Cytology Quiz: Introduction to Cell Structure

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Questions and Answers

What is the primary function of the cell membrane?

To store genetic information

To generate energy for the cell

To provide nutrients to the cell

To control what enters and leaves the cell (correct)

Which of the following best describes the Fluid Mosaic Model?

A rigid structure with proteins embedded

A simple bilayer without any embedded molecules

A thick layer of carbohydrates surrounding the cell

A dynamic arrangement of phospholipids and proteins (correct)

What term describes the study of the structure and functions of cells?

Pathology

Histology

Molecular Biology

Cytology (correct)

Which process involves molecules moving from an area of lower concentration to an area of higher concentration?

Active transport Signup and view all the answers

What are the polar phosphate heads of phospholipids in the cell membrane classified as?

Hydrophilic Signup and view all the answers

Which component of the cell is primarily responsible for energy production?

Mitochondria Signup and view all the answers

What happens during the process of endocytosis?

Substances are engulfed by the cell membrane Signup and view all the answers

What is the range of diameter for most human cells?

7.5 micrometers to 150 mm Signup and view all the answers

What is the primary function of microtubules in the cell?

To assist in the movement of organelles Signup and view all the answers

Which component of the cytoskeleton is known for forming a supporting framework in cells?

Intermediate filaments Signup and view all the answers

What is the function of centrioles during cell division?

They help organize the cell division process Signup and view all the answers

What role do glycoproteins play in the plasma membrane?

They act as identification markers. Signup and view all the answers

What type of junction prevents leakage between cells?

Tight junction Signup and view all the answers

What structure is responsible for increasing the surface area of the cell membrane?

Microvilli Signup and view all the answers

Which structure is primarily responsible for protein synthesis in cells?

Rough Endoplasmic Reticulum Signup and view all the answers

What is a significant function of the cytoplasm?

Metabolic reactions Signup and view all the answers

Which of the following statements regarding cilia is false?

They are long, tail-like structures. Signup and view all the answers

How do microfilaments contribute to cellular function?

By allowing cells to slide and shorten Signup and view all the answers

How do membrane proteins participate in signal transduction?

By reacting to specific chemicals Signup and view all the answers

What is the primary role of the centrosome in the cell?

As a microtubule-organizing center Signup and view all the answers

What is the primary function of the Smooth Endoplasmic Reticulum (SER)?

Lipid and cholesterol synthesis Signup and view all the answers

What type of molecules do ribosomes primarily synthesize?

Proteins Signup and view all the answers

What structural form does the Golgi Apparatus take?

Flattened membranous sacs Signup and view all the answers

What is a characteristic feature of the Rough Endoplasmic Reticulum?

It is studded with ribosomes. Signup and view all the answers

Which type of transport across the plasma membrane requires energy?

Active transport Signup and view all the answers

What happens to blood cells in a hypertonic solution?

They shrink and crenate Signup and view all the answers

What does facilitated diffusion primarily rely on?

Number of transport proteins Signup and view all the answers

What describes osmosis?

Movement of water across selectively permeable membranes Signup and view all the answers

Which of the following describes a hypotonic solution?

Less solutes than inside the cell Signup and view all the answers

Which type of junction allows chemical substances to pass between cells?

Gap junction Signup and view all the answers

What is a characteristic of simple diffusion?

Particles become evenly distributed Signup and view all the answers

What primarily drives passive transport mechanisms?

Concentration gradient Signup and view all the answers

What is formed when pseudopods extend and surround a particle during phagocytosis?

Phagosome Signup and view all the answers

Which process is often referred to as cellular drinking?

Pinocytosis Signup and view all the answers

Which type of diffusion involves transport proteins to speed the movement of molecules across the plasma membrane?

Facilitated Diffusion Signup and view all the answers

What occurs when a vesicle fuses with the plasma membrane during exocytosis?

It releases materials into the extracellular fluid. Signup and view all the answers

Which of the following best describes the role of channel proteins in facilitated diffusion?

