Cell Biology Flashcards
discrepancy
Exceptions to a general trend
discrepancies to the cell theory
- striated muscle
- fungi
- algae
- red blood cells
striated muscles
The type of tissue used for movement
Why are muscle fibres different from typical animal cells?
- they are much larger than most animal cells
- they have more than one nucleus (up to hundreds)
Why are fungi different from typical cells?
- made up of hyphae, which are narrow tubelike structures
- have many nuclei spread out along the hyphae
Why are algae different from typical cells?
- autotrophic (they photosynthesise) and have a simpler structure than plants (due to being unicellular)
- can grow to be much larger than normal cells despite being unicellular and mononuclear
key components of a cell
- plasma membrane
- cytoplasm
- DNA
- ribosomes
prokaryote
simple, single-called organism lacking a nucleus or membrane-bound organelles
components of a prokaryote
- cell membrane
- cell wall
- pili
- flagellum
- nucleoid
- circular DNA
why are RBCs different from typical cells?
lacks:
- nucleus
- organelles
they can’t synthesise proteins either
Common features of all cells
- cell membrane
- genetic material storing all instructions for cell activities
- most of the activities are chemical reactions catalysed by enzymes produced inside the cell
- has its own internal energy release system
functions of life
- metabolism
- response
- homeostasis
- growth
- reproduction
- nutrition
- excretion
metabolism
the chemical reactions occurring in organisms to maintain life
response
the ability to react to changes in the environment
growth
an irreversible increase in size
excretion
the ability to remove waste products occurring as a consequence of metabolism
metabolism
chemical reactions occurring for the purpose of releasing energy
homeostasis
keeping the internal conditions of the organism stable and relatively constant
reproduction
producing offspring
how does paramecium exhibit the nutrition function of life
by ingesting small organisms and digesting through endocytosis
how does chlamydomonas exhibit the nutrition function of life
contains a chloroplast, so it produces its own food via photosynthesis
how does paramecium exhibit the growth function of life
nutrients from digestion are used to provide energy and materials required for growth
how does chlamydomonas exhibit the growth function of life
can grow through the absorption of minerals and photosynthesis
how does paramecium exhibit the excretion function of life
waste products from metabolism are removed by diffusing out of the membrane
how does chlamydomonas exhibit the excretion function of life
waste products from photosynthesis are removed via diffusion
how does paramecium exhibit the response function of life
cilia helps the cell move around - it moves toward or away from external stimuli
how does paramecium exhibit the metabolism function of life
paramecium contains enzymes in the cytoplasm that catalyse metabolic reactions
how does paramecium exhibit the reproduction function of life
paramecium can undergo asexual (mitotic) as well as sexual (meiotic) reproduction
how does paramecium exhibit the homeostasis function of life
contractile vacuoles in the cell fill up with water and remove it from the cell by expelling it through the plasma membrane, keeping water levels constant
how does chlamydomonas exhibit the response function of life
chlamydomonas have an eyespot that can detect light - it moves towards light, exhibiting response to external stimuli
how does chlamydomonas exhibit the metabolism function of life
contains enzymes in the cytoplasm that catalyse metabolic reactions
how does chlamydomonas exhibit the reproduction function of life
asexual (mitotic) and sexual (meiotic) reproduction
how does chlamydomonas exhibit the homeostasis function of life
contractile vacuoles in the cell fill up with water and remove it from the cell by expelling it through the plasma membrane, keeping water levels constant
components of the nucleus
- chromatin
- nucleoplasm
- nuclear envelope
- nuclear pore
- nucleolus
chromatin
combination of DNA and proteins
nucleoplasm
a gel-like sticky liquid that supports the chromosomes and nucleolus
nuclear envelope
consists of 2 phospholipid bilayers
nuclear pores
small holes spanning the nuclear envelope that allow movement in and out of the nucleus
nuclear pore complex
a set of proteins that control movement in and out of the nucleus
nuclear lamina
a network of proteins that supports and gives shape to the nuclear envelope
nucleolus
the site in which new ribosomes are assembled
process of ribosome synthesis
1) some chromosomes have sections of DNA to encode ribosomal RNA (a type of structural RNA)
2) the ribosomal RNA is transcribed from the DNA and combined with proteins to form ribosome subunits
3) they’re transported out via the nuclear pores
4) they combine to form ribosomes outside the nucleus
cell theory
- cells are the main building blocks of structure in living things
- cells are the smallest unit of life
- cells are formed from pre-existing cells by division
- cells contain hereditary info (DNA) passed on during cell division
evidence for cell theory: cells are the smallest unit of life
- organelles: when removed from cells their lifespan becomes extremely short
- virus: they may not actually be living things. they are non-cellular crystalline structures that only reproduce when in a host.
