life at the cellular level (1) - cells Flashcards
what is the cell
the functional unit of all living things
It is composed of cells and each cell is a membrane-bound volume of cytoplasm, containing DNA with the necessary genetic information to direct the development of the cell
how many cells do all organisms consist of
one or more
how do cells arise
all cells only arise from pre-existing cells
what do all cells have
a cell membrane and cel organelles
what are cell organelles
the machinery of the cell
what must all substances entering or leaving the cell cross
the cell membrane
List the features common to most cells
Plasma membrane Cytoplasm Cytosol Ribosomes Nucleus (eukaryote) Nucleoid (prokaryote)
Eukaryotic cells possess a complex cytoskeleton and is organised into internal compartments
what are the domains of life
prokaryotes
eukaryotes
archea (but we will not be looking at this)
what domain of life do human cells belong to
eukaryotes
what domain of life do bacterial cells belong to
prokaryotes
what domain of life do multicellular animal and plant cells belong to
eukaryotes
what do eukaryotic cells contain
nucleus with membrane
membrane bound organelles
what do prokaryotic cells contain
lack nuclear membrane
no mitochondria
no membrane bound organelles
what are stem cells
cells that can differentiate into many (multipotent) or any (pluripotent) cell types of the body
why are stem cells clinically of great interest
as recent advancements in medical science now allow stem cells to be used in the treatment of certain diseases including some cancers
what can undifferentiated stem cells do
divide and give rise to daughter cells
what do differences in gene expression and the local cellular environmental cause
the daughter cells to develop into different cell types
what is apoptosis
controlled, programmed cell death
is apoptosis a normal process
yes, it is a normal process and essential for normal finction
what is apoptosis intimately coupled with
cell proliferation
what is cell proliferation
the process by which a cell grows and divides to produce two daughter cells
what is a loss of balance between apoptosis and proliferation associated with
some cancers
what is necrosis
it describes the untimely death of cells in response to injury or infection
is necrosis a normal process
no
what are cancer cells
they divide with out any control
fail to coordinate with normal cells
fail to differentiate into specialised cells
displace and replace the normal cells - if not stopped
what is the cell membrane
Sometimes called the plasma membrane or plasmalemma
Comprises a double layer of lipid with attached phosphate groups = phospholipid bilayer
Forms a selective barrier, (being choosy about what it allows to cross in or out of the cell)
Embedded in the membrane are proteins which act as receptors to detect chemical messengers and signalling molecules in the fluid surrounding cells (extracellular fluid)
cells are very small, more than 200 red blood cells could fit easily on a pin head, why is being small advantageous
there is a high surface are to volume ratio meaning there is a lot more surface are for substances to enter and leave the cell, making the work of the cell more efficient
what is the nucleus
Contains DNA, nucleoprotein and some RNA
Nucleoli are sites of ribosomal RNA synthesis and ribosomal assembly
The nucleus is enclosed in the nuclear membrane which, like all biological membranes, is a phospholipid bilayer. It is closely associated with the Rough Endoplasmic Reticulum
what are the different types of endoplasmic reticulum (ER)
rough (RER) and smooth (SER)
why is it called the rough ER
because it has ribosomes attached giving it the “rough” appearance
what do ribosomes do
synthesise proteins
what does the RER do
modifies proteins
what does the SER do
SER has no ribosomes attached and is mainly associated with lipid and steroid hormone production and metabolism of toxins
what does the golgi apparatus do
packages up protein (including enzymes) in preparation for transport out of the cell
what is the structure of the mitochondria
Mitochondria are organelles bound by a phospholipid bilayer
Outer membrane contains pores
Inner membrane has cristae (folds)
Matrix contains most of the enzymes required for metabolising food molecules (e.g. Krebs cycle)
what is the golgi aparatus
a membrane bound organelle
a series of flattened membrane discs
what is the endoplasmic reticulum
a membrane bound organelle
forms a network of membrane tubules continuous with the nuclear membrane
facts about the mitochondria
They have their own circular DNA
They have their own ribosomes – similar to bacterial ribosomes
They synthesise most of their own proteins
They can self-replicate
what are enzymes
one form of protein packages by the golgi apparatus
what do enzymes do
catalyse reactions in cells but need to be stored untill needed
what are lysosomes
membrane bound vesicles containing enzymes - they separate enzymes from the rest of the cell
when/where are lysosomes used
in autophagy (digestion of cells own materials) or digestion of engulfed particles (e.g. bacteria)
what is the cytoskeleton
Supports and maintains cell shape
Holds organelles in position
Helps move organelles around the cell
It is compromised of one of three forms of protein
what are the three forms of protein
microfillaments
intermediate fillaments
microtubules
what form of protein is the cytoskeleton made of
microtubules
what are microfillaments
made up of strands fo the protein actin
often interact with stands of other proteins
what are intermediate filaments
made up of fibrous proteins organised into tough, rope-like assemblages that stabilize a cell’s structure and help maintain its shape
what are microtubules
long, hollow cylinders made up of many molecules of the protein tubulin.
what is tubulin
consists of two subunits α-tubulin and β-tubulin
what do some cells have that is supported by the cytoskeleton
surface projections
what are cilia and eukaryotic flegella made of
microtubules
what is cilia
short, usually many present, move with stiff power stroke and flexible recovery stroke
what is flagella
longer, usually one or two present, movement is snakelike
