b1 : cells Flashcards
What are three common features of plant and animal cells (eukaryotes)?s
1) Cell membrane 2) Cytoplasm 3) Genetic material in a nucleus
Which are bigger; bacterial cells (prokaryotes) or eukaryotes?
Eukaryotes
True or false? “Prokaryotic cells have a cell wall.”
True
True or false? “Prokaryotic cells have a nucleus.”
False
In what form is the genetic material in a prokaryotic cell?
A single DNA loop
Name five common parts of animal and plant cells.
1) Nucleus 2) Cytoplasm 3) Cell membrane 4) Mitochondria 5) Ribosomes
Name two further features of a plant cell.
1) Chloroplasts 2) Permanent vacuole (filled with cell sap)
Describe the function of the nucleus.
Contains the genetic material of the cell
Describe the function of the cytoplasm.
The location of cellular reactions
Describe the function of the cell membrane.
To determine what is allowed into and out of the cell
Describe the function of the mitochondria.
Where aerobic respiration occurs to release energy
Describe the function of the ribosomes.
To bond amino acids together to form proteins (protein synthesis)
Describe the function of the chloroplasts.
The location of photosynthesis
Describe the function of the permanent vacuole.
A storage area for ions and water, sometimes pigments
Which strong material is the cell wall of plant and algal cells made from?
Cellulose
What is the definition of a cell?
The individual unit of an organism
What is the definition of a tissue?
Cells of the same type working together to perform a specific function
What is the definition of an organ?
A structure made from multiple tissue types to perform a specific function
What is the definition of an organ system?
Multiple organs working together to perform a specific function
Describe a specialisation of a sperm cell.
Mobile due to flagellum; many mitochondria to allow high energy release for movement; streamlined head; digestive enzymes in head to break down egg membrane
Describe a specialisation of a nerve cell.
Many mitochondria to provide lots of energy for active transport; many proteins embedded in cell membrane to allow ion movement
Describe a specialisation of a muscle cell.
Many mitochondria to provide lots of energy for contraction; many ribosomes to synthesise proteins
Describe a specialisation of a root hair cell.
Elongated shape to increase surface area for ion absorption; many mitochondria to provide lots of energy for active transport
Describe a specialisation of a xylem cell.
Little cell contents to allow easy movement of water and ions through each cell
Describe a specialisation of a phloem cell.
Needs a companion cell to work optimally
What is “cell differentiation”?
The process of a stem cell dividing and becoming a specialised cell
When do most animal cells differentiate?
At an early stage of development
What is different about plant cells’ differentiation?
They retain the ability to differentiate throughout life
In mature animals, what is cell differentiation used for?
Repair and replacement of old/damaged cells
What are the two advantages of electron microscopes over light microscopes?
- Increased magnification 2. Increased resolution
What is the “resolution” or “resolving power” of a microscope?
The ability to determine two close objects as separate images
What are the three forms of equation used to calculate magnification (M), the image size (I) or the actual size of an object (A)?
- A=I/M 2. I=A x M 3. M=I/A
What is 1340000 nm expressed in standard form?
1.34 x 10^6 nm
What is 0.0000001 µm expressed in standard form?
1 x 10^-7 µm
What is the difference between mm, µm and nm?
A factor of 1000
By what process do bacterial cells divide?
Binary fission
If provided with enough nutrients and a suitable temperature, how often can bacterial cells divide?
Around every 20 minutes
Describe the two ways bacteria can be grown in a laboratory.
- In a nutrient broth solution 2. On an agar gel plate/petri dish
What is a “contaminant”?
An unwanted species of microorganism growing in your culture
What should you do with Petri dishes and culture media before use?
Sterilise it at high temperature to kill contaminants
How do you sterilise inoculating loops?
Pass them through a Bunsen burner flame before use
How should a Petri dish be stored in school?
Upside down, with tape securing the lid
What is the maximum temperature cultures should be incubated at in schools or colleges?
25°C
Explain why the maximum incubation temperature for bacterial cultures in schools is 25⁰C.
To avoid growing potential pathogens
If you were asked to calculate the cross-sectional area of a circular clear area around a disinfectant, what equation would you use?
pr^2
What is a chromosome?
A coiled thread-like structure of nucleic acids (DNA) and protein found in the nucleus of eukaryotic cells
What are genes?
Sections of DNA that contain the code for a particular protein
In what arrangement are chromosomes found normally?
