Cell Biology and Organization Overview
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Questions and Answers

What role do glycolipids play in the cell membrane?

  • They link fatty acids to carbohydrates. (correct)
  • They are involved in cell communication.
  • They serve as energy storage.
  • They enhance membrane flexibility.

How does cholesterol affect the structure of the cell membrane?

  • It increases bond strength between fatty acids.
  • It promotes fluidity within the lipid bilayer. (correct)
  • It enhances the rigidity of the membrane.
  • It limits the movement of membrane proteins.

Which type of membrane protein is primarily responsible for transportation across the membrane?

  • Extrinsic proteins
  • Intrinsic proteins (correct)
  • Adhesion proteins
  • Signal receptors

What is one of the main functions of peripheral proteins?

<p>To attach to lipids or proteins (D)</p> Signup and view all the answers

What composes the liquid part of the cytoplasm?

<p>Cytosol (B)</p> Signup and view all the answers

What is the primary function of ribosomes in the cell?

<p>To facilitate protein synthesis (B)</p> Signup and view all the answers

Which compartment of the protoplasm contains the nuclear content?

<p>Carioplasm (A)</p> Signup and view all the answers

Which of these is NOT a function of membrane proteins?

<p>Petroleum storage (A)</p> Signup and view all the answers

What are microvilli primarily composed of?

<p>Non-contractile bundles of actin filaments (A)</p> Signup and view all the answers

Which of the following best describes the diameter of intermediate filaments?

<p>Intermediate diameter between microfilaments and microtubules (B)</p> Signup and view all the answers

What structural role do microtubules play in the cell?

<p>Regulate intracellular movement and maintain shape (B)</p> Signup and view all the answers

How are centrioles arranged within the centrosome?

<p>In pairs at right angles to each other (D)</p> Signup and view all the answers

What is the primary function of actin filaments in microvilli?

<p>Enhance cell's surface area (B)</p> Signup and view all the answers

What is the composition of each microtubule?

<p>13 protofilaments of α- and β-tubulin dimers (A)</p> Signup and view all the answers

Which structure is involved in the movement of cilia and flagella?

<p>Microtubules (A)</p> Signup and view all the answers

What characteristic defines the mechanical properties of microtubules?

<p>Dynamic and changeable in length (B)</p> Signup and view all the answers

What is the primary function of the lysosomes?

<p>To degrade macromolecules and cellular debris (D)</p> Signup and view all the answers

Which component maintains the acidic pH required for lysosomal enzyme activity?

<p>Proton pumps in the lysosomal membrane (C)</p> Signup and view all the answers

How do vesicles containing enzymes become lysosomes?

<p>By fusing with other existing lysosomes or endocytotic vesicles (D)</p> Signup and view all the answers

What distinguishes a primary lysosome from a secondary lysosome?

<p>Primary lysosomes are formed in the Golgi and contain active enzymes (D)</p> Signup and view all the answers

Which of the following correctly describes the trans face of the Golgi apparatus?

<p>It is the exit site for vesicles containing processed proteins (D)</p> Signup and view all the answers

What role do clathrin proteins play in the formation of lysosomes?

<p>They coat vesicles that bud from the Golgi apparatus (D)</p> Signup and view all the answers

Which statement is true regarding the composition of the Golgi apparatus?

<p>It is composed of 65% lipids and 35% proteins (D)</p> Signup and view all the answers

Which type of lysosome is characterized by storing compounds resistant to complete digestion?

<p>Tertiary lysosome (A)</p> Signup and view all the answers

What is the arrangement of the lipid molecules in the plasma membrane?

<p>Nonpolar tails on the inside and polar heads on the surface. (C)</p> Signup and view all the answers

Which component of the plasma membrane provides flexibility?

<p>Cholesterol (B)</p> Signup and view all the answers

What type of lipid molecules are found in lower proportions compared to phospholipids?

<p>Glycolipids and cholesterol (A)</p> Signup and view all the answers

Which part of a glycolipid is hydrophilic?

<p>Polar head (D)</p> Signup and view all the answers

What maintains the structural integrity of the plasma membrane?

<p>Hydrophobic interactions of nonpolar tails. (D)</p> Signup and view all the answers

Which of the following describes glycolipids?

<p>Lipids containing both a polar part and a nonpolar part. (C)</p> Signup and view all the answers

Cholesterol is best described as which type of molecule within the membrane?

<p>Steroid (C)</p> Signup and view all the answers

What is the main function of the hydrophilic heads in the plasma membrane?

<p>Interacting with the aqueous environment outside the cell. (C)</p> Signup and view all the answers

The double layer structure of the plasma membrane allows for what characteristic?

<p>Flexibility while maintaining integrity. (A)</p> Signup and view all the answers

Which part of the glycolipid is typically involved in cell recognition?

