biology

Question 1

what are two types of cells?

Answer 1

eukaryotic and prokaryotic.

eukaryotic cells = complex and made up of animal and plant cells

prokaryotic = smaller and simple e.g bacteria.

Question 2

what are 5 subcellular structures of animal cell/ plant cell?

Answer 2

1. nucleus = contains genetic material and controls activities of cell
2. cytoplasm = jelly like substance where most of chemical reactions happen. it contains enzymes that control these chemical reactions
3. cell membrane= holds cell together and controls what goes in and out.
4. mitochondria = where most aerobic respiration happens
5. ribosomes = these are where proteins are made.

Question 3

what are 3 extra subcellular structure a plant cell has but animal cell doesn’t have?

Answer 3

1. cell wall = made a cellulose. it supports cell and strengthens it
2. permanent vacuole = contains cell sap ( a weak solution of sugar and salts)
3. chloroplasts = this where photosynthesis occurs. contains a green substance called chlorophyll which absorbs the light needed for photosynthesis.

Question 4

what are subcellular structures of bacteria cell?

what is different about bacteria cell?

Answer 4

1. cytoplasm
2. cell membrane
3. cell wall
4. plasmids = small ring of DNA

difference
- they don’t have a “true” nucleus instead they have a single strand of DNA that floats freely in cytoplasm

• don’t have chloroplast or mitochondria.

Question 5

what are microscopes?
what are light microscopes and the problems?

Answer 5

-Microscopes allow us to magnify
-Light microscopes use light and lenses to form an image (make it look bigger).They let us see individual cells and large subcellular structures like nuclei
Problems:
-Limited resolution
-Limited magnification

Question 6

what are electron microscopes?
what are the benefits of it?

Answer 6

-Electrons use electrons instead of light to form an image
Benefits:
-Higher magnification
-Higher resolution
-Lets us see small smaller things in more detail like the internal structure of mitochondria and chloroplasts.
-They even let us see tinier things like ribosomes and plasmids

Question 7

How to write figures in standard form?

Answer 7

example- mitochondrion is approx 0.0025 mm long. Write this figure in standard form

1)First number needs to be between 1 and 10 so the decimal point needs to move after 2
2)Count how many places the decimal point has moved -power of 10.Dont forget the decimal point has moved right

Question 8

What are the 5 steps to prepare a slide? (onion)

Answer 8

1) Add a drop of water to the middle of a clean slide
2) Cut up an onion and separate out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) Using tweezers place the epidermal tissue into water on the slide
4) Add a drop of iodine solution. Iodine solution is a stains. Stains are used to highlight objects in a cell by adding colours to them
5) Place a cover slip on top to do this stand the cover slip upright next to the water droplet. Then carefully tilt and lower it so it cover the specimen.

Question 9

What are the steps to use a light microscope?

Answer 9

1) Clip the slide you prepared onto the stage

2) Select the lowest powered objective lens

3)Use the coarse adjustment knob to move the stage up just below the objective lens

4)Look down the eyepiece. Use coarse adjustment knob to move the stage downwards until the imagine is roughly in focus

5)Adjust the focus with the fine adjustment knob until you get a clear image of what’s on the slide

6)If you need to see the slide with greater magnification swap to higher powered objective lens and refocus

Question 10

what is differentiation?
what happens as the cells change?
when does most differentiation occur ?
what do cells that differentiate in mature animals used for?

Answer 10

Differentiation is the process by which a cell changes to become specialised
-As the cells change they develop different subcellular structures and turn into different types of cells.This allows them to carry their function
-The cells that differentiate in mature animals are mainly used for repairing and replacing cells such as skin, blood etc

Question 11

what is a stem cell?

Answer 11

Undifferentiated cell

Question 12

what is sperm cells?

Answer 12

Sperm cell is to get the male dna into the female dna it has a long tail and a streamlined head to help it swim to the egg.There are lots of mitochondria in the cell to provide the energy needed it also carries enzymes in its to digest it way through the egg cell memebrane

Question 13

what is nerve cell?

Answer 13

Function of nerve cell is to carry electrical impulses from one part of the body to another.These cells are long to cover more distance and have branched connections at the ends to connect to other never cells to form a network throughout the body

Question 14

What is muscle cell?

Answer 14

Muscle cell is to contract quickly.These cells are long so that they have space to contract and contain lots of mitochondria to generate energy needed for contraction

Question 15

what is root hair cell?

Answer 15

Root hair cells on the surface of plant roots which grow into long hairs that stick out into the soil.This give the plant a big surface are for absorbing water and mineral ion from the soil

Question 16

what is phloem and xylem cells?

Answer 16

Phloem and xylem cells form tubes which transport substances such as food and water around plants.To form tubes the cells are long and joined end to end.Xylem cells are hollow in the centre and phloem cells have very few subcellular structures so that stuff can flow through them

Question 17

what are chromosomes?
what does each chromosome carry?
what do body cells normally have?
How many chromosomes does a human cell have?

Answer 17

-Chromosomes are coiled up lengths of dna molecules
-Each chromosomes carries large number .Different types of genes control the development of different characteristics eg hair colour
-Body cells normally have 2 copies of each chromosome one from the mother another from the father
-23 pairs of chromos

Question 18

what do body cells in multicellular organisms do?
what is the stage of the cycle where the cells divide call?
what does the end of the cell cycle result in?

