chap 2- the cell & its functions (b1- foundation) Flashcards
2 major parts of the cell
nucleus and cytoplasm
- nucleus is separated from cytoplasm by nuclear membrane
- cytoplasm is separated from the surrounding fluids by cell membrane (plasma membrane)
protoplasm + 5 basic substances
the different substances that make up the cell (“the living part of the cell”) - includes everything inside the cell membrane
5 basic substances: water, electrolytes, proteins, lipids, and carbohydrates
importance of cell membrane
- Protective mechanical barrier
- Allows cell recognition
- Determine composition of cells
- Maintain ion concentration difference between ICF and ECF.
- Cell to cell communication
straight from slides
composition of the cell membrane (in percents)
protein: 55%
phospholipids: 25%
cholesterol: 13%
other lipids: 4%
carbohydrates: 3%
she said to know this
components of cell membrane: lipids (3 types)
-
phospholipids: most abundant in cell membrane, hydrophilic polar head with hydrophobic non-polar tails
- middle is permeable to fat soluble molecules (O2, CO2, alcohol) and impermeable to water soluble molecules (ions, glucose, urea) -
sphingolipids: complex sphingolipids protect from harmful environment factors, do signal transmission, and are adhesion sites for extracellular proteins
- derived from amino alcohol sphingosine
- present in small amounts -
cholesterol: help determine the degree of permeability and control fluidity
- are dissolved in the lipid bilayer
components of cell membrane: proteins (2 types- another flashcard does them in detail)
integral and peripheral
- membrane proteins are mainly glycoproteins
glycocalyx + 4 main functions (imp)
“glyco-“ portions (glycolipids & glycoproteins) protrude towards outside of cell
proteoglycans: loosely attached to outer surface of cell
together form the glycocalyx which is the “sugar coating” on the outside of cell membrane which has functions:
- Have negative electrical charge that give cells overall negative charge to repel other negatively charged objects
- glycocalyx of some cells attaches to glycocalyx of other cells for cell to cell interaction
- act as receptors for binding hormones (such as insulin)
- role in immune reactions & self-identity marker
lipid rafts
small, specialized areas in cell membrane that are needed for communication between cells
- have proteins in them that act as receptors to extracellular chemical messengers
are rich in cholesterol & sphingolipids
integral proteins + 4 functions
protrude all the way through the membrane
1. Channels: water-filled pores: allow specific molecules only (usually water or ions) to diffuse through
- ex. aquaporins
2. Carrier Proteins: bind to a specific molecule inducing a conformational change that then transports the molecule across the membrane
- can also do active transport to go against the electrochemical gradient
- ex. glucose transporter (GLUT)
3. Enzymes: speed up chemical reactions on the membrane
- ex. ATP Synthase in mitochondria
4. Receptors (for water-soluble chemicals): specific ligands bind to receptor causing conformational change in receptor protein
- triggers response inside cell using second messengers to relay the signal inside
peripheral proteins + 6 functions
attached only to the surface of the membrane and do not penetrate all the way through
- usually attached to integral proteins
1. Membrane Bound Enzymes: enzymes attaches to the membrane that help speed up chemical reactions
- ex. acetylcholinesterase
2. Controllers of transport through pores: regulate channel or pore activity by opening/closing when needed
- ex. regulatory proteins that control ion channels in nerve cells
3. Cell Adhesion Molecules (CAMs): protrude from membrane surface that help cells stick to each other or to surfaces (imp for tissue formation)
- ex. interns that help cells attach to surroundings
4. Cell identity markers (w/ carbs): proteins combine with carbs (glycoproteins) that act like ID card for cell
- ex. MHC
5. Docking marker acceptor: on inner surface for secretory vesicles, help vesicles dock and release their contents (exocytosis)
- ex. SNARE proteins guide vesicles carrying neurotransmitters to the membrane
6. Enzymes: not bound to membrane but help out in reactions nearby
- ex. adenylate cyclase, which helps make cAMP, important signaling molecule
fluid mosaic model + parts
structure of cell membrane is not solid but rather “fluid” that is flexible and moves freely
also a mosaic bc a mixture of different parts that include:
- phospholipid bilayer
- proteins (integral & peripheral)
- cholesterol
- carbohydrates
membranous vs non-membraneous organelles
membranous:
- Endoplasmic reticulum
- Golgi complex
- Lysosomes
- Peroxisomes
- Mitochondria
non-membranous:
- Ribosomes
- Proteasomes
- Vaults
- Centrioles
- Cytoskeleton
what type of cells might have more than 1 nuclei or no nuclei?
