Lecture 4: Cells Flashcards
What is the cell theory?
- all living organisms are composed of one or more cells
- the cell is the basic unit of life
- all cells come form preexisting cells
What are the key differences between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have both.
What organelles are found in both prokaryotic and eukaryotic cells?
Cell membrane, cytoplasm, ribosomes, and DNA.
What are prokaryotic cells?
single-celled organisms of domains bacteria and archaea.
What are the components and functions of prokaryotic cells?
-plasma membrane
-cytoplasm
-ribosomes
-DNA
-Cell wall
-Capsule: extra layer to protect cell from chemicals and drying out
-Flagella: for movement
-Pili (or fimbriae): hair-like appendages used for attachment to other cells
-Inclusion: non-living cytoplasmic structures that serve as storage for nutrients, pigments, and other materials
What are eukaryotic cells?
multicellular membrane bound organelles that has a nucleus, found in plants, animal, fungi, and protists
-The 5 membrane bound organelles are nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes
What is the plasma membrane and its functions?
-Biological membrane that separates the interior of the cell form its external environment
-important for homeostasis, selective permeability, protection, communication, and cell adhesion
What is the structure and function of the lipid bilayer?
2 layers of phospholipids with hydrophobic tail facing inward and hydrophilic tails facing outward
It provides fundamental structure and barrier properties of the membrane
What are the proteins found in the plasma membrane?
Integral proteins that span across the membrane and are involved in transport, signal transaction, and cell recognition
Peripheral proteins attach to exterior and interior surface and plays role in signaling and structural support.
What role do carbohydrates play in plasma membrane?
They attach to proteins or lips and are involved in cell recognition, adhesion and communication
What is the role of cholesterol in plasma membrane?
Interspersed within the lipid bilayer modulates membrane fluidity and stability.
What is the fluid mosaic model?
It can describe the plasma membrane because fluid means freely and mosaic means different molecules and in the plasma there are different molecules like proteins and lipids that move freely around the membrane
What is the nucleus and its components?
The nucleus stores genetic material
-parts include:
-nuclear envelope: double membrane protecting DNA
-nuclear pores: allows exchange of materials
-nucleolus: site of ribosome synthesis
-Chromatin: Uncoiled DNA, condenses into chromosomes
What is the endomembrane system and why is it important.
Network of organelles that work together to modify, package, and transport proteins and lipids
-it is important because it allows for segregation of different biochemical processes within distinct membrane-bound compartments, regulates metabolic pathways, signal transduction, and cellular homeostasis, mediating repair and detoxification processes, and facilitates the targeted transport of proteins and lipids.
What is the endoplasmic reticulum and its role?
Endoplasmic reticulum consist of the rough and smooth ER
-rough ER: consist of ribosomes, involved in protein synthesis and quality control
-smooth ER: lack ribosomes, involved in lipid synthesis, detoxification and calcium storage
What is Golgi apparatus?
Series of flattened membrane-bound sacs that modify, sort, and package proteins and lipids for secretion or delivery to other organelles
What are lysosomes?
membrane-bound organelles
containing hydrolytic
enzymes that digest
macromolecules, cellular debris, and forge in pathogens.
-Lysosomes are often
referred to as the digestive system of the cell due
to their role in degrading and recycling cell waste
What is the difference between vacuole and vesicles?
Vacuole are in plant cells and they maintain tugor pressure and stores nutrients and waste products
Vesicles are small membrane-bound sacs that transport materials between organelles and the plasma membrane
What is the mitochondria and its structure and function?
Structure:
-Double-membraned:
Outer membrane: Smooth and protective.
Inner membrane: Folded into cristae to increase surface area. contains the protein complexes of ETC and ATP synthesis
Matrix: Contains mitochondrial DNA, ribosomes, and enzymes that are involved in the Krebs cycle and fatty acid oxidation.
Function:
-Performs cellular respiration (converts glucose into ATP).
-Produces energy (ATP) for cellular processes.
-Contains its own DNA and ribosomes, allowing independent replication.
-signaling cell growth or death
What is the cytoskeleton?
Network of protein fibers that maintain cell shape enable cellular movement and plays role in intracellular transport and division signaling
What are the 3 main components of cytoskeleton?
Microfilaments (Actin Filaments): Thin filaments involved in cell movement and shape changes.
Intermediate Filaments: Provide mechanical strength and stabilize organelles.
Microtubules: Hollow tubes that transport materials, form cilia and flagella, and are involved in cell division.
What are microfilaments, and what are their functions?
-Made of actin proteins, thin-thread like flexible and have diameter of 7nm
Functions:
-Help with cell movement (e.g., muscle contraction)
-Maintain cell shape.
-Aid in cytokinesis (division of cytoplasm during mitosis).
-provides mechanical support
What are intermediate filaments, and what do they do?
-Made of fibrous proteins with a diameter of 10 nm (e.g. keratin in skin cells).
-Provide tensile strength and support the nuclear envelope.
-Help cells resist mechanical stress (important in skin and nerve cells).
-anchor organelles in place
What are microtubules, and what are their functions?
-Made of tubulin proteins, forming hollow tubes with diameter of 25 nm.
