CTJan27 Online JMSS Exam Prep - Cell Structre

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A Tour Inside the Eukaryotic Cell

Welcome to the fascinating world of the eukaryotic cell, the fundamental building block of complex life forms like plants, animals, fungi, and protists. Unlike simpler prokaryotic cells, eukaryotic cells have a 'true nucleus' and a variety of other membrane-bound compartments called organelles, each with a specific job.

The Command Center: The Nucleus

The nucleus is often called the 'brain' of the cell because it houses the cell's genetic material, DNA (Deoxyribonucleic acid), and controls all of the cell's activities, such as growth, metabolism, and reproduction.

  • Nuclear Envelope: This is a double membrane that surrounds the nucleus, separating its contents from the cytoplasm. It has tiny holes called nuclear pores, which act as gateways, carefully controlling what molecules can enter and exit the nucleus.
  • Nucleolus: A dense structure found inside the nucleus. Its main job is to produce ribosomes, the cell's protein-making machinery.

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The Cell Membrane: The Cell's Gatekeeper

Imagine a cell as a bustling city. The cell membrane is its smart, selective border patrol. This thin, flexible barrier surrounds every cell, separating its internal environment from the outside world.

Key Features

  • Phospholipid Bilayer: The membrane is made of two layers of fat molecules called phospholipids. This structure creates a durable yet fluid barrier that is naturally oily, preventing most water-soluble substances from passing through freely.
  • Selective Permeability: It isn't a solid wall. Special proteins are embedded within the membrane, acting as channels and pumps. They carefully control what enters and leaves, such as nutrients, ions, and waste products.
  • Cell Communication: The membrane surface also holds receptors that receive chemical signals from other cells, allowing the cell to sense and respond to its environment.
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Cell Structure

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A Tour Inside the Eukaryotic Cell

The Cell's Interior

  • Cytoplasm and Cytosol: The cytoplasm refers to everything within the cell membrane but outside the nucleus. It consists of the cytosol, a jelly-like substance made mostly of water, salts, and organic molecules, in which all the other organelles are suspended.

Organelles for Manufacturing and Energy

  • Ribosomes: These are the protein factories of the cell. They can be found floating freely in the cytosol or attached to the Endoplasmic Reticulum. They read instructions from the DNA (via a messenger molecule) to build proteins.
  • Rough Endoplasmic Reticulum (Rough ER): This is a network of membranes connected to the nuclear envelope. It's called 'rough' because its surface is studded with ribosomes. Proteins made by these ribosomes are modified and prepared for transport here.
  • Smooth Endoplasmic Reticulum (Smooth ER): This network of membranes lacks ribosomes, giving it a 'smooth' appearance. Its functions include synthesizing lipids (fats), detoxifying harmful substances, and storing calcium ions.
  • Golgi Apparatus (or Golgi Complex): Think of this as the cell's post office. It receives proteins and lipids from the ER, further modifies them, sorts them, and packages them into vesicles (small membrane-bound sacs) for delivery to other destinations inside or outside the cell.
  • Mitochondria: These are the 'powerhouses' of the cell. They perform cellular respiration, a process that converts the chemical energy from food (like glucose) into a usable form of energy for the cell, called ATP (Adenosine Triphosphate).
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A Tour Inside the Eukaryotic Cell

Cleanup, Support, and Structure

  • Lysosomes: These are the recycling centers of the cell. They are vesicles filled with powerful digestive enzymes that break down worn-out organelles, food particles, and engulfed viruses or bacteria.
  • Cytoskeleton: This is a network of protein fibers extending throughout the cytoplasm. It provides structural support, helps maintain the cell's shape, and is involved in cell movement and the transport of organelles within the cell.
  • Cell Membrane (Plasma Membrane): This is the outer boundary of all cells. It is a flexible, selectively permeable barrier that regulates which substances enter and leave the cell, protecting its internal environment.

Special Structures in Plant Cells

Plant cells have a few additional structures not typically found in animal cells:

  • Cell Wall: A rigid layer located outside the cell membrane, made primarily of cellulose. It provides structural support and protection to the plant cell.
  • Chloroplasts: These are the sites of photosynthesis. They contain a green pigment called chlorophyll, which captures light energy to convert carbon dioxide and water into glucose (food).
  • Central Vacuole: A large, membrane-bound sac that can take up 30-80% of the cell volume. It stores water, nutrients, and waste products. By pushing against the cell wall, it helps maintain turgor pressure, which keeps the plant rigid.
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1

A protein is synthesized by a ribosome and is destined for secretion out of the cell. Which of the following describes the correct pathway for this protein?

