1. CELL BIOLOGY

What is binary fission?

A form of asexual reproduction in which the parent divides into two approximately equal parts

How do you work out mean division time?

2^(how many divisions take place)

What does it mean to culture something?

growing it

What is a culture medium?

An artificial environment that provides water and nutrients for the microorganism to grow

How do you make an agar plate?

hot agar jelly is poured into shallow round plastic dishes called petri dishes

What can you grow bacteria on?

agar plates

What temperature are harmful pathogens most likely to grow at?

above 25c

What is an antiseptic?

chemicals that kill bacteria on living things

What happens to non-resistant strains of bacteria given antibiotics on an agar plate?

it dies and disappears only leaving a zone of inhibition

How can you tell the effectiveness of a antibiotic through the inhibition zone?

larger = more effective

How do you measure zones of inhibition?

find an average of the diameter

divide this number by 2

use πr^2 to find area

What is a bacterial colony?

a cluster of identical bacterial cells

Are animal and plant cells eukaryotes or prokaryotes?

eukaryotes

What is a eukaryotic cell?

cell with a nucleus

What is a prokaryotic cell?

cell with no nucleus

What is a eukaryote?

an organism made up of eukaryotic cells

What is a prokaryote?

an organism made of prokaryotic cells

What subcellular structures are in an animal cell?

nucleus, mitochondria, cytoplasm, cell membrane, ribosomes

What subcellular structures are in a plant cell?

nucleus, cytoplasm, mitochondria, cell membrane, ribosomes, CELL WALL, PERMANENT VACUOLE, CHLOROPLASTS

what is the purpose of the nucleus?

contains genetic information and controls activities of the cell

what is the purpose of the cytoplasm?

gel-like substance where most chemical reactions happen

contains enzymes

what is the purpose of the mitochondria?

where most of the aerobic respiration happens to make energy

what is the purpose of the cell membrane?

holds together cell and controls what goes in/out

what is the purpose of the ribosomes?

protein synthesis

what is the purpose of the cell wall?

made of cellulose

supports & strengthens the cell

what is the purpose of the permanent vacuole?

contains cell sap ( a solution of sugar and salts )

what is the purpose of the chloroplasts?

where photosynthesis happens

makes food for the plant

contain chlorophyll

what is the purpose of chlorophyll?

green substance that absorbs light efficiently for photosynthesis

what type of cells are bactera?

prokaryotic

What subcellular structures are in a bacteria cell?

cell wall, cell membrane, cytoplasm, strand of DNA, plasmids

what is a plasmid?

a small ring of DNA

how do light microscopes work?

they use light and lenses to form an image of a specimen

what is the equation for magnification

magnification = image size / actual size

what is a slide

strip of clear glass/ plastic onto which specimen is mounted

how do you use a microscope to look at an onion cell? (REQ P)

1. add a drop of water to the middle of the slide

2. cut up the onion and use tweezers to peel off some epidermal tissue

3. place the tissue onto the slide

4. add a drop of iodine solution

5. place a cover slip on top without getting air bubbles

6. clip slide onto the stage

7. select lowest objective lens

8. use coarse adjustment knob to move stage up/down. use eyepiece to see the cell. use fine adjustment knob to adjust the focus

9. switch to a higher objective lens with a greater magnification if needed

what is a stain and the most common one?

a solution used to highlight objects in a cell by adding colour e.g. iodine

what is needed when drawing observations from a microscope? (4)

pencil

no shading, clear lines

labels

title of observation

what is differentiation?

the process by which a cell changes to become specialised for its job

what are the cells that differentiate in mature animals usually used for?

repairing and replacing cells

what are undifferentiated cells called?

stem cells

what are the 5 types of specialised cells on the spec?

sperm cells

nerve cells

muscle cells

root hair cells

phloem & xylem cells

how are sperm cells specialised and what for?

REPRODUCTION

the function is to get the male DNA to the female DNA

adaptations:

-long tail & streamlined head for swimming

-lots of mitochondria for energy

-carries enzymes to digest through egg cell membrane

how are nerve cells specialised and what for?

RAPID SIGNALLING

the function is to carry electrical signals around body

adaptations:

-long to cover more distance

-have branched connections at ends to connect to other nerve cells to form a network in the body

how are muscle cells specialised and what for?

CONTRACTION

the function is to contract quickly

adaptations:

-long so they have space to contract

-lots of mitochondria to generate energy for contracting

how are root hair cells specialised and what for?

ABSORBING WATER & MINERALS

cell on plant roots that grow into long hairs that stick into the soil

adaptations:

-big surface area for better absorption

how are phloem and xylem cells specialised and what for?

TRANSPORTING SUBSTANCES

form from phloem and xylem tubes which transport food and water around plants

adaptations:

-long and joined end to end to form tubes

-xylem cells are hollow in the centre and phloem have few subcellular structures so stuff can flow through them

how is genetic material stored in the human body?

chromosomes

what are chromosomes?

long coiled molecules of DNA that carries genetic information in the form of genes

What do genes control?

the development of different characteristics

how many copies of each chromosome do body cells usually have and where from?

2

mother and father

how many chromosomes does a human cell have?

23 pairs

46 chromosomes

why does the cell cycle make new cells?

growth, development, and repair

what is the cell cycle?

series of events that cells go through as they grow and divide

what are the two types of cell division?

meiosis and mitosis

why do multicellular organisms use mitosis?

grow or replace damaged cells

what does a cell have to do before the process of mitosis?

the cell has to grow and increase the amount of subcellular structures it has through duplicating its DNA so there's a copy for each new cell. the DNA forms into pairs of X-shaped chromosomes.

what is the process of mitosis?

