Cell Biology Flashcards
What are the two types of cells?
Eukaryotic (plants and animals) and prokaryotic (bacteria)
What are the differences between eukaryotic and prokaryotic cells?
Prokaryotic cells are much smaller than eukaryotic cells
Eukaryotic cells contain membranes bound-organelles and a nucleus containing genetic material, while prokaryotes don’t
What do animal cells contain?
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
What do plant cells contain?
cell wall, cell membrane, cytoplasm, vacuole, nucleus and chloroplasts
What do bacteria cells contain?
cell wall, plasma membrane, cytoplasm, capsule, ribosomes, plasmid, pili, nucleotide and bacteria flagellum
What are prokaryotic cells?
Cells without a nucleus
What are eukaryotic cells?
Cells with a nucleus
What is an organelle?
A tiny cell structure that carries out a specific function within the cell
What is the function of the nucleus?
Contains DNA coding for particular protein needed to build new cells and enclosed in the nuclear membrane
What is the function of the cytoplasm?
Liquid substance in which chemical reactions occur, contains enzymes and organelle are found in it
What is the function of the cell membrane?
controls what enters and leaves the cell
What is the function of the mitochondria?
Where aerobic respiration reactions occur and providing energy for the cell
What is the function of the ribosomes?
Where protein synthesis occurs
What is the function of chloroplasts?
where photosynthesis takes place (providing food for the plant)
What is the function of the permanent vacuole?
Contains cell sap, found within the cytoplasm, improves cell’s rigidity
What is the function of the cell wall?
Made from cellulose fibres and strengthens the cell and supports the cell
What is the function of the capsule?
Prevents drying, helps organism evade immune system
What is the function of the plasma membrane?
To protect the cell from harmful stuff and to let in stuff it needs.
What is the function of the plasmid?
A small ring of DNA
What is the function of the pili?
Attachment
What is the function of the singular circular strand of DNA?
As bacteria cells have no nucleus, this floats in the cytoplasm
What is cell specialization?
Cells throughout an organism can develop in different ways to perform different tasks
What are stem cells?
unspecialized cells from which differentiated cells develop
What are stem cells used for?
Growth and repair
What are sperm cells specialised for?
Specialised to carry the males DNA to the egg cell (ovum) for successful reproduction
How are sperm cells in animals adapted to their function?
Haploid nucleus - contains genetic information
Tail - enables movement
Mitochondria - provides energy for tail movement
Acrosome - contains enzymes that digest the egg cell membrane
What are the features of sperm cells?
- male gametes
- tale and lots of mitochondria to supply energy to swim
- acrosome on head to digest layers of ovum allowing it to penetrate leading to fertilisation
What are nerve cells specialised for?
Specialised to transmit electrical signals quickly from one place in the body to another
How are nerve cells in animals are adapted to 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 from other nerve cell, muscles and glands
What are the features of nerve cells?
Long, has branches and has insulation
What are root hair cells specialised for?
Absorbing water by osmosis and mineral ions by active transport
How are root cells in plants are adapted to their function?
Large surface area - to absorb nutrients and water from surrounding soil
Thin walls - that don’t restrict water absorption
What are the features of a root hair cells?
• Large surface area for water to enter by osmosis
• Cellulose cell wall is freely permeable to water
• Large numbers of mitochondria to provide atp for active transport of mineral ions
• Large numbers of protein carriers embedded in membrane for active transport of mineral ions
What are xylem cells specialised for?
Specialised to transport water and mineral ions up the plants from the roots to the shoots
How are xylem cells in plants adapted to their function?
No upper or lower margins between cells - to provide a continuous route for water to flow.
Thick, woody side walls - strengthen their structure and prevent collapse.
What are the features of a xylem cells?
- transports water and minerals the roots up the plant stem and into the leaves
- consists of dead cells
What are phloem cells specialised for?
Specialised to carry the products of photosynthesis (food) to all parts of the plant
How are phloem cells in plants adapted to their function?
Sieve plates - let dissolved amino acids and sugars be transported up and down the stem.
Companion cells - provide energy needed for active transport of substances along the phloem.
What is cell differentiation?
The process in which cells become specialized.
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital functions in the human body.
What time do animal cells differentiate?
At an early stage and then lose this ability
For how long do plant cell retain the ability to differentiate?
Throughout their entire life cycle
What is the purpose of cell division in mature animals?
Repair and replacement of cells
What changes does a cell go through as it differentiate?
Becomes specialised through acquisition of different sub-cellular structure to enable a specific function to be performed by the cell
What is magnification?
