Science - Biology - Cell Structures - B1 Flashcards
roughly, what size are animal cells?
vary from 0.01mm-0.05mm
roughly, what size are plant cells?
vary from 0.01mm-0.1mm
what is the job of a microscope?
magnify image of biological specimen so it appears larger
what type of microscope is generally used in schools?
compound microscope
name 2 lenses compound microscopes use to magnify specimen?
eyepiece and objective lens
how do you calculate magnification of a microscope?
magnification of eyepiece x magnification of objective
If magnification of eyepiece is x10, and magnification of objective is x40, what is magnification of microscope?
x400
what is the best unit to measure most cells?
micrometere(μm)
for sub-cellular structures, such as ribosomes, what is the best unit of measurement?
nanometre (nm)
describe the method of how to prepare a biological cell for examination in animal cheek cells
- put a small drop of water on microscope slide
- gently swab inside of your mouth with a clean cotton bud
-gently rub the cotton bud in the drop of water, you will be able to see the cells with the naked eye
describe the method on how to prepare a biological cell for examination in plant cells - Onion epidermal cells
- put a small drop of water on microscope slide
- peel some onion skin from inside one of the leaves in an onion bulb
- use forceps to transfer the drop of water, make sure onion skin is flat, and there is no trapped air bubbles. Stain cells with iodine
describe the method on how to prepare a biological cell for examination - human hair or animal fur
- put a small drop of glycerol on microscope slide
- cut a small piece of hair or fur
- use forceps to transfer to a drop of glycerol
- place a small square or circle of thin glass called a coverslip over the specimen
- put a drop of the stain on the slide, next to the coverslip
- draw the stain under the coverslip by placing a piece of filter paper next to it
why is a coverslip needed for examining cells ?
it protects the microscope and prevents the slide from drying out when it’s being examined
what is a mounted needle used for?
holding specimen in place as coverslip is lowered
why are stains used?
stains are used to add contrast as most cells are colourless,certain stains are also used to stain specific cell structures or cell products
name 3 risks when using a microscope
-care must be taken when looking down the microscope if the illumination is too bright.
-care when using microscope stains.
-care when handling coverslips, microscope slides and mounted needles.
describe the method on how to use a microscope
- rotate the objective lenses so that the low power, eg x10, is in line with the stage
- turn the coarse focus so that the stage is as close to the objective lens as possible. You should not look through the microscope to do this
- place the microscope slide – either one you have prepared, or a permanent slide – on the stage. Line it up so that the specimen – if you can see it – is in the centre of the stage, where the light passes through
- focus the slide towards you by turning the coarse focus adjustment
- draw a low power image or record a digital image of what you see. Then, rotate the objectives so that the high power objective, eg x40, is in line with the stage
- bring the slide back into focus using the fine focus adjustment. If you do not succeed, go back to low power and re-focus, then try again
why is a low power diagram used when examining cells?
-as a plan to show the arrangement of any distinct regions of the tissue, for example the tissues in a plant root
-to show the outline of individual cells that make up the tissue, if the tissue is uniform
why is a high power diagram used when examining cells?
a detailed image of a part of the slide. It is usually drawn to show a single cell, eg of a single cheek cell or onion cell
describe the microscope in the 1590s
dutch spectacle makers Janssen experimented with putting lenses in tubes. they made the first compound microscope. None of their microscopes have survived, but they are thought to have magnified from ×3 to ×9
describe the microscope in 1650
robert hooke - observed and drew cells using a compound microscope.
describe the microscope in the late 1600s
dutch scientist Antonie van Leeuwenhoek constructed a microscope with a single spherical lens. it magnified up to ×275
describe the microscope in the 1800s
the optical quality of lenses increased and the microscopes are similar to the ones we use today
what is the maximum magnification using a light microscope?
x1500
name a limit of the light microscope
resolution
what do electron microscopes use instead of light rays?
a beam of electrons
name 2 types of electron microscope
- scanning electron microscope (SEM)
- transmission electron microscope (TEM)
give a disadvantage of the electron microscope
it’s expensive
what is cytoplasm ?
a jelly-like material that contains dissolved nutrients and salts and structures called organelles. it is where many of the chemical reactions happen
what is the function of the nucleus?
contains genetic material, including DNA, which controls the cell’s activities
what is the function of cell membrane?
its structure is permeable to some substances but not to others. it therefore controls the movement of substances in and out of the cell
what is the function of mitochondria ?
organelles that contain the enzymes for respiration, and where most energy is released in respiration
what is the function of ribosomes ?
tiny structures where protein synthesis occur
what 3 additional structures to plant cells have that animal cells don’t ?
