Cell Membrane Functions

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Questions and Answers

What is the main function of the plasma membrane?

To synthesize proteins

To store genetic information

To generate energy for the cell

To regulate what enters and leaves the cell (correct)

What type of molecules are membrane lipids?

Electrolytic

Amphipathic (correct)

Hydrophobic

Hydrophilic

What holds the lipid bilayer together?

Hydrophobic effect and weak Van der Waals forces (correct)

Hydrogen bonds

Covalent bonds

Ionic bonds

What is the function of phospholipids in the membrane?

To regulate cell signaling Signup and view all the answers

What type of proteins are embedded in the plasma membrane?

Integral and peripheral proteins Signup and view all the answers

What is the unique characteristic of membranes due to their lipid bilayer structure?

Fluidity Signup and view all the answers

What is the type of lipid found in all membranes except the inner mitochondrial membrane?

Cholesterol Signup and view all the answers

What is the function of Golgi apparatus in the cell?

Protein modification and packaging Signup and view all the answers

Where does fatty acid metabolism (degradation) occur?

Mitochondrial Matrix Signup and view all the answers

What is the function of the mitochondrial DNA (mtDNA)?

To synthesize proteins for the mitochondria Signup and view all the answers

What is the main function of the Citric Acid Cycle (Krebs Cycle)?

To oxidize fuel molecules to produce energy Signup and view all the answers

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

To synthesize proteins for secretion Signup and view all the answers

What is the function of the Smooth Endoplasmic Reticulum (SER)?

To synthesize lipids for the cell membrane Signup and view all the answers

What is the function of biotransformation in the Smooth Endoplasmic Reticulum (SER)?

To convert lipid-soluble molecules to water-soluble molecules Signup and view all the answers

What is the function of the Smooth Endoplasmic Reticulum (SER) in muscle cells?

To pump calcium ions into the cytosol and trigger muscle contraction Signup and view all the answers

What is the site of Oxidative Phosphorylation reactions?

Inner Mitochondrial Membrane Signup and view all the answers

What is the main function of proteins in the plasma membrane?

To catalyze biochemical reactions and transport molecules across the membrane Signup and view all the answers

Which metabolic pathway takes place in the cytoplasm of the cell?

Glycolysis Signup and view all the answers

What is the main function of the cytoskeleton in the cell?

To provide structural support and maintain cell shape Signup and view all the answers

What is the function of the outer membrane of the mitochondria?

To allow the passage of most molecules into the mitochondria Signup and view all the answers

What is the function of microtubules in the cytoskeleton?

To form the axons and dendrites in nerve cells Signup and view all the answers

What is the function of proteins on the surface of immune cells?

To help against virus infection and in the preparation of drugs Signup and view all the answers

What is the function of the matrix in the mitochondria?

To store enzymes and other molecules involved in energy production Signup and view all the answers

What is the fluid-mosaic model of the plasma membrane?

A model that describes the plasma membrane as a dynamic, fluid structure with proteins embedded in it Signup and view all the answers

What is the function of the ribosomes?

Protein synthesis Signup and view all the answers

Where are the newly synthesized proteins folded into their functional shape?

In the endoplasmic reticulum lumen Signup and view all the answers

What is the main function of the Golgi apparatus?

Packaging and secretion of cell products Signup and view all the answers

What factors determine the number and distribution of ribosomes in a cell?

Metabolic activity and type of protein synthesized Signup and view all the answers

What type of cells have a large number of ribosomes?

Cells with high rates of protein synthesis Signup and view all the answers

What is the function of the ribosomal subunits?

Protein synthesis Signup and view all the answers

What is the location of the Golgi apparatus?

Near the nucleus and endoplasmic reticulum Signup and view all the answers

What are hydrolytic enzymes made in and then transferred to the Golgi for further processing?

Endoplasmic reticulum Signup and view all the answers

What is the primary function of lysosomes in a cell?

To break down and recycle cellular waste and foreign substances Signup and view all the answers

What is the pH of the lysosome's contents?

5.0-5.5 Signup and view all the answers

What is the function of the ATP-driven V-type proton pump in lysosomes?

