P1: Cell Biology Flashcards
Explain how a root hair cell is specialised for its function.
-Large surface area so it can absorb large amounts of water and mineral ions.
What is the name of the smallest biological component in the human body?
An organelle
What is the largest biological component in the human body?
An organ system.
What are living organisms made up of?
Cells
Are bacteria cells bigger or smaller than animal and plant cells?
Smaller
State the components of an animal cell.
Cell membrane, ribosomes, nucleus, cytoplasm, mitochondria.
State the components of a plant cell.
Cell membrane, ribosome, nucleus, cytoplasm, mitochondria, chloroplasts, vacuole and cell wall.
Are plant and animal cells prokaryotic or eukaryotic?
Eukaryotic, meaning they have a nucleus.
What do microscopes do?
Magnify the image of a biological specimen so that it appears larger.
What are the names of the two lenses that a microscope uses to magnify something?
The eyepiece and an objective lens.
What is the eyepiece in a microscope?
The lens at the top of a compound microscope.
In a microscope, what is the objective lens?
The lens closest to the specimen.
How do you convert a millimetre to a metre?
Divide it by a thousand
State the equation linking magnification, image size and actual size.
Image size = actual size x magnification.
How do you convert a micrometre to a millimetre?
Divide it by a thousand.
How do you convert a nanometre to a micrometre?
Divide it by a thousand.
What does the coarse focus of a microscope do?
Raises the stage.
What should you place a specimen on before looking at it under a microscope?
A slide
What should you place a specimen on before looking at it under a microscope?
Electron microscope
What are the cons of electron microscopes?
Very expensive and hard to use.
What can you use electron microscopes to study?
Sub-cellular structures.
What are the names of the things the stage in a microscope has to hold the slide in place?
Clips
What is the name of the light below the stage in a microscope?
Lamp. Some microscopes have a mirror instead.
Describe how to use an optical microscope to view a prepared slide (long answer).
-Place the slide onto the stage, using the clips to hold it in place.
-Select the lowest power objective lens, and slowly turn the coarse focussing dial to position the objective lens so it almost touches the slide.
-Look through the eyepiece lens, and turn the coarse focussing dial the other way to increase the distance between the lens and slide again, to bring the object into focus
-Use the fine focusing dial to bring the cells into a clear focus.
What is the name of the microscope part that we look through?
The eyepiece
How do you calculate total magnification?
Eyepiece lens x objective lens.
What is the function of the cytoplasm?
Contains dissolved nutrients and salts. 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 the 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 the mitochondria?
Contain the enzymes for respiration, and where most energy is released in respiration.
What is the function of the chloroplast?
Contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. Contains the enzymes needed for photosynthesis.
What is the function of the ribosome?
Protein synthesis.
What is the function of the cell wall?
Strengthens the cell and supports the plant.
What is the function of the vacuole?
Filled with cell sap to help keep the cell turgid.
Are bacterial cells eukaryotic or prokaryotic?
Prokaryotic.
How do eukaryotic cells divide?
Mitosis.
How do prokaryotic cells divide?
Binary fission.
Where is the genetic material in a prokaryotic cell?
DNA is in a single molecule, found free in the cytoplasm. Also found on plasmids
Describe the adaptations of a sperm (3 points)
-Head contains enzymes and genetic material for fertilisation
-Middle piece contains mitochondria to release energy needed to swim
-Tail enables sperm to swim.
Where is the genetic material in a eukaryotic cell?
DNA is in a nucleus.
Describe the adaptations of a nerve cell. (2 points)
-Cell has extensions and branches so that it can communicate with other nerve cells, muscles and glands.
-Covered in fat, which insulates the cell.
Describe the adaptations of muscle cells. (2 points)
-Contain filaments of protein that slide over eachother to cause muscle contraction.
-Contain many mitochondria to provide the energy for muscle contraction.
Describe the adaptations of a root hair cell. (2 points)
-Large surface area to provide contact with soil water.
-Has thin walls to increase the rate of osmosis, and active transport.
Describe the adaptation of a xylem cell (2 points)
-Walls are thickened with lignin
-No top and bottom walls between xylem vessels, so there is a continuous column of water running through them.
Describe the adaptations of a phloem cell. (2 points)
-Companion cells are next to the tubes to provide energy required to transport substances in the phloem.
-Dissolved sugars and amino acids can be transported both up and down the stem.
What do chromosomes do?
Carry genetic information in a molecule called DNA.
How many chromosomes does each human body cell contain?
46, or 23 pairs.
What are the two chromosomes that code for a female?
XX
What are the two chromosomes that code for a male?
XY
When do cells divide? (2 reasons)
-When an organism grows
-When an organism becomes damaged and needs to produce new cells.
Explain the cell cycle (3 steps).
-Interphase: the cell gets ready to divide. The cell grows, DNA duplicates and more organelles are made
-Mitosis: the genetic material separates to different ends of the cell, and it gets ready to divide into two daughter cells
-Cytokinesis: at the end of mitosis, the cytoplasm and cell membrane split, and two new daughter cells are made.
What is produced in mitosis?
Two daughter cells that are identical to the parent cell.
Describe the process of mitosis.