Functions:
-Serve as tracks for motor proteins (kinesin & dynein) to transport vesicles.
-Form spindle fibers during cell division.
-Make up cilia and flagella (for movement).
-maintain cell shape
What are peroxisomes, and what is their function?
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small, membrane-bound
organelles present that contain enzymes that catalyze oxidation
reactions. They break down fatty acids and toxins.
Contain catalase to decompose hydrogen peroxide (H₂O₂), a harmful byproduct.
What is lipid metabolism?
Lipid Metabolism includes Beta-oxidation of Fatty Acids and plasmalogen synthesis:
this is when Peroxisomes break down very long-chain fatty acids into medium-chain fatty acids.
Plasmalogen Synthesis: They are involved in the
synthesis of plasmalogens, a type of phospholipid critical
for the normal function of mammalian brains and lungs.
Explain peroxisomes play a role in hydrogen Peroxide Decomposition?
Hydrogen Peroxide Decomposition: Enzyme catalase
decomposes hydrogen peroxide (H2O2), a toxic
byproduct of fatty acid oxidation, into water and oxygen. also oxidize a variety of substrates, including alcohols and other toxic molecules.
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What do peroxisomes do in plant cells?
Convert stored fats into sugars in plant cells through the glyoxylate cycle
What is passive transport? What are the three types of passive transport?
The movement of molecules down their concentration gradient (high to low concentration) without requiring energy
-Simple diffusion: Direct movement of small, nonpolar molecules across the membrane.
-Facilitated diffusion: Movement through a protein channel or carrier to move ions or polar molecules.
-Osmosis: Diffusion of water through a semipermeable membrane.
What is tonality and what are the three types of osmotic solutions?
Tonicity is when the solution outside the cell can change a cells volume by affecting osmosis
-Hypotonic – The solution concentration is lower. Water moves into the cell; cell swells and may burst.
-Isotonic – No net water movement; cell remains the same size.
-Hypertonic – Higher concentration of solute particles and lower concentration of water. Water moves out of the cell; cell shrinks (crenation/plasmolysis).
Q: What is active transport?
The movement of molecules against their concentration gradient (low to high concentration) using ATP energy.
The movement of molecules against their concentration gradient (low to high concentration) using ATP energy.
What are the two types of active transport
-Primary Active Transport – Directly uses ATP (e.g., sodium-potassium pump).
-Secondary Active Transport – Uses an ion gradient to power transport (e.g., glucose transport via Na+ gradient).
What is the sodium-potassium (Na+/K+) pump, and why is it important?
Pumps 3 Na+ out and 2 K+ in, using ATP.
Maintains resting membrane potential in nerve and muscle cells.
Example of primary active transport.
What is bulk transport, and what are the two types?
Movement of large molecules or particles using vesicles.
Endocytosis – Bringing substances into the cell.
Exocytosis – Releasing substances out of the cell.
What are the three types of endocytosis?
-Phagocytosis: “Cell eating” (engulfing large particles like bacteria).
-Pinocytosis: “Cell drinking” (taking in fluids and dissolved molecules).
-Receptor-mediated endocytosis: Uses receptors to selectively take in molecules (e.g., cholesterol uptake).
What is exocytosis, and what is an example?
Vesicles fuse with the plasma membrane, releasing contents outside.
Example: Neurons release neurotransmitters via exocytosis.
What are intracellular connections (cell junctions), and why are they important?
-Structures that connect adjacent cells for communication, adhesion, or barrier formation.
- Functions:
- Maintain tissue structure
- Allow cell signaling
- Control substance movement between cells.
What do plasmodesmata do?
Plasmodesmata are channels that connect the cytoplasm of neighboring plant cells.
-Allow water, nutrients, and signals to pass between plant cells.
What are the 3 types of intracellular connections in animals cells?
- Tight Junctions – Prevent leakage.
- Desmosomes – Provide strong adhesion.
- Gap Junctions – Allow communication.
What are tight junction, and what do they do?
Tight junctions are composed of transmembrane proteins such as Claudius and accludins
- Form a seal between adjacent cells
- Prevent leakage of substances between cells (e.g., in intestines, blood-brain barrier).
Where are tight junctions found in the body?
-Epithelial cells lining the intestines.
- Blood-brain barrier to control brain substances.
- Kidney tubules to regulate fluid movement.
What are desmosomes and their functions?
Desmosomes are composed of desmoglzins and desmocollins connected to intermediate filaments via desmoplakin and other link proteins
- Anchoring junctions that anchor the cytoskeletons of adjacent cells to keep cells together.
- Resist mechanical stress (e.g., in skin, heart tissue).
- Connect to intermediate filaments inside cells for strength.
Where are desmosomes found?
-Skin cells (epidermis).
- Heart muscle (to prevent tearing during contractions).
- Uterus (to provide structural support).
What are gap junctions, and what is their function?
Gap junctions are channels made of connexons that allow direct exchange of ions and molecules between cells.
- Enable rapid communication.
Where are gap junctions found?
-Cardiac muscle (synchronize heart contractions).
- Neurons (electrical synapses).
- Smooth muscle (coordinate contraction in intestines).
