UNIT 1 CELL BIOLOG

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Questions and Answers

Which of the following structures is responsible for energy production in eukaryotic cells?

Chloroplasts

Endoplasmic Reticulum

Golgi apparatus

Mitochondria (correct)

What type of DNA structure is found in eukaryotic cells?

Circular, in nucleoid region

Linear, in the cytoplasm

Linear, in nucleus (correct)

Circular, within mitochondria

Which component of eukaryotic cells is primarily involved in synthesizing proteins?

Chloroplasts

Lysosomes

Ribosomes (correct)

Plastids

In what way do plant cells differ from animal cells?

Plant cells have a cell wall. Signup and view all the answers

Which statement is true regarding eukaryotic cell size compared to prokaryotic cells?

Eukaryotic cells are typically larger than prokaryotic cells. Signup and view all the answers

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

Chloroplasts Signup and view all the answers

What is the function of the Golgi apparatus in eukaryotic cells?

Packages proteins and lipids Signup and view all the answers

Which statement describes the fluid mosaic model of the plasma membrane?

The membrane contains a mixture of lipids, proteins, and carbohydrates. Signup and view all the answers

Which statement accurately describes the characteristics of all cells?

All living organisms are composed of one or more cells. Signup and view all the answers

Which function of life is concerned with the ability to respond to environmental changes?

Sensitivity Signup and view all the answers

What does the endosymbiosis theory propose about the origin of certain organelles in eukaryotic cells?

They originated from free-living prokaryotic organisms engulfed by larger cells. Signup and view all the answers

How do you calculate the magnification of an image in microscopy?

Image Size ÷ Actual Size Signup and view all the answers

What is a key characteristic of stem cells that distinguishes them from other cell types?

They can differentiate into various specialized cell types. Signup and view all the answers

Which of the following correctly describes prokaryotic cells?

They lack a nucleus and have a single circular DNA molecule. Signup and view all the answers

What is the process called through which prokaryotic cells divide to form two cells?

Binary Fission Signup and view all the answers

What ethical concern is associated with the use of embryonic stem cells in research?

Their use involves the destruction of embryos. Signup and view all the answers

What is the primary role of cholesterol in the cell membrane?

To stabilize the membrane and reduce fluidity Signup and view all the answers

What distinguishes integral proteins from peripheral proteins in the membrane?

Integral proteins are permanently attached to the membrane Signup and view all the answers

What type of molecules can typically pass through the cell membrane via simple diffusion?

Small, nonpolar molecules Signup and view all the answers

In which direction do molecules move during passive transport?

From higher to lower concentration Signup and view all the answers

What structural feature do phospholipids possess that is essential for membrane formation?

They have hydrophilic heads and hydrophobic tails Signup and view all the answers

How does cholesterol affect membrane fluidity at low temperatures?

It prevents solidification of the membrane Signup and view all the answers

Which aspect of the cell membrane does its semi-permeable property reflect?

Its selective ability to regulate material passage Signup and view all the answers

Which process is NOT an example of passive transport?

Active transport Signup and view all the answers

What is the primary purpose of the G1 phase in the cell cycle?

Cell growth and protein synthesis Signup and view all the answers

What occurs during the S phase of interphase?

DNA replication Signup and view all the answers

What distinguishes cytokinesis in plant cells from that in animal cells?

Cell plate formation in plant cells Signup and view all the answers

Which phase of the cell cycle is primarily responsible for the actual division of the nucleus?

M Phase Signup and view all the answers

What is the significance of the mitotic index?

Measuring the rate of cell division in a population Signup and view all the answers

What is the primary characteristic of facilitated diffusion?

It uses proteins to assist larger or polar molecules. Signup and view all the answers

What is the process of osmosis primarily concerned with?

Diffusion of water through a selectively permeable membrane. Signup and view all the answers

Which of the following best describes active transport?

Requires energy to move molecules against a concentration gradient. Signup and view all the answers

In which process do white blood cells engulf and destroy pathogens?

Phagocytosis Signup and view all the answers

What does the endosymbiosis theory explain?

The existence of double membrane structures in certain organelles. Signup and view all the answers

Which type of transport involves vesicles for moving larger molecules?

Vesicular transport Signup and view all the answers

What defines a hypertonic solution in relation to a cell?

Water leaves the cell, causing it to wrinkle. Signup and view all the answers

Which of the following correctly describes primary active transport?

