Cell Biology Flashcards
What is binary fission?
Process by which prokaryotic organisms like bacteria divide and reproduce
Its a type of cell division AND reproduction
What structures are present in bacteria?
- Cell wall
- Cytoplasm
- Cell membrane
- Large circular strand of DNA
- Plasmids - circles of DNA (non-essential genes)
- Flagellum
How many cells does binary fission produce?
2
What 2 things does a bacterial cell need to do before it divides?
- Grow
- Replicate genetic material so there is enough for each new cell (plasmids and large strands of DNA)
What happens during binary fission?
- Cell grows
- Replicates genetic material
- 2 large circular strands move to each sides of cell, plasmids arranged randomly - 1 offspring might end up getting more
- Grows a new cell wall down in the middle of the cell
- Allows the 2 halves to pull apart
How often does bacteria divide?
Every 20 minutes, population divides every 20 min
How can you work out how many cells will produce if you are given a mean division time?
- Convert hours to minutes and divide it by mean division time
- Find out rounds of division
- If there are for eg 3 divisions do 1 X 2 X 2 X 2
What are the optimum conditions for bacteria to grow?
- Warm
- Moist
- Plently of nutrients
How do you prepare a slide?
- Add a drop of water to middle of clean slide
- Cut up an onion and separate it into layers. Tweezers to pull off some epidermal tissue
- Tweexers to place tissue into water on slide
- Drop of iodine solution - highlight objects in a cell by adding colour to them
- Place cover slip on top - stand cover slip upright on the side next to water droplet, carfeully tilt and lower so it covers speciment - no air bubbles - obstruct view
How to use light microscrope
- Clip slide onto stage
- Select lowest-powered objective lens (produces lowest magnification)
- Use coarse adjustment knob to move stage up to just below OL
- Look from the side while using coarse adjustment knob to move stage upwards until objective lens almost touches the slide
- Adjust focus with fine adjustment knob, until clear image
- Calc total magnificaiton
Rules for sketches of cells
- Pencil with sharp point
- Drawing takes at least half of space
- Clear, unbroken lines
- No colouring/shading
- Subcellular structures should be drawn in proportion
- Title + magnification it was observed under
- Label important feautures - using straight uncrossed lines
What does 1 order of magnitude mean?
10X larger
What is 100 larger in terms of order of magnitude?
2 orders of magnitude
What are objective lenses?
There are usually 3 and they control the magnification
What is the eyepeice and what does it contain?
Where you look down to view speciment, it has the eyepiece lens w/ magnifcation of 10x
What happens if we look through the eyepiece while positioning the objective lens?
Risk that we could damage the slide
How do you calc total magnification?
Mag of eyepiece lens X mag of objective lens
Adaptations of root hair cells
- Hair - increases SA of root, so it abosrbs water and dissolved minerals more effectively
- Dont have chloroplasts cuz they’re underground
Adaptations of xylem cells
- Form long tubes - carry water and dissolved minerals from roots to leaves
- Thick walls with lignin - supports plant
- However, cell walls are sealed with lignin, so xylem cells die
- End walls between cells have been broken down - allows for flow in a long tube
- No nucleus, cytoplasm, vasuole or chloroplastsin xylem cells - easy to flow
Adaptations of phloem cells
- Phloem vessel cells have limited cytoplasm, so less mitochondria - so its has a companian cell connected by claws - companian cells provide enegry for phloem vessel cell
2 types of cells in the phloem
- Phloem vessel cells - no nucleus and only limited cytoplasm
- Sieve plates - end of walls of vessel cells, have pores called sieve plates
Requored practical 3 - effects of osmoiss on plant tissue
Method
- Peel potato - skin can prevent osmosis
- Use cork borer to produce 3 cylinders of potato - same diamtere
- Use scalpel to trum cylinders to same length (3cm)
- Measure length of each cylinder using ruler and mass using a balance
- Place each cylinder into a testt ube
- Add 10cm3 of a 0.5 molar sugar solution to first tt
- Add 10cm3 of 0.25 molar sugar solution to second tt
- Add 10cm3 of distilled water to third tt
- Leave potato clinders over night
- Remove potato cylinders and gently rolly them on paper towel to remove any surface moisture
- Measure length and mass again
- Calc percentage change
Adaptations of sperm cells
- Long tail and streamlined head - helps it swim
- mitochondria in cell to provide energy
- enzyme in head to digest through the egg cell membrane
Adaptations of nerve cells
- long, branched connections at their ends to connect to other nerve cells and form a network throughout the body
- sends electrical signals
Where are chromosomes?
in nucleus
what are chromosomes
coiled up lengths of DNA molecules
How many pairs of chromosomes do we have?
23
What is mitosis and why is it done?
division of the cell - to grow or replace cells that have been damaged
Are the daughter cells produced in mitosis identical?
