Chpt 4 Anatomy and Function of Eukaryotic Cells: Organelles, Membranes, and Cell Connections

What is the smallest unit with the properties of life?

A cell.

What three components do all cells start out with?

A plasma membrane, a region of DNA, and cytoplasm.

Why is there no typical cell in the body?

All cells have specific functions and their makeup is a composite structure created for study purposes.

What are some structures associated with cells that allow them to perform their functions?

Plasma membrane, cytoplasm, nucleus, Golgi apparatus, mitochondria, endoplasmic reticulum, vesicles, and others.

What is the function of the plasma membrane?

It defines the cell as a distinct entity and separates metabolic activities from random events outside the cell.

How does the plasma membrane regulate the movement of substances?

Water, oxygen, and carbon dioxide enter and leave freely, while nutrients, ions, and other substances require escorts.

What is the structural basis for cell membranes?

The lipid bilayer.

What role do proteins play in the cell membrane?

Diverse proteins embedded in the lipid bilayer carry out most membrane functions, acting as channels, pumps, or receptors.

What is the significance of cholesterol in cell membranes?

Cholesterol mixes with phospholipid molecules to maintain membrane fluidity and prevent breakage.

What are glycolipids and lipoproteins?

Glycolipids are formed when membrane lipids combine with carbohydrates, and lipoproteins are formed when lipids unite with proteins.

How do proteins interact with the phospholipid bilayer?

Proteins may become anchored within the bilayer or attached to one side of the membrane, depending on their amino acid composition.

What are membrane rafts?

Stiff groupings of membrane molecules, often rich in cholesterol, that help organize membrane components and facilitate transport into the cell.

How do membrane proteins control the movement of substances?

They have openings that allow water-soluble molecules to pass through, and specific transport proteins allow only certain types of molecules to cross.

What is the role of transport proteins in cell membranes?

They facilitate the passage of specific types of molecules through the membrane.

What is the function of the cytoplasm in a cell?

It serves as the medium where various cellular processes occur and houses organelles.

What is the role of the nucleus in a cell?

It contains the cell's DNA and regulates gene expression.

What is the function of the Golgi apparatus?

It modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

What is the function of mitochondria?

They generate ATP through cellular respiration, providing energy for the cell.

What is the role of endoplasmic reticulum in a cell?

It synthesizes proteins (rough ER) and lipids (smooth ER) and transports them throughout the cell.

What are vesicles?

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

How do cells compartmentalize tasks?

By forming membranes that create distinct environments for different cellular processes.

What role do membrane proteins play in cell identification?

They form glycoprotein molecules that act as identification markers, allowing the immune system to distinguish between 'self' and 'non-self' cells.

How do membrane proteins function as enzymes?

Some membrane proteins catalyze cellular reactions.

What is signal transduction in relation to membrane receptors?

It is the process by which cells translate signals received by membrane receptors, meaning to carry a message across a membrane.

What is the function of the Endoplasmic Reticulum (ER)?

Rough ER synthesizes proteins for export via the Golgi apparatus, while smooth ER synthesizes lipids, steroid hormones, and carbohydrates, and stores Ca++.

What does the Golgi apparatus do?

It synthesizes carbohydrates, combines them with proteins, and packages them as glycoprotein globules.

What are vesicles and their function?

Vesicles are membranous bags that temporarily contain molecules for transport or later use.

What is the role of lysosomes in a cell?

Lysosomes contain digestive enzymes that break down defective cell parts and ingested particles, functioning as the cell's digestive system.

What are proteasomes and their function?

Proteasomes are hollow protein cylinders that break down proteins tagged by ubiquitin for destruction and recycling.

What is ubiquitin and its role in protein recycling?

Ubiquitin is a small regulatory protein that labels proteins for destruction and directs them to proteasomes.

What do peroxisomes contain and their function?

Peroxisomes contain enzymes that detoxify harmful substances.

What is the primary function of mitochondria?

Mitochondria are responsible for catabolism and ATP synthesis, acting as the cell's power plant.

What is the function of ribosomes in a cell?

Ribosomes are the site of protein synthesis, acting as the cell's protein factory.

How do some membrane proteins contribute to cell structure?

They bind to other membrane proteins to form connections between cells or anchor support filaments within the cell.

