Cell Structure (1.1) (M) Flashcards
What type of cells are plant and animal cells?
Eukaryotic cells
What type of cell is a bacterial cell?
Prokaryotic
What is the size difference between eukaryotic and prokaryotic cells?
prokaryotic cells are much smaller in comparison
What is the difference in cell structure between eukaryotic and prokaryotic cells?
Eukaryotic: have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
Prokaryotic: have cytoplasm, a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids.
What are the sub-cellular structures of animal and plant cells?
- nucleus (both)
- cytoplasm (both)
- cell membrane (both)
- mitochondria (both)
- ribosomes (both)
- chloroplasts (plant only)
- permanent vacuole filled with cell sap (plant only)
- cell wall
What is the function of the cell membrane?
Controls the movement of substances into and out of the cell
What is the function of the cytoplasm?
Jelly-like substance, where chemical reactions happen
What is the function of the nucleus?
Carries genetic information and controls activities of the cell
What is the function of the mitochondria?
Where most respiration reactions happen
What is the function of the ribosome?
Where protein synthesis occurs
What is the function of the permanent vacuole?
Contains a liquid called cell sap, which keeps the cell firm
What is the function of the chloroplasts?
Structures which contain the green pigment chlorophyll; the site of photosynthesis
What is the function of the cell wall?
made of cellulose, which strengthens the cell
How are sperm cells adapted to their function? (4 points)
- has a flagellum for locomotion to swim towards the egg
- middle section full of mitchondria, which transfer the energy needed for the flagellum to work
- acrosome stores digestive enzymes for breaking down the outer layers of the egg
- only has 23 chromosomes in nucleus so chromosome number doesn’t double at fertilisation
How are muscle cells adapted to their function? (3 points)
- contain special proteins that slide over eachother making fibres contract
- contain many mitochondria to transfer energy needed for chemical reactions that take place as the cells contract and relax
- can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer energy needed for fibres to contract
How are nerve cells adapted to their function? (4 points)
- myelin sheath for insulation
- lots of dendrites to make connections to other nerve cells
- an axon that carries the nerve impulse along it - it is very long which allows for quicker communication
- synapses/nerve endings are gaps between nerve cells or neurone, neurotransmitters are released and diffuse across the gap and bind to receptors which stimulate an electrical impulse
How are root hair cells adapted to their function? (4 points)
- greatly increase surface area with root hair so more water can move into the cell via osmosis
- have a large permanent vacuole that speeds up osmosis from soil to cell (as more water can be stored)
- have many mitochondria that transfer energy needed for the active transport of mineral ions into the root hair cells
- don’t have chloroplasts as they are underground and light won’t reach them, so more space for other subcellular structures
What happens as an organism develops (in terms of differentiation)?
As an organism develops, cells differentiate to form different types of cells.
When do most animal cells differentiate?
At an early stage
When can most plant cells differentiate?
They retain the ability to differentiate throughout life.
in mature animals, differentiation is restricted to…
Repair and replacement
What happens as a cell differentiates (in terms of importance)?
it acquires different sub-cellular structures to enable it to carry out a certain function.
Important for multi-cellular organisms
What do we call it when a cell has fully differentiated?
It has become a specialised cell.
Why have microscopy techniques improved over time?
Improving technology
Why are electron microscopes useful?
They can produce images of higher magnification and higher resolution than light microscopes
Therefore smaller subcellular structures (e.g. ribosomes, mitochondria) can be seen under an electron microscope (but not a light microscope), which has led to a greater understanding of subcellular structures.
What is magnification?
how much bigger an object appears compared to its actual size
What is resolution (resolving power)?
how well you can distinguish between objects close together (how detailed the image is)
What is the formula for magnification?
magnification = image size / actual size
What is binary fission?
Bacteria multiply by simple cell division
How often can binary fission occur?
as often as once every 20 minutes if they have enough nutrients and a suitable temperature
What formula do we use to determine the number of bacteria in a population after a certain time if given the mean division time?
2n, where n = total time / mean division time
Where are two places bacteria can be artificially grown?
- a nutrient broth solution
- as colonies on an agar gel plate
What is required for investigating the action of disinfectants and antibiotics?
uncontaminated cultures of microorganisms
Describe how to prepare an uncontaminated culture using aseptic technique
Pre-inoculation
- Petri dish and agar sterilised before use to kill unwanted bacteria
- inoculating loop passed through flame / sterile swab to sterilise/kill (other) bacteria
Inoculation
- loop/swab used to spread/streak bacterium onto agar
- lid of Petri dish opened as little as possible
- to prevent microbes from air entering (or microbes leaving)
Post-inoculation
- sealed with adhesive tape (to prevent unwanted microorganisms from air entering, but not fully as anaerobic conditions encourage pathogen growth) and stored upside down (to prevent condensation falling onto culture medium
- incubate at 25oC to allow growth of bacteria, but this is below optimum conditions (for safety)
How would you determine which antibiotic is best to use? How would you measure it?
Measure zone of inhibition (cross-sectional area were no bacteria is growing).
πr2
After inoculation, why are there areas where no bacteria are growing?
Bacteria have been killed
Why might an antibiotic with the largest zone of inhibition not necessarily mean that it’s the best one to use?
It may be harmful to people
Student may need to investigate this (toxicity)
What does a labelled animal and plant cell look like?
Do prokaryotic and eukaryotic cells have mitochondria and ribosomes?
Eukaryotic - both
prokaryotic - only ribosomes, no mitochondria
What are the key features of a biological drawing?
- Title
- Magnification
- Draw what is observed in the full field of view (if it asks for this, it may ask for one cell)
- Draw only the sub-cellular structures that are visible
- Labels of sub-cellar structures (cell wall for plant cell rather than cell membrane)
- No shading/arrow heads/need straight lines
- Draw what can be seen rather than a standard animal/plant cell diagram
Label a microscope
- coarse adjustment - moves stage up and down*
- fine adjustment - brings image into focus*
Name on type of cell that does not have mitochondria and explain why?
Prokaryotic/bacterial cell
Mitochondria is larger than prokaryotic cell (so aerobic respiration occurs in cell membrane)