The number of times bigger an image appears compared to the size of the real object
What is resolution?
The smallest distance between two object can be distinguished
How does a light microscope work?
Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
What are the advantages of light microscopes?
Inexpensive, easy to use, portable, observe both dead and living specimens
What are the disadvantage of light microscopes?
Limited resolution
How does an electron microscope work?
It uses a beam of electrons which are focused using magnets, the electrons hit a fluorescent screen which emits visible light and producing an image.
What are the two types of electron microscopes?
transmission electron microscope (TEM) and scanning electron microscope (SEM)
What are the advantages of electron microscopes?
Greater magnification and resolution
Why do electron microscope have a great magnification and resolution?
They use a beam of electrons which has a shorter wavelength than photons of light
How have electron microscopes enabled scientists to develop their understanding of cells?
Allow small sub-cellular structures to be observed in detail and enable scientists to develop more accurate explanations about how cell structure relates to function.
What are the disadvantages of electron microscopes?
Expensive, large so less portable, require training to use and only dead specimens can be observed
How came magnification be calculated?
Magnification = size of image / size of real object
What are the pieces of laboratory equipment you could have used to prepare cells to view using a microscope?
Slide, coverslip, dye/stain, pipette/dropper, scalpel and forceps/tweezers
How do bacteria multiply?
Binary fission (simple cell division)
How often do bacteria multiply?
Once every 20 minutes if enough nutrients are available and the temperature is suitable.
What are the ways that bacteria can grow?
Nutrient broth solution and 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 and other minerals.
What are uncontaminated cultures of microorganisms needed for?
Investigating disinfectant and antibiotic action.
Describe the preparation of an uncontaminated culture using aseptic technique
- Use pre-sterilised plastic Petri dishes or sterilise glass Petri dishes and agar gel before using with 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 tape. Label accordingly then turn and store upside down.
- Incubate the culture at 25oC in school laboratories.
Why must Petri dishes and culture media before sterilised before use?
To kill any bacteria already present.
Why must inoculating loops be sterilised by passing them through a Bunsen burner flame?
To kill any bacteria present on the inoculating loop.
Why must the Petri dish lid be secured with 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 in a lack of oxygen.
Upside down to prevent condensation from forming and dripping down onto the colonies
Why are cultures incubated at 25C in school laboratories?
Harmful pathogens are less likely to grow at this temperature
What is the formula used to calculate cross-sectional area of a bacterial colony or clear area around a bacteria colony?
Pi x radius^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 the given time period from the mean division time.
- Use the following equation to calculate the number of bacteria:
Number of bacteria in population at end of time period = number of bacteria at the beginning of the time period x 2number of divisions in the time period .
Express the answer in standard form if possible.
What are chromosomes made of?
DNA and proteins
What is gene?
A section of DNA which codes for a protein
How many chromosomes are found in the nucleus of human body cells?
46 chromosomes
How many chromosomes are found in the nucleus of gametes?
23 chromosomes
How are chromosomes arranged in the nucleus of a body cell?
Arranged in pairs - 46 chromosomes form 23 pairs.
What are the three main stages of the cell cycle?
- Replication of DNA and synthesis of organelles
- Mitosis
- Division of cell
Why is mitosis important?
Produces identical cells which all have the same genetic information and produces additional cells for growth and repair.
Describe the first stage of the cell cycle
Longest stage - cells grow and increase in mass, replicate DNA and synthesise more organelles (eg. mitochondria, ribosomes).
Describe the second second stage of the cell cycle
Each chromosomes in a pair is pulled to opposite poles of the cell then then nucleus divides
Describe the third stage of the cell cycle
The cytoplasm and cell membrane divide - two identical daughter cells are produced.
What is the function of stem cells in embryos?
Embryonic stem cells can replicate themselves and differentiate into many other types of cell and embryonic stem 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?
Adult stem cells can differentiate into several cell types to replace dead or damaged tissues (for example, bone marrow stem cells can form many different types of blood cell)
What is the function of stem cells in plant meristems?
Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan - they can differentiate into any cell which is required by the plant.
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.
What are the advantages of cloning plants using meristem stem cells?
● Can prevent rare plants from becoming extinct.
● Can produce large numbers of plants with a favourable characteristic.
● Can produce identical plants for research.
What are issues are associated with the use of embryonic stem cells?
● Many embryonic stem cells are sourced from aborted embryos - some people have an ethical/religious objection.
● Development of stem cell therapies is slow, expensive and difficult.
● Adult stem cells infected with viruses could transfer infections to patients.
● If donor stem cells do not have a similar genetic makeup to the patient, an immune response could be triggered.