<p>Polar head with sugars (B)</p> Signup and view all the answers

What is the primary function of the cell membrane?

<p>Regulates interactions with other cells (A)</p> Signup and view all the answers

Which of the following components constitutes about 30% of the proteins in the cell membrane?

<p>Extrinsic proteins (A)</p> Signup and view all the answers

Which type of lipid is the most abundant in the cell membrane?

<p>Phospholipids (B)</p> Signup and view all the answers

What characteristic of the cell membrane allows it to maintain a potential difference?

<p>Selectively permeable nature (C)</p> Signup and view all the answers

What role do glycoproteins play in the cell membrane?

<p>Recognize molecules and other cells (A)</p> Signup and view all the answers

Which statement about the cell membrane is incorrect?

<p>It is primarily composed of carbohydrates. (A)</p> Signup and view all the answers

Which of the following molecules makes up the polar head of phospholipids?

<p>Phosphate bridge (A)</p> Signup and view all the answers

What is the combined percentage of lipids and proteins in the cell membrane?

<p>100% (C)</p> Signup and view all the answers

Which component of the cell membrane helps to maintain its fluidity?

<p>Cholesterol (D)</p> Signup and view all the answers

What distinguishes intrinsic proteins from extrinsic proteins in the cell membrane?

<p>Location within the membrane (C)</p> Signup and view all the answers

What is the primary function of the Rough Endoplasmic Reticulum (RER)?

<p>Protein synthesis. (D)</p> Signup and view all the answers

Which of the following features distinguishes the Smooth Endoplasmic Reticulum (SER) from the RER?

<p>Function in lipid synthesis. (B)</p> Signup and view all the answers

What role do ribosomes play in protein synthesis?

<p>They read the mRNA and add amino acids. (A)</p> Signup and view all the answers

What is the structural composition of the Golgi Apparatus?

<p>Stacked cisternae surrounded by vesicles. (A)</p> Signup and view all the answers

What happens to proteins synthesized in the RER?

<p>They may be integrated into the RER membrane or released. (D)</p> Signup and view all the answers

Which cellular structure is primarily associated with the synthesis of proteins destined for the cell membrane?

<p>Rough Endoplasmic Reticulum. (C)</p> Signup and view all the answers

Which face of the Golgi Apparatus is closest to the RER?

<p>Cis face. (D)</p> Signup and view all the answers

What type of cellular components do polyribosomes primarily synthesize?

<p>Proteins destined for the cell itself. (D)</p> Signup and view all the answers

Flashcards

Cell Membrane

The barrier that encloses the cell, separating the inside from the outside environment.

Phospholipid Bilayer

The cell membrane is made up of a double layer of lipids with embedded proteins. This arrangement creates a selective barrier that controls the passage of substances in and out of the cell.

Phospholipids

Phospholipids are the most abundant lipids in the cell membrane. They consist of a hydrophilic head and a hydrophobic tail. The hydrophilic heads face the watery environment inside and outside the cell, while the hydrophobic tails are buried in the interior of the membrane.

Integral Proteins

Proteins embedded within the phospholipid bilayer. They perform various functions, such as transport, signaling, and anchoring.

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Peripheral Proteins

Proteins attached to the surface of the phospholipid bilayer. They play a role in cell recognition and communication.

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Cholesterol

A type of lipid found in the cell membrane that helps maintain its fluidity and stability.

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Selective Permeability

The cell membrane's ability to control the movement of substances in and out of the cell.

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Receptors

These are molecules embedded in the cell membrane that bind to signaling molecules, triggering a response inside the cell.

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Transport Proteins

These are specialized proteins that transport molecules across the cell membrane, such as nutrients and waste products.

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Protein Synthesis

The process where ribosomes use mRNA as a template to create proteins. This involves adding amino acids based on the mRNA code.

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Polyribosome (Polysome)

A complex made of multiple ribosomes attached to a single mRNA molecule, allowing for efficient protein synthesis.

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Smooth Endoplasmic Reticulum (SER)

A network of interconnected tubules and sacs within a cell, responsible for lipid synthesis, detoxification, and calcium storage. It lacks ribosomes.

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Rough Endoplasmic Reticulum (RER)

A network of interconnected tubules and sacs within a cell, covered in ribosomes, involved in protein synthesis and modification.

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Golgi Apparatus

A stack of flattened membranous sacs involved in processing, packaging, and sorting proteins and lipids. It has a cis and trans face.

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Cis Face of Golgi

The side of the Golgi apparatus closest to the RER, where vesicles enter and begin processing.

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Trans Face of Golgi

The side of the Golgi apparatus farthest from the RER, where processed proteins and lipids are packaged into vesicles for export.

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Vesicles

Small membrane-bound sacs that transport molecules within the cell.

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What are Glycolipids?

