B1: Cell Biology Flashcards
Give the two types of cells
- prokaryotic and eukaryotic
Give the two types of cells
- prokaryotic and eukaryotic
State the differences between eukaryotic and prokaryotic cells
- eukaryotic cells contain membrane bound organelles and a nucleus containing genetic material whereas prokaryotes do not
- prokaryotes are much smaller
What is the prokaryotic cell wall composed of
peptidoglycan
How is genetic information stored in a prokaryotic cell?
found free within the cytoplasm as:
- chromosomal DNA ( a single loop of circular DNA)
- plasmid DNA
Define plasmids
- small circular loops of DNA found free in the cytoplasm and separate from the main DNA
- carry genes that provide genetic advantages
Define ‘ order of magnitude ‘
- a power to the base 10 to quantify and compare size
List the components of both plant and animal cells
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribosomes
List the additional cell components found in plant cells
- chloroplasts
- permanent vacuole
- cell wall
What is the function of the nucleus
- controls cellular activities
- stores genetic infromation
Give the 2 functions and describe the structure of the cytoplasm
function:
- site of cellular reactions
- transport medium
structure:
- fluid component of the cell
- contains organelles, enzymes , dissolved ions and nutrients
what is the function of the cell membrane?
- controls the entry and exit of substances into and out of the cell
what is the function of the mitchondria
- site of later stages of aerobic respiration in which ATP is produced
What is the function of the ribosomes?
- joins amino acids in a specific order during translation for the synthesis of proteins
What is the plant cell wall made of
- cellulose
What are the 2 functions of the plant cell wall
- provides strength
- prevents the cell bursting when water enters by osmosis
what is the function of the permanent vacuole and what does it contain
function:
- supports the cell, maintaining the cell’s turgidity
contain:
- cell sap (solution of salt sugar and organic acids)
what is the function of chloroplasts ?
- site of photosynthesis
Give the function of a sperm cell
reporduction ( passes on father’s genes ) to fertilise eggs
Describe how sperm cells in animals are adapted to their function (4)
- haploid nucleus which contains genetic information
- acrosome in the head contains digestive enzymes that digest the egg cell membrane
- mitochondria to release energy (via respiration) for the tail
- The tail rotates, propelling the sperm cell forwards (allowing it to move/swim)
What is the function of nerve cells?
to carry electrical signals from one part of the body to another
Describe how nerve cells are adapted for their function
- long axon allows electrical impulses to be transmitted all over the body from the central nervous system
- dendrites from the cell body connect to and receive impulses
- myelin sheath insulates the axon and speeds um transmission of impulses
What is a muscle cells function?
- contraction for movement
Describe how muscle cells are adapted to their function
- arrangement of protein filament allow them to slide over each other to produce muscle contraction
- mitochondria to provide energy for contraction
- merged cells in skeletal muscle allow muscle fibre contraction in unison
What is the function of a root hair cell in plants
absorption of water and mineral ions from soil
Describe how root hair cells in plants are adpated to their function
- large surface area to absorb nutrients and water from surrounding soil
- thin walls that do not restrict water absorption due to shorter diffusion distance
Describe how xylem cells in plants are adapted to their function
- no end walls to provide a continuous route for water to flow
- outer walls are thickened with lignin that strengthen their structure and prevent collapse
what is the function of a xylem cell?
- plant vascular tissue that transports water and dissolved ions
Give the function of a phloem cell
moves food substances that the plant has produced by photosynthesis
Describe how phloem cells in plants are adapted to their function
- sieve plates allow for the transportation of dissolved amino acids and sugars up and down the stem
- companion cells provide energy needed for active transport of substances along the phloem
Define cell differentiation
- the process by which cells become specialised
Why is cell differentiation important?
- allows production of different tissues and organs that perform various vital functions in the human body.
At what point in their life cycle do most animal cells differentiate
- early in their life cycle
For how long do plant cells retain their ability to differentiate
- throughout their entire life cycle
what changes does a cell go through as it differentiates
- becomes specialized through acquisition of different sub cellular structures to enable a specific function to be performed by the cell
Define magnification
the ability to make small objects seem larger
Define resolution
- the ability to distinguish two objects from each other
How does a light microscope work
- passes a beam of light through a specimen
- this travels through the eyepiece lens
- allowing the specimen to be observed
Give 4 advantages of light microscopes
- inexpensive
- easy to use
- portable
- observe both dead and living specimens
give a disadvantage of light microscopes
- limited resolution
How does an electron microscope work?
- uses a beam of electrons which are focused using magnets
- the electrons hit a fluorescent screen which emits visible light producing an image
What is the advantage of electron microscopes?