What is diffusion?
the net movement of particles from an area of high concentration to an area of low 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
How are single-celled organisms adapted for diffusion?
They have a large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organism’s needs.
How is surface area to volume 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)
What is osmosis?
The movement of water from a dilute solution to a concentration 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?
The concentration of the external solution is lower than that of internal solution (inside cell).
What may happen when an animal cell is placed in a hypotonic solution?
Water moves into the cell, causing it to burst.
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 hypotonic solution?
Water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in dice then the cell membrane may pull away from the cell wall, causing the cell to become plasmolysed
What is active transport?
The movement of molecules from a more dilute solution to a more concentration solution against a concentration gradient, using energy from respiration
How do plant root hair cells use active transport?
Root hair cells 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?
Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. Glucose is then transported to the tissues where it can be used in respiration.
How do you test for starch?
Add a drop of dilute iodine solution to the subject. If starch is present it will turn a ‘blue-black’ colour.
How do you test for sugar?
Put your food sample in a test tube and add some Benedict solution (which is blue) then heat it if it goes yellow/orange then sugar is present
How do you test for fat?
Add the food sample to a test tube with some ethanol and water in it, then shake it up with your thumb over the top. If the solution goes milky white, fat is present
How do you test for proteins?
Add Biuret A and Biuret B (sodium hydroxide and copper sulphate) in equal amounts;
If the solution turns purple, it is a positive test and protein is present; otherwise, remains pale blue
How do you test for lipids?
shake the test substance with ethanol for a minute and pour solution into water any lipid produces will show a milky emulsion
- the more lipids the more notisable milky colour
What is a red blood cell?
Type of blood cell that is made in the bone marrow and found in the blood
What is the red blood cells function?
transport oxygen from lungs to body cells
What is the structure of a red blood cell?
small, flexible, biconcaved disc
What is a white blood cell?
A cell that destroys disease-causing germs
What is the white blood cells function?
fight infection/disease
What is the structure of a white blood cell?
Large cell containing a big nucleus, different types have slightly different structures and functions
Why does red cell bursts in a beaker of water?
Water enters in the cell by osmosis and the cell starts to swell
Why does plant cell doesn’t burst in a beaker of water?
Plants cell has a cell wall (which prevents it from bursting)
What is binary fission?
How bacteria asexually reproduce
What are colonies?
A visible mass of many bacteria
What are nutrient broth solution?
A liquid food culture media to grow bacteria
What are agar gel plates?
A solid food culture media to grow bacteria
What is an aseptic technique?
A way of preventing contamination when growing bacteria
What is inoculating loop?
A sterile looped piece of wire which can transfer bacteria between culture media
What is an incubator?
A machine with a set temperature to grow bacteria
What is contamination?
When unwanted bacteria or other microorganisms grow in the culture media
What is culture media?
A liquid or solid food source to grow bacterial cultures in
What is an antiseptic?
A substance which kills bacteria and other microorganisms
What is an antibiotic?
A medication which is used to kill specific bacteria
What is sterilisation?
method of removing microorganisms from surfaces usually by means of chemicals or heat
What are disinfectants?
A substance which prevents the growth of bacteria and other microorganisms
What is a zone of inhibition?
An area of media where bacteria cannot grow that shows the effectiveness of a disinfectant or antibiotic
What is a muscle cell?
An animal cell that contains sliding protein fibres to contract and allow movement
What is a nerve cell?
An extended animal cell with many branches that sends electrical messages around the body
What is an intestinal epithelial cell?
An animal cell that is responsible for molecule absorption in the intestines, these cells have many tiny folds called microvilli that increase the surface area for absorption
What is a root hair cell?
A plant cell which has a large surface area and thin walls to absorb water and minerals
What is a xylem cell?
A hollow plant cell with thick walls containing lignin to transport water and minerals through the plant
What is a phloem cell?
A living plant cell with sieve plate pores to transport dissolved sugars throughout the plant
What is an undifferentiated cell?
A cell that has not yet acquired a special structure or function, such as a stem cell
What is the cell division of undifferentiated cells?
Occurs in developing organisms or embryos prior to cell specialisation
What is the function of an axon?
The longest part of a nerve cell which carries the electrical impulse
What is the function of a dendrite?
The parts of the nerve cell which makes connections
What is the function of a myelin sheath?
The fatty insulation of a nerve axon
What is the function of an acrosome?
Part of the head of a sperm cell that contains digestive enzymes to penetrate the egg cell
What is the function of a lignin?
A chemical that provides support to xylem cells and prevents the unwanted movement of water into nearby cells
What is a DNA loop?