Smooth ER → Golgi Apparatus → Lysosome

Rough ER → Cytosol → Cell Membrane

Nucleolus → Rough ER → Golgi Apparatus → Cytosol

Rough ER → Golgi Apparatus → Vesicle → Cell Membrane
2

What is the primary function of the cell membrane?

To synthesize proteins

To produce energy for the cell

To control which substances enter and leave the cell

To store the cell's genetic material
3

The cell membrane is primarily composed of a:

Phospholipid bilayer

Sugar-phosphate backbone

Cellulose wall

Protein matrix
4

Which of the following types of molecules would pass most easily through the lipid bilayer of the cell membrane?

Ionic compounds

Large proteins

Large polar molecules

Small nonpolar molecules
5

What is the main role of the nucleus in a eukaryotic cell?

It packages and sorts proteins for transport.

It breaks down waste materials.

It contains the cell's genetic material and controls its activities.

It acts as the site of cellular respiration.
6

The complex of DNA and proteins found inside the nucleus of eukaryotic cells is called:

Ribosome

Nucleolus

Chromatin

Cytoplasm
7

The nucleus is often referred to as the ________ of the cell.

shipping department

recycling plant

control center

powerhouse
8

What is the structure that separates the nucleus from the cytoplasm?

The nuclear envelope

The plasma membrane

The cell wall

The Golgi apparatus
9

The nuclear envelope is perforated with nuclear pores. What is the function of these pores?

To produce energy for the nucleus

To synthesize DNA

To regulate the passage of molecules in and out of the nucleus

To allow the nucleus to move within the cell
10

What is the primary function of the nucleolus?

Storage of genetic information

Breakdown of cellular waste

Synthesis of ribosomes

Detoxification of poisons
11

Where is the nucleolus located within a eukaryotic cell?

Inside the nucleus

Freely floating in the cytoplasm

Embedded in the cell membrane

Inside the mitochondrion
12

What is the key difference between cytoplasm and cytosol?

Cytoplasm is only found in plant cells, while cytosol is in animal cells.

Cytosol is the jelly-like substance inside the nucleus.

There is no difference; the terms are interchangeable.

Cytosol is the fluid portion, while cytoplasm includes the cytosol and all organelles except the nucleus.
13

Many metabolic pathways, such as glycolysis, occur in which part of the cell?

The mitochondrion

The nucleus

The lysosome

The cytosol
14

Which organelle is responsible for generating most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy?

Chloroplast

Ribosome

Nucleus

Mitochondrion
15

The mitochondrion is often called the 'powerhouse' of the cell because it is the site of:

Lipid storage

Cellular respiration

Protein synthesis

Photosynthesis
16

A unique feature of mitochondria is that they contain their own:

DNA and ribosomes

Cytoskeleton

Cell wall

Lysosomes
17

What is the primary function of ribosomes in a cell?

Energy production

Waste breakdown

Cell division

Protein synthesis
18

Ribosomes are composed of which two types of macromolecules?

Lipids and carbohydrates

DNA and proteins

RNA and proteins

Phospholipids and DNA
19

In a eukaryotic cell, where can ribosomes be found?

Both free in the cytosol and attached to the rough endoplasmic reticulum

Only floating freely in the cytosol

Only inside the nucleus

Only attached to the Golgi apparatus
20

The rough endoplasmic reticulum (RER) appears 'rough' because it is studded with:

Mitochondria

Golgi bodies

Ribosomes

Lysosomes
21

What is a major function of the rough endoplasmic reticulum?

Synthesizing and modifying proteins that will be secreted from the cell

Storing calcium ions

Performing photosynthesis

Synthesizing lipids and steroids
22

The membrane of the rough endoplasmic reticulum is continuous with which other organelle's membrane?

Mitochondrion

Lysosome

Nuclear envelope

Cell membrane
23

Which of the following is a primary function of the smooth endoplasmic reticulum (SER)?

Production of ATP

Synthesis of proteins

Digestion of cellular waste

Synthesis of lipids and detoxification of drugs
24

Unlike the rough ER, the smooth ER lacks which structures on its surface?

Channels

Ribosomes

Enzymes

Pores
25

In which type of human cells would you expect to find an abundance of smooth ER?

Skin cells

Nerve cells

Liver cells

Muscle cells
26

Which organelle functions to modify, sort, and package proteins and lipids for secretion or delivery to other organelles?