Answer 18

-Body cells in multicellular organisms divided to produce new cells as part of the cell cycle
-Mitosis
-Ends in two identical cells to the original cell with the same number of chromosomes

Question 19

what are the stages of GROWTH AND DNA REPLICATION?

Answer 19

1) in a cell thats not dividing dna is spread out in long strings
2) Before it divides cell has to grow and increase the amount of subcellular structures such as mitochondria/ribosomes
3) It then duplicates its DNA so there’s 1 copy for each cell .DNA is copied and forms x shaped chromosomes is an exact duplicate of the other

Question 20

what are the stages of MITOSIS?
what does the cell produce at the very end?

Answer 20

1) The chromosomes line up at the centre pf the cell and cell fibres pull them apart. Two arms of each chromosome go to opposite ends of the cell
2) Membrane form around each of the sets of chromosomes. These become nuclei of 2 new cells nucleus has divided
3) Lastly, the cytoplasm and cell membrane divide

Cell has now produced 2 daughter cells theyre identical to the parent cell

Question 21

what is differentiation?
what is undifferentiated cells?

Answer 21

-Differentiation is the process by which a cell changes to become specialised for it’s job
-Undifferentiated cells called stem cells can divide to produce lots more undifferentiated cells. They can differentiate into different types of cell depending on what instructions they’re given

Question 22

where are stem cells found?
where are adult stem cells found?
where are stem cells from embryos and bone marrow can be grown?

Answer 22

-Stem cells are found in early human embryos ,they have the potential to turn into any kind of cell at all
-Adult stem cells but they’re only found in certain places like bone marrow ,they can’t turn into any type of cell at all
only certain ones
-They can be grown in a lab to produce clones (genetically identical)and made to differentiate into specialised cells to use in medicine or research

Question 23

what are the 3 stem cells to cure some diseases?
what is 1 risk?

Answer 23

1)Adult stem cells eg stem cells transferred from the bone marrow of a healthy person can replace fault blood cells

2)Embryonic cells could also be used to replace faulty cells in sick people. You could make insulin producing cells for diabetes and nerve cells for people paralysed by spinal injuries

3)Therapeutic cloning an embryo could be made to have to have the same genetic information as the patient. This means that stem cells produced from it would also contain the same genes and so wouldn’t be rejected by the patient’s body if used to replace faulty cells

RISK:
-FOR EXAMPLE stem cells grown in the lab may be contaminated with a virus which could be passed on to the patient and make them sick

Question 24

What are 5 reasons against stem cell research?

Answer 24

1) They feel that human embryos shouldn’t be used for experiments since each one is a potential human life

2) That curing existing patients who are suffering is more important than the rights of embryos

3) Embryos used for research usually unwanted ones from fertility clinics if they weren’t used for research they would probably get destroyed. Campaigners want this banned

4) These campaigners feels that scientist should focus more on finding and developing other sources of stem cells so people could be helped without using embryos

5) In some countries stem cells research are banned

Question 25

what can stem cells produce ?
where are stem cells found?
what can stem cells be used to produce?
what can they be used to grow?
what can they be used to grow?
what happens throughout the plants entire life?

Answer 25

-Stem cells can produce identical plants
-Stem cells are found in meristems
-Stem cells can be used to produce clones of whole plants quickly and cheaply
-They can grow more plants of rare species to prevent them being wiped out
-They can be used to grow crops of identical plants that have desired features for farmers eg disease resistance
-Throughout plant’s cells in the meristem tissues can differentiate into any type of plant cell

Question 26

what is filtration?
what can it be used for?

Answer 26

-Filtration separates insoluble solids from liquids
-It can be used for purification

Question 27

what is a soluble?
what are the two methods to separate soluble salt from a solution and their steps?

Answer 27

-Soluble is a solid can be dissolved
-Evaporation and crystallisation

EVAPORATION:
1) pour the solution into an evaporating dish
2) Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually crystals will start to form
3) Keep heating the evaporating dish until all you are left with is dry crystals

CRYSTALLISATION:
1) Pour the solution into an evaporating dish and gently heat the solution .Some of the solvent will evaporate and the solution will get more concentrated
2) Once some of the solvent has evaporated or when you see crystals start to form remove the dish from the heat and leave the solution to cool
3) The start should start to form crystals as it becomes insoluble to the cold highly concentrated solution
4) Filter the crystals out of the solution and leave them in a warm place to dry. You could use a drying oven or a desiccator

Question 28

what can filtration and crystallisation be used to separate?
what are the 4 steps to separate salt/sand?

Answer 28

-Rock salt, a mixture of salt and sand
-Salt and sand are both compounds salt dissolves in water but sand doesn’t

TO SEPARATE:
1) Grind the mixture to make sure the salt crystals are small so dissolve easily
2) Put the mixture in water and stir. The salt will dissolve but the sand won’t
3) Filter the mixture .The grains of sand won’t fit through the tiny holes in the filter paper ,so they collect on the paper instead. The salt passes through the filter paper as it is part of the solution
4)Evaporate the water from the salt so that it forms dry crystals

Question 29

what is the rf value equation for paper chromatography?

Answer 29

RF=distance moved by substance
DIVIDED BY
distance moved by solvent

Question 30

what is diffusion?
what are 2 things that make the rate of diffusion faster?

Answer 30

-Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration
-2 things to make diffusion faster:
-bigger concentration gradient
-higher temperature (more energy)