example was of skeletal muscle cells & RBC’s have no nuclei
structure of the nuclear membrane (aka nuclear envelope)
2 separate bilayer membranes with the outer membrane continuous with the Endoplasmic reticulum membrane and has ribosomes attached to it
- penetrated by several nuclear pores that allow molecules through
nucleolus
- darkly stains
- has no limiting membrane but instead is just a dense collection of RNA & proteins
- enlarges when cell is synthesizing
- place for synthesis of ribosomes
chromatin
- fibers of DNA & proteins
- stores information for synthesis of proteins
- contains genetic info
- arrangement into chromosomes
structure of nucleus
nuclear envelope: protective shell around the nucleus (made of 2 layers- inner and outer membrane), keeps DNA safe inside while separating it from the rest of the cell
nuclear pores (nucleoporins): tiny holes in the nuclear envelope, act like gates allowing important molecules (RNA and proteins) to move in and out of cell while keeping harmful substances out
nuclear lamina (jali like region): line inner part of the nuclear envelope, providing support and helps maintain shape of the nucleus
nucleolus: dense, round structure inside the nucleus, site where ribosomes are made
nucleoplasm: gel-like substance inside nucleus that surrounds the DNA and nucleolus (contains enzymes, proteins, and other molecules needed for the nucleus to function)
think nuclear EPL
functions of the nucleus
- controls hereditary characteristics of an organism & stores hereditary material in the form of DNA
- responsible for cell division, growth, and differentiation
- produces ribosomes (protein factories)
- site for transcription (mRNA are produced for protein synthesis*
- involved in DNA repair
structure of mitochondria
2 lipid bilayer membrane - outer and inner membrane
- inner membrane contains inholdings called cristae that increase surface area, and have oxidative enzymes attached to it for electron transport chain
- inside is filled with matrix that contains enzymes for Krebs cycle (citric acid cycle) \
- the outer layer is smooth
mitochondrial reticulum
network of interconnected mitochondria inside cell
- instead of separate, round mitochondria, are joined together in a web-like structure
benefits:
- helps cell distribute energy (ATP) more efficiently
- allows mitochondria to share resources like proteins and DNA
- helps in cell signaling and responding to stress
- common in muscle (skeletal) cells, where energy needs to be spread quickly and evenly
what does it mean by “mitochondria network is dynamic”?
expands in response to contractile activity (exercise) in skeletal muscle
what is the role of mitochondria in programmed cell death? (imp)
mitochondria receives signal to self-destruct (apoptosis) → releases cytochrome c (protein normally used in energy production) into the cytoplasm → activates intra-cellular protein snipping enzymes → slice cell into small, disposable pieces
what are functions of the mitochondria?
- ATP production
- Role in apoptosis
- Storage of Ca2+
- heat production (in brown fat cells through thermogenesis)
- ketone bodies production (in the matrix)
3 unique features of the mitochondria
- self replicating (also has it’s own DNA thats more prone to mutations)
- maternal inheritance
- number per cells vary according to energy cells
functions of the rough endoplasmic reticulum
- transport of substances
- protein formation (sort and processing)
- sends proteins to their destinations
what type of cells is rough ER extensive in?
extensive in cells specialized for protein secretion (cells that secrete digestive enzymes) and cells that require extensive membrane synthesis (growing cells such as immature egg cells).
