Cell structure
59 flashcards covering Cell structure for the MCAT Biology & Biochemistry section.
Cell structure refers to the organization and components of cells, which are the basic units of life in all organisms. At its core, this topic covers the various parts of a cell, such as the nucleus that holds genetic material, mitochondria that produce energy, and the cell membrane that controls what enters and leaves. These elements work together to perform essential functions like growth, reproduction, and responding to the environment, forming the foundation of biology.
On the MCAT, cell structure appears frequently in the Biology and Biochemistry section through multiple-choice questions that test identification of organelles, their roles in processes like protein synthesis or cellular respiration, and comparisons between prokaryotic and eukaryotic cells. Common traps include confusing similar structures, such as the endoplasmic reticulum with the Golgi apparatus, or overlooking how environmental factors affect cell membranes. Focus on mastering diagrams, transport mechanisms, and real-world applications to handle these questions effectively.
A concrete tip: Practice labeling cell diagrams from memory to reinforce key details.
Terms (59)
- 01
Cell theory
Cell theory states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.
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Prokaryotic cell
A prokaryotic cell lacks a true nucleus and membrane-bound organelles, typically found in bacteria and archaea, with genetic material in the nucleoid region.
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Eukaryotic cell
An eukaryotic cell has a true nucleus enclosed by a membrane and contains membrane-bound organelles, found in plants, animals, fungi, and protists.
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Nucleus
The nucleus is a membrane-bound organelle that contains the cell's genetic material in the form of chromosomes and controls cellular activities through gene expression.
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Nuclear envelope
The nuclear envelope is a double membrane surrounding the nucleus, with nuclear pores that regulate the transport of molecules between the nucleus and cytoplasm.
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Nucleolus
The nucleolus is a dense region within the nucleus where ribosomal RNA is synthesized and ribosomes are assembled.
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Chromatin
Chromatin is the complex of DNA, RNA, and proteins that forms chromosomes in the nucleus, condensing into visible chromosomes during cell division.
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Mitochondrion
The mitochondrion is a membrane-bound organelle responsible for producing ATP through cellular respiration, often called the powerhouse of the cell.
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Cristae
Cristae are the folds of the inner mitochondrial membrane that increase surface area for the electron transport chain in ATP production.
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Mitochondrial matrix
The mitochondrial matrix is the space inside the inner membrane where the Krebs cycle occurs, containing enzymes and mitochondrial DNA.
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Chloroplast
The chloroplast is a membrane-bound organelle in plant cells and some protists that conducts photosynthesis, converting light energy into chemical energy.
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Thylakoid
Thylakoids are membrane-bound structures within chloroplasts that contain chlorophyll and are the site of the light-dependent reactions of photosynthesis.
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Stroma
The stroma is the fluid-filled space surrounding the thylakoids in chloroplasts, where the Calvin cycle occurs to produce sugars.
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Endoplasmic reticulum
The endoplasmic reticulum is a network of membranes in the cytoplasm involved in protein and lipid synthesis, existing as rough or smooth types.
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Rough endoplasmic reticulum
Rough endoplasmic reticulum has ribosomes on its surface and is primarily involved in synthesizing and modifying proteins for secretion or membrane insertion.
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Smooth endoplasmic reticulum
Smooth endoplasmic reticulum lacks ribosomes and functions in lipid synthesis, detoxification, and calcium storage.
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Golgi apparatus
The Golgi apparatus is a stack of membranes that modifies, sorts, and packages proteins and lipids for transport to their destinations in the cell.
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Lysosome
A lysosome is a membrane-bound organelle containing hydrolytic enzymes that break down waste materials, cellular debris, and engulfed particles.
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Peroxisome
A peroxisome is a membrane-bound organelle that breaks down fatty acids and detoxifies harmful substances using enzymes that produce and break down hydrogen peroxide.
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Vacuole
A vacuole is a large membrane-bound sac in plant and fungal cells that stores nutrients, waste, and maintains turgor pressure, while in animal cells it is smaller and temporary.
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Ribosome
A ribosome is a non-membrane-bound structure composed of RNA and proteins that assembles amino acids into proteins during translation.
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Cytoplasm
Cytoplasm is the material within the cell membrane excluding the nucleus, consisting of cytosol, organelles, and inclusions where metabolic reactions occur.
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Cytosol
Cytosol is the fluid component of the cytoplasm, excluding organelles, where many biochemical reactions like glycolysis take place.
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Cytoskeleton
The cytoskeleton is a network of protein fibers in the cytoplasm that provides structural support, enables cell movement, and facilitates intracellular transport.
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Microtubule
Microtubules are hollow tubes made of tubulin proteins that form part of the cytoskeleton, aiding in cell shape, division, and transport of organelles.