- cell wall
- permanent vacuole
- chloroplasts
what is the function of the cell wall ?
made from cellulose fibres and strengthens the cell and supports the plant
what is the function of the chloroplasts ?
organelles that contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. contains the enzymes needed for photosynthesis
what is the function of the vacuole ?
filled with cell sap to help keep the cell turgid
how can cell size be measured ?
using an eyepiece graticule
what are prokaryotic cells ?
a simple cell that does not have a nucleus - the DNA is free in the cytoplasm
what are cells of bacteria called ?
prokaryotic cells
what are eukaryotic cells?
a type of cell that has a nucleus
what are cells of plants, animals, and fungi called ?
eukaryotic cells
what size is a eukaryotic cell ?
most are 5 μm – 100 μm
what size is a prokaryotic cell ?
most are 0.2 μm – 2.0 μm
name outer layers of the eukaryotic cell
cell membrane - surrounded by cell wall in plants and fungi
name outer layers of the prokaryotic cell
cell membrane - surrounded by cell wall
what is the cell contents of a eukaryotic cell ?
cytoplasm, cell organelles include mitochondria, chloroplasts in plants and ribosomes
what is the cell contents of a prokaryotic cell ?
cytoplasm, ribosomes, no mitochondria or chloroplasts
where is the genetic material in a eukaryotic cell ?
DNA in a nucleus - plasmids are found in a few simple eukaryotic organisms
where is genetic material in a prokaryotic cell ?
DNA is a single molecule, found free in the cytoplasm - additional DNA is found on one or more rings called plasmids
what type of cell division do eukaryotic cells use ?
mitosis
what type of cell division do prokaryotic cells use ?
binary fission
what is a specialised cell ?
specialised cells are cells designed to carry out a particular role in the body
name specialised functions of a sperm cell
- head of the sperm contains the genetic material for fertilisation
- acrosome in the head contains enzymes so that the sperm can penetrate an egg
- middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg
- tail enables sperm to swim
name specialised functions in a nerve cell
- nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system
- cell has extensions and branches, so that it can communicate with other nerve cells, muscles and glands
- nerve cell is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse
name specialised functions in a muscle cell
- muscle cells contain filaments of protein that slide over each other to cause muscle contraction
- well-developed mitochondria to provide the energy for muscle contraction
name specialised functions in a root hair cell
- large surface area to provide contact with soil water
- thin walls so as not to restrict the movement of water
name specialised functions in a xylem cell
- no top and bottom walls between xylem vessels, so there is a continuous column of water running through them
- walls become thickened and woody. They therefore support the plant
what do chromosomes carry?
genetic information in a molecule called DNA
where are chromosomes found?
in the nucleus
what is DNA ?
material inside the nucleus of cells, carrying the genetic information of a living being
where is DNA ?
in the nucleus, within chromosomes
what is archaea ?
microorganisms which are similar in size and structure to bacteria but are genetically different
what is a biological specimen ?
in microscopy, a whole organism, cells, tissues, a small piece of tissue, or other structures, eg hair, pollen grains, that are viewed with a microscope
what does calibrate mean ?
to set an instrument or scale against a standard
what is a compound microscope ?
compound microscope uses two lenses, the objective lens and the eyepiece. The very short focal length objective lens produces a greatly-magnified image, then the short focal length eyepiece magnifies this further
what is a eukaryotic cell ?
a type of cell that has a nucleus
what is an eyepiece ?
the lens at the top of a compound microscope. It has a longer focal length than the objective lens and magnifies the image produced by the objective
what is field of view ?
the area seen when looking through a microscope
what is a graticule ?