structure of endoplasmic reticulum
network of tubular & flat vesicular structures present in the cytoplasm
- walls made of lipid bilayer
- space inside tubules and vesicles is filled with endoplasmic matrix
function of ribosomes
composed of a mixture of rRNA + ribosomal proteins
Function:
- translates mRNA into chains of amino acids
- Brings togethers mRNA, tRNA, and amino acids
- Provides enzymes and energy for protein formation
functions of the smooth endoplasmic reticulum
- Lipid synthesis (esp phospholipids and cholestrol that are rapidly integrated into the lipid bilayer growing the endoplasmic reticulum)
- Provide enzymes for glycogen breakdown
- Detoxification of substances e.g drugs (in liver by coagulation, oxidation, hydrolysis etc)
- Stores and releases calcium ions (in muscles as sarcoplasmic reticulum)
ER exit site & COPII (coat protein II)
ER exit site: where newly made proteins and lipids leave the smooth endoplasmic reticulum to be sent to the Golgi apparatus for further processing
- happens through vesicle formation that is controlled by protein coat COPII
COPII: these proteins recognize & attach to specific proteins on the smooth ER membrane at the exit site
- COPII proteins then start to curve the ER membrane forming a dome-shaped bud around newly synthesized products → vesicles then branch off to move towards the Golgi apparatus
(the lipids that are synthesized are constantly going into the lipid membrane so to prevent overgrowth, these vesicles pop off the smooth ER)
ubiquitin-proteasome pathway
used by cells to identify & destroy misfolded, damaged, or unneeded proteins
misfolded proteins → tagged with ubiquitin (doom tag) → labelled flawed protein for destruction → directed out of ER to one of the many proteasomes to be SLICED
proteasome (nonmembranous organelle) function
protein degradation machine
function: multiple protein-digesting enzymes break down ubiquinated proteins into recyclable building blocks
structure of Golgi complex
- Membranes similar to SER.
- Composed of four or more stacked layers of parallel, thin, flat enclosed vesicles or cisternae
- Prominent in secretory cells.
functions of the endoplasmic reticulum
- Processing of products formed in endoplasmic reticulum:
a: processing of the raw material into finished products.
b: Sorting and directing the finished product to their final destination - Synthesis of certain carbohydrates (like hyaluronic acid and chondroitin sulfate)
- Sorts and packages products into secretory vesicles
I cell disease (Golgi apparatus)
happens when failure of Golgi apparatus to add phosphate tag to mannose
- M6P protein is missing and ends up secreted outside of the cell instead of going to the lysosome
- inherited disorder
- features: coarse facial features, clouded cornea, restricted joint movements, high plasma levels of lysosomal enzymes
- fatal in child hood
exocytosis is stimulated by entry of what ions?
calcium ions
- calcium ions interact with the vesicular membrane and cause its fusion w/ the cell membrane, followed by exocytosis– opening of the membrane’s outer surface and extrusion of content inside cell
proteoglycans vs glycoproteins
glycoproteins → more proteins, less carbs
proteoglycans → subclass of glycoproteins, but have more glucose (carbohydrate) than proteins
steps for packaging, docking, and release of secretory vesicles (using vSNARE docking markers)
Recognition markers in membrane of outermost golgi sac capture and bind with sorting signals of protein to be secreted →
membrane closes beneath the bud, pinching off the secretory vesicle → vesicle loses its coating, exposing v-SNARE docking markers on the vesicle surface → v-SNAREs bind ONLY with the t-SNARE docking marker acceptors of the targeted plasma membrane, ensuring that secretory vesicles empty the contents to the cell’s exterior
4 types of hydrolases in lysosomes
polysaccharide hydrolyzing enzymes: digest polysaccharides into simpler sugars
- ex. beta-galactosidase, alpha-glucosidase, lysozyme
lipid hydrolyzing enzymes: digest lipids (fats & phospholipids)
- ex. fatty acyl esterase, phospholipases
protein hydrolyzing enzymes: digest proteins into smaller peptides or amino acids
- ex. cathepsins, collagenase, elastase, peptidases
nucleic acid hydrolyzing enzymes: digest genetic material (DNA & RNA)
- ex. ribonuclease, deoxyribonuclease
2 ways that peroxisomes are different from lysosomes
- formed by self-replication (or by budding off from smooth ER) instead of from Golgi apparatus (like lysosomes)
- contain oxidases rather than hydrolases
secretory lysosomes + 3 examples
secretory lysosomes: unlike regular lysosomes (that break down waste), they store and release bioactive molecules in response to specific signals
-
perforin: protein that immune cells use to kill virus-infected cells
- present in cytotoxic T lymphocytes & natural killer cells -
melanin: pigment protein for hair, skin, and eye color
- present in melanocytes -
serotonin: neurotransmitter and signaling molecule that affects mood, blood clotting, and inflammation
- present in mast cells
4 functions of lysosomes
1. Cellular digestion: digest waste, foreign invaders, and damaged cell parts
- residual body: leftover waste after digestion by lysosome
2. Role In immunity:
- lysozyme: dissolves bacterial cell walls, tearing them apart
- lysoferrin: binds iron, preventing bacteria from using it to grow
- acidic pH: (~5.0) - acidic environment helps activate lysosomal enzymes to digest pathogens effectively
3. Regression of tissues: help break down excess cells
- ex. of uterus shrinking after pregnancy
4. Autophagy (self-eating): remove digested or damaged organelles to keep cells healthy
3 examples of lysosomal storage diseases
- tay sachs
- gaucher disease
- fabry disease
enzymes in peroxisomes
Peroxisomes contain over 40 enzymes, mainly:
Catalases → Break down hydrogen peroxide (H₂O₂) into water and oxygen, preventing cell damage.