- greater magnification and resolution
Why do electron microscopes have a greater magnification and resolution?
- they use a beam of electrons which has a shorter wavelength than photons of light
Give two ways electron microscopes have enabled scientists to develop their understanding of cells
- allow small sub-cellular structures (e.g.) mitochondria, ribosomes) to be observed in detail
- enable scientists to develop more accurate explanations about how cell structure relates to function
What are the 4 disadvantages of electron microscope
- expensive
- large so less portable
- require training to use
- only dead specimens can be observed
How can magnification of an image be calculated?
magnification= image size/ actual size
write these numbers in standard form
- 0.005
-10382
- 5 x 10^-3
- 1.0382 x 10^4
practical:
how to prepare a slide to view onion cells
1) add a drop of water to the middle of a clean slide
2) cut up an onion and use tweezers to peel off epidermal tissue
3) place the epidermal tissue into the water on the slide
4) add a drop of iodine solution
5) place a cover slip on top by carefully tilting and lowering it so it covers the specimen
Give the 6 parts of a light microscope
- eyepiece
- coarse adjustment knob
- fine adjustment knob
- light
- high and low power objective lenses
- stage
Why is iodine solution added to substances on a slide
to make the organelles easier to see
Practical:
How to use a light microscope to look at your slide
- clip the prepared slide onto the stage
- select the lowest powered objective lens
- use the coarse adjustment knob to move the stage downwards until the image is in focus
- adjust the focus with the fine adjustment knob until you get a clear image of what’s on the slide
- if higher magnification is needed swap to a higher-powered objective lens and refocus
Give the formula for total magnification
total magnification = power of objective lens x power of eyepiece lens
what are chromosomes made up of?
- consist of DNA molecules combined with proteins.
- They contain genes which provide the instructions for protein synthesis
what is a gene?
a section of DNA which codes for a protein
How many chromosomes are found in the nucleus of human body cells?
46
How many chromosomes are found in the nucleus of gametes
23
Give the three main stages of the cell cycle
interphase: replication of DNA and synthesis of organelles
mitosis
cytokinesis: division of cell
Why is mitosis important ?
- produces identical cells which all have the same genetic information
- produces additional cells for growth and repair
Describe the first stage of the cell cycle
- cells grow and increase in mass
- replicate DNA and synthesize more organelles
Describe the second stage of the cell cycle
- mitosis
- each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.
Describe the third stage of the cell cycle
The cytoplasm and the cell membrane divide - two identical daughter cells are produced
What is a stem cell?
- an unspecialized cell which is capable of differentiating into other cell types
Give the three different types of stem cells
- embryonic stem cell
- adult stem cell
- meristem cells
What is the function of stem cells in embryos ?
-pluripotent: can replicate themselves and differentiate into many other types of cells
- may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells
What is the function of stem cells in adult bone marrow?
- multipotent
- can differentiate into several cell types to replace dead or damaged tissues
What is the function of stem cells in plant meristems ?
- retain the ability to differentiate into any type of plant cell throughout their lifespan
- fully differentiated
What is therapeutic cloning
- a cloning method where an embryo is produced with the same genetic makeup as the patient
- the stem cells which originate from the embryo will not be rejected by the patient’s immune system so can be used to treat certain medical conditions
Give three advantages of cloning plants using meristem cells?
- can prevent rare plants from becoming extinct
- can produce large numbers of plants with a favorable characteristic
- can produce identical plants for research
Give two pros and cons of using embryonic stem cells
embryonic stem cells:
adv: easy to extract from embryo
adv: pluripotent : produces any type of cell
disadv: sourced from aborted embryos there may be an ethical objection
disadv: embryos cannot consent and have a right to live
Give two pros and cons of using adult stem cells
adv: potential to treat a wide variety of diseases
adv: organs developed from patient’s own stem cells reduces the risk of organ rejection and the need to wait for organ donation
disadv: - risk of mutations which may develop into cancer cells
disadv: difficult and risky to find and extract from tissue
what is diffusion?
- the net movement of particles from an area of higher concentration to an area of lower concentration
What three main factors affect the rate of diffusion
concentration gradient: larger gradient, faster diffusion
temperature: higher temperature, faster diffusion
surface area - larger surface area, faster diffusion
Give and explain examples of substances transported by diffusion in the lungs and the kidney
lungs:
-oxygen diffuses into the blood from the lungs
- carbon dioxide diffuses into the lungs from the blood
- both down their concentration gradient
kidney:
- urea diffuses from cells into blood plasma so it can be excreted in urine
How are single-celled organisms adapted for diffusion?
