deoxyribose-phosphate backbone
- adenine
- thymine
- guanine
- cytosine
how are the 2 strands of DNA held together
hydrogen bonds between the bases
what is DNA wrapped around
histone proteins
what does DNA wrapped around histone form
nucloeosomes
how is RNA transcribed
from DNA
what does helicase do
unwind double helix
how is DNA synthesised
in 5’ to 3’ direction
are introns coding regions
no
what are the phases of cell cycle
G1
S
G2
M
how long does it take to complete a cycle
20-24 hours
what are the phases of mitosis
- prophase
- metaphase
- anaphase
- telophase
when is p53
between G1 and S
what are main components of DNA replication
- DNA helicase
- DNA primase
- DNA polymerase
- DNA binding proteins
how does DNA helicase work
hydrolyses ATP to unwind the double helix
how to DNA strands pair up
antiparallel fashion
what is the leading strand
3–>5
what does DNA primase do
synthesise a short RNA molecule which acts as a primer
what does DNA polymerase do
extends the primer by adding nucleotides to 3’ end
what are the little bits of DNA on the lagging strand called
Okazaki fragments
what does DNA ligase do
join the two DNA fragments together
Okazaki fragments
what is prophase
centrosome forms
at the end the nuclear membrane breaks down and spindle attach
what is metaphase
chromosomes are aligned
what is anaphase
cohesin breaks down and sister chromatids are pulled in opposite directions
what is telophase
new membrane forms around the daughter cells
where are most of the cells during cell cycle
in G0
what does cyclin E activated
CDK 2
what does cyclin D activate
CDK4
what does CDK 4 activate
Rb
what does Rb release
transcription factor E2F
what does cyclin B activate
CDK 1
what is mature mRNA transported through
the nuclear pore into the cytoplasm
what is mRNA translated into
ribosomes
where are ribosomes formed
in nucleolus
what is primary protein structure
sequence of amino acids
examples of secondary protein structure
- alpha helice s
- beta strand
- triple helix
what is tertiary proteins structure
3D arrangement
what is folding of polypeptides facilitated by
molecular chaperones
e.g. heat shock protein
