Cell Organelles and Functions Quiz
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Questions and Answers

What is the primary function of centrioles in animal cells?

  • Organizing microtubules for spindle fiber formation (correct)
  • Producing ATP molecules
  • Synthesis of ribosomal RNA
  • Contracting muscle fibers

Which structure is responsible for controlling the exchange of materials between the nucleus and cytoplasm?

  • Centrosome
  • Rough endoplasmic reticulum
  • Nuclear pores (correct)
  • Cristae

What type of cells contain centrioles?

  • Both plant and animal cells
  • Neither plant nor animal cells
  • Animal cells only (correct)
  • Plant cells only

Which component within the nucleus is directly responsible for ribosomal RNA synthesis?

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

What is the shape of the chloroplasts found in plant cells?

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

During what phase of the cell cycle do centrioles replicate?

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

What is the main role of the nuclear DNA?

<p>Carrying genetic instructions for protein synthesis (B)</p> Signup and view all the answers

Which of the following organelles is NOT found in plant cells?

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

What process occurs in the Golgi apparatus that involves the addition of carbohydrates to proteins?

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

Which of the following correctly describes the function of lysosomes?

<p>Digestion of excess or worn-out organelles (A)</p> Signup and view all the answers

How are the enzymes in lysosomes synthesized and transported?

<p>Synthesized on the rough endoplasmic reticulum and transported to the Golgi body (B)</p> Signup and view all the answers

What role does the cristae in mitochondria serve?

<p>Increase surface area for ATP synthesis (D)</p> Signup and view all the answers

What is the primary role of the Golgi apparatus?

<p>Package and transport proteins and lipids (C)</p> Signup and view all the answers

What is the structure of mitochondria characterized by?

<p>Rod shape with double membrane bound (B)</p> Signup and view all the answers

Which structural feature distinguishes mitochondria from bacteria?

<p>Presence of cristae (D)</p> Signup and view all the answers

What type of DNA is found in prokaryotic cells?

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

Which statement about the Golgi apparatus is false?

<p>It synthesizes hydrolytic enzymes directly. (C)</p> Signup and view all the answers

Which of the following organelles can only be observed using an electron microscope?

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

What is primarily found in the matrix of mitochondria?

<p>Circular DNA and ribosomes (D)</p> Signup and view all the answers

Which component is found in eukaryotic cells but not in prokaryotic cells?

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

What is the primary function of the slime capsule in prokaryotic cells?

<p>To protect against dehydration and immune response (C)</p> Signup and view all the answers

How does the average size of prokaryotic cells compare to that of eukaryotic cells?

<p>Prokaryotic cells are smaller, averaging 0.5-5 micrometers (A)</p> Signup and view all the answers

What type of ribosomes do prokaryotic cells primarily contain?

<p>70S ribosomes (D)</p> Signup and view all the answers

Which feature is shared by both mitochondria and chloroplasts?

<p>Double membrane structure (B)</p> Signup and view all the answers

What is the main purpose of using centrifugation in cell fractionation?

<p>To separate cell structures based on their relative density (C)</p> Signup and view all the answers

Which organelle is primarily responsible for protein synthesis and localization in cells?

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

Which of the following is NOT a membranous organelle?

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

What is the primary function of the thylakoids in chloroplasts?

<p>Site of light-dependent reactions in photosynthesis (A)</p> Signup and view all the answers

What characterizes membranous organelles in a cell?

<p>They contain enzymes that can function in an isolated environment (C)</p> Signup and view all the answers

Which component of the chloroplast is responsible for the site of light-independent reactions?

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

Which statement accurately describes the structure of a large permanent vacuole?

<p>Occupies 80% of the total plant cell volume (B)</p> Signup and view all the answers

Which organelle is involved in the synthesis of ATP and is often referred to as the powerhouse of the cell?

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

What is a function of plasmodesmata in plant cells?

<p>Facilitates communication and transport between cells (B)</p> Signup and view all the answers

Which process is used to track the pathway of secreted proteins in a cell?

<p>Use of radioactively labelled amino acids (D)</p> Signup and view all the answers

What structure connects the endoplasmic reticulum to the nuclear envelope?

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

What is the role of the tonoplast in a large permanent vacuole?

<p>Regulates exchange of substances via osmosis (C)</p> Signup and view all the answers

What is the primary characteristic of amyloplasts?

<p>They store starch in a colorless form (C)</p> Signup and view all the answers

What differentiates non-membranous organelles from membranous ones?