a glass or plastic disc fitted into the eyepiece of a microscope. The graticule has a scale ruled on it and is used to estimate the size of a specimen when viewed with a microscope
what is a light microscope ?
device that uses visible light and a series of lenses to produce an enlarged image of an object
what is magnification ?
the amount that an image of something is scaled up when viewed through a microscope
what is a micrograph ?
a photograph taken of a microscopical image
what is mitochondria ?
structures in the cytoplasm of all cells where aerobic respiration takes place
what is a mounted needle ?
a needle mounted in a wooden or metal handle for use in microscope work or dissection
what is an objective lens ?
the lens near the specimen being examined - which magnifies the image at different levels
what is order of magnitude ?
a number, to the base ten, often used to make comparisons. For each order of magnitude, a number is ten times the previous one
what is a prokaryotic cell
a simple cell that does not have a nucleus - DNA is free in cytoplasm
what is resolution ?
the fineness of detail that can be seen in an image - the higher the resolution of an image, the more detail it holds. In computing terms, resolution is measured in dots per inch
what happens in the ribosome ?
the site of protein synthesis
what is a stage micrometre ?
a glass slide with a scale etched on it. It is used to calibrate the eyepiece graticule of a microscope
what does sub-cellular mean ?
structures smaller than a cell that are found within it
what is a tissue ?
group of similar cells that carry out the same function
what is a virus ?
an ultramicroscopic infectious non-cellular organism that can replicate inside the cells of living hosts, with negative consequences
when cells are ready to divide, what happens to DNA?
it copies itself, coils, and condenses to form the chromosomes you see in micrographs
how many chromosomes are in a human body cells ?
46 chromosomes, arranged into 23 pairs
what are the female sex chromosomes referred to ?
XX - as they’re identical in shape
what are the male sex chromosomes referred to ?
XY - as one of the chromosomes is a different shape
when do cells divide ?
- when an organism grows
- when an organism is damaged and needs to produce new cells
explain the cell cycle
cell growth
DNA synthesis - chromosomes are now double stranded
further growth occurs and DNA is checked for errors
mitosis
cytoplasm separates - 2 cells are formed
temporary cell resting period or cell stops dividing
explain mitosis
cell begins to divide
DNA replicates to form 2 copies of each chromosome
nuclear membrane breaks down, chromosomes line up across the centre of the cell
one set of chromosomes is is pulled to each end of cell and nucleus divides
cytoplasm and cell membranes divide to form 2 identical cells
how do you calculate length of different stages of the cell cycle?
observed number of cells at that stage/ X total length of
total number of cells observed time of cell cycle
where can adult stem cells be found ?
brain
eyes
blood
heart
liver
bone marrow
skin
muscle
Can adult stem cells differentiate into any type of cell ?
no, related cell types only
where does cell division in plants happen ?
in the meristems
can cells in the meristems differentiate into any type of plant cell ?
yes
name specialised cells in animals
circulatory system
excretory system
muscular system
nervous system
respiratory system
reproductive system
skeletal system
name specialised cells in plants
palisade mesophyll
spongy mesophyll
guard cells
sieve tubes
companion cells
xylem vessels
growing points
what do cells in the circulatory system do ?
transport substances, defend the body, regulate temperature
what do cells in the excretory system do ?
remove waste products and unwanted substances, regulate the water content of the body
what do cells in the muscular system do ?
bring about movement
what do cells in the nervous system do ?
respond to internal and external stimuli and conditions, carry messages for the body work as a coordinated whole
what do cells in the respiratory system do ?
deliver oxygen for respiration and remove waste
what do cells in the reproductive system do ?
bring about fertilisation to produce new offspring
what do cells in the skeletal system do ?
to bring about movement, support and protect internal structures, produce blood cells, store and release calcium
what do palisade mesophyll cells do ?
carry out photosynthesis
what happens in the spongy mesophyll ?
allow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis
what do guard cells do ?
open and close to control the exchange of gases – carbon dioxide, water vapour and oxygen
what do sieve tubes do ?
transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed
what do companion cells do ?
provide the energy required for transporting substances in sieve tubes
what do xylem cells do ?