Oxidases → Use oxygen (O₂) to remove hydrogen (H⁺) from organic molecules, producing H₂O₂ as a byproduct.
PPARs (peroxisome proliferator-activated receptors) and peroxins
PPARs: nuclear regulators that regulate formation of new peroxisomes by increasing numbers when needed
- respond to fatty acids & other signals to enhance lipid metabolism
peroxins: chaperone proteins that help transport proteins into peroxisomes so they can function properly
functions of peroxisomes
- β-oxidation of long chain fatty acids: fatty acids are broken down into smaller molecules
-
Detoxification of harmful chemicals: remove toxins via oxidases (use O2 to neutralize harmful substances)
- leads to production of hydrogen peroxide (H2O2) - Removal of H2O2: catalase quickly converts the H2O2 to water (H2O) and oxygen (O2) to prevent cell damage
- synthesis of important molecules: like Bile acids, myelin and cholesterol
- Breakdown of purines into uric acid: if uric acid builds up, can lead to gout which is a painful joint condition
microtubules are mainly composed of which protein?
tubulin
structure of microtubule
made of protein tubulin, specifically α-tubulin and β-tubulin, which form dimers that stack together (like a long dandi thats kind of hollow in the middle)
- long, hollow, unbranched tubes
are also the largest components of the cytoskeleton
functions of microtubules
1. Positioning organelles: help position cytoplasmic organelles within the cell (lil baby organizers)
2. Maintain cell shape/structure: esp for cells that are asymmetric like neurons that need support
3. Facilitate complex movements: act as tracks for intracellular transport
- help move vesicles, organelles, and molecules
4. Stabilize neuron axons: along with intermediate filaments, support long axons in neurons, preventing them from collapsing
5. Cilia & Flagella: microtubules are the main structural components of cilia and flagella and help them move
6. Form mitotic spindle: during mitosis and meiosis, help separate chromosomes and distribute them into daughter cells
basically stability for structure and conveyer belts
3 components of the cytoskeleton
- microtubules (largest)
- intermediate filaments
- microfilaments (smallest)
axonal transport
in neurons, chemicals formed in cell body need to be transported to the axon to reach the synapse
happens along microtubules that act as the highways for transporting vesicles, organelles, and proteins along the axon
motor proteins (like kinesis & dynein) attach to these particles & use ATP to “walk” along the microtubules while carrying their cargo to destination
basically the moving across the highway is axonal transport
kinesin (globular motor protein)
has two “feet,” a stalk, and a fan like tail and carries secretory vesicles to the end of an axon
- uses tubulin molecule (microtubules) as stepping stones
- expenditure of ATP
lil cutie carrying that cargo on the highway and steps so funny too awww
dynein vs kinesin
kinesin is the motor protein that moves “forward” (toward the cell membrane) while dynein moves “backward” (back to the nucleus or cell center)
dyenin: carries debris vesicles back (which have waste and stuff) but also uses ATP like kinesin
myosin V
myosin V: motor protein that carries things inside the cell (like delivery truck)
- walks along actin filaments (different from axonal transport where they walk across microtubules and that is long distance)
- does short-distance transport
different from myosin II which is responsible for muscle contractions and works by forming thick filaments
reverse axonal transport + effects
dynein moves in the opposite direction (instead of going back to cell center, goes to the cell membrane) inside of nerve cells
some viruses can hijack dynein to cause this including:
- poliomyelitis virus
- rabies virus
- herpes virus
do dynein and kinesin only exist in nerve cells?