<p>Non-membranous organelles do not have a surrounding membrane (A)</p> Signup and view all the answers

Which organelle is primarily associated with the endosymbiont theory?

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

Which of the following is NOT a characteristic of both chloroplasts and mitochondria?

<p>They both carry out photosynthesis (B)</p> Signup and view all the answers

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

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

Where are 70S ribosomes typically found?

<p>In prokaryotic cells and mitochondria (C)</p> Signup and view all the answers

What characterizes the Smooth Endoplasmic Reticulum (SER)?

<p>It is involved in the synthesis of lipids and steroid hormones. (C)</p> Signup and view all the answers

What do small sacs bud off from the Rough Endoplasmic Reticulum form?

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

Which of the following describes the Golgi apparatus?

<p>A stack of flattened membrane-bound sacs with no interconnecting membranes (A)</p> Signup and view all the answers

Which type of ribosome is primarily associated with the synthesis of proteins for intracellular use?

<p>Free ribosomes in the cytoplasm (A)</p> Signup and view all the answers

Which of the following is true about the differences in ribosomal types?

<p>80S ribosomes are associated with eukaryotes. (C)</p> Signup and view all the answers

What is the function of polypeptide chains that enter the cisternal space of the Rough Endoplasmic Reticulum?

<p>They undergo folding and modification. (D)</p> Signup and view all the answers

Flashcards

Mitochondria

The powerhouse of the cell; responsible for aerobic respiration and producing ATP (energy currency).

Centrioles

Non-membranous organelles found in animal cells, but not plant cells. They are hollow cylinders made up of nine groups of microtubules, each in triplets.

Nucleus

The control center of the cell; contains DNA (genetic material) and controls all cell activities.

Grana

Stacks of flattened membrane-bound sacs called thylakoids within chloroplasts, where light-dependent reactions of photosynthesis occur.

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Thylakoid

Individual flattened sacs within chloroplasts, containing chlorophyll and other pigments for capturing light energy.

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Chloroplast

The organelle responsible for photosynthesis in plant cells. It contains chlorophyll and other pigments for capturing light energy.

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Nucleolus

The site where ribosomes are assembled and modified.

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Mitochondria

Lipid synthesis occurs in the.

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Rough ER

A type of endoplasmic reticulum (ER) that is studded with ribosomes, involved in protein synthesis and modification.

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Translation

The process of creating proteins from messenger RNA (mRNA) at the ribosomes.

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Smooth ER

A type of endoplasmic reticulum (ER) that lacks ribosomes and is involved in lipid synthesis, detoxification, and steroid hormone production.

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Ribosomes

Small, non-membranous organelles that are the site of protein synthesis.

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70S Ribosome

Type of ribosome found in prokaryotes, mitochondria, and chloroplasts. Smaller in size than eukaryotic ribosomes.

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80S Ribosome

Type of ribosome found in eukaryotic cells. Larger in size than prokaryotic ribosomes.

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Golgi Apparatus

A stack of flattened membrane-bound sacs (cisternae) involved in modifying, packaging, and sorting proteins and lipids.

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Vesicles

Small, membrane-bound sacs that transport proteins and lipids within the cell.

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Cell Fractionation

A technique used to separate cell structures based on their density. It involves spinning cells at high speed in a centrifuge. Larger structures have greater density and settle lower in the tube.

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Radioactive Labeling

Using radioactively labeled molecules, like amino acids, to track their movement and interactions within the cell. This allows for studying specific processes like protein synthesis.

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Membranous Organelles

Organelles enclosed by membranes, creating separated compartments within the cell. This allows for specific functions and conditions within each organelle.

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Non-Membranous Organelles

Organelles without surrounding membranes, directly interacting with the cytoplasm.

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Endoplasmic Reticulum

A network of interconnected membrane-bound sacs and tubules found within the cytoplasm of eukaryotic cells. It plays a vital role in protein synthesis, lipid metabolism, and detoxification.

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Cisternae

Flattened membranous sacs or tubules within the ER where proteins are synthesized and modified.

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Radioactive labeling of proteins

The process of using radioactive labeled amino acids to track the synthesis and movement of proteins through the endomembrane system.

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Secretory Pathway

The movement of proteins from the ribosomes to the ER, Golgi apparatus, and finally to the plasma membrane.

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Intergranal lamellae

Membrane connections between grana in chloroplasts, allowing movement of substances.

