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?
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?
What happens to the rate of diffusion if the temperature increases?
When water enters a plant cell and pushes on the cell wall causing it to swell
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
Concentration of the solutes in the solution surrounding the cell is higher than inside the cell
Concentration if solutes surrounding the cell is lower than inside the cell (more water)
The liquid in which a substance dissolves
The substance which dissolves in a liquid
When red blood cells gain water, swell and burst in a more dilute solution
When red blood cells lose water and shrink in a more concentrated solution
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
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
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
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?
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?
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