Cell Structure

_____ is/are identical in structure to centrioles.

Basal bodies and centrioles have identical structures.

Which of the following is true concerning both mitochondria and chloroplasts?

Both mitochondria and chloroplasts contain DNA and ribosomes.

Cytoplasm

The internal volume of the cell exclusive of the nucleus

Which of the following statements about the nuclear envelope is false?

The nuclear envelope is continuous with the Golgi apparatus. The statement is false; the nuclear envelope is continuous with the endoplasmic reticulum. Right answers (Molecules pass into and out of the nucleus through nuclear pores. Nuclear pores are made up of a group of proteins that are collectively called the nuclear pore complex. The nuclear envelope is composed of two lipid bilayers.)

If the surface area of a cell increases by a factor of 100, the volume of that cell will

increase by a factor of 1000.

The smooth endoplasmic reticulum functions in synthesis of

lipids

If you were shown an electron micrograph of a section of a cell and were asked to identify the cell as plant or animal, one thing you might do is

look for plastids or a large vacuole.

One reason that it might be difficult to separate lysosomes from peroxisomes by centrifugation techniques is that

lysomsomes and peroxisomes are similar in size

Which of the following groups of organelles contain acid hydrolases, catalase, and detoxifying enzymes for drugs, respectively?

lysosome, peroxisome, smooth endoplasmic reticulum

The major structural elements of the cytoskeleton are

microtubules, microfilaments, and intermediate filaments.

Ribosomal subunits are manufactured by the __

nucleolus

Which of the following organelles has only a single membrane around it?

peroxisome

Role of the eukaryotic cytoskeleton

1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. . 2. Many cell organelles, most notably the nucleus, are anchored by intermidiate filaments which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microtubules. 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfililaments. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermidiate filaments . 6. During muscle contractions, myosin motor proteins move across tracks of microfililaments. The eukaryotic cytoskeleton is appropriately named because, at the cellular level, these fibers and their associated motor proteins perform similar roles as an animal's musculoskeletal system. Microfilaments are responsible for cell locomotion and the cell's structural characteristics. Microtubules serve as intracellular highways for transporting vesicles and organelles; they are also required for cellular locomotion via flagella and cilia. Intermediate filaments are rope-like structures that anchor organelles and intercellular junctions called desmosomes. They are specialized for bearing tension.

Cell wall; extracellular matrix

Cell wall and extracellular matrix are separate structures with no particular relationship to each other.

Mitochondrion; crista

Crista is a constituent part of mitochondrion.

Cell wall; extracellular matrix

Cytoskeleton is a constituent part of cytoplasm.

Cytoplasm; cytoskeleton

Cytoskeleton is a constituent part of cytoplasm.

The nucleus contains most of a cell's ..

DNA

Which molecules do not normally cross the nuclear membrane?

DNA (All processes involving DNA take place in the nucleu).

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.

False (Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process).

_____ are surface appendages that allow a bacterium to stick to a surface.

Fimbriae

If you were asked to determine which organism the ribosomal components were from, how could you do this?

For the rRNA you could sequence it. For the ribosomal proteins you could sequence the proteins. For the ribosomal proteins you could sequence the genes that encode the proteins.

Golgi complex; nucleus

Golgi complex and nucleus are separate structures with no particular relationship to each other.

Chloroplast; granum

Granum is a constituent part of chloroplast.

Where is calcium stored?

In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.

What types of intermolecular forces do you think are holding the individual proteins and rRNAs together in this supramolecular complex?

Individual proteins and rRNA in a complex are held by various forces such as H-bonding, ionic bonding, Van Der Waals interactions as well as hydrophobic interactions. But covalent bonding is not observed.

Which of these provides the cell with structural support?

Microfilaments are a component of the cytoskeleton.

Which of these are hollow rods that shape and support the cell?

Microtubules are rods that also play a role in organelle movement.

Which of these organelles carries out cellular respiration?

Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.

Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins.After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results?

Only one of the two fusion proteins possesses a nuclear localization signal. (The nuclear localization signal is only present in the fusion protein that enters the nucleus).