- they have a large surface area to volume ratio
- maximizes the rate of diffusion of molecules to meet the organism’s needs
How is surface area to volume ratio calculated ?
surface area = number of sides x (side length x side width)
volume = length x width x depth
ratio= surface area : volume
What four factors increase the effectiveness of a gas exchange surface?
- large surface area
- thin membrane (short diffusion path)
- efficient blood supply ( animals )
- ventilation (animals )
Define osmosis
- the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane
What is meant when a solution is isotonic to a cell?
- the concentrations of the external and internal (inside cell) solutions are the same
what is meant when a solution is hypertonic to a cell
- the concentration of the external solution is higher than that of the internal solution (inside cell)
What is meant when a solution is hypotonic to a cell?
- concentration of the external solution is lower than that of internal solution
What may happen when an animal cell is placed in a very hypotonic solution
- water moves into the cell, causing it to burst
What may happen when an animal cell is placed in a very hypertonic solution?
- water moves out of the cell, causing it to shirvel up
How do plant leaves and stems remain rigid?
turgor pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall
What may happen when a plant cell is placed in a very hypertonic solution?
- water moves out of the cell by osmosis and the vacuole and cytoplasm decreases in size.
- the cell membrane may pull away from the cell wall, causing the cell to become plasmolysed
Define active transport.
- The net movement of particles from an area of low concentration to an area of higher concentration against a concentration gradient, using energy from respiration
How do plant root hair cells use active transport
- use active transport to take up mineral ions from a more dilute solution in soils
- ions such as magnesium and nitrates are required for healthy growth
How is active transport used to absorb the products of digestion?
- used to transport glucose from a lower concentration in the gut to a higher concentration in the blood
- glucose is transported to the tissues where it can be used in respiration
How does temperature affect diffusion
- the higher the temperature, the more kinetic energy the particles of that substance will have
- they will move faster and so diffuse at a faster rate
Describe the practical to observe the effect of sugar solution son plant tissue:
- give the method
- independent variable
- dependent variable
- peel the potato
- use a cork borer to produce three cylinders of potato
- use a scalpel to trim the cylinders to the same length
- measure the length of each cylinder using a ruler and the mass of each cylinder using a balance
- Now place the cylinders into the test tubes. Add varying concentrations of sugar solution into each sylinder-
- one test tube must be of distilled water
- leave the potato cylinders overnight to allow osmosis to take place
- remove the potato cylinders and gently roll them on paper towel to remove any surface mositure
- measure the length and the mass of the cylinders again
- calculate the percentage change of the mass using the equation: percentage change = change in value/ original value x 100
IV: concentration of sucrose solution
DV: mass and length of potato
CV: volume of solute, temperature , time
How do bacteria multiply?
binary fission ( simple cell division )
how often do bacteria multiply, given certain conditions?
- once every 20 minutes if enough nutrients are available and of suitable temperature
state two ways in which bacteria can be grown
- nutrient broth solution
- colonies on an agar gel plate
what nutrients make up a nutrient broth solution?
all nutrients required for bacteria to grow including:
- nitrogen for protein synthesis -
- carbohydrates for energy
- other minerals
why are uncontaminated cultures of microorganisms needed for ?
investigating disinfectant and antibiotic action
describe the preparation of an uncontaminated culture using aseptic technique
- sterilise glass Petri dishes and agar gel in an autoclave
- Pour the sterile agar gel into the Petri dish and allow time to set
- sterilise the inoculating loop by passing it through a Bunsen burner flame
- dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar
- put the lid on the Petri dish and secure it with tap.. Labell accordingly then turn and store upside down
- Incubate the culture at 25oC in school laboratories
why must Petri dishes and culture media be sterilised before use?
to kill any bacteria already present
why must inoculating loops be sterilised by passing them through Bunsen burner flame
to kill any bacteria present on the inoculating loop
give three reasons why the Petri dish lid be secured with adhesive tape and the whole dish stored upside down
- stops bacteria in the air contaminating the culture
- the lid is not fully sealed to prevent the growth of anaerobic bacteria due to a lack of oxygen
- upside down to prevent condensation from forming and dripping down onto the colonies
why are cultures incubated at 25oC in school laboratories?
- harmful pathogens are less likely to be grow at this temperature
what is the formula used to calculate cross-sectional area of a bacterial colony or clear around a bacterial colony
πr*2
how is the number of bacteria in a population after a certain time calculated from the mean division time?
- calculate the number of times the bacteria will divide in a population after a certain time period from the mean division time
- use the following equation
number of bacteria at beginning of time period x 2n
n= number of divisions in the time period
