CELL Flashcards
- The basic structural and functional unit of living organisms.
- Make up living things and carry out activities that keep a living thing alive.
CELL
- A collection of ideas and conclusions from many different scientists over time that describes cells and how cells operate.
Cell Theory
– discovered cell
Robert Hooke (1665)
– observed living cell
Anton Van Leeuwenhoek (1674)
– discovered nucleus
Robert Brown (1883)
– discovered fluid content of cell
Felix Dujardin (1835)
– proposed all plants are made
up of cells.
Matthias Schleiden (1838)
- made up of only one cell
- Ex: Euglena, Paramecium, Yeast
Unicellular Organisms
– named fluid content of cell as
protoplasm.
J.E. Purkinje (1839)
- Made up of more than one cell
- Ex: Plants, animals, fungus
Multicellular Organisms
Size of Cells
- Most cells are very small (microscopic),
some may be very large (macroscopic) - The unit used to measure size of a cell is micrometer
- 1 μm = 1/1000 millimeter
Size of Cells
- Most cells are very small (microscopic),
some may be very large (macroscopic) - The unit used to measure size of a cell is micrometer
- 1 μm = 1/1000 millimeter
Shape of Cells
- Variation depends mainly upon the function of cells
- Some cells like euglena and Amoeba can change their shape, but most cells have a fixed shape.
Human RBCs are circular biconcave for easy passage through human capillaries
Nerve cells are branched to conduct impulses from one point to another
Human WBCs can change their shape to engulf the microorganisms enter the body.
Shape of Cells
- Variation depends mainly upon the function of cells
- Some cells like euglena and Amoeba can change their shape, but most cells have a fixed shape.
Human RBCs are circular biconcave for easy passage through human capillaries
Nerve cells are branched to conduct impulses from one point to another
Human WBCs can change their shape to engulf the microorganisms enter the body.
Structure of Cell
- The detailed structure of a cell has been studied under compound microscope and electron microscope
- Certain structures can be seen only under an electron microscope.
- The structure of a cell as seen under an electron microscope is called ultrastructure.
Compound microscope – 2000x
Electron microscope – 500,000x
Structure of Cell
- The detailed structure of a cell has been studied under compound microscope and electron microscope
- Certain structures can be seen only under an electron microscope.
- The structure of a cell as seen under an electron microscope is called ultrastructure.
Compound microscope – 2000x
Electron microscope – 500,000x
Structure of Cell
Plasma Membrane
Cell Wall
Nucleus
Cytoplasm
Endoplasmic Reticulum
Golgi body
Lysosomes
Vacuoles
Mitochondria
Plastids
Chloroplasts
Centrosome
Cytoskeleton
- Extremely delicate, think, elastic, living and semi- permeable membrane
- Made up of two layers of lipid molecules in which protein molecules are floating
- Thickness varies from 75-110 A
- Can be observed under an electron microscope only
Plasma Membrane
Functions:
Maintain shape and size of the cell
Protects internal contents
Regulates entry and exit of substances in and out of the cell
Maintains homeostasis
Plasma Membrane
- Non-living and outermost covering of a cell (plants and bacteria)
- Can be tough, rigid and sometimes flexible
- Made up of cellulose, hemicellulose and pectin
- May be thin or thick, multilayered structure
- Thickness varies from 50-1000 A
Cell Wall
Functions:
Provides definite shape, strength and rigidity
Prevents drying up (desiccation) of cells
Helps in controlling cell expansion
Protects cell from external pathogens
Cell Wall
- Dense spherical body located near the center of the cell
- Diameter varies from 10-25 μm
- Present in all the cells except red blood cells and sieve tube cells
- Well developed in plant and animal cells
- Undeveloped in bacteria and blue-green algae (cyanobacteria)
Nucleus
- Colorless dense sap present inside the nucleus known as
- contains round shaped nucleolus and network of chromatin fibers
Nucleoplasm
are composed of deoxyribonucleic acid (DNA) and protein histone
Fibers
contain stretches of DNA called genes
Chromosomes
transfer the hereditary information from one generation to the next
Genes
- Jelly-like material formed by 80 % of water
- Present between the plasma membrane and the nucleus
- Contains a clear liquid portion called cytosol and various particles
- Particles are proteins, carbohydrates, nucleic acids, lipids and inorganic ions
- Also contains many organelles with distinct structure and function
- Some of these organelles are visible only under an electron microscope
- Granular and dense in animal cells and thin in plant cells
Cytoplasm
Functions:
Control all the cell activities like metabolism, protein synthesis, growth and cell division