-chromosomes line up at the centre of the cell and the cell fibres pull them

-the two arms of each chromosome split and go to opposite ends of the cell (the arms both have the same DNA)

-membranes form around each of the sets of chromosomes and these sets become the nuclei of 2 new daughter cells (nucleus has divided)

-the cytoplasm and cell membrane divide. two new daughter cells are made that are identical to each other and their parents

what is the end product of mitosis?

2 identical daughter cells (diploid)

what is the process of binary fission?

1. circular DNA and plasmids replicate

2. the cell gets bigger and the circular DNA strands move to opposite ends of the cell

3. the cytoplasm divides and new cell walls form

4. the cytoplasm divides and 2 new daughter cells are made. each has one copy of the circular DNA but can have variable numbers of copies of the plasmids

which cells use binary fission?

prokaryotic

what is the end product of binary fission?

two daughter cells:

each has one copy of the circular DNA

variable number of plasmid copies

what are the right conditions for bacteria to divide? (2)

warm environment

ts

what happens if the conditions for bacteria are unfavourable?

they stop dividing and die

what does a culture medium contain?

the carbohydrates, minerals, proteins, and vitamins the microorganism needs

what culture mediums are there? (2)

agar jelly

nutrient broth solution

what is the practical for investigating the effect of antibiotics on bacterial growth?

1. place paper disks soaked in different types/concentrations of antibiotics on an agar plate with an even covering of bacteria

2. the antibiotic should diffuse into the agar jelly

3. antibiotic resistant bacteria will continue to grow around the paper discs but non-resistant strains will die. a clear area will be left where the bacteria has died (an inhibition zone)

4. leave the plate for 48 hours at 25c

5. the more effective the antibiotic, the larger the inhibition zone

why do you need to use uncontaminated cultures?

contamination by unwanted microorganisms will affect results and could grow pathogens.

how do you avoid contaminated cultures?

1. sterilised petri dish and culture medium to kill unwanted microorganisms on them

2. the tools used to transfer the bacteria should be sterilised in a hot flame beforehand

3. the petri dish should be stored upside down to stop condensation falling onto the agar plate

what stem cell can turn into any type of cell?

embryonic stem cell

what do stem cells do?

divide to produce more undifferentiated cells and then these cells can differentiate into any cell

where are stem cells found? (2)

early human embryos

adult bone marrow

what is bad about adult stem cells?

they can't turn into any cell, they turn into certain ones

how can a lab grow stem cells?

the stem cell is taken from a human embryo or adult bone marrow and grown in a lab to produce clones. these cells are made to differentiate to use in medicine or research

why are stem cells useful?

can cure diseases

what is one use of stem cells from bone marrow?

replace faulty blood cells

how can an embryonic stem cell be used in medicine? (2)

replace faulty cells:

provide nerve cells for paralysed people

provide insulin-producing cells for diabetic people

what type of cloning makes an embryo have the same genetic information as the patient?

therapeutic cloning

why is therapeutic cloning done?

reduces the chances of the body rejecting the stem cells

why are people against stem cell research?

they believe the embryo has potential to be human life so they shouldn't be experimented on

why are some people for stem cell research?

they believe suffering patients are more important than an embryo

what are stem cells in plants called?

meristems cells

where are stem cells in plants found?

meristems ( parts of the plant where growth occurs )

what are meristems cells used for?

• produce clones of whole plants cheaply & quickly

• can be used to grow more plants of same species

• grow crops of identical plants that have desired features such as disease resistance

what is diffusion?

the net movement of particles from a higher concentration to a low concentration down a concentration gradient through a membrane

which states of matter does diffusion happen in?

liquid

gas

what is the concentration gradient?

the difference in concentration

how does concentration gradient affect the rate of diffusion?

bigger concentration gradient = faster diffusion rate

what affects the rate of diffusion?

concentration gradient, temperature, surface area

how does temperature affect rate of diffusion?

higher temp = faster diffusion

how does surface area affect rate of diffusion?

the larger the surface area, the faster the rate of diffusion

what can move in and out cells through diffusion?

small molecules

what are examples of molecules that can diffuse through cell membranes? (4)

oxygen

glucose

amino acids

water

what can't diffuse through cell membranes?

big molecules

what are some examples of things that can't diffuse through cell membranes? (2)

starch

proteins

what is osmosis?

diffusion of water molecules across a partially permeable membrane from a region of high water concentration to low

what is a partially permeable membrane?

a membrane with very small holes in it that only allows tiny molecules through them

what cannot go through partially permeable mebranes?

sucrose

why can particles move both ways through membranes?

they move randomly

what is the practical for observing how sugar solutions affect plant tissue? (osmosis)

1. cut potato into identical cylinders

2. put into beakers many different sugar solutions (but one should be pure water and another should be very concentrated)

3. measure the mass of the potato cylinders then leave one in each beaker for 24hrs

4. take out the cylinders and dry with a paper towel

5. measure the mass of each cylinder

6. the higher the increase in mass, the more water drawn in by osmosis. if there is a decrease, water has been drawn out.

what is the independent and dependent variable for observing how sugar solutions affect plant tissue?

dependent - potato mass

independent - concentration of sugar solution