To accumulate H+ ions in the lysosome Signup and view all the answers

What is the term for the process by which cells recycle their own damaged cell parts?

Autophagy Signup and view all the answers

What is the primary function of peroxisomes?

To remove H+ atoms from substrates, producing H202 Signup and view all the answers

What are the reactive oxygen species (ROS) produced by peroxisomes?

Superoxide radical, hydrogen peroxide, hydroxyl radical, and single oxygen Signup and view all the answers

What is the function of acid phosphatase in lysosomes?

To digest molecules at acidic pH Signup and view all the answers

What is the term for the process by which white blood cells engulf and destroy foreign substances?

Phagocytosis Signup and view all the answers

Study Notes

Plasma Membrane

Proteins are responsible for most of the functions of the membrane and are mobile within it, describing the membrane as a fluid-mosaic model.
Biochemical functions of the plasma membrane:
Energy conversion processes such as oxidative phosphorylation
Regulation of molecular and ionic composition of cell compartments through pumps and channels
Control of genetic information flow between cells
Production and reception of chemical signals
Consists of important enzymes that catalyze reactions such as lipid biosynthesis and xenobiotic metabolism

Cytoplasm

Important cellular compartment and central reaction space of the cell
Many important pathways of metabolism take place in the cytoplasm, including:
Glycolysis
Pentose phosphate pathway
Gluconeogenesis
Fatty acid synthesis
Protein biosynthesis (translation)
Glycogenesis (glycogen synthesis) and glycogenolysis (glycogen degradation)
Consists of a supportive network of proteinaceous fibers and filaments called the cytoskeleton
Functions of the cytoskeleton:
Maintaining each cell's shape
Facilitating cell movements
Guiding the movement of organelles within the cell
Components of the cytoskeleton:
Microtubules (found in axons and dendrites of nerve cells)
Microfilaments (found in protein actin in muscle)
Intermediate fibers (found in protein keratin in skin)

Mitochondria

Sausage-shaped structure bounded by two membranes: outer membrane (smooth and permeable to most molecules) and inner membrane (impermeable to ions and other molecules)
Functions:
Fatty acid metabolism (degradation) occurs in the matrix
Oxidative phosphorylation reactions occur, producing energy as ATP in the presence of O2
Citric acid cycle (Krebs cycle) occurs in the mitochondria, oxidizing amino acids, fatty acids, and carbohydrates
Mitochondria has its own protein synthesizing apparatus, including DNA (mtDNA), ribosomes, tRNA, and mRNA, and plays a role in its own replication (DNA synthesis)

Endoplasmic Reticulum (E-R)

System of interconnected membranous tubules
Two forms of E-R:
Rough E-R: involved in the synthesis of proteins for membrane and exporting it from the cell, with ribosomes attached to it
Smooth E-R: functions in lipid synthesis, calcium storage, and biotransformation (converting lipid-soluble molecules to water-soluble and excreting them)

Ribosomes

Small organelles that function in the biosynthesis of proteins
Complex structure containing two irregularly shaped subunits of unequal size
Number and distribution of ribosomes depend on:
Metabolic activity
Type of protein synthesized
Cells with high rates of protein synthesis have larger numbers of ribosomes

Golgi Apparatus

Flattened sac-like membranous vesicles located near the nucleus and close to the E-R and plasma membrane
Functions:
Packaging and secretion of cell products such as newly synthesized proteins and lipids
Modifying products of ER like glycoproteins and membrane phospholipids
Manufacturing macromolecules such as polysaccharides

Lysosomes

Small sac-like organelles produced in E-R and Golgi apparatus
Functions:
Breaking down cell components either micro or macromolecules by digestive enzymes
Digesting cell organelles
Autophagy: recycling the cell's own organic material

Peroxisomes

Small spherical membranous organelles that contain oxidative enzymes
Functions:
Generating and breaking down toxic molecules such as reactive oxygen species (ROS)
Removing H+ atoms from substrates to oxygen, producing H2O2 (hydrogen peroxide)

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Description

Quiz about the functions of plasma membrane, including energy conversion, regulation of molecular and ionic composition, and control of genetic information flow.