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Flashcards in Cell Structure Deck (150):

What is a cell?

The smallest structural unit of life capable of functioning and replicating independently


Name the parts of 5 parts of an animal cell?

Ribosomes, mitochondria, nucleus, cytoplasm, cell membrane


Name the 7 parts of a plant cell?

Ribosomes, mitochondria, chloroplast, vacuole, nucleus, cell membrane, cell wall


Function of the nucleus?

Holds cell DNA on chromosomes and controls activities of the cell


Function of the cytoplasm?

Where chemical reactions occur. Contains enzymes to control these reactions


Function of the mitochondria?

Site of respiration/energy release


Function of ribosomes?

Site of protein synthesis


Function of the cell membrane?

Controls what goes in and out of the cell


Function of the vacuole?

Contains cell sap, a weak solution of sugar and salts and supports the cell


Function of chloroplasts?

Contains chlorophyll which absorbs light for photosynthesis


Function of the cell wall?

Strengthens and supports the cell


5 characteristics of a eukaryotic cell?

Has a nucleus, has membrane bound organelles, dna held on chromosomes in the nucleus, has a membrane present, cell wall if present is made of cellulose


5 characteristics of a prokaryotic cell?

No nucleus, circular loops of DNA within the cytoplasm, man be one or more small rings of DNA (plasmids),cell wall is present is made of murien


Which is bigger prokaryotic or eukaryotic?



How many times bigger is 1 order of magnitude?

10 times bigger


5 characteristics of a light microscope?

Can magnify up to 2000 times, relatively cheap, can magnify live objects, reliant on a light source, 2D image produced


6 characteristics of an electron microscope?

Expensive, higher magnification, more detailed image, magnify up to 2 million times, beams of electrons instead of light, 3D image produced


Equation for magnification?

Size of image = magnification x size of real object


How is a root hair cell adapted to its function?

Large surface area to absorb water


How is a ciliated epithelial cell adapted to its function?

Has many hair like structures which brush away mucus


How is a sperm cell adapted to its function? 4 ways

Head is streamline and has a tail which helps it to swim to the egg, contains many mitochondria to provide energy, carries enzymes in its head to digest through the egg cell membrane


How is a palisade cell adapted to its function?

Has lots of chloroplasts to carry out photosynthesis


How is a nerve cell adapted to its function? 2 ways

Lots of dendrites make connections to other cells and form a network throughout the body, long axon to carry impulses from one place to another


How is a red blood cell adapted to its function? 2 ways

Large surface area for oxygen to pass through, haemoglobin joins to the oxygen


How is a xylem adapted to its function? 2 ways

Waterproof walls make sure the plant does not fall over when the water is being carried from the roots to leaves, form tubes which are joined end to end and are hollow in the centre so water can flow through


How is a phloem adapted to its function? 2 ways

Companion cells keep it alive and provide the energy needed to transport food from the leaves to the rest of the plant, form tubes which have very few subcellular structures so food can flow through


What is differentiation?

When organisms develop and cells become specialised for a particular function


What is a gene?

A shaker section of DNA which codes for a particular characteristic such as hair or eye colour


What is a gamete?

Sex cell


What is fertilisation?

Process of a sperm and egg meeting


What is a chromosome and how many do we have in our body cells?

A long strand of DNA wrapped up in a helical structure, 46 in our body cells


Whah is a zygote?

Fertilised egg cell


Is an XX chromosome male or female?



Is an XY chromosome male or female?



What is a stem cell?

An undifferentiated cell which is able to differentiate into specialised cell types, they can divide to produce many more undifferentiated cells


Which two sources do stem cells commonly come from and where are they found?

Embryos formed in blastocyst phase of embryological development and adult bone marrow , found in different types of tissue


5 uses of stem cells?

To replace or rejuvenate damaged tissue, to make more specialised tissue which has been lost due to injury or disease, treat blood based diseases, test different drugs, prevent plants becoming extinct


Why is human embryonic stem cell research ethically and politically controversial?

It involves the destruction of human embryos


What type of cell is one which contains 23 pairs of chromosomes?



