B1 - Cell-Level Systems Flashcards
What are the two main types of cells?
1) Eukaryotic cells
2) Prokaryotic cells
Give some features of eukaryotic cells.
1) contain genetic material in a nucleus
2) complex
3) relatively large (10μm-100μm)
What type of cells are plant and animal cells?
Eukaryotic cells
Give some features of prokaryotic cells.
1) do not contain a nucleus. Their genetic material floats in the cytoplasm
2) simple
3) typically smaller than eukaryotic cells (1μm-10μm)
What type of cells are bacteria cells?
Prokaryotic cells
Which subcellular structures do eukaryotic cells contain?
1) nucleus
2) cytoplasm
3) cell membrane
4) mitochondria
What is the role of the nucleus?
1) controls the activities of the cell
2) contains the organism’s genetic material, arranged as chromosomes
3) contains instructions to make new cells or new organisms
What is the role of the mitochondrion?
To carry out respiration
What is the role of the cell membrane?
1) controls which substances pass into and out of the cell
2) contains receptor molecules
What is the role of the cytoplasm?
To carry out chemical reactions
Which subcellular structures do plant cells contain?
1) nucleus
2) cytoplasm
3) cell membrane
4) mitochondria
5) chloroplasts
6) vacuole
7) cell wall
What is the role of the chloroplast?
Contains green chlorophyll which is used in photosynthesis
What is the role of the vacuole?
1) contains cell sap, a watery solution of sugar and salts
2) helps to keep the cell rigid
3) supports the plant and keeps it upright
What is the role of the cell wall?
Supports the cell
What are the smallest living organisms?
Bacteria
What are the seven life processes?
1) Movement
2) Reproduction
3) Sensitivtiy
4) Growth
5) Respiration
6) Excretion
7) Nutrition
Give some examples of prokaryotes.
1) Escherichia coli (E. coli)
2) Streptococcus bacteria
3) Stretomyces bacteria
Which subcellular structures do prokaryotic cells contain?
1) cell wall
2) genetic material
3) cell membrane
4) cytoplasm
What is the name given to the one long strand of DNA that floats freely in the cytoplasm of prokaryotic cells?
Bacterial chromosome
What extra subcellular structures can some types of bacteria cells have?
1) flagella
2) pili
3) slime capsule
4) plasmid
What is the role of a flagellum?
To allow the cell to move through liquids
What is the role of pili?
1) enables the cell to attach to structures
2) transfers genetic material between bacteria
What is the role of the slime capsule?
1) protects a bacterium from drying out
2) helps the bacteria to stick to smooth surfaces
What is the role of a plasmid?
To store extra genes
How can you observe cells through a microscope?
1) Move the stage to its lowest position
2) Select the objective lens with the lowest magnification
3) Place the slide, which has cells on it, on the stage
4) Turn the coarse knob focus slowly until you see your object (it will normally be blurred)
5) Turn the fine focus knob slowly until your object comes into clear focus
6) To see the cells in greater detail, repeat the steps above using a higher magnification objective lens
State the formula used to calculate the total magnification.
total magnification = eyepiece lens magnification x objective lens magnification
Why do scientists stain cells?
To make them easier to observe
Give some examples of common stains.
1) methylene blue
2) iodine
3) crystal violet
How do you apply a stain?
1) Place the cells on a glass slide
2) Add one drop of stain
3) Place a coverslip on top
4) Tap the coverslip gently with a pencil to remove air bubbles
What are the two types of electron microscopes?
1) Transmission electron microscopes (TEM)
2) Scanning electron microscopes (SEM)
Give some advantages for light microscopes.
1) cheap to buy and operate
2) small and portable
3) simple to prepare a sample
4) natural colour of sample is seen unless staining is used
5) specimens can be living or dead
Give some disadvantages for electron microscopes.
1) expensive to buy and operate
2) large and difficult to move
3) sample preparation is complex
4) black and white images produced
4) specimens are dead
What is a long molecule of DNA called?
Chromosome
How many chromosomes do humans have in each of their cells?
46
What is a gene?
A short section of DNA that codes for a characteristic
How many strands is DNA made up of?
2
How are the two DNA strands joined together?
By bases
What are the small units that DNA is made up of?
Nucleotides
What shape does DNA form?
Double helix
What are nucleotides made of?
1) sugar
2) phosphate
3) base
What are the four bases?
1) adenine
2) thymine
3) cytosine
4) guanine
What does adenine always bond with?
Thymine
What does cytosine always bond with?
Guanine
Why can DNA not leave the nucleus of cells?
It is too big
What is mRNA?
A copy of DNA
After mRNA moves out of the nucleus, where does it travel to?
Ribosomes in the cytoplasm
What are proteins made from?
Amino acids
What is the process that makes proteins called?
Translation
The ribosome ‘reads’ the nucleotides on mRNA in groups of what number?
