Cell Biology Flashcards
features of eukaryotic cells
cell membrane
cytoplasm
nucleus containing dna
features of prokaryotic cells
smaller
cell wall
cell membrane
cytoplasm
single circular strand of DNA and plasmids
function of nucleus
contains dna coding for a particular protein needed to build cells
enclosed in a nuclear membrane
function of cytoplasm
liquid substance in which chemical reactions occur
contains enzymes
organelles are found in it
role of cell membrane
controls what enters and exits the cell
role of mitochondria
where aerobic respiration reactions occur, providing energy for the cell
role of ribosomes
where protein synthesis occurs
function of chloroplasts
where photosynthesis takes place, providing food for the plant
contains chlorophyll pigment which harvests the light needed for photosynthesis
function of permanent vacuole
contains cell sap
found within the cytoplasm
improves cells rigidity
function of cell wall
made from cellulose
provides strength to the cell
difference of cell wall in bacterial cells
made of a different compound
where are single circular strands of dna found in bacterial cells
float un the cytoplasm as have no nucleus
what are plasmids in bacterial cells
small rings of dna
what is differentiation?
a process that involves the cell gaining new sub cellular structures in order for it to be suited to its role
how often can stem cells differentiate
their whole life
how many times can cells differentiate in animals?
once
how many times can cells regenerate in plants?
retain the ability to regenerate whenever
what is the function of a sperm cell?
specialised to carry the males dna to the egg for successful reproduction
what adaptions do sperm cells have?
streamlined head and long tail
many mitochondria for energy for cell to move
acrosome has digestive enzymes which break down the outer layers of membrane of the egg cell
what is the function of nerve cells?
transmit electrical signals quickly from one place in the body to another
what are the adaptions of nerve cells
axon is long so impulses can be carried along long distances
lots of extensions from the cell body called dendrites meaning branches connections can form with other nerve cells
the nerve endings have many mitochondria which supply the nerve to make neurotransmitters
what is the function of muscle cells
specialised too contract quickly to move bones or squeeze therefore causing movement
what adaptations do muscle cells have
special proteins that slide over each other causing the muscle to contract
lots of mitochondria to provide energy from respiration for contraction
store glycogen which is used in respiration
what is the function of a root hair cell
specialised to take up water by osmosis and mineral ions by active transport from the soil
adaptations of root hair cells
large surface area from root hairs for more water to move in
large permanent vacuole affects the speed of movement for water from soil to the cell
mitochondria to provide energy for the active transport of mineral ions to the root hair cell
function of xylem cells
specialised to transport water and mineral ions up the plant from the roots to the shoots
adaptations of xylem cells
lignin causes the cells to die and become hollow to join end to end and form a tube of water for mineral ions to move through
lignin is deposited in spirals which helps the cells withstand the water pressure
what is the function of phloem cells
specialise dto carry the products of photosynthesis to all parts pf the plants
what is the adaptations of phloem cells
cell wall for sieve plates when they break down allowing substances to move from cell to cell
what do bacterial cells have instead of a nucleus?
single circular strand of DNA that floats freely in the cytoplasm
what are plasmids?
small rings of dna in a bacterial cell
magnification calculation
magnification = image size / real size
what do light microscopes do?
use light and lenses to form an image of a specimen and magnify it
what do light microscopes let you see?
individual cells and large sub cellular structures like nuclei
what do electron microscopes do?
use electrons to form an image with a higher magnification than light microscopes
what do electron microscopes let us see?
smaller things like internal structure of mitochondria and chloroplasts, ribosomes and plasmids due to the higher resolution
what is resolution
the ability to distinguish between two points
what is differentiation?
the process by which a cell changes to become specialised for its job
what happens as cells change to help them carry out new functions?
different subcellular structures developed
when does differentiation usually occur?
as an organism develops
when is the ability to differentiate lost in animal cells
early stage
when is the ability for plant cells to differentiate lost
never in most plants
what are the cells that differentiate in mature animals used for?
