Cell Membrane Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of lysosomes in the cell?

Intracellular digestion (correct)

Energy production

Protein synthesis

DNA replication

Which process is NOT associated with lysosomes?

Transport of oxygen (correct)

Recycling of cell membrane

Synthesis of carbohydrates

Formation of lysosome

In which process do lysosomes play a significant role?

Cellular respiration

Apoptosis

Intracellular digestion (correct)

Cell division

What is formed as part of the overall functioning of lysosomes?

Digestive enzymes for breaking down materials Signup and view all the answers

Which of the following is a secondary function of lysosomes?

Recycling of cell membrane Signup and view all the answers

What is the primary role of the cristae in cellular respiration?

To facilitate oxidative phosphorylation and ATP production Signup and view all the answers

What is the shape of the cristae in steroid-secreting cells?

Tubular Signup and view all the answers

Which of the following processes occurs on the cristae?

Electron transport chain Signup and view all the answers

Which enzymes are found within the cristae?

Enzymes involved in oxidative phosphorylation Signup and view all the answers

What would happen if the enzymes located in the cristae were malfunctioning?

ATP production would decrease Signup and view all the answers

What property of the tails in a membrane contributes to their positioning at the center?

They are hydrophobic and nonpolar. Signup and view all the answers

What is the first step in the process when a ligand binds to its receptors on the surface of a cell?

The receptors invaginate to form coated pits. Signup and view all the answers

What gives rise to the trilaminar appearance in membranes?

Stain accumulation in head regions only. Signup and view all the answers

What structure is formed as the invaginated coated pit continues to develop?

A coated vesicle. Signup and view all the answers

Which characteristic is NOT associated with the membrane tails?

They interact favorably with water. Signup and view all the answers

What is the role of staining in observing membrane structure?

Staining helps visualize the head regions of the membrane. Signup and view all the answers

After the formation of a coated vesicle, what is the next stage that occurs with the early endosome?

It moves deep into the cytoplasm. Signup and view all the answers

What is the final destination of the early endosome as it progresses through the cytoplasm?

It transforms into a late endosome. Signup and view all the answers

Which statement about the membrane's structure is accurate?

The heads are polar and face the aqueous environment. Signup and view all the answers

Which of the following statements about receptor-ligand interactions is true?

The coated pits increase in size before pinching off. Signup and view all the answers

What structures are formed when the two membranes fuse together?

Nuclear pores Signup and view all the answers

Which cellular components does the nuclear pore connect?

Nucleus and cytoplasm Signup and view all the answers

What is the primary function of nuclear pores in a cell?

Regulating the exchange of materials between the nucleus and cytoplasm Signup and view all the answers

Which of the following best describes the location of nuclear pores?

At the points where the nuclear membranes fuse Signup and view all the answers

Which statement about nuclear pores is incorrect?

They function independently of the nuclear envelope. Signup and view all the answers

Where are peripheral proteins primarily located in the cell membrane?

Mainly on the inner surface Signup and view all the answers

What is a defining feature of integral proteins?

They are embedded in the lipid bilayer. Signup and view all the answers

What is the term for integral proteins that extend from one side of the membrane to the other?

Transmembrane proteins Signup and view all the answers

Which of the following accurately describes peripheral proteins?

They are attached to the lipid bilayer but not embedded. Signup and view all the answers

Which statement about integral proteins is true?

They are completely embedded in the membrane. Signup and view all the answers

Study Notes

Cell Membrane

The plasma membrane (cell membrane), plasma lemma, or limiting membrane is extremely thin (7.5 to 10 nm).
It's not visible under Light Microscopy (LM) without special stains (e.g., silver).
Electron Microscopy (EM) reveals a trilaminar appearance: two electron-dense layers separated by a translucent layer.
The membrane is primarily composed of a phospholipid bilayer with glycolipids and cholesterol.
Phospholipid molecules have a hydrophilic head and hydrophobic tails.
The hydrophilic heads face the intracellular and extracellular environments.
The hydrophobic tails position themselves within the membrane.
The trilaminar appearance results from the staining of the hydrophilic heads on either side of the membrane.
Proteins are embedded in the membrane.
Proteins can be peripheral (located on the membrane surface) or integral (integrated within the bilayer), and some span both the inner and outer surfaces (transmembrane proteins).
Carbohydrates are also present predominantly on the outer membrane surface, linked to lipids (glycolipids) or proteins (glycoproteins) forming a glycocalyx.
The cell membrane acts as a barrier and regulates the passage of substances into and out of the cell, maintaining a constant intracellular environment.
It also plays a role in cell signaling.