transport water and dissolved minerals from the roots, up the plant
what do meristems do ?
produce new cells as they divide
why are plants cloned ?
to produce identical plants quickly and economically, to produce new individual from rare and endangered plants, to help preserve the species
stem cells can be used to divide into new cell types, they therefore have the potential to be transplanted into patients to treat medical conditions and disease, they could be used to replace cells which have been damaged or destroyed, give examples of what could be treated with the use of stem cells and what type of stem cells could be used ?
in type 1 diabetes
in cases of multiple sclerosis which could lead to paralysis
in cases of spinal cord or brain injury which could lead to paralysis
- stem cells used could be
embryonic stem cells
adult stem cells
which stem cells can differentiate into a wider range of cells ?
embryonic stem cells or adult stem cells
embryonic stem cells
give an example of of an adult stem cell transplant ?
bone marrow transplant
what can a bone marrow cell differentiate into ?
different types of red blood cells
when can bone marrow transplants be carried out ?
in cases of blood cell cancer, e.g leukaemia and lymphoma
when blood cells have been destroyed by cancer treatment
give clinical issues with the use of stem cells
-There is no guarantee how successful these therapies will be, for example the use of stem cells in replacing nerve cells lost in Parkinson’s disease patients.
-The current difficulty in finding suitable stem cell donors.
-The difficulty in obtaining and storing a patient’s embryonic stem cells. These would have to be collected before birth - some clinics offer to store blood from the umbilical cord when a person is born.
-Mutations have been observed in stem cells cultured for a number of generations, and some mutated stem cells have been observed to behave like cancer cells.
-Cultured stem cells could be contaminated with viruses which would be transferred to a patient.
give ethical issues of stem cells
-A source of embryonic stem cells is unused embryos produced by in vitro fertilisation (IVF)
-For therapeutic cloning is it right to create embryos for therapy, and destroy them in the process?
-Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person.
-At what stage of its development should an embryo be regarded as, and treated as a person?
give social issues of stem cells
-Educating the public about what stem cells can, and can’t do, is important.
Whether the benefits of stem cell use outweigh the objections.
-Much of the research is being carried out by commercial clinics, so reported successes are not subject to peer review. —-Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages.
what is an adult stem cell ?
a type of stem cell found in specific locations in adults. Adult stem cells can only differentiate into a limited number of related cell types
what is agar gel ?
a jelly-like substance that is derived from a type of seaweed and used in the lab as a medium on which to grow bacteria and fungi
what is bone marrow ?
soft tissue found inside bones that produces new blood cells
define the function of the brain
the organ of the central nervous system of mammals where vital functions are coordinated
define cancer
a disease caused by normal cells changing so that they grow and divide in an uncontrolled way. the uncontrolled growth causes a lump called a tumour to form
what is the cell cycle ?
the series of stages that a cell goes through as it is growing and dividing
what is a chromosome ?
the structure made of DNA that codes for all the characteristics of an organism
what is cloning ?
a scientific method by which genetically identical copies are made of animals or plants
what is a culture medium?
a gel or liquid used to grow microorganisms, or cells, tissues or organs
define cuttings
part of a plant stem, leaf, or root cut off and used for producing a new plant. An artificial propagation method
what are daughter cells ?
when a cell divides, the new cells produced are called daughter cells
define diabetes
a serious disease in which the body is unable to regulate blood sugar
define differentiation
when an unspecialised cell becomes a more specialised cell type
define disease
illness affecting plants and animals
what is DNA ?
deoxyribonucleic acid. the material inside the nucleus of cells, carrying the genetic information of a living being
what is an egg cell ?
the female reproductive cell
what is an embryo ?
an organism in the early stages of development
what is an embryonic stem cell ?
a type of stem cell found in the embryo, capable of dividing into almost any cell type
define ethical
relating to right and wrong, eg ethical companies are often ones that act in a responsible way
what is fertilisation ?
the joining of a male and female gamete
what is a gene ?
the basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell’s chemistry - particularly protein production
what is genetic engineering ?
process which involves the artificial transfer of genetic information from one donor cell or organism to another
what is an immune system ?