What happens when two cells join together?

Some membrane proteins connect the cell membrane to another membrane, forming a larger mass of tissue.

How do membrane proteins interact with hormones?

Some membrane proteins act as receptors that react to hormones or regulatory chemicals, triggering metabolic changes in the cell.

What is the significance of glycoproteins in the immune response?

Glycoproteins serve as markers that help the immune system identify and attack abnormal cells, such as cancer or bacterial cells.

What is the function of smooth ER in relation to calcium?

Smooth ER removes and stores calcium ions from the cell's interior.

What is the quality control mechanism for protein synthesis in cells?

Proteasomes destroy misfolded or abnormal proteins, ensuring quality control during protein synthesis.

How do ubiquitin tags affect protein location in the cell?

Ubiquitin tags can direct proteins to specific locations in the cell, influencing various protein and cell mechanisms.

What is the primary function of the cytoskeleton?

Acts as a framework to support the cell and its organelles, functions in cell movement, and forms cell extensions like microvilli, cilia, and flagella.

What is the role of the centrosome in a cell?

It is the microtubule organizing center that includes two centrioles, assisting in forming and organizing microtubules.

What are microvilli and their function?

Tiny, finger-like extensions that increase a cell's absorptive area.

What distinguishes cilia from flagella?

Cilia are hairlike extensions that move substances over the cell surface, while flagella propel sperm cells.

What is the function of the nucleolus?

It plays an important role in the formation of ribosomes.

What is cytoplasm and what does it contain?

Cytoplasm is a gel-like substance composed of various organelles and molecules suspended in cytosol, aiding in chemical reactions.

Where is cytoplasm located in a cell?

It is found between the plasma membrane and the region of DNA.

What are the three main structures of a eukaryotic cell?

The cell membrane, the cytoplasm, and the nucleus.

How do integrins function in cell connections?

Integrins help hold cells in place within a tissue by spanning the cell membrane and connecting to the extracellular matrix.

What types of proteins assist in direct cell-to-cell connections?

Selectins, cadherins, and immunoglobulins facilitate most cell-to-cell connections.

What is the function of desmosomes?

They act like spot welds between cells, holding them together, as seen in skin cells.

What are gap junctions and their effects?

They are formed when membrane channels of adjacent cells adhere, creating gaps that join the cytoplasm of two cells and fuse their plasma membranes.

What characterizes tight junctions?

They occur when cells are joined near their apical surfaces by tightly fused membranes.

Why are most cells not larger despite some exceptions?

Larger cells, like bird egg yolks, are primarily food reserves and do not perform many metabolic tasks.

What is the surface to volume ratio and its significance?

It describes how an object's volume increases with the cube of its diameter while surface area increases with the square, limiting cell size as tasks increase.

What happens to the efficiency of chemical reactions in crowded cytoplasm?

The crowding of molecules and organelles improves the efficiency of chemical reactions.

What is the role of ribosomes in the cytoplasm?

Ribosomes are molecular structures on which proteins are built.

What is the composition of cytosol?

Cytosol is the watery fluid that suspends organelles and molecules in the cytoplasm.

What is the importance of the nucleus in eukaryotic cells?

The nucleus houses the DNA and is a membrane-bound internal sac.

How do cells connect to the extracellular matrix?

Cells attach directly to the extracellular matrix, which surrounds them, often with the help of integrins.

What is the relationship between cell size and metabolic tasks?

Generally, the more tasks a cell has to perform, the smaller it will be.

What is the effect of increasing cell size on surface area and volume?

As cell size increases, the surface area increases at a slower rate than volume, leading to constraints.

What happens to the surface area in relation to volume as a cell increases in size?

The surface area does not increase in proportion with the volume, leading to less binding sites, pumps, and channels for larger cells.

Why can smaller cells perform work more efficiently than larger cells?

Smaller cells can exchange nutrients at a much more rapid rate per working unit inside the cell.

What occurs when a cell's girth becomes too great?

The inward flow of nutrients and outward flow of wastes may not keep up with the metabolic activity, potentially resulting in a dead cell.

How does the size of a cell affect the movement of materials through its cytoplasm?

Larger cells have trouble moving materials through their cytoplasm, while smaller cells can distribute substances more efficiently due to random molecular motion.