Why do we need cell division? (3 reasons)

Allow growth, replace worn out cells, repair damaged tissue


What is diffusion?

The movement of particles from a high concentration to a low concentration


What is osmosis?

The overall movement of water through a partially permeable membrane from a region of high water concentration to low water concentration


What is active transport?

The movement of particles from a low concentration to high concentration


Which process needs carrier proteins in the cell membrane?

Active transport


What happens to the rate of diffusion if the temperature increases?

It increases


Define turgid

When water enters a plant cell and pushes on the cell wall causing it to swell


Define plasmolysed

When water leaves a plant cell and the cell contents shrink and the cell membrane pulls away from the cell wall


Define partially permeable

A membrane which allows some substances to pass through but not others


Define hypertonic

Concentration of the solutes in the solution surrounding the cell is higher than inside the cell


Define hypotonic

Concentration if solutes surrounding the cell is lower than inside the cell (more water)


Define solvent

The liquid in which a substance dissolves


Define solute

The substance which dissolves in a liquid


Define haemolysis

When red blood cells gain water, swell and burst in a more dilute solution


Define crenation

When red blood cells lose water and shrink in a more concentrated solution


Define osmoregulation

Involving the kidneys ensures that the concentration of the blood stays about the same as the concentration of the cell contents in terms of water


Define isotonic

Contains a high concentration of water molecules


What happens to red blood cells in a hypotonic solution?

They gain water and swell becoming turgid


What happens to red blood cells in a hypertonic solution?

They shrink and become wrinkled


What is embryo screening?

A method where embryos from presumed chromosomally normal genetic parents are tested for abnormalities, involves removing a cell from an IVF embryo to test it before transferring it to the uterus


Give 2 possible sources of error in the osmosis potato experiment

Concentration of solution, accuracy of balance


How do you focus a microscope?

Turn the fine focus knob until the cells are in focus


How do you get a more detailed image on a microscope?

Rotate the objective lens to a higher power to increase magnification


How do you convert millimetres into micrometers?

1millimetre is 100micrometres


Why should you calculate percentage change of carrots in an osmosis experiment?

It makes it easier to compare each of them as they may have started with a different mass


In the osmosis experiment what kind of line of best fit do you use?

A straight line because the points are in a straight line. Half the points must fall one side of the line and half the other


Why do boiled carrots not change in mass in an osmosis experiment?

The high temperature of boiled water distort the partially permeable membrane


How does vaccinating a large proportion of the population reduce the spread of a virus?

Vaccinating people makes them immune (they don’t get ill). Less chance of non immune people becoming exposed to pathogen


What is the difference between antibody production after the vaccine and after exposure to the virus? 4 points

Greater number of antibodies produced, they stay for longer, they are produced spooner because the white blood cells recognise the pathogens antigens, memory cells produce specific antibodies to fit the antigens and break the pathogen down


Convert picograms to nanograms

1 picogram is 0.001 nanograms


Convert nanograms to grams

1 nanogram is 1x10^-9 grams


Convert picograms to grams

1 picogram is 1x10^-12 grams


What happens in each three stages of the cell cycle?

In stage 1, number of organelles increases and dna is replicated. In stage 2 (mitosis) one set of chromosomes moves to each end of a cell and the nucleus divides. In stage 3 the cell membrane splits to form two genetically identical cells


Give 7 advantages of therapeutic cloning in medical treatments

may be used to treat diseases, produce replacement cells, cells/tissues of any type can be produced, cells are unlikely to be rejected by the patient, many cells produced, cells could be used in research, reduce waiting time for transplants


Give 6 disadvantages of therapeutic cloning in medical treatments

Potential life is killed, shortage of donors, egg collection/donation has risks, do net yet know risks or side effects of procedure on patient, may transfer infection, poor success rate to produce viable eggs


Identify the 5 stages of mitosis

After contents and DNA have been copied chromosomes line up in cell and spindle fibres pull them apart, two arms of each chromosome go to opposite ends of cell, membranes form around each set of chromosomes which become the nuclei of the two new cells -the nucleus has divided, cytoplasm and cell membrane divide, identical daughter cells are produced - DNA is identical to parent cell's DNA


Is mitosis asexual or sexual?

