The Cell And Its Functions Flashcards
2 major parts of a cell
- nucleus
2. cytoplasm
nucleus separated from cytoplasm by
nuclear membrane
cytoplasm separated from the surrounding fluids
cell membrane or plasma membrane
different substances that make up the cell are called
protoplasm
protoplasm consist of
- water
- electrolytes
- proteins
- lipids
- carbohydrates
water is absent in which cells
fat cells
principal fluid medium of the cell
water in a concentration of 70-85%
ions present in the cell
phosphate, potassium, magnesium, sulfate, bicarbonate and small quantities of calcium, sodium, chloride.
most abundant substance present in the cell after water
proteins constituting 10-20% of cell mass
2 types of proteins
structural proteins
functional proteins
form of structural proteins
long filaments that are polymers of individual protein molecules.
function of structural protein
- microtubules: cytoskeleton for cellular organelles as cilia, nerve axon, mitotic spindle and a tangled mass of thin filamentous tubules that hold parts of the cytoplasm and nucleoplasm in place.
- fibrillar protein: present outside the cell especially in the collagen and elastin fibres of connective tissue and in blood vessels walls, tendons, ligaments and so forth
form of structural proteins
composed of a combination of few molecules in tubular-globular Form. they are mobile on cell fluid. and adherent to membranous structures in the cells.
function of functional proteins
enzymes of the cells: come into direct contact with cellular fluid and catalyze intracellular chemical reactions
Subtances with the property of being soluble in fat solvent
lipids
main lipids
- cholesterol
- phospholipids
they make up 2% of cell mass
cell membrane
lipid bilayer the envelopes the cell within which proteins are embedded also called “fluid mosaic model”
endoplasmic reticulum
a network of tubular and flat vesicular structures in the cytoplasm.
nucleus
control center of the cell containing DNA which are the genes that determines the characteristics of the proteins and also promotes cell reproduction
2 types of endoplasmic reticulum
- granular ER
2. agranular (smooth)ER
oxidative phosphorylation
it is the process by which ATP is synthesized in the mitochondria by respiratory enzymes
phagocytosis
is a form of endocytosis where in large particles are ingested such as bacteria, damaged tissue etc.
pinocytosis
is a form of endocytosis where in minute particles are ingested that form vesicles of extracellular fluid and particulates constituents inside the cell cytoplasm
triglycerides
type of lipid called neutral fats some cells contain large amounts of it eg. fat cells makes up 95%of the cells mass.
function of fat cells
fats stored in these cells is main storehouse for energy giving nutrients that can be later used to provide energy to the body whenever needed
amount of carbohydrates present in the body
mains small amounts of carbohydrates about 1% of their total mass but can also increase to as much as 3% in muscles cells and even 6% in liver cells
forms of carbohydrates in the body
as glycoprotein , glycolipids, in the form of glucose in the extracellular fluid so that it is readily available, and within the cell in the form of glycogen.
glycogen
are insoluble polymers of glucose that can be depolymerized and used rapidly to supply cells energy needs.
highly organized physical structures contained by the cells
intracellular organelles
function of lipids in the cell membrane
to prevent the flow of water soluble subtances and water through the membrane
characteristics of the cell membrane
also know as plasma membrane envelopes cell is thin pliable and about 7.5-10nm thick contains 55% proteins, 25% phospholipids, 13% cholesterol, 4% other lipids, 3% carbohydrates
basic lipid bilayer is composed of
phospholipids, cholesterol, sphingolipids.
structure of phospholipids
are made up on a hydrophobic and a hydrophilic part the phosphate portion is the hydrophilic part and the fatty acid portion is the hydrophobic part
how are phospholipids arranged in the membrane
the fatty acids portion since it is hydrophilic and repels water they are mutually attracted to one another and have a natural tendency to attach in the middle of the membrane . thus the phosphate portion makes up the two surfaces in contact with intracellular fluids and extracellular fluid.