the body’s defence system against entry of any foreign body, including pathogens and agents such as pollen grains. The role of the immune system is to prevent disease
what is a meristem ?
a region in plant shoots and roots in which cells are dividing, and so are undergoing mitosis
what is a micrograph ?
a photograph taken of a microscopical image
what is mitosis ?
a type of cell division which produces daughter cells identical to the parent
define multicellular
having more than one cell
what is multi sclerosis ?
a condition, usually autoimmune, in which the myelin sheaths of the neurones of the brain and spinal cord are damaged, reducing the transmission of nerve impulses, and leading eventually to paralysis
what is the function of a nucleus ?
the nucleus controls what happens inside the cell. Chromosomes are structures found in the nucleus of most cells
define paralysis
the loss of muscle function in part of the body
what are plant hormones ?
substances that can modify or control the growth of plants
what are runners ?
a slender fast growing stem that grows horizontally over the soil surface and puts down roots to form new plants eg strawberry
what does specialised mean ?
a cell that has become differentiated to carry out a particular function, eg red blood cell
what’s a spinal cord ?
the part of central nervous system of a mammal which runs inside its backbone
define a stem cell
a cell found in foetuses, embryos and some adult tissues that can give rise to a wide range of other cells
define synthesis
made or put together
define therapeutic cloning
using cloning technology for medicinal purposes. One example is to use a person’s DNA to clone one of their organs for use in transplanting
define tissue culture
a technique where animal or plant cells or tissue are isolated and transferred to a sterile culture medium. If successful, the cells will continue to grow and divide, though not indefinitely
what is a transplant ?
surgical procedure in which a tissue or organ is replaced
what is a vacuole ?
a space within the cytoplasm of plant cells that contains cell sap
what is a zygote ?
a fertilised egg cell
do particles move to a higher or lower concentration ?
low concentration
state examples of diffusion in a leaf cell
oxygen moves out of cells by diffusion, carbon dioxide moves into cells by diffusion
state examples of diffusion in the lungs
oxygen diffuses from high concentration in alveolus to low concentration in blood, carbon dioxide diffuses from high concentration in blood to low concentration in alveolus
how can the concentration gradient affect the rate of diffusion?
greater the rate of concentration, greater rate of diffusion
how can temperature affect the rate of diffusion ?
higher the temperature, the more kinetic energy particles will have so they will move and mix more quickly
give an example of how large organisms increase surface area proportionality
additional absorbing areas or adaptations of shape
why would organisms living in harsh environmental conditions, such as cacti reduce their surface area ?
to reduce surface area
does a dilute solution contain a high or low concentration of water molecules ?
a high concentration
what molecules does osmosis mainly occur in ?
water molecules
when in osmosis will there be no net movement of water molecules ?
when the concentration of water is the same on both sides of the membrane
when in plant cells does osmosis occur ?
-isolated plant cells in a dilute solution or water will take in water by osmosis
-if soil is wet or moist, root hair cells will take up water by osmosis
leaf cells of land plants have a tendency to lose water unless what ?
unless it’s raining or the humidity is high
in pure water the cell contents push against the wall the cell becomes what ?
turgid
what happens to plant cells in a concentrated solution ?
cell contents lose water by osmosis, they shrink and pull away from cell wall- the cell becomes flaccid and is becoming plasmolysed
what happens to plant cells in highly concentrated solutions ?
cell becomes fully plasmolysed as cell loses more water
how would plant cells lose water by osmosis in the soil ?
if they were not watered, or plants in drought conditions
animal cells take in and lose water by osmosis. they do not have a cell wall, so what does this mean when put into different solutions are at a different concentration to the cell contents ?
they will change size and shape
what happens to red blood cells when put into a concentrated solution ?
they lose water and shrink
what happens to red blood cells when put into distilled water or more dilute solution
they gain water and swell and burst in a more dilute solution
name risks when doing the effects of osmosis on a plant tissue experiment ?
-make sure that the potato is placed on a ceramic tile when using the cork borer – do not cut the potato cylinders towards your hand.
-care must be taken when using the scalpel.
