Cells Flashcards
The cell
is the simplest bit of living matter that can exist independently
Unicellular Organisms’ Characteristics
Unicellular organisms demonstrate all basic life processes nutrition respiration movement excretion growth irritability and reproduction
Cell Shapes and Sizes
Cells come in a variety of shapes and sizes including round square rectangular and star-shaped with some able to change shape
Cell Size Range
Cell sizes vary greatly from tiny bacterial cells (1 µm) visible only with powerful microscopes to large ostrich egg yolk cells (100 mm)
Chlamydomonas
A motile unicellular organism with a cup-shaped chloroplast (fig. 10-1A); it’s a free-living autotroph performing all life activities
Chlamydomonas Protoplasm Complexity
The protoplasm in Chlamydomonas is complex enabling it to carry out all the functions of a living organism
Chlamydomonas and Starch
Chlamydomonas cells form starch grains in their cytoplasm when exposed to light indicating their ability to produce food
Chlamydomonas Movement
Chlamydomonas cells move using flagella and are sensitive and responsive to environmental changes
Chlamydomonas Light Response
Chlamydomonas cells exhibit phototaxis moving from dimly lit areas to brighter ones
Chlamydomonas Water Regulation
Chlamydomonas cells eliminate excess water via contractile vacuoles which repeatedly fill and expel water
Chlamydomonas Reproduction
Young Chlamydomonas cells grow to their full size and reproduce through sexual or asexual methods (fig. 10-1B)
Amoeba
The Amoeba is the simplest heterotrophic unicellular organism (fig. 10-2)
Amoeba’s Food Sensitivity
Amoeba is sensitive to the presence of food in its environment and quickly moves toward it
Amoeba’s Food Acquisition Features
Amoeba has features that aid in obtaining food sensitivity to organic substances movement with pseudopodia and food capture/ingestion via pseudopodia into food vacuoles
Amoeba’s Water Regulation
An Amoeba uses a contractile vacuole to get rid of excess water that enters the cell
Amoeba’s Growth and Division
The Amoeba cell grows to a certain size ceases growing and reproduces by dividing into two daughter cells
Paramecium
Paramecium is also a unicellular organism but its cell body is more complex than that of the Amoeba (fig. 10-3)
Paramecium’s Movement and Feeding Structures
Paramecium has cilia that aid in movement direct food into its gullet and strain food particles
Paramecium’s Digestive Pathway
Paramecium has a fixed mouth for food intake and an anal pore for expelling undigested food; food vacuoles circulate along a set path in the cytoplasm
Paramecium’s Sensory Structures
Paramecium has sensory cilia that help it move to areas where food is abundant
Paramecium’s Water Balance System
Anterior and posterior contractile vacuoles with radiating channels remove excess water from the body
Euglena
Another common unicellular organism is Euglena
Chlamydomonas Preparation for Observation
To observe a Chlamydomonas cell prepare a wet-mount using a drop of water from a Chlamydomonas culture
Chlamydomonas Light Response Experiment
To observe the response of Chlamydomonas cells to light of different intensities take a tube containing a culture of Chlamydomonas cells
Amoeba Preparation for Observation
To observe an Amoeba remove a drop of the sediment from an Amoeba culture and prepare a wet-mount
Paramecium Preparation for Observation
To observe a Paramecium examine a wet-mount of a Paramecium under low power
Paramecium Slowing Movement
Add a little cotton wool to the slide to slow down the movement of the organisms then examine one Paramecium under high power
Euglena Preparation for Observation
To observe a Euglena prepare a wet-mount of Euglena culture
Euglena Movement Study
Study the manner in which Euglena moves
Freshwater Sample Collection
Collect some water from an aquarium or pond to examine freshwater samples
Euglena’s Combined Traits
This protist has both plant-like and animal-like features it has chloroplasts for making food and a gullet for taking in food
Unicellular Protists as Living Units Conclusion
Based on observing the behavior and lifestyle of these unicellular protists we can conclude that a cell is a living unit
Simple Multicellular Plant Examples
Simple multicellular plants include colonial forms like Volvox and filamentous forms like Spirogyra
Volvox Colony Organization
A Volvox colony is composed of numerous Chlamydomonas-like cells arranged in a single layer to form a hollow ball with cells connected by cytoplasmic strands
Volvox Colony Movement Coordination
Each cell has flagella that beat in a coordinated manner enabling the colony to move in a specific direction
Volvox Reproduction by Cell Division
Cell division occurs when a daughter colony is formed
Volvox Cell Specialization Limitation
Unlike Chlamydomonas cells cells in Volvox lose the ability to move about independently
Spirogyra Filament Structure
In Spirogyra (fig. 10-4) identical cells are joined end to end forming unbranched filaments
Spirogyra Cell Autonomy
Each cell functions as an independent living cell capable of dividing transversely and growing
Spirogyra Filament Growth
The filament grows in length in this manner
Simple Multicellular Animal Examples
Simple multicellular animals include some colonial protozoa sponges and Hydra