3
What is formed when amino acids join together in a chain?
Protein
What are enzymes made up of?
Proteins
What is the active site?
Where molecules of substances bind to the enzyme.
What is the molecule that binds to the enzyme called?
Substrate
How many types of substrate molecules can enzymes bind to?
1
What factors affect the rate of an enzyme-catalysed reaction?
1) temperature
2) pH
3) concentration of enzyme
4) concentration of substrate
What happens if the temperature becomes too high in an enzyme-catalysed reaction?
1) the amino acid chains in the protein start to unravel
2) the shape of the active site changes
3) the enzyme denatures
How could a change in pH affect enzymes?
1) may make the enzyme unfold
2) the shape of the active site changes
What is your metabolic rate?
The speed at which chemical reactions in your cells transfer energy from its chemical stores in food
What do carbohydrase enzymes break down?
Carbohydrates
What do amylase enzymes break down?
Starch
How many amino acids are there?
20
What are lipids
Fats and oils
What are lipids synthesised from?
Three fatty acid molecules and a glycerol molecule
What do lipase enzymes break down?
Lipids
Where does the oxygen needed for respiration come from?
Air
State the word equation for aerobic respiration.
glucose + oxygen → carbon dioxide + water (+energy)
State the symbol equation for aerobic respiration.
C6H12O6 + 6O2 → 6CO2 + 6H2O
How many molecules of ATP does aerobic respiration make?
38
How is the ATP produced during respiration used?
1) to synthesise larger molecules from smaller ones to make new cell material
2) for movement
3) to stay warm
Where does respiration take place?
Mitochondria
What does the number of mitochondria in a cell tell you?
How active the cell is
What type of reaction is respiration?
Exothermic
State the word equation for anaerobic respiration.
glucose → lactic acid (+energy)
State the symbol equation for anaerobic resipiration
C6H12O6 → 2C3H6O3
Why does aerobic respiration produce more ATP molecules per glucose molecule?
The glucose molecule is fully broken down
What happens when lactic acid builds up in muscle cells?
1) cramp
2) pain
3) fatigue
What is oxygen debt?
The extra oxygen inhaled that reacts with the lactic acid, breaking it down
What is fermentation?
Anaerobic respiration in microorganisms and plant cells
State the word equation for fermentation.
glucose → ethanol + carbon dioxide
State the symbol equation for fermentation.
C6H12O6 → 2C2H5OH + 2CO2
How do plants take in carbon dioxide?
Diffusion from the air into the plant through the stomata
How do plants take in water?
Enters the roots from the soil through the root hair cells by osmosis
State the word equation for photosynthesis.
carbon dioxide + water → glucose + oxygen
State the symbol equation for photosynthesis.
6CO2 + 6H2O → C6H12O6 + 6O2
Where does photosynthesis occur?
Chloroplasts
Where does photosynthesis mainly occur?
Leaves
Why are leaves and stems green?
They contain the pigment chlorophyll inside their chloroplasts
What are the two main stages of photosynthesis?
1) stage 1 - light dependent (energy transferred from light splits water molecules into oxygen gas and hydrogen ions)
2) stage 2 - light independent (carbon dioxide gas combines with the hydrogen ions to make glucose)
What type of reaction is photosynthesis?
Endothermic
What happens to the glucose produced in photosynthesis?
1) respiration
2) sucrose - stored in fruit
3) starch - food store
4) cellulose - to form cell walls
5) (+nitrogen) proteins - for growth and repair
6) fats and oils - food store and growth
How can you test that photosynthesis has taken place?
Test for starch
What are the limiting factors of photosynthesis?
1) light intensity
2) carbon dioxide
3) temperature
How can you measure the rate of photosynthesis?
Use pondweed. The volume of oxygen given off per minute is a measure of the rate of photosynthesis
State the formula used to calculate the rate of photosynthesis.
rate = 1/t
How does light intensity affect the rate of photosynthesis?
The higher the light intensity, the faster the rate of photosynthesis. Until photosynthesis reaches its maximum rate
How does carbon dioxide affect the rate of photosynthesis?
The greater the carbon dioxide concentration, the faster the rate of reaction
How does temperature affect the rate of photosynthesis?
The higher the temperature the faster the rate of reaction. If the temperature is too high the enzymes will denature and the reactions will stop
State the inverse square law
relative light intensity = 1/(distance from light source)2
How can you study the effect of light intensity on the rate of photosynthesis?
Place a light source at different distances from the pondweed
How can you study the effect of carbon dioxide concentration on the rate of photosynthesis?
Add different masses of potassium hydrogen carbonate powder to the water. Potassium hydrogen carbonate releases carbon dioxide to the atmosphere
How can you study the effect of temperature on the rate of photosynthesis?
Place the apparatus in water baths at different temperatures