-wear eye protection when using chemical solutions
what is active transport ?
a process that is required to move molecules against a concentration gradient .the process requires energy
describe active transport in plants
for plants to take up mineral ions, ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil. active transport then occurs across the root so that the plant takes in the ions it needs from the soil around it
describe active transport in animals
in animals, glucose molecules have to be moved across the gut wall into the blood. the glucose molecules in the intestine might be in a higher concentration than in the intestinal cells and blood – for instance, after a sugary meal – but there will be times when glucose concentration in the intestine might be lower.
all the glucose in the gut needs to be absorbed. when the glucose concentration in the intestine is lower than in the intestinal cells, movement of glucose involves active transport. the process requires energy produced by respiration
which of the following process requires energy : diffusion, osmosis or active transport ?
active transport
define aerobic respiration
respiration that requires oxygen
what are amino acids ?
the building blocks that make up a protein molecule
what is an anomalous result ?
a result that is very different from the rest of the results
define aquatic
within water
define bacteria
single celled microorganisms, some of which are pathogenic in humans, animals and plants
what is blood plasma ?
the liquid part of the blood containing useful things like glucose, amino acids, minerals, vitamins and hormones, as well as as waste materials such as urea
define a cell
basic unit of life - unicellular organisms only have one cell,multicellular organisms have many cells
what is a cell membrane ?
a selectively permeable membrane surrounding the cell and controlling the entry and exit of materials
what is cell sap ?
the liquid found in the vacuole of plant cells, consisting of water with dissolved sugars, salts and amino acids
what is a cell wall
outer structure which provides support and prevents the cell from bursting from the uptake of water by osmosis. plant, fungal and bacterial cell walls have different structures and chemical compositions
what is cellulose
a carbohydrate. it forms the bell wall in plant cells
define concentration
the concentration of a solution tells us how much of a substance is dissolved in water. higher the concentration, the more particles of the substance are present
what is a concentration gradient ?
the difference in the concentration of a chemical across a membrane
define cytoplasm
the living substance inside a cell (not including nucleus)
define diffusion
the movement of molecules from an area of higher concentration to an area of lower concentration
define dilute
of low concentration
define dissolve
when a substance breaks up and mixes completely with a solvent to produce a solution
define flaccid
lacking turgor. lacking in stiffness or strength . soft and flappy
define humidity
the amount of water vapor in the atmosphere measured as a percentage
define interpolated
to determine a data point from a known set of data points from a graph
define an ion
electrically charged particle,formed when an atom or molecule gains or loses electrons
what is a light microscope
a device that uses visible light and a series of lenses go produce an enlarged image of an object
what is a mean
the mean is calculated by adding all of the data and dividing by the number of items of data
define median
the median is the value of the middle item of data when all the data is arranged in order
what is a molecule ?
a collection of two or more atoms held together by chemical bonds
define multicellular
having more than one cell
define net
overall
define organism
living entity, animals, plants or microorganisms
define osmosis
the movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration
define partially permeable
also called semi permeable- a partially permeable membrane allows water and other small molecules to pass through, but not larger molecules such as starch
define passive transport
transport of molecules that occurs as a result of the random movement of particles, so that there is a next movement from a higher to a lower concentration- does not require energy
define plasmolysed
description of a plant cell in which the vacuole has shrunk and the membrane has pulled away from the wall due to water loss by osmosis
define range
the difference between the highest and lowest values in a set of data
what is a root hair cell ?
a specialized cell that increased the surface area of the root epidermis to improve the uptake of water and minerals
define solute
the dissolved substance in a solution
define solution
mixture formed by a solute and a solvent
define solvent
the liquid in which the solute dissolved to form a solution
define sucrose
a disaccharide made from glucose and fructose
what is sugar ?
a simple carbohydrate that is sweet to taste
what is a tissue ?
a group of similar cells that carry out the same function , e.g muscle tissue
what is tissue fluid ?
fluid which is derived from blood plasma that passes through the walls of capillaries
define turgid
enlarged and swollen with water. having turgor. description of a plant cell in which the vacuole had swollen due to water gain by osmosis
what is a vacuole ?
a space within the cytoplasm of plant cells that contains cell sap