repairing and replacing cells such as skin and blood cells
what are undifferentiated cells called
stem cells
phloem and xylem cells adaptations
form tubes which transports food and water around plants
xylem cells hollow and phloem cells few subcellular structures for flow of movement
how do stem cells turn into different types of cell
divide to produce more undifferentiated cells
can differentiate from here depending on instructions given
where are stem cells found in humans?
embryos , bone marrow
what can’t adult stem cells do?
can’t turn into any cell type but only certain ones such as blood cells
what can stem cells be used for?
replacing fault cells in the body
what happens in therapeutic cloning
embryo made to have the same genetic information as the patients to avoid rejection
what is the risk of therapeutic cloning
contaminated with a virus from the lab
why are people against stem cell research
potential human life should be cared for
concentrate on developing other sources of stem cells without embryo use
why are people for stem cell research
patients who already exist are more important than embryo rights
usually embryo stem cells are unwanted ones from fertility clinics
where are stem cells found in plants
meristems
where are stem cells found
human embryos
adult bone marrow
what is the difference between embryonic stem cells and bone marrow stem cells?
bone marrow stem cells can’t turn to any cell type
how are stem cells used in medicine?
grown in a lab to produce genetically identical cells and made to differentiate into specialised cells
what could embryonic stem cells be used for producing?
insulin producing cells
neural cells for diseases such as alzheimer’s
nerve cells for spinal cord injuries
what is therapeutic cloning?
an embryo being produced with the same genes as the patient
why does therapeutic cloning help stem cell use?
stops the patient rejecting them
what is the risk of therapeutic cloning?
may become contaminated with a virus from the lab
what are the benefits of stem cell research
can be used to replace damaged or diseased body parts
unwanted embryos from fertility clinics would have a use
researches into the process of differentiation
problems with stem cell research (5)
hard to control stem cells to form the cells we desire
destroys the embryo
religious or ethical objections due to interference with natural process or reproduction
could catch a virus from the lab which would be transferred to the patient
money and time could be spent on other areas of medicine
where are stem cells found in plants?
meristems ( found in roots and shoot tips)
how are plant stem cells used
differentiate into any type of plant for its whole life
make clones of the plant quickly and cheaply
grow plants of rare species at risk of extinction
grow crops of plants with desirable features
where is genetic information found?
chromosomes in the nucleus which contain coils of dna
what does each chromosome carry
a large number of genes
what are genes?
a short section of dna that codes for a protein and controls characteristics eg hair colour
how many chromosomes are in body cells
23 pairs (one from mother one from father)
how many chromosomes are in each cell?
46
what cell is the exception for number of chromosomes?
sex cells (gametes) 23 chromosomes total in each cell
what is the cell cycle?
a series of steps that the cell has to undergo in order to divide
what is mitosis
a stage in the cell cycle when the cell divides
what happens in the first main stage of the cell cycle
dna is spread out in long strings
the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
duplicates its dna for one copy for each new cell. dna is copied and forms x shaped chromosomes and each arm is identical
what happens during mitosis
chromosomes line up at the centre of the cell and cell fibres pull them apart , two arms go to opposite ends of the cell
membranes form around the sets of chromosomes and become the nucleus of the two new cells as the nucleus has divided
cytoplasm and cell membrane divide
cell has now produced two new daughter cells with the same dna , and same dna as parent cell
what is cell division by mitosis for?
in multicellular organs for growth and development
replacing damaged cells
asexual reproduction
what is binary fission?