subtances permeable through the lipid layer
Carbon dioxide, oxygen, alcohol
subtances impermeable to the lipid layer
ions, glucose, and urea
what are sphingolipids
derived from an amino alcohol sphingosine. it has a hydrophilic and hydrophobic part. it is present in small amounts in the membrane especially in Nerve cells
function of sphingolipids
- protection from environmental factors
- conduction of signals
- adhesion sites for extracellular proteins
why are cholesterol called lipids
because their steroid nuclei dissolved in fat soluble solvent.
function of cholesterol
molecules are dissolved in the bilayer some important functions are
- determines degree of permeability of the membrane to water soluble subtances
- controls much of the fluidity of the cells walls
two types of protein present in the membrane
proteins are in the form of glycoprotein
- integral proteins
- peripheral proteins
what are integral proteins
proteins that penetrate all the way through the membrane and protrude from both sides
peripheral proteins
present only on one of the surfaces of the membrane they do not penetrate through it
function of integral proteins
- structural channels
- carrier proteins
- enzymes
- receptors
how do integral proteins act as structural channels
these proteins allow the diffusion of water soluble substances like ions through the lipid membrane. these channels have selective properties that allow preferential diffusion of some substances over others.
carrier proteins
transport substances that otherwise cannot penetrate through the lipid bilayer. sometimes these proteins carry substances against their electrochemical gradient this is called “active transport”
how do proteins serve as receptor’s
proteins act as receptor’s to water soluble chemicals like peptide hormones . interaction of receptor with specific ligands that bind to the receptor cause conformational changes in its structure this enzymatically activate the interior part of the protein or induce interaction between the receptor and proteins in the cytoplasm that act as second messenger
function of peripheral proteins
enzymes and controllers of transport of subtances
in what form does carbohydrates occur
occur with proteins and lipids in the form of glycoproteins or glycolipids
proteoglycan
are carbohydrate subtances bound to a small protein core. which are loosely attached to the outer surface of the cell membrane
glycocalyx
is a loose carbohydrate coat present on the entire outer surface of the cell membrane
function of the carbohydrate moieties on the surface of the membrane
- most of them carry a -ve charge which give the overall surface a -ve charge which repels other-ve objects
- glycocalyx of one cell attaches to the glycocalyx of another
- acts as receptor substances and binds to hormones
- some enter into immune reaction
jelly like fluid portion of the cytoplasm
cytosol
content of the cytosol
proteins, electrolytes, glucose
organelles dispersed in the cytoplasm
ribosomes, glycogen granules, secretory vesicles, neutral fat globules and the five most important organelles: mitochondria, endoplasmic reticulum, lysosomes, peroxisomes, Golgi apparatus
structure and characteristics of the endoplasmic reticulum
made up of tubular and flat vesicles structures that are interconnected. wall constructed of lipid bilayer membrane. total surface area can be as much as 30-40times the cells surface.its is filled with endoplasmic matrix. space inside the ER is connected with the space between the 2 membranes of the nucleus.
function of ER
Help process substances formed by cells and then transport it to it specific destination inside or outside the cell.
granular ER
on the outside surface of many parts of the ER are attached minute granules called ribosomes. help synthesize proteins
composition and function of ribosomes
consist of RNA and proteins and function to synthesize new protein molecules
agranular /smooth ER
has no attached ribosomes. function to synthesize lipid molecules
structure of Golgi apparatus
consist of 4or more flat, thin enclosed vesicles lying to one side of the nucleus. more prominent in secretory cell and are present on the side from where secretory fluids are extruded
vesicles pinched of from the ER
transport vesicles/ ER vesicles
function of Golgi apparatus
functions in association with ER. transport vesicles come and fuse with the Golgi apparatus . substance in the vesicles are then processed by the Golgi apparatus to form lysosomes, secretory vesicles and other cytoplasmic components.
how are lysosomes formed
they are organelles formed by breaking off from the Golgi apparatus and dispersed into the cytoplasm.
function of the lysosomes
they act as a digestive system and digest:
- damaged cellular structure
- food particles ingested by the cell
- unwanted matter like bacteria