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Stroma

The fluid-filled space within chloroplasts, containing DNA, starch grains, ribosomes, and enzymes for light-independent reactions.

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Large permanent vacuole

A large, fluid-filled sac within plant cells, containing water, ions, minerals, and sugars. Surrounded by the tonoplast membrane, it regulates the movement of substances between cytoplasm and vacuole.

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Plasmodesmata

A cytoplasmic bridge connecting adjacent plant cells, allowing communication and movement of water through the symplastic pathway.

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Amyloplast

A double-membrane bound organelle in plant cells, storing starch (amylose and amylopectin). They are colorless.

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Bacterial cell wall

A layer of peptidoglycan (murein) consisting of parallel chains of polysaccharide cross linked by short peptides, creating a net-like structure. It provides strength and structural support to the bacterial cell.

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What is the Golgi apparatus?

The stack, constantly forming at one end (Forming Face) from fusion of vesicles from the ER, and broken down at the other end (maturing face) to form Golgi vesicles. These vesicles transport proteins and lipids to other parts of the cell or outside the cell via exocytosis.

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Capsule (Slime layer)

A protective layer found outside the cell wall of some bacteria, composed of starch, gelatin, protein, or glycolipid. It helps bacteria avoid being engulfed by phagocytes and shields them from antibiotics and antibodies.

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Bacterial DNA

A circular loop of DNA located in the cytoplasm of prokaryotic cells, containing the cell's genetic information.

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What is a key function of the Golgi apparatus?

The Golgi apparatus modifies proteins by adding carbohydrates to form glycoproteins (like mucus) in a process called glycosylation. It also modifies lipids.

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Starch granules

Concentric layers of amylopectin granules found in plant cells, mainly in storage organs like potatoes. They represent the primary storage form for starch in plants.

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What are lysosomes?

Lysosomes are small, spherical sacs surrounded by a single membrane, containing hydrolytic enzymes like proteases and lipases. They are responsible for the breakdown of worn-out organelles, food particles (in simple organisms), and engulfed viruses or bacteria.

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Nucleoid

A region within the cytoplasm of prokaryotic cells where the single circular DNA molecule is located. It's not enclosed by a membrane, unlike the nucleus in eukaryotic cells.

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How are lysosomes formed?

The enzymes in lysosomes are synthesized on the rough endoplasmic reticulum, transported to the Golgi, and packaged into Golgi vesicles that bud off to form primary lysosomes.

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Describe the structure of a mitochondrion?

Mitochondria are double-membrane bound organelles, typically about 1 micrometer in diameter, with a rod shape for efficient ATP production. The inner membrane folds into cristae to increase surface area for ATP synthesis during aerobic respiration. The outer membrane is more permeable.

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Plasmids

Small circular DNA molecules found in the cytoplasm of some bacteria, carrying extra genes that offer advantages like antibiotic resistance or toxin production.

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Pili

Tiny hair-like structures on the surface of some bacteria, allowing them to adhere to surfaces. This helps them establish colonies and spread.

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What are the intermembrane space and matrix of a mitochondrion?

The intermembrane space is the fluid space between the outer and inner membranes of the mitochondrion. The matrix is the interior solution containing circular DNA, 70S ribosomes, and stalked particles. This allows mitochondria to synthesize their own proteins and replicate independently.

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What is the function of cristae in mitochondria?

The inner membrane of the mitochondria is folded into cristae to increase surface area for ATP synthase, which is critical for aerobic respiration. This allows mitochondria to produce more ATP.

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70S ribosomes in mitochondria and chloroplasts

Organelles present in both chloroplasts and mitochondria, sharing characteristics like circular DNA and 70S ribosomes. They're also double-membrane bound and are involved in energy production.

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Why can mitochondria replicate independently?

Mitochondria have their own circular DNA and 70S ribosomes, allowing them to synthesize their own proteins and replicate independently.

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Study Notes

Cell Organelles and Their Functions

  • Cell fractionation uses centrifugation to separate cell structures based on their density. Higher centrifuge speeds allow for better separation of smaller particles.
  • Radioactive labelling of chemical substances within cells helps researchers pinpoint their location within the cell. An example is using radioactively labelled amino acids to track protein synthesis.
  • Ribosomes, the rough endoplasmic reticulum, the Golgi apparatus, and the plasma membrane participate in protein synthesis. Ribosomes produce proteins, the rough ER modifies those proteins, and the Golgi apparatus packages the proteins for transport.
  • The labelled protein's path, from ribosomes to rough endoplasmic reticulum to the Golgi apparatus to the plasma membrane, is tracked using microscopy or electrophoresis.