the process of reproduction in prokaryotic cells
what are the steps of binary fission
circular dna and plasmids replicate
cell gets bigger and circular dna strands move to opposite poles of the cell
cytoplasm begins to divide and new cell walls begin to form
cytoplasm divides and two daughter cells produced with one copy of the circular dna but a variable number of copies of the plasmids
what speeds up bacterial division
warm environments , lots of nutrients
what happens if conditions become unfavourable for bacterial cells division
cells will stop dividing and eventually begin to die
what is diffusion
the spreading out of particles from an area of higher concentration to an area of lower concentration
why is diffusion passive
No energy is required
What does a molecule need to be to diffuse
Small
Which molecules can diffuse
Glucose , amino acids , water
How does oxygen diffuse in the body
Moves through membranes of alveoli into red blood cells
Carried to body cells for respiration
How does carbon dioxide diffuse out of the body
Moves from red blood cells to the lungs to be exhaled
What is the movement of oxygen into and carbon dioxide out of the lungs called
Gas exchange
How does urea diffuse
Moves from the liver cells into blood plasma to be transported to the kidney for excretion
Which factors affect the rate of diffusion
Concentration gradient
Temperature
Surface area of the molecule
How does concentration gradient affect diffusion
Greater the difference in concentration , faster the rate of diffusion .
More particles are randomly moving down the gradient than are moving against it
How does temperature affect the rate of diffusion
Greater the temperature , the greater the movement of particles resulting in more collisions and a faster rate
How does surface area affect the rate of diffusion
Greater the surface the more space for particles to move through
What is a surface area to volume ratio
The size of the surface area of the organism compared to its volume
How do you calculate surface area to volume ratio
Volume x (length x width)
Write the ratio in smallest whole numbers
What is the effect of a large sa to vol ratio
Less likely to require specialised exchange surfaces and a transport system
How can single celled organisms use diffusion to transport molecules into their body from air
Have a large sa to vol ratio and have low metabolic demands so diffusion across the surface is sufficient to meet their needs
Why do multicellular organisms need to have adaptations to increase cell movement in and out
Sa to vol ratio is small so cannot rely on diffusion alone
What is an adaptation of alveoli to increase diffusion
Covered in tiny capillaries which supply blood
What is the role of the villi for diffusion
Cell projections
Digested food is absorbed over the membrane of these cells into the bloodstream
What is the role of gills in diffusion
Water with oxygen passes through mouth over the gills
Have gill filaments and gill lamellae where diffusion of oxygen into blood and diffusion of co2 into water happens
Blood flows in one direction and water flows in the other
what is the adaptation of the roots of plants for diffusion
Root hair cells with large surface area
Project into soil and take up water and mineral ions
What is the role of the stomata in diffusion of leaves
Carbon dioxide diffuses through
Oxygen and water vapour move out
How does having a thin membrane affect diffusion
Short diffusion pathway
How does having an efficient blood supply or being ventilated affect diffusion
Steep concentration gradient
What is osmosis
The movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrane
What kind of concentration of water does a dilute sugar solution have
High and a high water potential
What does the cytoplasm contain that affects osmosis
Contains salts and sugars
When a cell is placed in a dilute solution water will move in
What is an isotonic solution
When the concentration of sugar in external solution is the same as the internal and there is no movement
What is a hypertonic solution
If the concentration of the sugar in external solution is higher than the internal , water moves out
What is a hypotonic solution
If the concentration of sugar in external solution is lower than the internal , water moves in
What happens in animal cells if the external solution is more dilute
It will swell up and burst
What happens to animal cells if the external solution is more concentrated
Excess water will leave the cell causing it to become shrivelled
What happens in plant cells if the external solution is more dilute
Water will move into the cell and the vacuole causing it to swell and resulting in pressure called turgor
What happens in plant cells if the external solution is less dilute
Water will move out of the cell
Cell becomes soft
Cell membrane will move away from the cell wall (plasmolysis) and will die
What is active transport
Movement of particles from an area where they are in lower concentration to an area in higher concentration against a concentration gradient using energy from respiration
How does active transport work in root hairs
Take up water and mineral ions from soil
Mineral ions Usually in higher concentration in the cells meaning diffusion cannot take place
Requires energy from respiration
How does active transport work in the gut
Substances such as glucose and amino acids from food move from gut to bloodstream
Lower concentration of sugar in the gut than blood so active transport required to move sugar to the blood against its concentration gradient