Nucleolus synthesizes ribonucleic acid (RNA) to constitute ribosomes
Store hereditary Information In genes
Nucleus
- Network of tubular and vesicular structures which are interconnected with one another
- Some parts are connected to the nuclear membrane, while others are connected to the cell membrane
- Two types. Smooth (lacks ribosomes) and rough (studded with ribosomes)
Endoplasmic Reticulum
Functions
Gives Internal support to the cytoplasm
RER synthesize secretory proteins and membrane proteins
SER synthesize lipids for cell membrane
In liver cells SER detoxify drugs & poisons
In muscle cells SER store calcium Ions
Endoplasmic Reticulum
Functions:
Modifies, sorts and packs materials synthesized in the cell
Delivers synthesized materials to various targets Inside the cell and outside the cell
Produces vacuoles and secretory vesicles
Forms plasma membrane and lysosomes
Golgi body
- Discovered by Camillo Golgi
- Formed by stacks of S-8 membranous sacs
- Sacs are usually flattened and are called the cisternae
- Has two ends: cis face situated near the endoplasmic reticulum and trans face situated near the cell membrane
Golgi body
- Small, spherical, single membrane sac
- Found throughout the cytoplasm
- Filled with hydrolytic enzymes
- Occur in most animal cells and in few types of plant cells
Lysosomes
Functions:
Help in digesting of large molecules
Protect cell by destroying foreign invaders like bacteria and viruses
Degradation of worn-out organelles
In dead cells perform autolysis
Lysosomes
- Single membrane sac filled with liquid of sap (water, sugar and ions)
- In animal cells, vacuoles are temporary, small in size and few in number
- In plant cells, vacuoles are large and more in number.
- May be contractile or non-contractile
Vacuoles
Functions:
Store various substances including waste products
Maintain osmotic pressure of the cell
Store food particles in amoeba cells
Provide turgidity and rigidity to plant cells
Vacuoles
- Small, rod shaped organelles bounded by two membranes - inner and outer
- Outer membrane Is smooth and encloses the contents of mitochondria
- Inner membrane Is folded in the form of shelf like inward projections called cristae
- Inner cavity Is filled with matrix which contains many enzymes
- Contain their own DNA which are responsible for many enzymatic actions
Mitochondria
Functions:
Synthesize energy rich compound ATP
ATP molecules provide energy for the vital activities of living cells
Mitochondria
- double membrane-bound organelles found inside plants and some algae.
- They are responsible for activities related to making and storing food.
- They often contain different types of pigments that can change the color of the cell.
Plastids
- produce and store pigments
- They are responsible for different colors found in leaves, fruits, flowers and vegetables.
Carrot - Pigment: Carotene
Mango - Pigment: Xanthophyll
Tomato - Pigment: Lycopene
Chromoplasts
- colorless plastids that store foods.
- They are found in storage organs such as fruits, tubers and seeds.
Potato tubers - Food: Starch
Maize grains - Food: Protein
Castor seeds - Food: oil
Leucoplasts
- Double membrane-bound organelles found mainly in plant cells
- Usually spherical or discoidal in shape
- Shows two distinct regions-grana and stroma
- Grana are stacks of thylakoids (membrane bound, flattened discs)
- Thylakoids contain chlorophyll molecules which are responsible for photosynthesis
- Stroma is a colorless dense fluid
Chloroplasts
Functions:
Convert light energy into chemical energy in the form of food
Provide green color to leaves, stems and Vegetables
Chloroplasts
- Centrosome is the membrane bound organelle present near the nucleus
- Consists of two structures called centrioles
- Centrioles are hollow, cylindrical structures made of microtubules
- Centrioles are arranged at right angles to each other
Centrosome
- Formed by microtubules and microfilaments
- Microtubules are hollow tubules made up of protein called tubulin
- Microfilaments are rod shaped thin filaments made up of protein called actin
Cytoskeleton
Functions:
Determine the shape of the cell
Give structural strength to the cell
Responsible for cellular movements
Cytoskeleton
- Nucleus is undeveloped
- Only one chromosome is present
- Membrane bound organelles are absent
- Size ranges from 0.5-5 μm
- Examples: Bacteria and blue green algae
Prokaryotic Cell
- Nucleus is well developed
- More than one chromosome are present
- Membrane bound organelles are present
- Size ranges from 5-100 μm
- Examples: All other organism
Eukaryotic Cell
- Generally small in size
- Cell wall is absent
- Plastids are absent
- Vacuoles are smaller in size and less in number
- Centrioles are present
Animal Cell
- Generally large in size
- Cell wall is present
- Plastids are present
- Vacuoles are larger in size and more in number
- Centrioles are absent
Plant Cell