Cell Structure and Organelles

  • Cell structures are divided into two groups:
    • Membranous organelles: These organelles, enclosed by membranes, maintain optimal pH and specialized functions within the cell. Examples include mitochondria for respiration, chloroplasts for photosynthesis, and lysosomes with hydrolytic enzymes.
    • Non-membranous organelles: Ribosomes, starch grains, and centrosomes are examples of non-membranous organelles.

Endoplasmic Reticulum

  • The endoplasmic reticulum (ER) is a network of membranes that extends throughout the cytoplasm. It connects to the nuclear envelope.
  • The ER exists as two types (with distinct functions):
    • Rough ER: Studded with ribosomes and involved in protein synthesis and modification. Proteins made travel through the sacs of the ER, and are often folded into their final form. The rough ER is also responsible for transporting the proteins.
    • Smooth ER: Lacks ribosomes and involved in lipid synthesis and detoxification. Some cells, like liver cells, have a lot of smooth ER involved in detoxification.

Ribosomes

  • Ribosomes are the site of protein synthesis within cells.
  • They are composed of two subunits, large and small, each made from ribosomal RNA and protein.
  • Ribosomes can be free-floating in the cytoplasm, or bound to the endoplasmic reticulum. The attached ones synthesize proteins meant for secretion or insertion into membranes.

Golgi Apparatus

  • The Golgi apparatus is a stack of flattened sacs involved in processing and packaging proteins and lipids that are produced in the cell and destined for secretion.
  • It collects proteins from the ER in vesicles, modifies them chemically, and packages them into secretory vesicles for transport to destinations within or outside the cell. Carbohydrates can also be added or modified.

Lysosomes

  • Lysosomes are membrane-bound organelles containing hydrolytic enzymes.
  • They are involved in digesting cellular waste, foreign materials, or damaged organelles/parts of the cell.

Mitochondria

  • Mitochondria are double-membrane organelles containing their own DNA.
  • They are responsible for aerobic respiration, producing ATP, the cell's primary energy currency.
  • The folded inner membrane (cristae) increases surface area allowing more respiration to happen.
  • They contain their own DNA and ribosomes. They are self-replicating.

Nucleus

  • The nucleus is the largest organelle in a eukaryotic cell.
  • It's a double-membraned organelle with a nuclear envelope containing pores that allow material to pass between the nucleus and the cytoplasm.
  • The nucleus contains the cell's DNA organized as chromatin, is the site of ribosome synthesis in the nucleolus.

Chloroplasts

  • Chloroplasts are double-membrane organelles found in plant cells and some other organisms. These organelles contain their own DNA and are where photosynthesis occurs.
  • They have an internal system of membranes that includes thylakoids and grana (stacks of thylakoids), where light-dependent reactions take place.
  • The stroma is the fluid-filled space surrounding the thylakoids and grana where the light-independent reactions of photosynthesis occur.

Large Vacuole

  • Large vacuoles are fluid-filled sacs that take up a large portion of the interior of a plant cell.
  • They maintain turgor pressure in the cell and are involved in storage of water, nutrients, ions, and waste products..
  • The membrane that surrounds the vacuole, the tonoplast, manages transport of molecules into and out of the vacuole.

Plasmodesmata

  • Plasmodesmata are channels in plant cell walls that connect the cytoplasm of neighboring cells.
  • They allow for communication and exchange of small molecules between the cells.

Amyloplasts

  • Amyloplasts are double-membrane-bound organelles specializing in starch storage.
  • They are found in many plant cells, particularly those with substantial starch deposits (such as potato tubers).

Prokaryotic vs. Eukaryotic Cells

  • Prokaryotic cells (like bacteria) lack a nucleus and other membrane-bound organelles. Their DNA is circular and located in the cytoplasm.
  • Eukaryotic cells (like animal and plant cells) have a nucleus and other membrane-bound organelles. Their DNA is linear and contained within the nucleus.

Cell Walls

  • Plant cells, fungi, and some bacteria have cell walls, rigid structures that provide support and protection.
  • Animal cells lack cell walls.
  • Bacterial cell walls are made of peptidoglycan (murein), plant cell walls from cellulose.

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