Yes with the same no of chromosomes
Describe mitosis
- cell grows + increases amount of subcellular substances like mitochondria/ribosomes
- duplicated DNA so theres 1 copy for each new cell
- Chromosomes line up at centre of cell
- cell fibres pull them to opposite ends of cell
- membranes form around each set of chromosomes
- These become the nucleu of the 2 new cells - nucleus has divided
- Lastly, cytoplasm and cell membrane divide
What is bacteria grown in?
A culture medium = has carbs, minerlas, proteins and vitamins to grow
What can a culture medium be?
A nutrient broth solution or solid agar jelly
How is an agar plate made?
- hot agar jelly poured into Petri dish
- when jelly has cooled, inoculating loops used to transfer microogranisms
- A sterile dropping pipette used to get an even covering of bacteria
- microorganisms multiply
Why arent microorganisms cultured above 25 in schools?
harmful pathogens can develop
Why are higher temps used in industrial conditions?
so they grow faster
Culturing microorganisms practical method
- place paper discs soaked in diff antibiotics on an agar plate that has an even covering of bacteria
- antibiotic should diffuse
- Antibiotic resistant bacteria will continue to grow
- Clear area where bacteria have died = inhibition zone
- Use a control = soak one in sterile water
- Leave plate for 48hrs at 25C
- the more effective antibiotic is, the larger the inhibition zone
CM
How can you avoid contamination in the practical?
- Pretri dish stored upside down = stops drops of condensation falling onto agar surface
- lid lightly taped on - stops microorganisms in air entering
- sterilise inoculating loop using fire
Differentiation
cell changes and becomes specialised for a job
What are stem cells?
2 types: embryonic and adult
both are undifferentiated
Where are adult stem cells found?
Bone marrow
What can adult stem cells turn into?
only blood cells
What can embryonic stem cells be used to do?
- replace faulty cells in the sick
- make insulin-producing cells
- nerve cells for paralysed
What is therapeutic cloning?
embryo ccould be made to have the same genetic info as patient
so stem cells produced aren’t rejected as it has the same genes
Risks in using stem cells in medicine
- stem cells in lab - contamination with a virus = more sick
Why are people against stem cell research?
- unethical - killing embryos which are potential human life HOWEVER the suffering in current patients is greater
- HOWEVER, its a good use - most are unwanted from fertility clinics, about to be destroyed
- banned, UK has to follow strict guidlines
Where are stem cells in plants found?
- meristems (where growth occur)
- Throughout its life, stem cells can differentiate
Uses of stem cells in plants
- produce clones of whole plants quickly and cheaply
- grow more rare species
- grow crops of identical plants with desires features eg disease resistant
Diffusion
s[reading out of paticles from an area of higher to lower conc in solutions and gases
What increases diffusion?
temperature higher, bigger conc gradient, larger sa
osmosis
movement of water molecules across a partially permeable membrane from a region of higher water conc to lower conc
Potato practical osmosis method
- cut up potato into identical lengths
- put into diff sugar solutions, one in pure water, other in very conc sugar solution, others in between
- measure mass of potato cylinders, leave for 24 hrs
- take out, dry and weight
- repeat, calc mean percentage change, control variable = temp, time, type of sugar iv = conc of sugar solution dv - chip mass
Active transport
- lower to higher conc against the conc gradient, requries energy from res
Examples of active transport
- Root hair cell = more mineral ions in root hair cells than soil
- Gut = lower conc of nutrients in gut, higher in blood
The larger an organism is
the smaller its SA compared to its V
Why can single-celled organisms use diffusion directly?
- High SA:V ratio so enough substances can be exchanged across the membrane to supply the vol of cell
Why cant multi-cellular use diffusion?
- smaller sa:v - not enough substances can diffuse from outside to inside
- Therefore they need exchange surfaces
Examples of exchange surfaces
- thin membrane - short distance to diffuse
- large SA - lots of substances can diffuse at once
- animals have lots of blood vessels - stuff in and out of blood quick
- gas exchange surfaces in animals are ventilisated - air moves in and out
Adaptations of alveoli
- good blood supply - maintains conc gradient
- thin walls - shortens diffusion distance
- moist lining for div=ssolving gases
- large sa
Adaptations of villi
- good blood supply - quick absorption
- single layer of surface cells
- incease SA
What is the gas exchange surface for fish?
gills
* water with oxygen enters fish mouth and passes through gills where ozygen diffuses into blood and co2 diffuses out
What are gills made of?
thin plates called - gill filaments
provides large SA for exchange of gases
What are gill filaments covered with?
tiny structures - lamallae
* increases SA
* thin surface layer - minimise diffusion distance
* blood flows into it in 1 direction, opposie comes water - maintains large conc gradient between water and blood
What controls size of stomata?
gaurd cells - w/o they will wilt
adaptations of leaf
- flattened shape - increases area
- air spaces inside increase area
Where does the water vapour evaporate from in leaves?
- from the cells
- then escapes by diffusion because there is a lot of it inside the lead and less in air outside