A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place?

Passive transport (A 25,000-dalton protein is small enough to diffuse through nuclear pores without any expenditure of energy)

Which of these organelles produces H2O2 as a by-product?

Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.

Comparing eukaryotic and prokaryotic cells

Prokaryotic only - nucleoid Eukaryotic only - Lysosome, Mitochondria, Nucleolus BOTH -: Ribosomes, Plasma membrane, Flagella Only bacteria and archaea have prokaryotic cells, which lack a nucleus and other membrane-enclosed organelles. Prokaryotic cells are smaller and, at the level of the individual cell, are generally less versatile than eukaryotic cells, which compartmentalize many of their metabolic pathways into organelles. Nevertheless, prokaryotes are indispensable in every known ecosystem, and certain species are capable of surviving in some of the harshest and most nutrient-limiting environments on Earth.

____ are the sites of protein synthesis.

Ribosomes

Several environments in which you are more likely to find archaea than bacteria are

Several environments in which you are more likely to find archaea than bacteria areextreme environments ex: acidic hot springs, swamp mud, great salt lake

The structure that regulates the passage of material into and out of this bacterial cell is indicated by the letter _____.

The plasma membrane is selectively permeable.

Cytosol

The semifluid portion of the cytoplasm.

- Structure and function of the chloroplast The structure of a chloroplast is closely tied to its function as the site of photosynthesis.

They contain the green pigment chlorophyll. They are the sites of reactions that convert solar energy into chemical energy. They have membranous sacs called thylakoids that are surrounded by a fluid called stroma.

Which of these is the double membrane that encloses the nucleus?

This is the nuclear envelope.

In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules?

To make the proteins easy to see (Fluorescent tags make the location of the proteins easy to visualize).

What other molecules would you have to add to the test tube in order for the ribosomes to make polypeptides? (This may require some sleuthing in later chapters.)

You would need to add amino acids, mRNAs, tRNAs, amino acyl-tRNA synthetases, and a source of ATP. Components required for translation: i. Messenger RNA ii. Transfer RNA iii. Amino acyl tRNA synthetases iv. Amino acids v. Energy source (ATP/GTP) vi. Ribosomes

A cellular structure that is visible with an electron microscope but not with a light microscope is

a ribosome.

Which of the following would be attributed to a peroxisomal dysfunction?

accumulation of very long chain fatty acids

A slice of raw apple placed in a concentrated sugar solution will

become flaccid as water is drawn out of its cells.

What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?

cell wall

Which of these is NOT a component of the cell cytoskeleton?

cellulose fibril

The _____ is composed of DNA and protein.

chromatin

The nucleic acid of a virus is composed of

either DNA or RNA but not both.

Tour of a Plant Cell: Structures and Functions (BioFlix tutorial)

plant cell wall - strong protective stucture made from cellulose fibrils central vacuole - regulates cytoplasm composition, creates internal pressure, and stores cell compounds chlorplast - makes sugar by converting light energy into chemical energy. mitochondrion - produces chemical energy (ATP) that can power the cell Golgi apparatus - modifies and packages protiends Each organelle in a plant cell carries out a specific function. Mitochondria and the Golgi apparatus serve the same functions in both plant cells and animal cells.

The _____ is a selective barrier, regulating the passage of material into and out of the cell.

plasma membrane

The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell.

plasma membrane

What is the function of a bacterium's capsule?

protection

Which sequence reflects the locations that a secretory protein will visit on its way from its production to its secretion outside the cell?

rough ER, ER vesicle, Golgi complex, secretory vesicle

Which of these manufactures cellular membranes by adding membrane proteins andphospholipids to its own membrane?

rough endoplasmic reticulum

The cytosol is best described as the

semifluid substance in which organelles are suspended.

Viral DNA makes mRNA by the process of _____.

transcription -Viral DNA co-opts the cell's reproductive machinery.

In which of the following properties are the archaea more like eukaryotes than the bacteria?

translation initiation

Which of these structures stores, modifies, and packages products?

The Golgi apparatus modifies, stores, and packages products of the ER.