Chapter 3- Cells and tissues Flashcards
what are cells
cells are the structural units of all living things
What is a generalised cell?
A generalised cell is a cell that contains the three main regions or parts, the nucleus, cytoplasm and plasma membrane.
Describe the structure of the plasma membrane?
The plasma membrane consists of two phospholipids (fats) layers that are arranged “tail to tail” with cholesterol and floating proteins scattered among them. Some phospholipids also have sugar groups attached to them, to form glycolipids. The phospholipid bilayer contains polar heads called hydrophilic “water loving” and nonpolar “tails” called hydrophobic “water fearing”
What are the functions of the proteins in lipid layer of the plasma membrane
Some proteins are enzymes
Most are receptors for hormones/other chemical messengers
Binding sites for anchoring the cell
Most protein are involved in transport
Some cluster together to form protein channels for water soluble molecules or ions to move
Others act as carriers that bind to a substance and move it through the membrane
Some act as receptors for bacteria, viruses or toxins can bind to
Some determine your blood type
Play a role in cell recognition and interactions
How are cells bound together
Glycoproteins in the glycocalyx act as an adhesive or cellular glue.
2. Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion.
3. Special cell membrane junctions are formed (Figure 3.2). These junctions
vary structurally depending on their roles
What are the functions of tight junctions
Tight junctions are impermeable junctions that encircle the cells
and bind them together into leak proof sheets. The adjacent plasma membranes
fuse together tightly together like a zipper, which prevents substances from passing
through the extracellular space between the cells.
Give an example of a tight junction
An example would be in the small intestine, the junctions prevent digestive
enzymes from leaking into the bloodstream.
What are the functions of desmosomes
Desmosomes are anchoring junctions that are scattered like rivets
along the sides of adjacent cells. They prevent cells subjected to mechanical stress
(such as heart muscle cells and skin cells) from being pulled apart. These junctions
are buttonlike thickenings of adjacent plasma membranes (plaques) that are
connected by fine protein filaments
What are the functions of gap junctions
The main function of gap junctions is communications. These
junctions are mainly found in the heart and between embryonic cells. In gap
junctions the neighbouring cells are connected by hollow cylinders composed of
proteins (called connexons) that span the entire width of the abutting membranes.
Why do phospholipids (which form the bulk of plasma membranes) organize
into a bilayer, tail to tail, in a watery environment?
,
The phospholipids have both polar (heads) and non polar (tails) regions.
Polar aligns with polar (water and other polar molecules inside and outside the cell).
Non polar aligns with non polar in the membrane interior.
The external faces of some membrane proteins have sugar groups attached to them
what are 3 roles these sugar-coated proteins play in the life of a cell?
They act as receptors, determine blood type, and play a role in cell-to-cell interactions.
What are the functions of the nucleus
The nucleus is the control center of the cell.
● The genetic material (DNA- Deoxyribonucleic acid) is stored in the nucleus of
the cell, it contains all the instructions needed for the building of the whole
body.
● DNA has genes, which carry the instructions for building proteins.
● DNA is also necessary for cell reproduction.
● The nucleus forms the shape of the cell.
● The nucleus has three recognisable regions or structures
What are the three regions or structures of the nucleus
Nucleolus
chromatin
Nuclear envelope
What are the functions of the nuclear envelope
The nuclear boundary is a double membrane barrier which is called the nuclear envelope or nuclear membrane.
● At various points the two layers of the nuclear envelope fuse, generating openings called nuclear pores.
● The nuclear envelope allows some but not all substances to pass through it,
through the relatively large nuclear pores in the nuclear envelope.
● The nuclear membrane encloses a jelly-like fluid which is called the neoplasm in which other nuclear elements are suspended.
What are the functions of the nucleolus
Nucleoli is plural for nucleolus. Nucleoli are the sites where cell structures
called ribosomes are assembled.
What are the functions of the chromatin
When a cell is not dividing, its DNA is carefully wound around proteins called
histones to form a loose network of “beads on a string” called chromatin.
● Chromatin is scattered throughout the nucleus.
● When a cell divides by mitosis to form two daughter cells, the chromatin
condenses to form dense, rod-like bodies called chromosomes.
What are the three main components of the cytoplasm
Cytosol
Inclusions
Organelles
What is the cytosol
The cytosol is a semi- transparent fluid that suspends the other elements.
Dissolved in the cytosol, which is largely water, nutrients and a variety of
other solutes.