Asexual because it only involves one parent cell


Function of xylem

Transport water in the transpiration stream


Function of phloem

Transport dissolved sugars using translocation


Where is water lost from in a leaf?



Why are there more stomata on the lower surface of a leaf?

The leaf has a waterproof upper surface to prevent evaporation. The sun shines on the top of the leaf so the lower surface is cooler and less evaporation occurs. More humid under the leaf so less water evaporates


Define meristem

Term given to stem cells in plants


Define cell cycle

Continuous cycle in which cells grow, replicate their DNA and organelle and undergo mitosis


Why is it important for some cells to contain a lot of ribosomes?

Site of protein synthesis. Proteins required for every important function in a cell


Name the 3 stages of the cell cycle

Interphase (longest stage), mitosis, cytokinesis


Identify 5 diseases which can be treated with stem cells

Cancers, Parkinsons, Alzheimers, spinal cord injuries, diabetes


Where are stem cells found in plants?

Tip of shoot or root


Identify the 3 stages of using therapeutic cloning to produce stem cells

Nucleus in egg cell replaced with nucleus from parent cell, egg triggered to develop into embryo, cells removed from embryo using a pipette then grown in a petri dish with nutrients


What is the function of muscle cells and how are they adapted? 2 ways

Contract quickly in order to move food. This aids digestion and action of enzymes. Long so they have space to contract, contain lots of mitochondria to generate energy needed for contraction


Define passive transport

Movement which does not require energy


Define concentration gradient

Difference in concentrations within a solution or on either side of the cell membrane


What are carrier proteins?

Proteins found in the cell membrane which change shape to allow molecules to pass during transport


Define alveoli

Exchange surface in the lungs where oxygen moves into the blood and carbon dioxide moves into the blood


Identify 7 structures of the thorax

Lung, diaphragm, alveolus, trachea, bronchus, ribs, bronchioles


What effect does the concentration gradient have on rate of diffusion?

Bigger the concentration gradient, faster the diffusion rate


Relationship between size of an organism and their SA:V

Bigger the size, lower the SA:V


How are gills (exchange surface) of a fish adapted to maximise rate of diffusion? 6 ways

Each gill is made of thin plates called gill filaments which give a big surface area for exchange of gases, gill filaments covered in lots of tiny structures called lamellae which further increase surface area, lamellae have lots of blood capillaries to speed up diffusion, lamellae have thin surface later of cells to minimise distance gases need to travel, blood flows through lamellae in one direction and water flows over in opposite direction so it maintains a large concentration gradient between water and blood, concentration of oxygen in the water is always higher than in the blood so as much oxygen diffuses as possible from water to blood


How are nutrients absorbed in the gut?

Active transport is used in the gut when there is a higher concentration of nutrients in the blood than in the gut. The epithelial cells of the villi transport nutrients from the lumen of the intestine into the capillaries. Absorption of majority of nutrients takes place in the jejenum


How to identify a prokaryotic cell n a diagram?

Genetic material is not inside a nucleus


How do you convert millimetres to micrometres?

Times by 1000


Why do most organisms on earth have an even number of chromosomes in body cells?

Chromosomes in body cells are found in pairs


What is the function of DNA?

Codes for a sequence of amino acids which make protein


Why is the ability of body cells to divide important?

Allow for tissue growth and repair


What is meant by the transpiration stream?

Water moves up the stem via the xylem from the root hairs to the leaves. It evaporates from the leaf via the stomata


How do plant roots mainly absorb ions?

Active transport because the concentration of mineral ions is usually higher in the root hair cell than in the soil


When a funnel with a thin membrane tied across the end which contains a concentrated sugar solution is put in a beaker of water, why does the level of solution in the funnel increase overtime?

Water enters the funnel through a partially permeable membrane via osmosis because the concentration is higher inside the funnel than outside in the beaker


When would the level rise more slowly when a funnel with a thin membrane tied across the end which contains a sugar solution is put in a beaker of water?

When you use dilute sugar solution instead of concentrated sugar solution because there is less difference in concentration


How does the fact many cells in a root store starch help plants absorb mineral ions from the soil?