Colonial Protozoa Cell Similarity
In most colonial protozoa the individual cells are identical in structure and function
Sponge Cell Specialization
Sponges have several specialized cell types (e.g. collar cells amoeboid cells reproductive cells skeleton-making cells)
Hydra Cell Specialization
In Hydra (fig. 10-6) there are several specialized cell types including sensory cells primitive nerve cells muscle cells and stinging cells
Hydra Tissue Organization
Groups of each cell type in Hydra work in a coordinated manner to perform particular functions representing a tissue level of organization
Hydra Body Wall Layers
These tissues form the body wall which consists of an outer ectoderm (protective) an inner endoderm (digestive) and a middle mesogloea (gelatinous layer)
Tissue Complexity Increase
Organisms more complex than Hydra have more types of specialized tissues
Tissue Function Specialization
Each tissue type usually performs only one specific function
Main Tissue Categories
The main tissue types in higher organisms are surface tissues (epithelial/dermal) connective/supportive/packing tissues vascular tissues (xylem/phloem/blood) muscular tissues and nervous tissue
Organ Formation by Tissues
In higher plants and animals different tissues group together to form an organ with a special function
Heart as an Organ Example
The heart is an organ composed of muscle tissue connective tissue nervous tissue and vascular tissue
Organ System Definition
Different functionally related organs form an organ system
Circulatory System as an Example
The heart blood and blood vessels form the circulatory system
Organ System Function
Several organ systems carry out all the functions of a highly complex organism
Cell Function in Simple Organisms
A cell in a simple organism can perform all the functions necessary for living and reproducing
Cell Inefficiency in Complex Organisms
Such a cell however cannot perform all its functions efficiently
Cell Specialization Necessity
Cell specialization had to occur for complex organisms to develop
Cell Specialization Changes
As a cell specializes for a particular function its structure and chemical content become modified
Cell Specialization Functional Trade-off
When a cell becomes specialized to carry out a particular function it usually loses its ability to carry out some of the other functions of a cell
Extreme Cell Specialization Limitation
Extremely specialized cells like nerve cells cannot even reproduce a basic function of all living cells
Specialized Cell Dependency
Specialized cells cannot live on their own like the Chlamydomonas cell or a cell from a Spirogyra filament
Specialized Cell Benefit
They are interdependent on other cells in the organism and their specialization enables them to carry out their functions efficiently
Microscope Use in Cell Study
To study organisms and cells we use a microscope
Light Microscope Lens System
A light microscope has two sets of glass lenses the objective lenses and the eyepiece lenses
Microscope Magnification Calculation
The magnifying power of a microscope is the product of the magnifications of the objective and the eyepiece
Microscope Resolution
A microscope not only magnifies the image but also separates minute details
Microscope Resolving Power Definition
The ability of a microscope to distinguish two very close objects as being separate is its resolution or resolving power
Light Microscope Resolving Power Limit
The resolving power is about half the wavelength of light (approximately 250 nm) limiting the light microscope’s ability to distinguish objects closer than 0.25 µm and to magnify beyond about 1500x
Electron Microscope Necessity
Many organelles in cells are too small to be viewed through a light microscope so an electron microscope is used
Electron Microscope Mechanism
It uses a beam of electrons with a much shorter wavelength than light
Electron Microscope Image Formation
The beam is focused by powerful electromagnets and the resulting image is shown on a fluorescent screen or captured as black and white photographs (electron micrographs)
Electron Microscope Capabilities
An electron microscope has a resolving power of around 1 nm and magnifies objects over 500000 times
Robert Hooke’s Observation
About 300 years ago Robert Hooke an English scientist observed a thin slice of cork through his crude microscope
Hooke’s Discovery
He saw that cork was made up of many little boxes which he named “cells” in 1665 after the Latin word for “small room”
Cell Theory Foundation
The cell theory a basic concept in biology is formulated from the findings and ideas of several scientists
Cell Wall Function
The cell wall is a non-living layer outside the cell membrane
Cell Wall Composition
It is made up of cellulose a complex carbohydrate that is indigestible in humans
Protoplasm Definition
This is the living material inside the cell membrane
Protoplasm Components
It consists of the nucleus and the cytoplasm
Nucleus Structure
Easily stained by dyes the nucleus (plural nuclei) is the largest and most important cell organelle
Nuclear Membrane and Pores
It is enclosed by a double-layered nuclear membrane with many pores
Nucleus Contents
The nucleus contains a thread-like network of chromatin granules which is the extended form of the chromosomes
Chromosome Composition
