chap 2- the cell & its functions (b1- foundation) Flashcards

Question

functions of the rough endoplasmic reticulum

Answer 1

- transport of substances - protein formation (sort and processing) - sends proteins to their destinations

Answer 2

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).

Answer 3

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**

Answer 4

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

Answer 5

- **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)

Answer 6

**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)

Answer 7

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

Answer 8

protein degradation machine **function**: multiple protein-digesting enzymes break down ubiquinated proteins into recyclable building blocks

Answer 9

- Membranes similar to SER. - Composed of four or more **stacked layers** of parallel, thin, flat enclosed vesicles or **cisternae** - Prominent in secretory cells.

Answer 10

- 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

Answer 11

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

Answer 12

**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

Answer 13

**glycoproteins** → more proteins, less carbs **proteoglycans** → subclass of glycoproteins, but have more glucose (carbohydrate) than proteins

Answer 14

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

Answer 15

**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*

Answer 16

1. formed by self-replication (or by budding off from smooth ER) instead of from Golgi apparatus (like lysosomes) 2. contain **oxidases** rather than hydrolases

Answer 17

**secretory lysosomes**: unlike regular lysosomes (that break down waste), they store and release bioactive molecules in response to specific signals 1. **perforin**: protein that immune cells use to kill virus-infected cells - present in *cytotoxic T lymphocytes & natural killer cells* 2. **melanin**: pigment protein for hair, skin, and eye color - present in *melanocytes* 3. **serotonin**: neurotransmitter and signaling molecule that affects mood, blood clotting, and inflammation - present in *mast cells*

Answer 18

**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

Answer 19

- tay sachs - gaucher disease - fabry disease

Answer 20

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.

Answer 21

**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

Answer 22

1. **β-oxidation of long chain fatty acids**: fatty acids are broken down into smaller molecules 2. **Detoxification of harmful chemicals**: remove toxins via oxidases (use O2 to neutralize harmful substances) - leads to production of **hydrogen peroxide (H2O2)** 3. **Removal of H2O2**: catalase quickly converts the H2O2 to water (H2O) and oxygen (O2) to prevent cell damage 4. **synthesis of important molecules**: like Bile acids, myelin and cholesterol 5. **Breakdown of purines into uric acid**: if uric acid builds up, can lead to gout which is a painful joint condition

Answer 23

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

Answer 24

**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*

Answer 25

- microtubules (largest) - intermediate filaments - microfilaments (smallest)

Answer 26

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*

Answer 27

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*

Answer 28

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

Answer 29

**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*

Answer 30

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**

Answer 31

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

Answer 32

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

Answer 33

motor protein **dynein** walks along the microtubules, causing them to bend the bending creates a **back-and-forth beating** in cilia and**wave like motion** in flagella

Answer 34

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

Answer 35

**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

Answer 36

**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*

Answer 37

**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.

Answer 38

**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

Answer 39

**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**

Answer 40

- sperm (by flagella) - white blood cells (most active crawlers) - fibroblasts (move to damaged area to repair damage) - skin cells *move by amoeboid movement*

Answer 41

type of cell movement where a cell crawls by extending parts of its body 4 steps using **microfilaments (actin filaments)**: 1. Extension: *pseudopodia formation (false foot)* 2. Attachment: pseudopodia attaches to a surface using adhesion proteins 3. Contraction & Forward movement: back of cell contract (with help of *actin & myosin*) pulling the cell forward 4. **De-adhesion**: pulling away of rear end from its attachment *entire mechanism is ATP dependent*

Answer 42

**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

Answer 43

They create a contractile ring to divide the cytoplasm

Answer 44

**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

Answer 45

Desmin filaments → Muscle cells Neurofilaments → Neuron cells Keratins → Epithelial cells

Answer 46

**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

Answer 47

**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*

Answer 48

- 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)

Answer 49

**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

Answer 50

**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)

Answer 51

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)

Answer 52

11 microtubules, with 9 double tubules around the periphery and 2 single tubules in the center

Answer 53

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)

Answer 54

1. **biopsy** from area of the body known to have cilia such as sinus cavities or the airway 2. **blood complete picture** to rule out anemia of chronic infection and active recurrent infection 3. **chest x ray** 4 **HRCT** (type of CT scan to get detailed images of lungs)

Answer 55

whip like movement (10-20 times/sec) fast forward and slow backward