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Microfilament
Microfilaments are thin filaments made of actin proteins that contribute to cell movement, contraction, and maintenance of cell shape.
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Intermediate filament
Intermediate filaments are rope-like structures made of various proteins that provide mechanical strength and maintain cell integrity.
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Centriole
Centrioles are cylindrical structures made of microtubules that organize the mitotic spindle during cell division in animal cells.
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Cilia
Cilia are short, hair-like projections on the cell surface made of microtubules that move fluids or particles along the cell's surface.
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Flagella
Flagella are long, whip-like structures made of microtubules that propel cells, such as sperm, through their environment.
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Plasma membrane
The plasma membrane is a selectively permeable barrier made of a phospholipid bilayer that regulates what enters and leaves the cell.
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Phospholipid bilayer
The phospholipid bilayer is the basic structure of the plasma membrane, with hydrophilic heads facing outward and hydrophobic tails inward, forming a barrier.
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Fluid mosaic model
The fluid mosaic model describes the plasma membrane as a dynamic structure of phospholipids and proteins that can move, allowing for flexibility and function.
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Integral membrane protein
An integral membrane protein is embedded within the phospholipid bilayer and often spans the membrane, playing roles in transport and signaling.
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Peripheral membrane protein
A peripheral membrane protein is attached to the surface of the membrane and can be easily removed, often involved in structural support or signaling.
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Diffusion
Diffusion is the passive movement of molecules from an area of higher concentration to lower concentration until equilibrium is reached.
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Osmosis
Osmosis is the diffusion of water across a semi-permeable membrane from an area of lower solute concentration to higher solute concentration.
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Facilitated diffusion
Facilitated diffusion is a passive transport process using carrier or channel proteins to move molecules across the membrane down their concentration gradient.
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Active transport
Active transport uses energy, typically ATP, to move molecules against their concentration gradient via pumps in the membrane.
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Sodium-potassium pump
The sodium-potassium pump is an active transport protein that exchanges three sodium ions out of the cell for two potassium ions in, maintaining electrochemical gradients.
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Endocytosis
Endocytosis is a process where the cell membrane engulfs extracellular material to form a vesicle, bringing substances into the cell.
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Exocytosis
Exocytosis is the process where vesicles fuse with the cell membrane to release substances from the cell to the exterior.
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Phagocytosis
Phagocytosis is a type of endocytosis where the cell engulfs large particles, such as bacteria, by extending its membrane around them.
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Pinocytosis
Pinocytosis is a type of endocytosis where the cell takes in extracellular fluid and dissolved substances by forming small vesicles.
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Receptor-mediated endocytosis
Receptor-mediated endocytosis involves specific receptors on the membrane binding to molecules, leading to their internalization via coated pits.
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Cell wall
The cell wall is a rigid structure outside the plasma membrane in plant cells and some bacteria, providing support and protection.
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Extracellular matrix
The extracellular matrix is a network of proteins and polysaccharides outside animal cells that provides structural and biochemical support to the surrounding tissue.
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Tight junction
A tight junction is a type of cell junction that seals adjacent cells together, preventing substances from leaking between them.
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Gap junction
A gap junction is a channel between adjacent cells that allows the passage of ions and small molecules for communication.
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Desmosome
A desmosome is a cell junction that anchors cells together, providing strength and resisting mechanical stress.
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Common trap: Plant vs. animal cells
A common error is assuming all cells have the same structures; plant cells have chloroplasts and a large central vacuole, while animal cells do not.
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Nernst equation for membrane potential
The Nernst equation calculates the equilibrium potential for an ion across a membrane, given by E = (RT/zF) ln([ion]out/[ion]in), used to understand ion gradients.
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Strategy for identifying organelles
To identify organelles in micrographs, look for distinct structures like the double membrane of mitochondria or the stacked membranes of the Golgi apparatus.
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Example of passive transport
In osmosis, water moves into a cell placed in a hypotonic solution, causing it to swell, as it follows the concentration gradient without energy input.
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Endomembrane system
The endomembrane system includes organelles like the ER, Golgi, and lysosomes that work together to modify and transport proteins and lipids within the cell.
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Signal sequence in proteins
A signal sequence is a short peptide at the start of a protein that directs it to the correct cellular location, such as the ER for membrane proteins.
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Nuclear pore complex
The nuclear pore complex is a large structure in the nuclear envelope that selectively transports molecules like RNA and proteins between the nucleus and cytoplasm.
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Microvilli
Microvilli are finger-like projections of the plasma membrane that increase surface area for absorption, commonly found in intestinal cells.
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Autophagy
Autophagy is a process where cells degrade their own components by enclosing them in vesicles that fuse with lysosomes, maintaining cellular homeostasis.