Glycolipids are molecules embedded in cell membranes with two fatty acid tails linked to a carbohydrate. They are positioned among phospholipids, resembling their arrangement.

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What is Cholesterol's role in the cell membrane?

Cholesterol is a lipid molecule present in the spaces between unsaturated fatty acid tails in the cell membrane. It restricts their movement, maintaining membrane fluidity and preventing tight packing of those tails.

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What are extrinsic or peripheral proteins?

These proteins are attached to the inner surface of the cell membrane, typically on the cytosolic side.

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What are intrinsic or integral proteins?

Integral proteins are embedded within the cell membrane, with some fully spanning the membrane (transmembrane).

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What is one function of membrane proteins?

Transport proteins facilitate molecule movement across the cell membrane, either by binding and carrying them or forming channels.

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What is another function of membrane proteins?

Adhesive proteins connect cells to each other or to the surrounding environment, and can support internal cellular components.

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What is another function of membrane proteins?

Receptor proteins on the cell membrane bind to signaling molecules from the environment or other cells, helping cells communicate.

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What is another function of membrane proteins?

Enzymes located on the cell membrane catalyze specific reactions close to the membrane surface, increasing their efficiency.

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Non-contractile bundles

Bundles of closely packed parallel filaments that form structures like microvilli, not involved in contraction.

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Contractile bundles

Bundles of filaments that are capable of contracting, driven by proteins like myosin.

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Actin

Thin filaments that are key to the structure of microvilli and are involved in cell movement and shape.

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Myosin II

A protein that interacts with actin and helps create the contractile force in muscle cells.

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Tropomyosin

A protein that stabilizes actin filaments and helps maintain the structure of microvilli.

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Intermediate filaments

Intermediate filaments are fibrous structures that support the cell, maintain its shape, support the nucleus, and anchor the cytoskeleton to the membrane.

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Microtubules

Hollow cylinders composed of α- and β- tubulin dimers that are highly dynamic and change length depending on the cell's needs. They are involved in cell shape, intracellular transport, cell division, and movement of cilia and flagella.

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Centrosome

A structure that is the microtubule organizing center of the cell. It is involved in the initiation and regulation of microtubule assembly.

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Trans Face

The concave face of the Golgi apparatus where vesicles exit and transport processed proteins to their final destination.

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Lysosomes

Organelles enclosed by a membrane that contain acid hydrolases, enzymes responsible for breaking down various cellular components like macromolecules, microorganisms, and organelles.

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Primary Lysosome

Vesicles formed in the Golgi apparatus that haven't yet participated in breaking down material. They are essentially the "freshly made" lysosomes.

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Secondary Lysosome

Vesicles that have undergone catabolic processes - meaning they have already broken down materials. They are essentially the "working" lysosomes.

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Tertiary Lysosome (Residual Body)

Lysosomes that contain undigested material that is no longer useful or cannot be broken down. They are essentially the "leftover" lysosomes.

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Transport of Proteins from RER

The process by which proteins synthesized and modified in the rough endoplasmic reticulum (RER) are transported to the Golgi apparatus for further processing and packaging.

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Clathrin

A protein coat that surrounds some vesicles, particularly those involved in transporting material from the Golgi apparatus to other organelles or the cell membrane.

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Plasma Membrane

A structural component of cell membranes that forms a barrier between the cell's interior and exterior. It is made up of a phospholipid bilayer, where the polar heads face outwards and the non-polar tails face inwards.

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Glycolipid

A type of lipid found in cell membranes that is similar to phospholipids with a polar head and a non-polar tail. They have a variety of functions, including cell recognition and communication.

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Membrane Fluidity

The ability of the plasma membrane to maintain its structure and flexibility. It is influenced by factors such as temperature and the presence of cholesterol.

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Membrane Transport

The property of the plasma membrane that allows for the movement of substances across its surface. This movement can be active (requiring energy) or passive (without requiring energy).

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Membrane Integrity

The ability of the plasma membrane to maintain its integrity and prevent the leakage of cellular contents. This is essential for the cell's survival.

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Lipid Bilayer

The region of the cell membrane where lipids are arranged with their polar heads facing outwards and their non-polar tails facing inwards, forming a barrier between the cell's interior and exterior.