It uses ATP to transport molecules directly. Signup and view all the answers

Study Notes

Introduction to Cells

All living organisms are composed of one or more cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
Exceptions to cell theory: striated muscle, giant algae, aseptate hyphae
Functions of life: metabolism, reproduction, sensitivity, homeostasis, excretion, nutrition, growth
Endosymbiosis theory: mitochondria and chloroplasts originated from free-living prokaryotic organisms engulfed by larger cells.
Cell size: can be measured using a microscope and magnification calculations.
Calculating Magnification (MIA): Magnification = Image Size ÷ Actual Size
Calculating Actual Size (AIM): Actual Size = Image Size ÷ Magnification
Cell organization: cells group to form tissues, tissues interact to form organs, organs combine to form body systems.
Stem cells: undifferentiated cells that can develop into various specialized cell types and self-renew.
Ethical considerations: Use of embryonic stem cells in research is debated due to embryo destruction.

Types of Cells

Prokaryotic cells: lack a nucleus, generally smaller and simpler than eukaryotic, have a single, circular DNA molecule, 70s ribosomes. Features: cell wall, membrane, pili, flagella, plasmids.
Binary fission: process of prokaryotic cell division involving DNA replication, attachment to the membrane, cell elongation, and cytokinesis.
Eukaryotic cells: have a nucleus, membrane-bound organelles, and a linear DNA molecule, 80s ribosomes. Features: mitochondria, membrane, Golgi apparatus, endoplasmic reticulum, lysosomes (animal), chloroplasts (plant), vacuoles (plant).
Cell specialization: Eukaryotic cells can be specialized to perform specific functions in multicellular organisms.

Membrane Structure

Fluid mosaic model: describes the plasma membrane as a mosaic of components (phospholipids, proteins, cholesterol) allowing for fluidity.
Phospholipid bilayer: consists of phospholipids with hydrophilic heads and hydrophobic tails, forming a barrier that restricts the passage of substances.
Cholesterol: fits between phospholipids, providing stability and preventing solidification at low temperatures.
Membrane Proteins: play various roles including junctions, enzymes, transport, recognition, anchorage, and transduction.

Membrane Transport

Cell membranes are semipermeable (allow some substances through) and selective (regulate material passage).
Passive transport: Movement of molecules across a cell membrane down the concentration gradient, requiring no energy input. Ex: simple diffusion, facilitated diffusion, osmosis.
Simple diffusion: movement of molecules from an area of higher concentration to one of lower concentration. Characteristics: equilibrium is reached, only small, nonpolar molecules can pass through the bilayer.
Facilitated diffusion: utilizes membrane proteins to help larger or polar molecules pass through the membrane. Characteristics: uses channel proteins and carrier proteins, requires no energy (ATP).
Osmosis: diffusion of water through a selectively permeable membrane. Characteristics: moves from an area of low solute concentration (high water potential) to an area of high solute concentration (low water potential).
Active transport: Movement of molecules across a cell membrane against the concentration gradient, requiring energy input (ATP). Types: primary (directly uses ATP), secondary (uses the energy from the electrochemical gradient created by primary active transport).
Vesicular transport: movement of large molecules or particles via vesicles, requiring energy.
Endocytosis: internalization of materials within a vesicle.
Exocytosis: release of materials from vesicles to the exterior of the cell.

Origin of Cells

Abiogenesis theory: life originated from non-living chemical substances through natural processes: synthesis of simple organic molecules, assembly of organic molecules into complex polymers, creation of self-replicating polymers, and formation of membranes.
Endosymbiosis theory: explains the origin of eukaryotic cells from prokaryotes, based on similarities between mitochondria and chloroplasts to prokaryotes, including double membrane, antibiotic resistance, circular DNA, division like fission, and 70S ribosomes.
Biogenesis theory: states that all living things come from pre-existing living things. Louis Pasteur's experiment (1861) disproved spontaneous generation.

Cell Division

Cell cycle: consists of interphase (G1, S, G2) and M phase (mitosis and cytokinesis).
Interphase: DNA replication, organelle duplication, cell growth, transcription/translation, nutrient acquisition, respiration.
Mitosis: division of a diploid nucleus into two genetically identical diploid cells (2n → 2n x2), important for tissue repair, organism growth, and asexual reproduction.
Cytokinesis: division of the cytoplasm to form two distinct daughter cells.
Mitotic Index: measures the proportion of cells in mitosis within a cell population.

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Description

Test your knowledge about the vital concepts of cell theory, cell functions, and the organization of life. This quiz covers key topics such as endosymbiosis, magnification calculations, and stem cell ethics. Perfect for students learning about biology at an introductory level.