Vesicular Transport

Endocytosis and exocytosis are two types of vesicular transport.
Endocytosis involves the pinching off of the cell membrane to form vesicles that engulf materials from outside the cell.
Pinocytosis ("cell drinking") is one form; it engulfs fluids.
Phagocytosis ("cell eating") involves engulfing larger particles or cells.
Receptor-mediated endocytosis is a specialized form where specific receptors bind foreign molecules, initiating the process.
Exocytosis is the release of materials from intracellular vesicles to the extracellular environment.
The process is affected by calcium levels in the cytoplasm; higher calcium leads to more exocytosis.
Exocytosis pathways include constitutive (continuous) and regulated (stimulated).

Mitochondria

Mitochondria have a distinctive shape, typically spherical or rod-like.
They are not visible in light microscopy (LM) without special vital stains like Janus green B.
Mitochondria are localized in cells according to their energy utilization, e.g., more prominent in active cells like heart muscle (cardiac cells) as well as in ion-transferring cells and spermatozoa.
They have their own DNA and can replicate independently from the cell.
Mitochondrial DNA and RNA are contained within the organelle.
The interior of the mitochondria is partitioned by inner membranes; folds are called cristae.
The inner membrane encloses the matrix, containing enzymes necessary for the citric acid/Krebs cycle, and the electron transport chain is present there.
The process of oxidative phosphorylation occurs on the cristae, generating ATP (energy).

Endoplasmic Reticulum

Endoplasmic reticulum (ER) is a network of channels and sacs formed by continuous membrane.
It is classified as either rough (RER), having ribosomes attached to its surface, or smooth (SER), lacking ribosomes.
RER appears as a basophilic area in the cytoplasm, while SER is not visible in light microscopy.
RER is associated with protein synthesis and modification, targeting proteins for secretion or insertion into the cell membrane.
SER is involved in steroid hormone synthesis, lipid metabolism, drug detoxification, calcium storage, and glycogen metabolism.

Golgi Apparatus

The Golgi apparatus is composed of flattened sacs (cisternae).
The Golgi apparatus is usually organized in stacks with dilated peripheries.
The Golgi apparatus has two faces: the cis (receiving) face and the trans (shipping) face.
The cis face is associated with small vesicles coming from the ER, carrying immature proteins.
The trans face is associated with large secretory vesicles containing mature proteins.
Functions include protein modification (such as glycosylation), concentration, packaging of proteins into secretory vesicles, lysosome formation, and membrane recycling.

Lysosomes

Lysosomes are sites for intracellular digestion.
Their enzymes optimally function in acidic pH.
The organelle can be seen in electron microscopy (EM).
Lysosomes are types: primary and secondary, containing enzymes that degrade cellular substances.

Peroxisomes

Peroxisomes are membrane-enclosed organelles.
Function in removing hydrogen peroxide and breaking down fatty acids into smaller molecules.
Peroxisomes utilize oxidative enzymes and generate hydrogen peroxide as a by-product.

Ribosomes

Ribosomes are non-membrane bound organelles.
Ribosomes are composed of rRNA and proteins.
Two forms are free in the cytoplasm and bound to RER.
Ribosomes function in protein synthesis by translating mRNA into amino acid chains.

Proteasomes

Proteasomes are non-membrane bound.
They are responsible for protein degradation.
They target improperly folded or damaged proteins for destruction.

Cytoskeleton

Cytoskeleton is vital for maintaining cell shape and facilitating internal movement.
Composed of microtubules, intermediate filaments, and microfilaments, or actin filaments.

Centrioles

Centrioles organize microtubules during cell division, playing a critical role in forming the mitotic spindle, determining the basis of cilia, and forming flagella.
Centrioles are composed of microtubules arranged in a specific configuration.

Cilia

Cilia are hair-like projections on the cell surface.
Cilia are responsible for moving substances across the cell surface.
Cilia have a characteristic structure of microtubules, organized in a 9+2 arrangement

Filaments

Filaments are protein fibers supporting cell structure.
Three types are thinner actin, intermediate filaments, and thick myosin filaments.

Inclusions

Inclusions are stored materials within the cell.
Includes stored food, pigments, and crystals. Lipofuscin is a type of aging pigment. Melanin is a natural skin pigment. Hemoglobin is an oxygen-carrying protein pigment found in red blood cells. Glycogen is a type of stored carbohydrate.

Nucleus

The nucleus is the largest and most prominent organelle in the cell.
It has a rounded or oval shape but can be irregular, and a central location within a cell body.
The nucleus can be observed by light microscopy (LM) and contains chromatin, nucleolus, nuclear envelope, and nuclear matrix.
Chromatin comprises DNA and associated proteins.
The nucleolus is a region within the nucleus where ribosome components are synthesized.
The nuclear envelope ensures the separation of the nucleus from the cytoplasm. It has a double membrane. Nuclear pores allow passage into and out of the nucleus.
The nuclear matrix provides structural support to the nucleus.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the structure and composition of the cell membrane, also known as the plasma membrane. It explores key concepts such as the phospholipid bilayer, the arrangement of hydrophilic and hydrophobic components, and the roles of proteins and carbohydrates within the membrane. Test your knowledge on the intricacies of this vital biological barrier!