-The cell begins to divide
-The DNA replicates to form two copies of each chromosome
-The nuclear membrane breaks down and the chromosomes line up across the centre of the cell
-One set of chromosomes is pulled to each end of the cell and the nucleus divides
-The cytoplasm and cell membranes divide to form two identical cells.
What are stem cells?
Cells that have not undergone differentiation.
Where are stem cells in relation to fertilisation?
The cells in the embryo.
Where can adult stem cells be found?
Bone marrow.
What is the difference between adult stem cells and standard stem cells?
Adult stem cells can only differentiate into related cell types (e.g bone marrow cells can differentiate into blood cells), but standard stem cells can differentiate into any cell type.
What can meristem cells do?
Differentiate to produce all types of plant cells at any time during the life of the plant
Where does cell division in plants occur?
The meristem.
What type of human cell can only be produced by stem cells?
Red blood cells, because they do not have a nucleus.
What can undifferentiated stem cells from a patient be used for by a doctor?
Growing new tissue or repairing damaged organs
What does therapeutic cloning involve?
Creating an embryo with the same genes as a patient.
What are the benefits of using embryonic stem cells in therapeutic cloning?
The cells will not be rejected by the patient as they contain the same genetic material
What are the concerns surrounding stem cells research? (5 points)
-Viruses can infect the stem cells
-Opposition of stem cell research on ethical or religious grounds
-No guarantee how successful therapeutic cloning will be
-There is current difficulty in finding suitable stem cell donors.
-Some mutated stem cells have been observed to behave like cancer cells
What are the uses of cloning plants?
-Cloning rare species to protect them from extinction
-Cloning disease resistant plants to introduce the trait into the gene pool
-Cloning crop plants to make large quantities for farmers
What do you need if you want to test antibiotics and disinfectants?
An uncontaminated culture of microorganisms.
What are the two things you can grow bacteria in?
An agar gel plate, or in a nutrient broth solution
Why do you need to make sure that your bacterial colonies that you are growing are not contaminated?
Because it can change your results or lead to the growth of dangerous pathogens.
State the aseptic techniques used when culturing microorganisms. (4 points)
-Inoculating wire loops that are used to transfer the microorganisms have to be passed through a flame to sterilise them before use.
-Secure Petri dishes using tape after placement of microorganisms
-Store petri dishes upside-down
-Incubate cultures at 25 degrees Celsius.
Why do we heat inoculating wire loops before using them when culturing microorganisms?
To sterilise them, and kill other microorganisms before use.
Why do we secure Petri dishes using tape when culturing microorganisms?
To reduce the risk of contamination from particles in the air, and reduce the risk of the culture being disturbed by water condensation.
Why do we store petri dishes upside down?
To reduce the risk of contamination from particles in the air, and reduce the risk of the culture being disturbed by water condensation.
Why do we incubate cultures at a temperature of 25 degrees Celsius?
It encourages growth of the culture without growing any pathogens that are harmful to humans.
How do bacteria cells divide?
Binary fission
How do we measure the size of a colony in a petri dish?
Use a ruler to measure the circular diameter. Divide this by two, then square and times it by Pi.
How short can the mean division time be for bacteria?
As short as 20 minutes.
How do you calculate the number of bacteria in a population?
Bacteria at the beginning of the growth period x 2^number of divisions
What is the definition of diffusion?
The net movement of particles from an area of high concentration to an area of lower concentration
What are the names of the 3 different types of movement?
Diffusion, osmosis, active transport.
Explain the process of therapeutic cloning. (4 points)
-A human egg cell from a donor is taken in, and the nucleus is removed and discarded.
-A cell from a patient is taken in, and the nucleus is removed from that cell and transferred to the donor egg cell.
-The cell is stimulated to divide, and develops into an embryo.
-After 4-5 days, the stem cells are removed and are cultured for therapeutic use.
State 3 examples of diffusion in biological systems.
-In a leaf, Oxygen and Carbon Dioxide move in and out of cells by diffusion
-In the lungs, Carbon Dioxide and Oxygen diffuses in and out of the alveoli during gas exchange
-Urea from cells diffuses into blood plasma for excretion in the kidney.
What three factors affect the rate of diffusion?
-The concentration gradient
-The temperature
-The surface area : volume ratio of the membrane.
In diffusion, the higher the concentration gradient, the…
faster the rate of diffusion.
In diffusion, the lower the temperature, the…
slower the rate of diffusion.
In diffusion, the larger the surface area, the…
faster the rate of diffusion
How is the small intestine adapted to absorb nutrients?
-Contains finger-like projections called villi that have thin walls and increase the surface area of the small intestine
How are the alveoli in the lungs specialised for gas exchange?
-Alveoli give the lungs a large surface area
-One cell thick
-Good blood supply to maintain concentration gradient
How are plant roots adapted for material exchange?
They are long and thin
How are leaves adapted for gas exchange?
-Large surface area, wide and flat with air spaces
How are fish gills adapted for gas exchange?
-Large surface area
-Good blood supply
What is active transport?
The movement of molecules against a concentration gradient that requires energy.
What is osmosis?
The movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration.
When is active transport used in plants?
For plants to take up mineral ions into root hair cells, active transport has to occur.
When is active transport used in animals?
For glucose molecules to be moved into the bloodstream from the gut wall, active transport has to be done, using energy produced by respiration.