What are inclusions
Are chemical substances that may or may not be present, depending on the cell type.
● Most inclusions are stored nutrients or cell products floating in the cytosol.
● They include the lipid droplets common in fat cells, glycogen granules
abundant in liver and muscle cells, pigments such as melanin in skin and hair
cells, mucus and other secretory products and various kinds of crystals.
What are the functions of the mitochondria?
“Powerhouses” of the cell
Change shape continuously
Carry out reactions where oxygen is used to break down food
Provides ATP for cellular energy
Site of aerobic respiration
ATP Synthesis
What are the functions of the ribosomes?
The site of protein synthesis
What are the two locations in the cell where ribosomes are found
Free in the cytoplasm
As part of the rough endoplasmic reticulum
What are the functions of the Rough ER?
The proteins that are made on the ribosomes which are on the rough ER migrate into the rough ER tunnels.
Rough ER is abundant in cells that make (synthesise) and export (secrete) proteins.
What are the functions of the Smooth ER?
The smooth endoplasmic reticulum plays no role in protein synthesis, because it
does not have ribosomes.
The main function of the smooth ER is lipid metabolism and detoxification of drugs and pesticides.
What are the functions of the Golgi Apparatus?
Its major function is to modify, package, and ship proteins (sent to it by the
rough ER via transport vesicles) in specific ways, depending on their final
destination
It also packages hydrolytic enzymes into membrane- bound organelles
called lysosomes that remain in the cell
What are the functions of the Lysosomes?
They are membranous “bags” containing powerful digestive enzymes.
Contain enzymes that digest worn-out or non-usable materials within the cell
Site of intracellular digestion. the stomach of the cell
What are the functions of the Peroxisomes?
Peroxisomes are membranous sacs containing powerful oxidase enzymes
that use molecular oxygen (O2) to detoxify a number of harmful or poisonous
substances, including alcohol and formaldehyde.
● Their most important function is to disarm dangerous free radicals
they replicate themselves by pinching in half
What are free radicals
Free radicals are highly reactive chemicals with unpaired electrons that can damage the structure of proteins and nucleic acids.
What is the cytoskeleton
The cytoskeleton is an elaborate network of protein structures that extend throughout the cytoplasm. This acts as the cells “bones or muscles” by furnishing an internal framework that determines cell shape, supports other organelles and
provides the machinery for intracellular transport and various types of cellular
movements.
what is the cytoskeleton made up of
Microtubules
Microfilaments
Intermediate filaments
What is the function of the Microfilaments and give an example
an example of microfilaments are actin and they are
mostly involved with the cells motility and in producing the changes in the cell shape.
transport of cell products throughout the cytoplasm
What is the function of the microtubules and give an example
They determine the overall shape of a cell and the distribution
of organelles. These structures are very important for cell division.
make up cilia and flagella.
they help with tansport of substances within. the cell
What is the function of the intermediate filaments and give an example
They help to form the desmosomes and
provide the internal guy wires to resist pulling forces on the cell.
gives the cell structural support
resists mechanical stress
what are the functions of the centrioles
Centrioles are best known for their role in generating microtubules and
directing the formation of the mitotic spindle during cell division.
what are flagella and where is it found
Are cilia projections that are longer found on a sperm cell
what are cilia and where is it found
Are whiplike cellular extensions that move substances along the cell surface.
For example mucus is carried up and away from the lungs on the ciliated cells lining
the respiratory system,
what are microvilli
Microvilli are tiny, fingerlike extensions of the plasma membrane that project from
an exposed cell surface. They increase the cells surface area tremendously and are
usually found on the surface of cells during active absorption such as the intestinal
and kidney tubule cells.
what are the different Cells that connect body parts and where are they found in the body.
Fibroblast- secretes cable like fibers
Erythrocyte (Red Blood cells)- this cell carries oxygen in the blood
what are the different Cells that cover and line body organs
Epithelial cells
what are the different Cells that move organs and body parts
Smooth, cardiac and muscle cells
what are the different Cells that store nutrients
Fat cells
What are the different Cells that fight disease
White blood cells
What are the Cells that gather information and
control body functions
Nerve cells
Define selectively permeable
Selective permeability means that a barrier allows some substances to pass
through it while excluding the others
what is a solution
A solution is a homogenous mixture of two or more components, for example
the air we breathe is a mixture of gases, seawater is a mixture between salt
and water etc
what is a solvent
The substance that has the largest amount is called the solvent (or
dissolving medium).