biology topic 1 cell biology

• what is the differences between prokaryotic and eukaryotic cells?

  - prokaryotic cells are much

  - prokaryotes has a cytoplasm and cell membrane surrounded by a cell wall

  - genetic material is not enclosed in the nucleus. it is a single loop of dna called plasmids
• what are the subcellular structures of a animal cell and what are there functions?

  -a nucleus- where dna is stored and controls the activities of the cell

  -cytoplasm- a jelly-like material that contains dissolved nutrients and salts and structures called organelles. It is where many of the chemical reactions happen.

  -cell membrane- controls the movement of substances in and out of the cell

  -mitochondria- organelles that contain the enzymes for respiration, and where most energy is released in respiration

  -ribosomes-a tiny organelle where protein synthesis occurs.
• what are the subcellular structures of a plant cell and what are there functions?

  -a nucleus- where dna is stored and controls the activities of the cell

  -cytoplasm- a jelly-like material that contains dissolved nutrients and salts and structures called organelles. It is where many of the chemical reactions happen.

  -cell membrane- controls the movement of substances in and out of the cell

  -mitochondria- organelles that contain the enzymes for respiration, and where most energy is released in respiration

  -ribosomes-a tiny organelle where protein synthesis occurs

  -chloroplasts- organelles that contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. Contains the enzymes needed for photosynthesis

  -permanent vacuole- filled with cell sap to help keep the cell turgid

  -cell wall- made from cellulose fibres and strengthens the cell and supports the plant.
• describe a microscope practical

  - add a drop of water to the middle of a clean slide

  - cut up onion and separate out into layers. use tweezers to peel of some epidermal tissue from the bottom of one of the layers.

  -using the tweezers, place the epidermal tissue into the water in the slide

  -add a drop of iodine solution

  -place a cover slip on top

  - clip the slide you've prepared onto the stage

  - select the lowest objective lens

  - use the coarse adjustment knob to move the stage up just below the objective lens

  - look down the eyepiece. use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

  -adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide

  - if you need to see the slide with greater magnification,swap to a higher-powered objective lens and refocus.
• why do we add iodine onto the slide?

  -it is use to highlight sub cellular structures
• how are sperm cells specialised for their function?

  they are specialized for fertilisation

  - the head contains all the genetic material for fertilisation and the acrosome in the head has enzymes to penetrate through the egg cell

  -flagellum and streamline head to swim to the egg

  -the middle is contained with lots of mitochondria to provide energy for movement
• how are nerve cells adapted to their functions?

  - they are specialised for rapid signalling,

  - long axon to carry impulses over long distances

  -they have extension branches at both ends so that it can communicate with other nerve cells, muscles and glands.

  -covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse.

  -dendrites - branched nerve fibres which receive nerve impulses and pass them towards a cell body.
• how are muscle cells adapted to their function?

  they are specialised for contraction, their function is to contract quickly

  
  

  - they contain lots of mitochondria to provide energy for contractions

  - they have protein filaments that slide over each other to cause the muscle to contract

  -the cells merge so that the muscle fibres contract in unison.
• how are root hair cells adapted to their function?

  - they have hairs which increase the surface area so it can absorb minerals and water effectively.

  -they have thin walls- for shorter diffusion distance

  -large surface area - for faster osmosis
• how are xylem cells adapted to their function?

  - consists of dead cells

  - They lose their end walls so the xylem forms a continuous, hollow tube.

  - They become strengthened by a substance called lignin

  - Lignin gives strength and support to the plant.
• how are phloem cells adapted to their function?

  - made out of living cells

  - phloem cells have pores in their end walls
• why is cell differentiation important?


  - so that they are able to perform a specialised function in the body
• when do most animal cells differentiate?

  -at an early stage
• when do most plant cells differentiate?

  - they retain the ability to differentiate throughout life
• in mature animals what is cell division mainly restricted to?

  - repair and replacement
• what happens as the cell differentiates?

  -it acquires different sub-cellular structures to enable it to carry out a certain function

  -it has become a specialised cell
• what are the differences between a light microscope and an electron microscope?

  - electron has much higher magnification and resolution

  -This means that it can be used to study cells in much finer detail

  -This has enabled biologists to see and understand many more sub-cellular structures.
• what is the equation for magnification?


  Magnification = size of image / size of object
• how do bacteria mulitiply?

  - by simple cell division (binary fission) as often as once every 20 minutes
• what are the two factors that effect the rate bacteria multiplies?

  -if they have enough nutrients

  -a suitable temperature
• how can bacteria be grown?

  - in a nutrient broth solution

  -colonies on an agar gel plate
• what are uncontaminated cultures of microorganisms required for?

  -investigating the action of disinfectants and antibiotics
• describe how to prepare an uncontaminated culture using aseptic technique

  - sterilise all Petri dishes bacterial nutrient broth & agar, kills all unwanted bacteria and prevents contamination

  - sterilise that inoculating loop by passing it through a Bunsen burner flame

  - After transferring bacteria onto the dish, attach the lead using adhesive tape which Will stop the lid from falling off & unwanted microorganisms from entering

  - place that agar plate upside down into an incubator this stops moisture from dripping down onto the bacteria

  - incubate at 25°C because that will reduce the chances of harmful bacterial growth
• why must petri dishes and culture media must be sterilised before use?

  - to kill any unwanted microorganisms and prevents contamination
• why must inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame?


  - to kill any unwanted microorganisms and prevents contamination
• why must the lid of the Petri dish should be secured with adhesive tape and stored upside down?

  - stops the lid from falling off

  - prevents any unwanted microorganisms from entering

  - stop moisture from dripping down onto the bacteria and disrupting the colonies
• why must in school laboratories, cultures should generally be incubated at 25°C?

  - this reduces the chances that harmful bacteria will grow
• required practical: effect of antibiotics on bacterial growth

  1. clean the bench with disinfectant solution. this kills microorganisms that could contaminate our culture

  2. sterilise an inoculating loop by passing it through a bunsen burner flame

  3. open a sterile agar gel plate near a bunsen burner flame. the flame kills bacteria in the air

  4. now use the loop to spread the chosen bacteria evenly over the plate

  5. place sterile filter paper discs containing antibiotic onto the plate

  6. incubate the plate at 25℃
• what does the nucleus of a cell contain?

  chromosomes
• what are chromosomes made up of

  dna molecules
• how are chromosomes normally found?

  in pairs
• how do cells divide?

  in a series of stages called the cell cycle
• what does the cell cycle do?

  they make new cells for:

  - growth

  - development

  - repair
• how many chromosomes do humans have?

  46 chromosomes (23 pairs)
• what are the 3 main stages of the cell cycle?

  growth

  dna replication and mitosis

  division
• what happens at the growth stage of the cell cycle?

  - the cell has to growth and increase the amount of subcellular structures e.g mitochondria and ribosomes
• what happens at the dna replication stage?

  - the cell duplicates

  - the dna is copied and forms x-shaped chromosomes
• what happens at the mitosis stage?

  - the chromosomes line up in the middle of the cell

  - cell fibres then pull the chromosomes to opposite sides of the cell

  - membranes then form around each sets of chromosomes

  - cytoplasm and membrane divide
• what has the cell produced at the end of mitosis?

  - two new identical daughter cells
• why does the cell duplicate

  so there is one copy for each new cell