They provide corridors for specific molecules or ions. Signup and view all the answers

Lysosomes play a critical role in which cellular process?

Phagocytosis Signup and view all the answers

Which statement correctly describes carrier proteins in facilitated diffusion?

They undergo changes in shape to translocate solutes. Signup and view all the answers

What happens during pinocytosis?

Cells absorb tiny droplets of extracellular fluid. Signup and view all the answers

Study Notes

Introduction

Cell is considered the fundamental living unit of any organism
All organisms are made up of cells.
Cells are responsible for metabolism, which is the sum of all chemical reactions within a cell.
Cells can mutate due to accidental changes in their DNA.
Cytology is the study of the structure and function of cells.

Cell Structure

Cell membrane acts as the outer boundary of the cell and controls what enters and leaves.
The membrane is a phospholipid bilayer with embedded proteins and is described by the fluid mosaic model.
The hydrophilic heads face outward and the hydrophobic tails face inward.
The membrane functions as a boundary, marker, and plays a role in transportation.
Cell recognition proteins allow cells to recognize other cells.
Some membrane proteins have carbohydrates attached to them, forming glycoproteins, which function in identification.
Some membrane proteins are receptors that react to specific chemicals. The process is called signal transduction.

Cytoplasm

Cytoplasm is a gel-like matrix that contains water, enzymes, nutrients, wastes, and gases.
It also contains cell structures (organelles).
The fluid surrounding the organelles is called cytosol.
Most of the cell's metabolic reactions take place in the cytoplasm.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a network of interconnected parallel membranes, continuous with the nuclear membrane.
There are two types of ER: rough ER and smooth ER.
Rough ER is studded with ribosomes and functions in protein synthesis and intracellular transportation of molecules.
Smooth ER lacks ribosomes and functions in lipid and cholesterol synthesis. It also stores calcium.

Ribosomes

Each cell contains thousands of ribosomes, many attached to the rough ER.
Ribosomes are non-membranous structures, composed of two subunits (large and small) that are made of rRNA.
The function of ribosomes is protein synthesis.
Proteins released from the ER are not mature, and need further processing in the Golgi complex.

Golgi Apparatus

The Golgi apparatus is made up of flattened membranous sacs (cisternae) that are arranged in stacks like pancakes.
The stacks are associated with many vesicles (membrane-bound sacs containing proteins).
Function: To modify, sort, and package proteins that were synthesized by the rough ER.

Mitochondria

Mitochondria are the “powerhouses” of cells
Produce the energy currency ATP ( adenosine triphosphate) for cell function.
Function: To generate energy through cellular respiration.
Mitochondria have their own DNA and ribosomes.

Lysosomes

Lysosomes are membrane-bound sacs containing digestive enzymes.
Function: To breakdown worn-out cell parts or foreign invaders.

Peroxisomes

Peroxisomes are small sacs that are important in breaking down fatty acids.
They contain enzymes that detoxify harmful substances such as alcohol.

Nucleus

The nucleus is the control center of the cell.
It houses the cell's DNA, which contains the genetic instructions for building and maintaining the cell.
The nucleus is enclosed by the nuclear envelope.
The nucleus contains nucleoli which synthesize rRNA.

Cytoskeleton

The cytoskeleton is a network of protein fibers that provides support and structure to the cell.
The cytoskeleton helps maintain the cell's shape, and provides a framework for the movement of the organelles within the cell.
The cytoskeleton is composed of three types of protein fibers: microfilaments, intermediate filaments, and microtubules.

Microfilaments

Microfilaments are thin, solid protein fibers made of actin that contribute to cell shape, muscle contraction, and cell division.
They are important component of cytoskeleton which offers support to cell structure.
Microfilaments can slide past each other, causing shortening of the cell.

Intermediate Filaments

Intermediate filaments are twisted protein strands slightly thicker than microfilaments.
They form much of the supporting framework in many types of cells.

