Cell Structure + Function Flashcards
What is the central idea of cell theory?
All cells come from pre-existing cells, all living things are made up of cells, and cells are the basic unit of structure and function in organisms.
What common features do all cells share?
They use ATP for energy, follow the central dogma (DNA → RNA → Protein), and have similar main organelles arranged in a consistent manner.
What is the difference between eukaryotic and prokaryotic cells?
Eukaryotic cells have membrane-bound organelles (including a nucleus) and are larger, whereas prokaryotic cells lack a membrane-bound nucleus and are generally smaller.
What is the primary function of the plasma membrane?
It controls which substances enter and leave the cell and acts as a physical barrier between the cytosol and the extracellular environment.
What are the main components of the plasma membrane?
A phospholipid bilayer, proteins, glycolipids, glycoproteins, and cholesterol.
What are phospholipids, and what is their structure?
Phospholipids consist of a hydrophilic (water-loving) polar head and a hydrophobic (water-hating) tail.
What does the Fluid Mosaic Model describe?
It explains that membrane components (lipids and proteins) are free to move laterally, creating a dynamic, mosaic-like arrangement.
What types of plasma membrane proteins are there?
Peripheral membrane proteins (associated but not embedded), integral membrane proteins (inserted in the bilayer), and transmembrane proteins (span the entire membrane).
What roles do plasma membrane proteins play?
They participate in enzymatic activity, signal transduction, cell-cell recognition, transport of molecules, and attachment to the cytoskeleton and extracellular matrix.
What is cytosol?
The fluid portion of the cytoplasm that contains dissolved substances and supports organelles (excluding the nucleus).
What components make up the endomembrane system?
The nucleus, endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, and the plasma membrane.
What is the main function of the nucleus?
It stores and protects DNA, regulates the transport of molecules via nuclear pores, and houses the nucleolus for ribosome assembly.
Describe the structure of the nucleus.
It is enclosed by a double membrane called the nuclear envelope, reinforced by a nuclear lamina, and features nuclear pores and a nucleolus.
How is DNA packaged within the nucleus?
DNA, a double helix, wraps around histones to form nucleosomes; nucleosomes coil into chromatin, which condenses into chromosomes during cell division.
How many chromosomes are found in a diploid human cell?
There are 46 chromosomes (22 autosomal pairs plus one pair of sex chromosomes).
What is a gene?
A segment of DNA that codes for a specific protein or phenotype.
What are ribosomes, and what is their function?
Ribosomes are complexes made of rRNA and proteins that synthesize proteins; they exist as free ribosomes in the cytosol or bound to the rough ER.
What is the difference between free and bound ribosomes?
Free ribosomes synthesize proteins for use within the cytosol, while bound ribosomes (attached to the rough ER) produce proteins destined for secretion or for use in organelles.
Describe the structure of the endoplasmic reticulum (ER).
The ER is a network of membranous tubules; the rough ER has ribosomes on its surface, and the smooth ER lacks ribosomes.
What is the function of the rough ER?
It produces non-cytoplasmic proteins (such as secreted and membrane proteins) and packages them into transport vesicles.
What is the function of the smooth ER?
It synthesizes lipids (steroids, phospholipids), stores enzymes and proteins, and detoxifies substances.
How is the Golgi apparatus structured?
It consists of a series of flattened membranous sacs called cisternae, with a cis face (entry) and a trans face (exit).
What role does the Golgi apparatus play in the cell?
It modifies, sorts, and packages proteins and lipids for transport to their destinations, including secretion or lysosomal delivery.
What are lysosomes, and what is their primary function?
Lysosomes are vesicles containing digestive enzymes that break down substances, recycle cellular components (autophagy), and digest entire cells if necessary (autolysis).
How do lysosomes maintain an acidic environment?
They use membrane proteins to pump H⁺ ions into the lysosome, ensuring optimal conditions for enzyme activity.
Describe the structure of mitochondria.
Mitochondria have a double membrane; the inner membrane is folded into cristae, enclosing a matrix that contains enzymes, and they possess their own ribosomes and circular DNA.
What is the main function of mitochondria?
They generate ATP through cellular respiration, earning the title “powerhouse of the cell.”
What is the role of the cytoskeleton in cells?
It maintains cell shape, provides structural support, organizes organelles, and facilitates intracellular transport and cell movement.
What are the three major components of the cytoskeleton?
Microfilaments, intermediate filaments, and microtubules.
What are microfilaments composed of, and what is their function?
They are made of actin, are about 7 nm in diameter, and are involved in cell movement, shape, and muscle contraction.
What are intermediate filaments, and what role do they play?
Intermediate filaments (such as keratin) provide mechanical support and help maintain cell integrity; they are less dynamic than microfilaments.
What are microtubules made of, and what functions do they serve?
Made of alpha and beta tubulin dimers, microtubules (about 25 nm in diameter) are involved in chromosome organization during cell division, vesicle transport, and support of cilia and flagella.
How do the different components of the cytoskeleton contribute to cell function?
Microfilaments aid in motility and shape changes, intermediate filaments provide tensile strength and structural support, and microtubules assist in intracellular transport and cell division.
What is the central dogma of molecular biology?
It is the process by which genetic information flows from DNA to RNA to protein.
How does cholesterol affect the plasma membrane?
Cholesterol modulates membrane fluidity and stability, making the membrane less permeable and more resilient.
What role do glycolipids and glycoproteins play in the plasma membrane?
They are involved in cell recognition and communication by acting as molecular signatures on the cell surface.
What are nuclear pores, and what is their function?
Nuclear pores are channels in the nuclear envelope that regulate the movement of molecules between the nucleus and cytoplasm.
What is the nucleolus, and why is it important?
The nucleolus is a region within the nucleus where ribosomal RNA is produced and ribosome subunits are assembled.
How is the rough ER connected to the nucleus?
The nuclear envelope is continuous with the rough ER, allowing direct transfer of materials between these organelles.
What is autophagy?
Autophagy is the process by which lysosomes digest and recycle damaged or old organelles.
What is the difference between cytosol and cytoplasm?
Cytosol is the fluid component within the cytoplasm that excludes organelles, whereas cytoplasm includes the cytosol plus the organelles (except the nucleus).
How do chromatin fibers condense during cell division?
Chromatin fibers condense into loops that further stack together to form chromosomes held together at the centromere.
What role does actin play in the function of microfilaments?
Actin provides structural support, enables cell movement, and is key in muscle contraction by forming dynamic filaments.
How do the components of the endomembrane system work together?
They collectively package, modify, and transport molecules—proteins and lipids are synthesized in the ER, processed in the Golgi, and distributed via vesicles.
Why is a functional cytoskeleton essential for the cell?
It maintains cell shape, enables transport of materials, supports organelle positioning, and facilitates cellular movement.
What is the role of the nuclear lamina?
The nuclear lamina provides structural support to the nucleus and helps maintain its shape.
How do enzymes in the Golgi apparatus contribute to protein processing?
They modify proteins (e.g., by adding carbohydrate groups) as they pass through the cisternae, ensuring proper folding and functionality.
How do mitochondria possess their own genetic material?
Mitochondria contain their own circular DNA and ribosomes, enabling them to produce some of their own proteins independently.