The chromosomes contain deoxyribonucleic acid or DNA the molecule that contains hereditary information in a code form
Chromatin Components
Among the chromatin are one or more darkly stained bodies called nucleoli
Nucleoli Composition
They are rich in proteins and nucleic acids
Nucleoli Function
These materials are used to manufacture molecules which act as messengers and carry information for the manufacture of proteins
Cytoplasm Location
The cytoplasm is the jelly-like material between the cell membrane and the nucleus
Cytoplasm Composition
It is mainly water but contains many dissolved substances such as salts sugars and amino acids as well as insoluble substances
Cytoplasm Organelles
Within the cytoplasm are various living structures known as organelles
Endoplasmic Reticulum (ER)
The endoplasmic reticulum (ER) is a network of double-membraned tubules and sacs (cisternae)
ER Types
There are two types of ER namely rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER)
Ribosomes
Ribosomes are very small spherical bodies found either free in the cytoplasm or attached to the surface of the RER
Ribosome Composition
They are made up of ribonucleic acid (RNA) and proteins
Ribosome Function
They play an important role in protein synthesis
Golgi Apparatus
The Golgi apparatus is made up of a stack of flattened membranous sacs (cisternae)
Golgi Apparatus Function
It modifies and packages proteins from the ER into small membrane-bound sacs called vesicles
Mitochondria
Mitochondria (singular mitochondrion) are small sausage-shaped bodies (fig 10-10)
Mitochondria Structure
Each mitochondrion is bound by a double membrane the inner one of which is folded inwards to form cristae
Mitochondria Function
They are the sites of cellular respiration and are the powerhouses of the cell
Plastids
Plastids are organelles found only in plant cells
Plastid Types
There are several types of plastids namely leucoplasts chromoplasts and chloroplasts
Leucoplasts
Leucoplasts are colourless plastids
Leucoplasts Function
They store starch oils and proteins
Chromoplasts
Chromoplasts are plastids which contain pigments other than green
Chromoplasts Function
They give colour to fruits and flowers
Chloroplasts
Chloroplasts are green plastids found mainly in the leaf cells
Chloroplast Structure
They are surrounded by a double membrane and contain numerous flattened sacs called thylakoids stacked together to form grana
Chlorophyll
The thylakoids contain the green pigment chlorophyll
Chlorophyll Function
Chlorophyll traps light energy for photosynthesis
Vacuoles
Vacuoles are fluid-filled sacs enclosed by a membrane
Vacuole Contents
The fluid may be water containing dissolved substances such as salts sugars and pigments
Vacuole Functions
Vacuoles store substances and in plant cells they also help to maintain the turgidity of the cell
Lysosomes
Lysosomes are small spherical bodies bounded by a single membrane
Lysosome Contents
They contain many kinds of digestive enzymes
Lysosome Function
They break down food substances and worn-out organelles
Centrioles
Centrioles are a pair of cylindrical structures found near the nucleus in animal cells
Centriole Function
They play a role in cell division
Cell Membrane
The cell membrane (plasma membrane) is a very thin membrane surrounding the cytoplasm
Cell Membrane Composition
It is made up mainly of protein and lipid (fat-like) molecules
Cell Membrane Function
It controls the passage of substances into and out of the cell
Cell Shape Variation
Cells vary greatly in shape according to their functions
Cell Size Variation
Cells also vary greatly in size
Cell Number Variation
The number of cells varies from one in unicellular organisms to many in multicellular organisms
Unicellular Organism
A unicellular organism consists of only one cell
Multicellular Organism
A multicellular organism is made up of many cells
Cell Theory
The cell theory states that all living organisms are made up of cells and cell products
Cell Division
Cells are formed by division of pre-existing cells
Cell Organization
In a cell the various organelles are organized in such a way that the cell is able to carry out all the life processes
Cellular Activities
The various activities that occur in a cell are all interrelated and interdependent
Cellular Malfunction Consequence
If any part of a cell fails to function properly the whole cell is affected
Cellular Interdependence in Multicellular Organisms
In multicellular organisms the cells are interdependent
Cellular Specialization Benefit
This specialization of cells allows them to carry out their functions more efficiently
Cellular Specialization Disadvantage
However they are unable to live independently
Cellular Organization Levels
In a multicellular organism the cells are organized into tissues organs and organ systems
Tissue Definition
A tissue is a group of similar cells performing a specific function
Organ Definition
An organ is a structure made up of different tissues working together to perform a specific function
Organ System Definition
An organ system is a group of organs that work together to perform a major bodily function
Cellular Organization Efficiency
This organization of cells into tissues organs and organ systems makes the organism more efficient
Cellular Organization Complexity
The more complex an organism is the more complex is its organization.