A single molecule of DNA that is found free in the cytoplasm of prokaryotes
What is a human embryo?
A source of stem cells which can become any type of cell
What is a bone marrow?
A source of stem cells which can become many types of cell including blood cells
What is an meristem?
The region in plant shoots and roots where mitosis occurs and a source of stem cells in plant tissue
What is diabetes?
A disease of the pancreas which may be treated with stem cells
What is a spinal cord injury?
A cause of paralysis which may be treated with stem cells
What are the potential risks of stem cell treatment?
Viral infection, cancer and rejection unless therapeutic cloning is used
What is a zygote?
A fertilised egg cell which divides to form an embryo
What are ethical objections?
Moral reasons people may be against stem cell treatments
What are religious objections?
Religious reasons people may be against stem cell treatments
What are advantages of bone marrow stem cells?
Can treat many blood-linked or immune-linked diseases, less ethical concerns than embryonic stem cells, bone marrow is easier to obtain than embryonic cells
What are the advantages of embryonic stem cells?
No consent required, obtainable via embryos discarded in IVF, can be used to make any type of cell, less risk of rejection if used via therapeutic cloning
What are the disadvantages of bone marrow stem cells?
Requires voluntary donors, bone marrow extraction can cause pain to an individual and requires consent, may have a risk of infection, can only form cells such as blood cells, risk of rejection
What are the disadvantages of embryonic stem cells?
Ethical considerations such as potential loss of life or harm to embryo, less easily obtainable than bone marrow stem cells, risk of rejection
What is mitosis?
A type of cell division where two identical daughter cells are formed with the same genetic material as the parent cell
What is the process of mitosis?
One set of chromosomes is pulled to each end of the cell, the nucleus then divides, the cytoplasm and cell membranes eventually divide, two identical cells are formed
What are daughter cells?
The new cells formed as a result of the division of a cell
What is mineral ions?
Charged particles needed for healthy plant growth
What is cell respiration?
The release of energy from molecules
What is the cells lining the gut?
Animal cells which use active transport to absorb sugar molecules
What is the active process?
A process that requires energy
What is the passive process?
A process such as diffusion or osmosis that does not require energy
What are dilute mineral ions?
The mineral ion concentration found in the soil
What are concentration mineral ions?
The mineral ion concentration found in plant tissues
What is the dilute solution?
A solution that contains a relatively small amount of dissolved solute
What is the concentration solution?
A solution that contains a relatively large amount of dissolved solute
What is a partially permeable membrane?
A membrane which allows some substances through but not others
What is turgidity?
When a plant cell is swollen due to the movement of water into the cell
What is flaccid?
When water moves out of the plant cell causing the cell to change shape and the vacuole to shrink
What is plasmolysed?
When water has completely moved out of plant tissue by osmosis and the vacuoles are empty
What is molarity?
The amount of substance in a certain volume of solution
What is a cork borer?
A device used to make plant tissue cylinders of the same diameter
What is isotonic solution?
Where the solute concentration is equal inside and outside of the cell
What do animals cells do in hypertonic and hypotonic solutions?
Animal cells will increase in size and burst in hypotonic solutions, animal cells will decrease in size and shrivel in hypertonic solutions
What do plant cells do in hypertonic and hypotonic solutions?
Plant cells will increase in size and become turgid in hypotonic solutions, plant cells will decrease in size and become plasmolysed in hypertonic solutions
What is gas exchange?
When oxygen and carbon dioxide move in and out of cells by diffusion
What is the purpose of gas exchange?
Organisms need oxygen for aerobic respiration, they also need to remove carbon dioxide which is a waste product in some organisms
What are the sites of gas exchange?
The alveoli of the lungs and respiring cells around the body
What has an effect of exchange surfaces?
Has a large surface area, a good blood supply, is well ventilated for gas exchange and has a thin membrane for diffusion
What structure are adapted for exchanging materials?
Small intestine, kidneys, lungs, gills in fish, roots and leaves in plants all have adaptations such as thin membranes and increased surface area
What is the transport system?
A system that is used for transporting substances around a multicellular living organism
What is an urea?
A waste product that is filtered and removed from the blood plasma via diffusion in the kidneys
What happen in gas exchange in plants?
Carbon dioxide diffuses into the plant in exchange for oxygen that diffuses out of the plant, this process is regulated by guard cells in the leaves that can open and close the stomata efficiently
What are lungs specialised for?
Are specialised in gas exchange due to the presence of many tiny sacs called alveoli that are adapted for diffusion due to being moist, one cell thick and surrounded by capillaries