Starch is an energy source/store for active transport


Identify 3 ways plant roots are adapted to absorb mineral ions from the soil?

Many cells store starch, root hair cell contain many mitochondria, plant root has thousands of root hairs which give it a large surface area


What is a prokaryote?

A prokaryotic cell (single celled organism)


What is a eukaryote?

Organism made up of eukaryotic cells


What can we see with light microscopes?

Individual cells and large subcellular structures like nuclei


What can we see with electron microscopes?

Internal structure of mitochondria and chloroplasts. Also tinier things like ribosomes and plasmids


How do you prepare a microscope slide when using a light microscope? 6 steps

Add a drop of water to middle of clean slide, cut up onion and separate into layers and use tweezers to peel off some epidermal tissue from the bottom of one layer, using tweezers place the epidermal tissue into water on the slide, add a drop of iodine solution (a stain used to highlight objects in a cell by adding colour to them), place a cover slip (square of thin, transparent glass or plastic) on top by standing cover slip upright on slide next to the water droplet then tilt and lower so it covers the specimen, try not to get air bubbles as they would obstruct your view of the specimen


What are the 6 main parts of a light microscope?

Coarse adjustment knob, fine adjustment knob, eyepiece, high and low power objective lenses, stage, light


How do you use a light microscope to look at your slide? 6 steps

Clip the prepared slide onto the stage, select the lowest power objective lens, use coarse adjustment knob to move up stage to just below objective lens, look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus, adjust focus with fine adjustment knob until you get a clear image of what is on the slide, to see the slide with a higher magnification swap to a higher powered objective lens and refocus


What is the difference between differentiation in a plant cell and differentiation in an animal cell?

Animal cells often lose the ability to differentiate at an early stage after they become specialised, lots of plant cells don't ever lose this ability


Why are stem cells in early human embryos able to turn into any kind of cell at all?

All the different types of cell in the human body have to come from those few cells in the early embryo


What is therapeutic cloning?

An embryo is made to have the same genetic information as the patient which means stem cells produced would contain the same genes and wouldn't be rejected by the patient's body if used to replace faulty cells


What are 6 negatives of developing stem cells in medicine?

Stem cells grown could become contaminated with a virus which could be passed on, patients treated with stem cells have to take drugs for the rest of their life to prevent rejection, risk of rejection, expensive to grow, human embryos should not be used for experiments because each one is a potential human life, stem cells can grow out of control to form cancerous tumours


What are 5 arguments for stem cell research?

Curing patients who already exist and are suffering is more important than the rights of unborn embryos, embryos used are usually unwanted ones from fertility clinics which would otherwise be destroyed, stem cells from an embryo can grow into any type of tissue, large numbers of stem cells can be grown in a laboratory, stem cells may be used in medical research or to treat human diseases


What 3 things are stem cells in the meristem used for in plants?

Produce clones of whole plants quickly and cheaply, grow more rare species to prevent them being wiped out, grow crops of identical plants that have desired features for farmers like disease resistance


How could the controversy over stem cells be avoided?

Concentrate on finding alternative sources. It may be possible to reprogramme differentiated adult cells back to an undifferentiated stage


What are chromosomes?

Long strands of DNA wrapped up in a double helix structure, contain large number of genes


What do genes do?

Control development of characteristics


Why do body cells have an equal number of chromosomes?

Chromosomes in body cells are found in pairs. One from father, one from mother


What do organisms use mitosis for?

Growth, development, replacement of damaged cells


What happens in the growth and replication stage of the cell cycle before mitosis? 4 steps

In a cell that isn't dividing the DNA is spread out in long strings. Before it divides the cell has to grow and increase amount of subcellular structures, it then duplicates its DNA so there's one new copy for each new cell, DNA is copied and forms X shaped chromosomes - each arm of the chromosome is identical to the other


What effect does concentration gradient have on rate of diffusion?

The bigger the concentration gradient, the faster the rate of diffusion


What effect does a higher temperature have on diffusion rate and why?

Faster diffusion rate because particles have more energy and move around faster


What 4 things can diffuse through membranes?