Ribosome

Nucleus

Mitochondrion

Golgi apparatus
27

The Golgi apparatus is often compared to a:

Post office or shipping center

Cell's brain

Construction site

Factory's power plant
28

The flattened membranous sacs that make up the Golgi apparatus are called:

Cristae

Cisternae

Vesicles

Thylakoids
29

Which organelle contains hydrolytic enzymes and is involved in the breakdown of waste materials and cellular debris?

Lysosome

Ribosome

Peroxisome

Vacuole
30

The process by which a cell digests its own components is called autophagy, which is carried out by:

Mitochondria

Lysosomes

The nucleus

Ribosomes
31

Due to their function, lysosomes are sometimes referred to as the cell's:

Recycling centers

Information database

Energy producers

Protein factories
32

The network of protein filaments and tubules in the cytoplasm of many living cells, giving them shape and coherence, is called the:

Cell wall

Cytoskeleton

Endoplasmic reticulum

Extracellular matrix
33

Which of the following is NOT a major component of the cytoskeleton?

Microtubules

Cellulose fibers

Microfilaments

Intermediate filaments
34

Which of the following organisms has a cell wall?

Insect

Oak tree

Human

Fish
35

The primary structural component of a plant cell wall is:

Chitin

Cellulose

Keratin

Peptidoglycan
36

What is the main function of the cell wall in a plant cell?

To store water and nutrients

To regulate the passage of materials into the cell

To perform photosynthesis

To provide rigid structural support and protection
37

Which organelle is the site of photosynthesis in plant cells?

Chloroplast

Mitochondrion

Nucleus

Vacuole
38

What is the green pigment found in chloroplasts that captures light energy for photosynthesis?

Melanin

Hemoglobin

Carotene

Chlorophyll
39

In which of the following cell types would you expect to find chloroplasts?

A root cell of a plant

A leaf cell of a plant

A human muscle cell

A fungal cell
40

A large central vacuole is a prominent feature of which type of cell?

Bacterial cells

Mature plant cells

Animal nerve cells

Fungal cells
41

What is the primary function of the central vacuole in a plant cell?

To carry out cellular respiration

To synthesize proteins for the cell

To control all cellular activities

To store water and maintain turgor pressure
42

A plant cell placed in pure water does not burst, but instead becomes turgid. This turgidity is a direct consequence of the interplay between which three structures?

Water influx into the central vacuole, pushing the cell membrane against the rigid cell wall.

Mitochondria actively pumping water out of the cell to balance osmotic pressure.

Chloroplasts producing sugars that increase the solute concentration of the cell wall.

The cytoskeleton reinforcing the cell membrane against the inward pressure of the cell wall.
43

Which of the following best describes the primary function of the cell membrane?

To synthesize proteins for the cell.

To control the movement of substances into and out of the cell.

To provide rigid structural support to the cell.

To store the cell's genetic material.
44

The nucleus is often called the "control center" of the cell. This is primarily because it contains the:

Lysosomes for breaking down waste.

Cell's genetic material (DNA).

Ribosomes for protein synthesis.

Mitochondria, which generate energy.
45

Which organelle is responsible for cellular respiration, the process that generates most of the cell's supply of adenosine triphosphate (ATP)?

Mitochondrion

Golgi apparatus

Vacuole

Chloroplast
46

The "rough" appearance of the Rough Endoplasmic Reticulum (RER) is due to the presence of which structures on its surface?

Golgi bodies

Lysosomes

Ribosomes

Mitochondria
47

A cell that is very active in detoxifying drugs and producing lipids, such as a liver cell, would be expected to have a large amount of which organelle?

Smooth Endoplasmic Reticulum (SER)

Nucleolus

Cytoskeleton

Rough Endoplasmic Reticulum (RER)
48

After proteins are synthesized in the Rough ER, they are transported to another organelle for modification, sorting, and packaging. What is this organelle?

Lysosome

Golgi Apparatus

Nucleus

Central Vacuole
49

Which organelle contains digestive enzymes and is responsible for breaking down waste materials, cellular debris, and engulfed viruses or bacteria?

Mitochondrion

Centriole

Ribosome

Lysosome
50

A key structural difference between a plant cell and an animal cell is the presence of a rigid outer layer made of cellulose in plant cells. What is this structure called?

Nuclear envelope

Cell membrane

Cell wall

Cytoskeleton
51

Photosynthesis, the process of converting light energy into chemical energy, occurs in which organelle found in plant cells?

Chloroplast

Mitochondrion

Ribosome

Nucleolus
52

In a mature plant cell, which organelle can take up a large portion of the cell's volume and is primarily responsible for maintaining turgor pressure against the cell wall?

Nucleus

Golgi Apparatus

Cytosol

Central Vacuole

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