evidence for cell theory: cells are the building blocks of living organisms
all biological organisms observed through microscopes thus far have been made up of cells
evidence for cell theory: all cells are formed from pre-existing cells
Louis Pasteur proved that the “spontaneous” generation of microorganisms was actually due to the presence of unnoticed cells
size of molecule
1 nm
size of cell membrane
10 nm
size of virus
100 nm
size of bacteria
1000 nm or 1 micron
size of organelles
10000 nm or 10 microns
size of cells
100000 nm or 100 microns
significance of SA:vol ratio
- SA affects rate of exchange and heat loss
- vol affects material consumption, heat production, and level of metabolic activity
- they don’t increase at the same rate
emergent properties
- unexpected traits revealed as a result of interaction between constituents
- can’t be predicted as its only when those parts interact that we can determine the emergent properties
differentiation
- when a cell becomes specialised to perform their function
- by expressing particular genes
- these genes influence the shape/function of the cell
specialisation
the structural adaptation of a cell to perform their special function
e.g. RBCs have no nucleus and large SA to carry as much O2 as possible
pluripotent
ability to differentiate into any type of specialised cell in the body
embryonic stem cells
pluripotent, immature stem cells
adult stem cells
- mature stem cells that have differentiated
- is no longer pluripotent
- can mitotically divide indefinitely
- has larger nucleus than normal cells
tissue-specific stem cells
- can be collected from the umbilical cord
- limited dividing capacity
stem cells
- pluripotent cells
- necessary in embryonic development
how do stem cells differ from other cells?
- unspecialised
- limitless mitotic reproduction
- pluripotent
- larger nucleus
example of use of stem cells in therapy
treating cystic fibrosis:
- cells are removed and genetically engineered
- they’re planted back into the patient
- this leads to healthy formation of cells in airway of lungs
nucleoid
- storage of genetic information
- DNA replication site
- circular chromosome with 4000 genes
ribosome
- protein synthesis site (translation of RNA)
- 70s type in prokaryotes, 80s type in eukaryotes
flagellum
- whip-like structure containing a ring of 9 double microtubules and 2 central microtubules
- aids movement
pili
- made of microtubules in helical arrangement
- enables adhesion to surfaces and other bacteria
- also assists in sexual conjugation
mesosome
permeable boundary allowing movement of nutrients and wastes
binary fission
asexual reproduction process of prokaryotes
process of binary fission
- DNA is replicated and attaches itself to the plasma membrane
- the cell elongates to separate the chromosomes
- the membrane invaginates, pulling itself together in the middle
- the cell then splits into 2 daughter cells
plasmid
- small DNA molecule physically separated from chromosomal DNA
- can independently replicate
- aids in DNA exchange
nucleus
- contains chromosomes consisting of DNA associated with histone
- chromatins are spread through the nucleus
- DNA replication and transcription (for mRNA) site
rough endoplasmic reticulum
- consists of cisternae
- ribosomes are attached to cisternae surface
- proteins synthesised by ribosomes pass into the cisternae and are carried by vesicles to the Golgi apparatus
cisternae
flattened membrane sacs
chromatin
uncoiled chromosomes
Golgi apparatus
- consists of cisternae
- many vesicles near it
- the cisternae here aren’t as long as in rER, and are typically curved
- modifies/processes proteins from rER, then transports them in vesicles to the plasma membrane
smooth endoplasmic reticulum
- consists of cisternae
- called smooth as they don’t have ribosomes sticking to them
- synthesises lipids and steroid hormones, and breaks down lipid-soluble toxins
mitochondria
- spherical/ovoid structures with a double membrane
- inner membranes are invaginated in places to form cristae
- liquid inside is called matrix
- fat is digested as an energy source
- provides energy for the cell in the form of ATP
- contains 70s type ribosomes
lysosome
- spherical structure formed from Golgi vesicles
- just 1 membrane
- contains over 50 different types of enzymes for intracellular digestion
- can be used to break down ingested food/organelles/self-destruct
chloroplast
- has double membrane
- has stacks of thylakoids
- typically spherical/ovoid
- produces a variety of organic compounds via photosynthesis
- starch grains may be present
thylakoid
flattened sacs of membrane
microtubule
- small cylindrical fibres
- has a variety of roles including moving chromosomes during cell division
similarities between eukaryotes and prokaryotes
- cell membrane
- DNA
- ribosomes
- cytoplasm
- metabolism
- require energy
differences between eukaryotes and prokaryotes
- prokaryotes are smaller
- only plant eukaryotes have a cell wall, while all prokaryotes have a cell wall
- prokaryotes’ DNA is in a single loop while eukaryotes’ DNA is in separate chromosomes
- prokaryotes’ DNA is free-floating
- prokaryotes have plasmids
- eukaryotes have mitochondria
- different types of ribosomes
- eukaryotes have membrane-bound organelles
differences between plant and animal cells
- plant cells have a cell wall
- plant cells have chloroplasts
- plant cells have a large vacuole accounting for 90% of cell volume while animal cells have significantly smaller vacuoles
cell wall
- maintains shape of cell
- provides structural support
- prevents excessive water uptake
animal extracellular matrix
- secretion (sometimes of glycoproteins)
- sits between cells, providing functions such as filtering/support/adhesion
- basis for formation of tissue
phospholipid
- hydrophilic phosphate head
- hydrophobic fatty acid tail
phospholipid bilayer
- hydrophilic outer layer of heads
- hydrophobic inner layer of tails
- barrier against all molecules except the smallest (CO2 and O2)
- dynamic and flexible
integral proteins
- spans from one side of the bilayer to the other
- involved in transport of substances across the membrane
peripheral proteins
- sits on the surface
- slides around the membrane and collides with each other
- the ones inside are involved in maintaining mobility and cell shape
- they may also be enzymes catalysing reactions in the cytoplasm
glycoprotein
- involved in cell recognition
- cell signal receptors (e.g. with hormones)
cholesterol
- binds together lipids in the plasma membrane
- this helps reduce membrane fluidity and stabilise its structure
how does the phospholipid bilayer structure remain stable?