no, but they play role in neurons bc neurons are long and need long distance transport
dynein: found in all cells that use microtubules for transport, also in cilia and flagella (to help with movement)
kinesin: important in cell division, ensuring chromosomes separate correctly
structure of cilia & flagella (axoneme, basal body)
basic internal structure is the same for both
axoneme: total internal structure, made of microtubules and arranged in 9+2 structure (9 pairs of microtubules [doublets] arranged in a circle, 2 single microtubules in the center, outer doublets connected to each other by dynein)
centriole move into the cell membrane, forming the basal body
basal body: base of the cilia/flagella that anchors it to the cell and controls its movement
- has 9+0 structure (9 microtubule triplets, no central pair)
cilia are shorter in size than flagella which are longer
how do cilia and flagella move?
motor protein dynein walks along the microtubules, causing them to bend
the bending creates a back-and-forth beating in cilia andwave like motion in flagella
role of centriole in the formation of cilia and flagella?
centrioles form the basal bodies, which provide the template for the “9+2” microtubule structure of axoneme
basal bodies help control number, position, and movement of cilia and flagella
3 functions of cilia (motile) in the body
1. Respiratory tract: move foreign particles (dust, mucus, bacteria) out of the airways, helping keep the lungs clean
2. Oviducts (fallopian tubes): help move the ovum (egg) toward the uterus for fertilization or menstruation
3. Brain & Spinal cord: in the fluid-filled brain chambers help with:
- producing cerebrospinal fluid (CSF)
- circulating CSF around the brain and spinal cord to provide protection and nutrients
primary cilium + 3 functions
primary cilium: single, non-motile cilium found in almost all human cells [only 1 present in all cells]
- unlike motile cilia, does not move but works like a sensor for the cell
Functions:
1. Sensory Organ: detects signals from the environment and helps cell respond
2. Receives Regulatory Signals: helps in cell communication by receiving signals that control growth and function
3. Controls Cell Growth & Division: helps regulate cell differentiation (specialization), cell proliferation (multiplication), and tissue development
crucial for proper development & involved in signaling pathways
2 diseases caused by defects in primary & motile cilia
1. Polycystic Kidney Disease (PKD) – Linked to Primary Cilium Defects
- kidney cells grow abnormally = fluid-filled cysts in kidneys = kidney enlargement & failure over time
2. Chronic Respiratory Disease – Linked to Motile Cilia Defects
- motile cilia don’t work properly = mucus builds up = chronic infections, coughing, and breathing problems.
formation of the mitotic spindle (microtubules & microfilaments)
Microtubules → nuclear division (separate chromosomes)
- mitotic spindle which is made of microtubules forms & pulls apart duplicated chromosomes so each daughter cell gets an equal share
- start from centrioles and are only present temporarily during mitosis
Microfilaments (Actin) → **cytokinesis ** (split the cytoplasm)
- contractile ring made of actin (microfilaments) tightens around the middle of the cell, pinching it into 2 daughter cells
structure & function of microfilaments
structure: made of actin protein that twists into strands (look like 2 strands twisted together)
- found in all eukaryotic cells, right beneath plasma membrane
functions:
1. Cell shape and support
2. Cell movement - involved in amoeboid movement (how some cells crawl)
3. Cytokinesis - form contractile ring that pinches the cell into 2
4. Intracellular support to move organelles & vesicles inside cell
5. Muscle contraction - works with myosin to help muscles contract
4 types of human cells that can move on their own imp viva question
- sperm (by flagella)
- white blood cells (most active crawlers)
- fibroblasts (move to damaged area to repair damage)
- skin cells
move by amoeboid movement
amoeboid movement seq
type of cell movement where a cell crawls by extending parts of its body
4 steps using microfilaments (actin filaments):
- Extension: pseudopodia formation (false foot)
- Attachment: pseudopodia attaches to a surface using adhesion proteins
- Contraction & Forward movement: back of cell contract (with help of actin & myosin) pulling the cell forward
- De-adhesion: pulling away of rear end from its attachment
entire mechanism is ATP dependent
Microvili + Actin’s role
microvili: tiny, non-motile, hair-like projections found on the surface of some epithelial cells (cells that line organs) - like intestines, kidneys
main role: increase surface area + improve absorption of nutrients
role of actin filaments: each microvillus supported by bundle of actin filaments that run inside it and act as stiff rods, preventing microvilli from collapsing or bending too much
Which of the following best describes the
involvement of actin microfilaments during cytokinesis?