Only very small molecules like water, amino acids, glucose, oxygen. Starch and proteins cannot fit


What effect does surface area have on diffusion and why?

The larger the surface area, the faster the diffusion rate because more particles can pass through at once


What is a partially permeable membrane?

One with very small holes in it so only tiny molecules can pass through


Which way do water molecules pass through the membrane in osmosis?

Both ways because water molecules move about randomly all the time but because there are more water molecules on one side there is a steady net flow of water molecules into the region with fewer molecules


What type of transport are diffusion and osmosis?



Describe a method to investigate effect of sugar solution on plant tissue. 3 steps

Cut up a potato into identical cylinders and measure mass of each, place potatoes in different sugar solutions (one should be very concentrated sugar solution e.g 1 mol/dm^3, one should be pure water and the others should have concentrations in between), after 24 hours take them out and measure their masses again to work out percentage mass change as they wouldn't all have started with the same mass)


What is the dependant variable in the osmosis experiment?

Chip mass


What is the independant variable in the osmosis experiment?

Concentration of sugar solution


What are 4 control variables in the osmosis experiment?

Type of sugar used, volume of solution, temperature, time left in solution


Identify 2 sources of error in the osmosis experiment

If some potato cylinders were not fully dried the excess water would give a higher mass, if water evaporated from the beakers the concentrations would change


How could you reduce effect of errors in the osmosis experiment?

Repeat the experiment and calculate a mean percentage mass change at each concentration


What do plants need mineral ions for?

Healthy growth


How does active transport stop humans starving?

Active transport is used in the gut when there is a lower concentration of nutrients in the gut but a higher concentration of nutrients in the blood. When there is a higher concentration of glucose and amino acids in the gut they diffuse naturally into the blood but sometimes there is a lower concentration of nutrients in the gut than the blood so active transport allows glucose to be taken into the bloodstream when its concentration in the blood is higher than in the gut then it can be transported to cells for respiration


How does surface area to volume ratio affect movement of substances in single celled organisms?

In single celled organisms, gases and dissolved substances can diffuse directly into or out of the cell across the cell membrane because they a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell


Give 2 examples of diffusion being used to take in substances an organism needs and get rid of waste products

Oxygen and carbon dioxide are transferred between cells and the environment during gas exchange, in humans urea (waste product produced from the breakdown of proteins) diffuses from cells into the blood plasma for removal from the body by the kidneys


How does surface area to volume ratio affect movement of substances in multicellular organisms?

They have a smaller surface area compared to their volume so not enough substances can diffuse from their outside surface to supply their entire volume. This means they need exchange surfaces for efficient diffusion


How are exchange surfaces adapted to maximise effectiveness? 4 ways

Thin membrane so only short distance for substances to diffuse, large surface area so lots of substances can diffuse at once, lots of blood vessels to get stuff in and out of the blood quickly, gas exchange surfaces in animals (e.g alveoli) are often ventilated so air moves in and out


What is the function of the lungs?

Transfer oxygen to the blood and remove waste carbon dioxide from it. To do this, lungs contain millions of air sacs called alveoli where gas exchange takes place


Give 4 adaptations of the alveoli

Enormous surface area, moist lining for dissolving gases, very thin walls, good blood supply


How is the absorption of food sped up in the small intestine?

The inside of the small intestine is covered in millions of tiny little projections called villi which have a single layer of surface cells and a very good blood supply to assist quick absorption, they increase the surface area in a big way so digested food is absorbed much more quickly into the blood


How is a leaf adapted for gas exchange? 6 points

Underneath of leaf is a exchange surface covered in biddy little holes called stomata which carbon dioxide diffuses in through and oxygen and most of the water vapour diffuse out, size of stomata is controlled by guard cells which close the stomata if the plant is losing water faster than it is being replaced by the roots, without guard cells the plant would wilt, flattened shape of leaf increases area of exchange surface, walls of cells inside leaf form another exchange surface -air spaces inside the leaf increase area of surface so there is more chance carbon dioxide can reach cells for photosynthesis, water vapour evaporates and escapes by diffusion