Microtubules

Microtubules are hollow tubes made of tubulin that help shape the cell.
They guide the movement of organelles ( their function is to move things around in the cell).
They help separate the chromosome copies in dividing cells.

Centrosomes and Centrioles

The centrosome is an area of the cytoplasm near the nucleus that coordinates the building and breaking of microtubules in the cell.
It is considered a “microtubule-organizing center.”
It plays an important role during cell division.
It contains a pair of centrioles.
Centrioles are self-replicating and made up of bundles of microtubules.
They help organize cell division.

Cell Membrane Surface Modifications

Cilia are short, hair-like cellular extensions that aid in moving substances through passageways.
Cilia are located in the lining of the respiratory tract and fallopian tubes.
Flagella are tail-like projections, typically only one per cell, that assist in cell locomotion.
Sperm cells have flagella.
Microvilli are small finger-like extensions of the external surface of the cell membrane. They function to increase surface area.
Microvilli are located in the lining of the digestive tract.

Membrane Junctions

Tight junctions are impermeable junctions that encircle the cell and prevent leakage.
Tight junctions are found in the blood brain barrier and skin.
Desmosomes are anchoring junctions scattered along the sides of cells. They prevent tissues from fraying apart.
Desmosomes are found in the stomach, uterus, and bladder.
Gap junctions allow chemical substances to pass between cells.
Gap junctions are found in the heart.

Transport Across The Plasma Membrane

There are two types of transport across the plasma membrane: passive transport and active transport.
Passive transport does not require ATP (energy). Substances move from an area of high concentration to an area of low concentration.
Examples of passive transport include: simple diffusion, osmosis, facilitated diffusion, and filtration.

Simple Diffusion

Simple diffusion is the random mixing of particles in solution.
Substances move down the concentration gradient.
Particles eventually become evenly distributed, reaching equilibrium.

Facilitated Diffusion

Diffusion through channel proteins or transport proteins.
Allows the passage of small inorganic ions (Na+, K+, Ca+2) and glucose, water soluble vitamins (B,C).
Facilitated diffusion is generally slower than diffusion across the lipid portion of the membrane.
It depends upon the number of available transporters.

Osmosis

Osmosis is a passive process where water diffuses across a selectively permeable membrane from an area of high water concentration (low solute) to an area of low water concentration (high solute).

Tonicity

Tonicity refers to how a solution affects cell volume.
A hypertonic solution has a higher concentration of solutes.
In a hypertonic solution, blood cells shrink and crenate.
A hypotonic solution has a lower concentration of solutes.
In a hypotonic solution, blood cells swell up and hemolyse.
An isotonic solution has similar concentrations of solutes.

Active Transport

Active transport requires ATP (energy) to move substances across the plasma membrane.
Active transport moves substances against their concentration gradient, from low to high concentration.

Examples of Active Transport:

Sodium-potassium pump - maintains the cell's resting membrane potential.
Endocytosis - cellular uptake of large molecules, particles, or fluids.
Exocytosis - cellular release of large molecules, particles, or fluids.

Endocytosis

Endocytosis is a process that brings substances into the cell.
Two types: phagocytosis and pinocytosis.

Phagocytosis

Phagocytosis (cell eating) involves engulfing large particles such as bacteria, viruses, or cell debris.
Phagocytosis is important for immune defense.

Pinocytosis

Pinocytosis (cell drinking) is the uptake of tiny droplets of extracellular fluid taken into the cell via formation of small vesicles.
Lysosomes fuse and degrade the particles, releasing the smaller useable particles.

Exocytosis

Exocytosis releases materials from a cell.
All cells carry out this process.
Examples include:
Secretory cells (release digestive enzymes, hormones, mucus, or other secretions).
Nerve cells (release neurotransmitters).
Vesicles fuse with the plasma membrane and release contents into the extracellular fluid.

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Description

Test your knowledge on the fundamental unit of life: cells. This quiz covers essential topics including cell metabolism, membrane structure, and the functions of various cellular components. Dive into the world of cytology and see how well you understand the intricacies of cell biology.