Cellular Transport
Materials are transported into and out of cells by various methods
Diffusion Definition
Diffusion is the movement of molecules from a region of their higher concentration to a region of their lower concentration
Diffusion Energy Requirement
It does not require energy from the cell
Diffusion in Living Systems
Diffusion is very important in living organisms
Osmosis Definition
Osmosis is the diffusion of water or any solvent through a semi-permeable membrane from a dilute solution to a concentrated solution
Osmosis Energy Requirement
It does not require energy from the cell
Osmotic Pressure
The pressure that develops as a result of osmosis is called osmotic pressure
Osmosis in Plant Cells
The cell wall of a plant cell is fully permeable whereas the cell membrane is semi-permeable
Turgor Pressure
The osmotic pressure of the cell contents pushes the cell membrane against the cell wall
Plasmolysis
If a living plant cell is placed in a concentrated solution it loses water to the solution by osmosis
Active Transport Definition
Active transport is the movement of substances across the cell membrane against a concentration gradient (i.e. from a region of their lower concentration to a region of their higher concentration)
Active Transport Energy Requirement
It requires energy from the cell
Active Transport Importance
Active transport is very important in the absorption of digested food in the small intestine and the absorption of mineral salts in root hairs
Endocytosis Definition
Endocytosis is the bulk transport of materials into the cell by engulfing
Endocytosis Types
There are two main types of endocytosis namely phagocytosis and pinocytosis
Phagocytosis
Phagocytosis is the engulfing of solid particles by the cell
Pinocytosis
Pinocytosis is the engulfing of liquid droplets by the cell
Exocytosis Definition
Exocytosis is the bulk transport of materials out of the cell by fusion of vesicles with the cell membrane
Cellular Metabolism
All the chemical reactions that occur in a cell are collectively referred to as metabolism
Metabolism Types
Metabolism is of two types namely anabolism and catabolism
Anabolism Definition
Anabolism is the building up of complex substances from simpler ones
Anabolism Energy Requirement
It requires energy
Catabolism Definition
Catabolism is the breaking down of complex substances into simpler ones
Catabolism Energy Release
It releases energy
Enzymes Definition
Enzymes are biological catalysts
Enzyme Function
They speed up the rate of metabolic reactions
Enzyme Specificity
Enzymes are very specific in their action i.e. each enzyme catalyses only one particular reaction
Enzyme Composition
Enzymes are made up of proteins
Enzyme Sensitivity
They are sensitive to temperature and pH
Optimum Temperature
Enzymes work best at a particular temperature called the optimum temperature
Optimum pH
They also work best at a particular pH called the optimum pH
Cellular Respiration Definition
Cellular respiration is the process by which food substances are broken down to release energy
Cellular Respiration Location
It occurs in the mitochondria
Cellular Respiration Types
There are two main types of cellular respiration namely aerobic respiration and anaerobic respiration
Aerobic Respiration
Aerobic respiration is the breakdown of food substances in the presence of oxygen to release energy
Aerobic Respiration Products
Carbon dioxide and water are produced
Anaerobic Respiration
Anaerobic respiration is the breakdown of food substances in the absence of oxygen to release energy
Anaerobic Respiration Products
In plant cells and some bacteria the food substance is broken down to alcohol and carbon dioxide
Fermentation
This type of anaerobic respiration is called fermentation
Anaerobic Respiration Products in Animal Cells
In animal cells e.g. muscle cells the food substance is broken down to lactic acid
Cellular Reproduction
Cells reproduce by cell division
Cell Division Types
There are two main types of cell division namely mitosis and meiosis
Mitosis Definition
Mitosis is the type of cell division in which each daughter cell has the same number and type of chromosomes as the parent cell
Mitosis Function
It is responsible for growth and repair in multicellular organisms
Mitosis Stages
Mitosis is divided into four stages namely prophase metaphase anaphase and telophase
Prophase
During prophase the chromatin network condenses to form chromosomes
Metaphase
During metaphase the chromosomes arrange themselves at the equator of the cell
Anaphase
During anaphase the centromeres split and the sister chromatids separate
Telophase
During telophase the chromosomes uncoil and become less distinct
Meiosis Definition
Meiosis is the type of cell division in which each daughter cell has half the number of chromosomes as the parent cell
Meiosis Function
It occurs during the formation of gametes (sex cells)
Meiosis Stages
Meiosis involves two successive divisions Meiosis I and Meiosis II each of which has four stages
Meiosis I
In Meiosis I the homologous chromosomes separate
Meiosis II
In Meiosis II the sister chromatids separate
Significance of Meiosis
Meiosis is important because it ensures that the chromosome number remains constant from one generation to the next during sexual reproduction