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Study Notes

Cell Biology

  • Cells are the fundamental functional and structural units of living organisms
  • Unicellular organisms consist of a single cell
  • Multicellular organisms have several cells grouped together, specialized in specific functions
  • Cells are organized into tissues, organs, and organ systems

Levels of Organization

  • Cells combine to form tissues
  • Tissues combine to form organs
  • Organs combine to form organ systems

Prokaryotic and Eukaryotic Cells

  • Prokaryotic cells (e.g., bacteria) lack a nucleus and other membrane-bound organelles
  • Eukaryotic cells (e.g., animal cells) have a nucleus and membrane-bound organelles

Animal Eukaryotic Cell

  • Surrounded by a plasma membrane
  • Contain cytoplasm, organelles (for specific functions), and a nucleus (genetic material)
  • The number and arrangement of organelles vary among cell types

Cell Membrane (Plasma Membrane)

  • A selectively permeable barrier between the cell's interior and the external environment
  • Maintains cell integrity
  • Regulates molecular exchange
  • Involved in cell-cell interactions
  • Receives and transmits signals
  • Composed primarily of lipids and proteins

Cell Membrane Components

  • Lipids (40-50%): Phospholipids, glycolipids, cholesterol
  • Proteins (60-50%):
    • Intrinsic proteins: integral (transmembrane) or partially integrated
    • Extrinsic proteins: peripheral

Phospholipids

  • The most abundant membrane lipids
  • Have a hydrophilic head and hydrophobic tails
  • Form a bilayer structure

Glycolipids and Cholesterol

  • Less abundant than phospholipids
  • Each plays a role in maintaining membrane structure and function

Membrane Proteins

  • Extrinsic/Peripheral proteins are associated with the membrane's surface
  • Intrinsic/Integral proteins are embedded within the membrane (transmembrane or partially integrated)
  • Functions: transport, adhesion, and signal reception

Functions of Membrane Proteins

  • Transport - moving molecules across the membrane
  • Adhesion - establishing cell junctions
  • Signal Reception - receiving external signals and transmitting them to the interior of the cell
  • Enzymes - catalyzing reactions at the membrane's surface

Protoplasm

  • The living substance of the cell
  • Divided into two compartments:
    • Cytoplasm - extends from the plasma membrane to the nuclear envelope
    • Cytosol - the liquid part of the cytoplasm
    • Carioplasm - forms the content of the nucleus

Cell Organelles

  • Specialized structures within a cell that perform specific function

Ribosomes

  • Small organelles composed of ribosomal RNA (rRNA)
  • Responsible for protein synthesis
  • Messenger RNA (mRNA) carries the genetic code
  • Transfer RNA (tRNA) brings amino acids to the ribosome, based on the mRNA code.

Ribosomes associated with membranes

  • Synthesize proteins destined for membranes or secretion from the cell

Endomembrane System

  • Involved in synthesis, processing, and transport of proteins and lipids
  • Includes endoplasmic reticulum (RER and SER), Golgi apparatus, and nuclear envelope

Endoplasmic Reticulum (ER)

  • Extensive network of membranes
    • Rough ER (RER), is studded with ribosomes and involved in protein synthesis and folding
    • Smooth ER (SER), lacks ribosomes and involved in lipid synthesis, steroid hormone production and detoxifying processes

Golgi Apparatus

  • Stacked flattened sacs (cisternae)
  • Modifies proteins and lipids produced in the ER
  • Sorts and packages these molecules into vesicles for transport to their final destinations

Lysosomes

  • Membrane-bound organelle containing hydrolytic enzymes
  • Degrades macromolecules, microorganisms, and damaged organelles
  • Maintains an acidic internal environment to protect other cellular components

Peroxisomes

  • Spherical or oval-shaped organelles
  • Contain enzymes for detoxifying reactions, including reactions producing hydrogen peroxide
  • Important in metabolism of harmful substances

Mitochondria

  • Powerhouse of the cell
  • Site of cellular respiration (using oxygen to produce ATP)

Inner Mitochondrial Membrane

  • Contains cristae, extensively folded to increase surface area for ATP synthesis
  • Contains protein complexes that form the Electron Transport chain

Mitochondrial Matrix

  • Contains enzymes for Krebs cycle, produces ATP

Nucleus

  • Largest organelle, contains genetic material (DNA)
  • Involved in gene expression and cell division
  • Contains the nucleolus, responsible for ribosome synthesis

Nuclear Envelope

  • Double-layered membrane surrounding the nucleus
  • Contains nuclear pores that regulate transport between the nucleus and cytoplasm

Chromatin

  • Complex of DNA and proteins (histones)
  • Condenses to form chromosomes during cell division

Chromosome

  • Structure containing DNA and proteins
  • Important in cellular division

Cytoskeleton

  • Network of protein filaments within the cytoplasm
  • Gives the cytoplasm shape and support
  • Involved in movement and intracellular transport.
  • Consists of:
    • Microfilaments (movement - muscle contraction)
    • Intermediate filaments (structural support)
    • Microtubules (structural support, intracellular transport - mitosis)

Centrioles


  • Cylindrical structures (composed of microtubules)
  • Important for organizing microtubules during cell division.
  • Part of the centrosome

Cilia & Flagella

  • Extensions of the cell membrane
  • Structure: microtubule-based axonemes
  • Involved in movement of substances or the entire cell

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