They create a contractile ring to divide the cytoplasm
structure & function of intermediate filaments
structure: various proteins forming irregular thread-like strands, 7-11 nm diameter
- unlike microfilaments and microtubules, intermediate filaments are more stable and do not easily assemble/disassemble
functions:
1. Provide mechanical strength: help cells resist stretching, compression, & mechanical stress
2. Maintain cell shape: give structural support to cell, anchor cells, and support nuclear envelope (lamin intermediate filaments)
3. Form cell junctions: keratin filaments in cell-cell adhesion
3 examples of intermediate filaments found in various cells
Desmin filaments → Muscle cells
Neurofilaments → Neuron cells
Keratins → Epithelial cells
Intermediate filaments: neurofilaments & keratin
1. Neurofilaments: found in axons of nerve cells (neurons)
- provide strength & stability to long nerve cell extensions, preventing them from breaking.
- imp for maintaining structure & function of neurons
2. Keratin: (in skin, hair, and nails)
- form protective network in skin cells
- help create waterproof outer layer of skin
- provide strength & durability to skin, hair, and nails, preventing damage from mechanical stress
Amyotrophic Lateral Sclerosis (ALS) – Lou Gehrig’s Disease
cause: disorganized neurofilaments block axonal transport of crucial materials along microtubular highways, choking off vital supplies from the cell
leads to progressive degeneration of motor neurons → gradual loss of control of skeletal muscles (including muscles of breathing) = death
Stephen hawking had this
5 types of cells that exhibit ameboid movement
- white blood cells (tissue macrophages)
- fibroblasts (move to repair damage)
- germinal cells of skin
- embryonic cells (to form babies)
- cancer cells (sarcomas- to metastasis to other areas of the body)
chemotaxis + 2 types & examples
chemotaxis: movement in response to chemical stimuli
positive chemotaxis: movement towards chemical signal
- ex. white blood cells move towards site of infection in response to chemical signals from damaged tissues or bacteria (leukocyte chemotaxis)
negative chemotaxis: movement away from a chemical signal
- ex. bacteria moving away from phenol
other examples: sperm towards egg during fertilization, migration of neurons & lymphocytes in baby development
requirements for mechanism of ciliary movement
1. Availability of ATP: provides energy for dynein motors to slide microtubules past each other, causing bending
2. Appropriate Ionic Conditions (Ca²⁺ & Mg²⁺): Ca²⁺& Mg²⁺ regulate dynein activity and strength of ciliary motion
3. Stroke Cycle of Ciliary Movement:
sudden forward whip-like stroke (effective stroke) & slow backward stroke (recovery stroke)
What protein is primarily involved in generating the motive force during ameboid movement?
Actin
Primary Ciliary Dyskinesia (PCD)
group of inherited disorders where cilia do not function properly due to structural or functional defects
effects:
- airway obstructions & recurrent lung infections due to mucus buildup
- dysfunctional flagella causes infertility in males
- retinal blindness b/c cilia are involved in photoreceptor cells
- cancer (cilia help regulate cell division, defects can lead to uncontrolled growth)
The structure supporting the motile cilium includes
11 microtubules, with 9 double tubules around the periphery and 2 single tubules in the center
CBL: Kartegener Syndrome + how are cilia affected?
in kartagener syndrome, cilia dont move (immotile) or dont move well (dysmotile)
- autosomal recessive inheritance pattern
symptoms: BDS
Bronchiectasis (mucus plus, destruction/dilation of bronchi)
Dextrocardia (heart is on the right side - bc cilia didnt move in embryogenesis)
Sinusitis (recurrent sinus infections)
investigations that can be carried out to confirm kartagener syndrome
- biopsy from area of the body known to have cilia such as sinus cavities or the airway
- blood complete picture to rule out anemia of chronic infection and active recurrent infection
- chest x ray
4 HRCT (type of CT scan to get detailed images of lungs)
what is the pattern of ciliary movement?
whip like movement (10-20 times/sec)
fast forward and slow backward