What adaptations do larger cells have to increase their surface area relative to volume?

Larger cells may be long or thin, or have outfoldings or infoldings to increase surface area.

How do surface to volume constraints influence the body plans of multicellular organisms?

They shape how cells are arranged, such as small cells attaching end to end in strand-like algae, or muscle cells being long and thin for efficient substance exchange.

What are some characteristics of eukaryotic cells?

Eukaryotic cells have ribosomes in their cytoplasm, a well-developed protein skeleton, a nucleus, and membrane-bound organelles.

What does the term 'eukaryote' mean?

'Eu' means true and 'karyote' means kernel, referring to the nucleus.

What advantages do eukaryotic cells have due to their outer membrane?

The outer membrane sustains a microenvironment for cell activities and controls the types and amounts of substances entering and leaving the cell.

How do mitochondria function in eukaryotic cells?

Mitochondria concentrate hydrogen ions in a sac and allow them to flow to form ATP.

What role do lysosomes play in eukaryotic cells?

Lysosomes digest large organic molecules and can digest the cells themselves if they escape.

How do specialized organelles in eukaryotic cells interact?

They interact in controlled ways to help keep the whole cell functioning properly.

What is the secretory pathway in eukaryotic cells?

It moves new polypeptide chains from ribosomes through the endoplasmic reticulum and Golgi bodies to the plasma membrane for release.

What is the endocytic pathway in eukaryotic cells?

It moves ions and molecules into the cytoplasm.

What role do vesicles play in eukaryotic cells?

Vesicles act like taxis, moving substances from one organelle to the next by pinching off from organelle membranes or the plasma membrane.

How is genetic material organized in eukaryotic cells?

It is distributed among several DNA molecules of different lengths, such as the forty-six DNA molecules in a human body cell.

What is the approximate length of DNA molecules if stretched out from a human nucleus?

About 6 ½ feet long.

What are the two main functions of the nucleus in eukaryotic cells?

The specific functions are not detailed in the notes, but typically include storing genetic information and regulating gene expression.

What is the primary function of the nuclear envelope?

To keep DNA from getting tangled with cytoplasmic machinery and isolate it from damaging reactions.

What are the two main components of the nuclear envelope?

It consists of two lipid bilayers pressed against each other.

How does the outer membrane of the nuclear envelope interact with the endoplasmic reticulum?

The outer membrane merges with the membrane of the endoplasmic reticulum (ER).

What is nucleoplasm?

A semifluid matrix that bathes the inner surface of the nuclear envelope.

What role do membrane proteins play in the nuclear envelope?

They function as receptors, transporters, and form pore complexes for molecule transport.

What is the cytoskeleton?

The internal supporting framework of the cell made up of rigid, rod-like pieces.

What is the function of microfilaments in the cytoskeleton?

They serve as part of the cellular muscles and allow movement by shortening the cell.

What are intermediate filaments and where are they commonly found?

Twisted protein strands that form the supporting framework in many cells, such as the protective outer layer of skin.

What are microtubules and what is their role in the cell?

Thick, hollow tubes made of protein subunits that move things around in the cell.

What is the centrosome and its function?

A region of the cytoplasm near the nucleus that coordinates the building and breaking apart of microtubules.

What are kinesins?

A group of motor proteins that move along microtubules and are vital for chromosome movement during mitosis.

How do kinesins move along microtubules?

They use a pseudo-processive asymmetric walking motion towards either the plus-end or minus-end.

What are the three types of cell extensions formed by the cytoskeleton?

Microvilli, cilia, and flagella.

What is the significance of the nuclear envelope in relation to DNA organization?

It helps keep DNA molecules organized and facilitates copying before cell division.

What is the role of fibrous proteins in the nuclear envelope?

They anchor DNA molecules and keep them organized.

How do ions and small water-soluble molecules cross the nuclear envelope?

They cross only at the pores that span both bilayers of the nuclear envelope.

What is the structure of microfilaments?

They are made of thin, twisted strands of protein molecules.

What is the primary function of microtubules in the cell?

To facilitate movement of cellular components.

What is the relationship between the cytoskeleton and organelles like mitochondria and ribosomes?

Cytoskeletal fibers support these organelles, which were previously considered free.

What is the composition of kinesins?

They typically contain two heavy chains with motor heads.