- hydrophobic hydrocarbon tails are attracted to each other
- hydrophilic phosphate heads are attracted to each other
- the tails repel water, creating a barrier between internal and external water environments as well as movement of polar molecules
- charges on phospholipids attract them to each other
- presence of cholesterol molecules helps increase stability
channel protein
- integral membrane protein
- contains passive/active membrane pumps
- allows movement of large molecules across
- only allows specific ions through
receptor proteins
- membrane protein
- detect hormones arriving at cells to signal changes in function
- involved in other cell/substance recognition processes
electron carrier protein
- membrane protein
- chain of peripheral and integral proteins
- allows electrons to pass across the membrane
- active pumps use ATP
simple diffusion
occurs when the molecules are so small they can simply pass through the plasma membrane
facilitated diffusion
- larger molecules can’t pass through the plasma membrane
- channel proteins can take them through
- these proteins act as a shield against the non-charged regions of the membrane
- the channels only allow a specific type of substance through
exocytosis
- the vesicle fuses with the plasma membrane
2. contents are released outside the cell
endocytosis
- plasma membrane encloses a target particle
- this is possible due to fluidity of membrane
- membrane seals back in itself
- one membrane encloses the particle to form a vesicle
- the vesicle breaks away from the membrane
stages in cell cycle
- G1 phase
- S phase
- G2 phase
- Mitosis
- Cytokinesis
G1 phase
- cytoplasm is still active
- cell continues activities of a growing cell
- everything is replicated except DNA
S phase
- DNA is replicated
- all chromosomes are copied and form chromatids
- these chromatids remain attached until they divide in mitosis
G2 phase
- more growth
- checks are made to see if duplication went well
- preparation for cell division takes place
stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
interphase
- when the cell is not actively dividing
- longest part of the cell cycle
- chromosomes disperse as chromatin and become involved in protein synthesis
- synthesis of new organelles occurs
- G1, S, and G2 phase
supercoiling
- condensation of chromosomes
- by repeatedly coiling the DNA
- this make the chromosome shorter and wider
prophase
- supercoiling
- nucleolus breaks down
- microtubules grow from MTOC to form a spindle-shaped array linking cell poles
- at the end, the nuclear membrane breaks down
MTOC
microtubule organising centre
metaphase
- microtubules continue to grow
- they attach to the centromeres on each chromosome
- chromatids attach to microtubules from different poles
- microtubules are all put under tension to test the arrangement
- this happens by shortening the microtubules at the centromere
- if the attachments are all correct, the chromosomes will remain on the equator of the cell
anaphase
- each centromere divides
- each pair of sister chromatids separate
- spindle microtubules pull them to the poles of the cell
telophase
- chromatids have reached the poles and are now called chromosomes
- at each pole the chromosomes are pulled into a tight group near the MTOC
- nuclear membrane reforms around them
- chromosomes uncoil
- nucleolus forms
cytokinesis
- plasma membrane is pulled inwards around the equator
- occurs due to a ring of contractile proteins (actin and myosin)
- cell is then pinched apart into 2 daughter cells
formation of tumours
tumours/cancers are formed due to uncontrolled cell division.
- mitosis is disrupted by mutation to the proto-oncogene
- cell begins dividing uncontrollably
- proto-oncogene mutates into oncogene
- cells form an irregular mass called the tumor
cause of tumor formation
- damage to DNA chromosomes
- due to accumulation of mistakes in DNA
- may have resulted from radiation, chemicals, infections, or hereditary factors