Cell Biology Flashcards
EUKARYOTIC
Plant and animal cells are both eukaryotic cells.
How is the DNA of a eukaryotic cell stored?
Enclosed within a nucleus.
PROKARYOTIC
Bacterial cells are prokaryotic cells.
How is the DNA of a prokaryotic cell stored?
Single circular chromosome found in the cytoplasm - sometimes also plasmids
Ribosomes
the site of protein synthesis in cells
mitochondria
generate energy inside of the cell
Why do we need mitosis?
- growth
- development
- repair
Cell Cycle
- Growth
- DNA replication (mitosis)
- Division (Cytokineses)
fancy word for cell division
cytokineses
fancy word for DNA replication
mitosis
When a cell is not dividing the DNA:
Condensed into 46 chromosomes, organised in 23 pairs
For mitosis, the cell duplicates each…
chromosome
Step by step explanation of mitosis
- Each chromosome is duplicated (the duplicate remains attached to the original at this point)
- When the cell is ready to divide, the chromosomes line up along the centre of the cell.
- Cell fibres from either side of the cell attach to their respective half of each chromosome pair.
- The fibres pull the arms of the chromosomes to the opposite side of the cell.
- The cell splits into two as the cytoplasm and cell membrane divides.
What is binary fission?
The process by which prokaryotic organisms like bacteria divide and reproduce.
Binary fission is NOT the same as
mitosis or meiosis
How is DNA in bacteria cells organised?
Large circular strand of DNA (contains vital genes)
And PLASMIDS which are loops of DNA that contain non-essential genes
Some bacteria cells have ______ which helps them to move easily. NOT ALL
flagellum plr (flagella)
Why is binary fission also a method of asexual reproducion?
Bacteria are single-celled organisms and binary fission is a form of cell division to multiply.
Before a bacterial cell can divide, it needs to do 2 main things:
- Grow
- Replicate genetic material
Explain the process of binary fission step-by-step:
- Replicates all DNA
- The strands of DNA move to opposite sides of the cell to prepare for cell division.
- Plasmids, although there are now twice the number, are arranged randomly so when division happens, each daughter cell might have a different number of plasmids.
- New cell wall formed along the centre of the cell, seperating the two strands of DNA
- Cell divides
colony of bacteria =
population
My explanation of how to calculate how many bacterial cells can be produced over a period of given time…
Divide the period of time given by the mean division time of the bacterial cell(s). This will give the power.
Then you multiply the number of cells you started with, can be 1 or 1000 or x, by 2 (because each time binary fission occurs, the number of cells doubles (x2), to the power we found before.
Example: A bacterial cell has a mean division time of 30mins.
How many cells would it produce after 3 hours?
3h = 180m
180/30 = 6
1 x 2^6 = 64
the answer is 64
Optimum conditions for bacterial growth:
warm
moist
plenty of nutrients
there are two types of stem cells in humans
embryonic / adult
Diffusion =
When substances (particles) move down their concentration gradient, from a high concentration to a low concentration.
Osmosis =
diffusion but just with water
Osmosis and Diffusion require no energy therefore they are _______ processes?
passive
Example of how osmosis is used?
To keep cells in plants turgid
Example of how diffusion is used?
In lungs - alveoli vs. blood stream
Active transport Grade 9 definition =
The movement of molecules across a cell membrane, from a region of lower concentration, to a region of higher concentration, that requires energy from cellular respiration.
Active transport requires energy so it is a _______ process
active
Active transport always needs…
membrane
Where does energy for active transport come from?
Cellular respiration
Cellular respiration is responsible for all energy that the cell uses - it occurs in the _________
mitochondria - glucose is broken down to release energy
Energy released by the breaking down of glucose in mitochondria can be stored by the cell in molecules known as…
ATP - takes energy to the parts of the cell/ organism that need it
Example of active transport: root hair cells and minerals from soil - step-by-step answer
- Plants need minerals from soil e.g. Magnesium + Nitrates
- Root hair cells have a high concentration of these minerals
- Need active transport in order to retreave those from the soil too
- Root hair cells are specialised to have many mitochondria (for cellular respiration - energy - active transport)
SPECIALISED EXCHANGE SURFACES examples
Humans: alveoli/villi
Plants: leaf/root hair cell
3 common features of all specialised exchange surfaces
1) large surface area - rate of diffusion is higher since more area for diffusion to happen across at the same time.
2) very thin - short distance for substances to diffuse across - diffusion takes place more quickly.
3) exchange surfaces are permeable to the substances that they specifically need to exchange.
features of specialised exchange surfaces in animals only
- good blood supply
- good supply of external medium (thing that comes from the outside)
both maintain a steep concentration gradient, enabling efficient exchange of substances.
STEM CELLS are able to:
- divide by mitosis
- able to differentiate into specialised cells
stem cell that can differentiate into any type of cell
embryonic stem cell
Adult stem cells in bone ______
bone marrow -> can differentiate into red blood cells, white blood cells, and platelets
Adult stem cells can
replace damaged cells
Adult stem cells cannot
form new tissues like embryonic stem cells
Where are plant stem cells found?
meristem tissue - part of plant that don’t stop growing, roots/shoots tips
What kinds of specialised cells can a stem cell in a plant differentiate into?
phloem/xylem cells
palisade cells
root hair cells
Unlike embryonic stem cells that stop existing when we are fully developed humans, plant stem cells…
persist for the plant’s entire life