Pairs
How many chromosomes does a human have?
23 pairs OR 46 in total
What has to happen within the cell before it can divide? (2 steps)
- Cell organelles (e.g. mitochondria and ribosomes) have to replicate 2. DNA has to be replicated (copied)
How many chromosomes will be present in a cell after DNA replication?
92 OR 46 pairs
To where do the chromosomes move to during mitosis?
To opposite ends of the cell
What occurs during cytokinesis?
The cytoplasm and cell membranes divide
Mitosis is critical for….
…growth, replacement and development of an organism
What is a stem cell?
An undifferentiated cell capable of giving rise to many more cells of the same type
Describe the function of stem cells in embryos.
To develop into multiple cell types aiding in the development of the embryo into a mature organism
Describe the function of stem cells in adult animals.
To be the source of cells used in growth and repair of the mature animal
Describe the function of stem cells in plant meristems.
To allow a plant to keep growing throughout its life (animals stop growing when mature) by specialising into any type of cell
What is a potential use of stem cells in medicine?
To treat conditions where cells have been damaged e.g. diabetes, paralysis
What is the principle of therapeutic cloning?
An embryo is produced with the same genes as the patient
Give an advantage of therapeutic cloning.
No rejection of the new cells by the patient (as they are the patient’s own cells)
Give two potential problems with therapeutic cloning.
- Risk of viral infection 2. Religious/ethical objections around the use of embryos
How are plant stem cells used in horticulture (commercial plant growing)?
To create plant cuttings (clones of the original plant)
Give two advantages of the use of clones in horticulture.
- Rare species can be cloned to prevent extinction 2. Crops with special adaptations (e.g. disease resistance) can be identically produced in large numbers
Name the process whereby substances move in and out of a cell across the cell membrane.
Diffusion
Define ‘diffusion’.
The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient across a partially-permeable membrane. passive process (no energy required)
Name three substances which move by diffusion within animal cells.
- Oxygen 2. Carbon dioxide in gas exchange 3. Urea out of cells to be excreted from the body
Name three factors which affect the rate of diffusion.
- The difference in concentrations (concentration gradient) 2. Temperature 3. Surface area of the membrane
Does a single-celled organism have a high or low surface area:volume ratio?
High
How do single-celled organisms get enough oxygen without having lungs?
Due to its small size, and therefore its high SA:vol, diffusion across its membrane allows sufficient gas exchange
An organism has a surface area of 50m2 and a volume of 20m3. What is its surface area to volume ratio?
2.5:1
Why do multicellular organisms tend to need exchange surfaces and transport systems?
Low SA:vol, therefore cannot rely on diffusion across cell membranes
Name two common features that aid the exchange of substances in animal small intestine & lungs; fish gills; plant roots and leaves.
- Large surface area 2. Thin membrane to provide a short diffusion path
Name two further features that aid the exchange of substances in animals but NOT plants.
- An efficient blood supply 2. The ability to ventilate (to allow air to move in and out of the organism)
Define osmosis.
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
the diffusion of water molecules from ana area of high-water concentration to an area of low-water concentration across a partially permeable membrane (passive process)
If an animal cell loses a lot of water, what happens?
It crenates (shrivels) and cellular reactions are slowed or stopped
If an animal cell gains a lot of water, what happens?
It can lyse (burst) and die
If a plant cell loses a lot of water, what happens?
It becomes plasmolysed (cell membrane shrinks away from the cell wall)
If a plant cell gains a lot of water, what happens?
It becomes turgid (cell membrane pushes up against the cell wall)
Define active transport.
The movement of substances from a low concentration to a high concentration (against a concentration gradient) requires energy
What two things does active transport require that diffusion doesn’t?
- A transport protein (found in the cell membrane) 2. Energy
From what reaction does the energy required for active transport come?
Respiration
Where does active transport happen within a cell?
The mitochondria
Give two examples of where active transport is used in Biology. (1 plant, 1 animal)
- Plant root hair cells absorbing mineral ions from the soil 2. Glucose absorption from the small intestine into the blood
hypotonic meaning
low solute concentration
(compared to cytoplasm)
hypertonic meaning
high solute concentration
(compared to cytoplasm)
isotonic
equal solute concentration
(compared to cytoplasm)
solvent
the substance that the solute is dissolved into typically a liquid
solute
the substance dissolved in the solvent forming a solution
solution
a mixture made when a solute is dissolved into a solvent
