Topic1: cell biology

What are the commonly used prefixes

• centi:0.01

• Milli : 0.001

• Micro: 0.000,001

• Nano: 0.000,000,001

What are eukaryotic cells

These are cells that have a nucleus and their genetic material is organelle bound

What are prokaryotic cells

These are cells that do not have nucleus and their DNA is free flowing

What are the parts of eukaryotic cells

• Nucleus

• Cytoplasm

• Cell membrane

• Mitochondria

• Ribosomes

What is the nucleus

It contains DNA that codes for a specific protein needed to build new cells

What is the cytoplasm

This is the liquid substance in which chemical reactions occur and contains enzymes

What is the cell membrane

This controls what enters and leaves the cell

What is Mitochondria

This is where aerobic reactions happen occur providing energy for the cell

What are ribosomes

This is where protein synthesis occurs and they are found on a structure called rough endoplasmic reticulum

What are the structures found only in plants

• chloroplasts

• Permanent vacuole

• Cell wall

What are chloroplasts

This is where photosynthesis takes place. Contains green pigment chrolophyll that traps sunlight for photosynthesis

What is the permanent vacuole

This contains cell sap and improves cell rigidity

What is cell wall

It provides strength to a cell and is made up of cellulose

What is the cell wall of bacteria made of

Peptidoglycan

What is plasmid

These are small rings of DNA

What is cell differentiation

This is the process of a cell gaining new sub-cellular structures in order for it to perform a specific role

What is cell specialization

This is the process by which a cell differentiates to perform a specific function

What are the examples of specialized cells in animals

• sperm cells

• Nerve cells

• Muscle cells

How are sperm cells specialized

• streamline head and long tail to aid swimming

• Many mitochondria which supply energy for the cell to move

• The acrosome has digestive enzymes to help break down the outer layers of the membrane of egg cells

How are nerve cells specialized

They are specialized to carry electrical signals quickly from one place to another

• the axon is long allowing signals to be carried along long distances

• Having lots of extensions from the cell body (dendrites) means branched connections can be formed with other cells

• Myelin sheath to insulate the nerve cell and prevent leaking of electrical signals

How are muscles cells specialized

Specialized to contract quickly to move bones

• special proteins ( myosin and actin) slide over each other causing the muscles to contract

• Lots of mitochondria to provide energy from respiration for contraction

• They store a chemical called glycogen which is used in respiration

What are specialized cells in plants

• root hair cells

• Xylem cells

• Phloem cells

How are root hair cells specialized

Specialized to take up water by osmosis and mineral ions by active transport from the soil

• have a large surface area which increases the rate of osmosis

• Mitochondria to provide energy for respiration for the active transport of mineral ions

• The large permanent vacuole affects the speed of movement of water

How are xylem cells specialized

Specialized to transport water and mineral ions from the roots to the shoots

• lignin is deposited in the walls of which causes the cell to die they become hollow and are joined end to end to form a continuous tube for water to pass through

• Lignin is deposited in spirals which helps the cell withstand the pressure of moving water

How are phloem cells specialized

Specialized to carry the products of photosynthesis around the plant

• cell walls form sieve plates when they break down allowing the movement of products

Microscopy

Check old books and sites

What is the magnification of a microscope

Magnification of eyepiece lens* magnification of the objective lens

What is the size of an object

Size of image/magnification

What are the two ways of growing microorganisms in the lab

• In nutrient broth solution

• On an agar gel plate

Describe nutrient broth solution

• This involves making a suspension of bacteria to be grown and mixing with sterile nutrient broth

• stoppering the flask with cotton wool to prevent air from contaminating it

• Shaking it regularly to provide air for bacteria

Describe culturing on an agar gel plate

• hot sterilized agar jelly is poured into a sterilized Petri dish which is left to cool and set

• Wire loops called inoculating loops are dipped in the solution of the microorganism and spread over the agar evenly

• A lid is taped on and the plate is incubated for a few days so the microorganism can grow

What steps are taken during culturing

• Petri dishes and culture media must be sterilized before use

• Inoculating loops must be sterilized by passing them through a flame

• The lid of the Petri dish should be sealed (not completely)

• The Petri dish must be stored upside down

• The culture should be incubated at 23 degrees

Why should the Petri dish and culture media be sterilized

• there could be contamination by other microorganisms which battle with the bacteria for space and nutrients

Why must be inoculating loops be passed through a flame

This kills unwanted microorganisms

Why must the lid of the Petri dish taped partially

Sealing stops airborne microorganisms from spreading about but it should not be completely sealed to prevent harmful anaerobic bacteria from growing

Why must the Petri dish placed upside down

To prevent condensation of the lid landing on the agar surface and disrupting growth

Why must the culture be incubated at 25 degrees

• 37 degrees is human temp

• Salmonella grows at 37 degrees

• 25 reduces the growth of bacteria that are harmful to humans

How do you calculate all the bacteria created in culturing

Bacteria at beginning x 2 raised to the power of number of divisions

What is a gene

This is a short section of DNA that codes for a specific gene

What is the cell cycle

This is a series of steps that the cell has to undergo in order to divide

What are the stages of mitosis

• interphase

• Mitosis

• Cytokinesis

What happens during interphase stage

The organelles grow and increase in number the synthesis of proteins occurs and DNA is replicated and energy stores are increased

What happens during mitosis stage

The chromosomes line up at the equator of the cell and cell fibers pull each chromosome of the “x” to each side of the cell

What happens during cytokinesis stage

Two identical daughter cells form when the cytoplasm and cell membranes divide

What is a stem cell

This is an undifferentiated cell that can undergo division to produce many more similar cells of which some differentiate to have different functions

What are the types of stem cells

• embryonic stem cells

• Adult stem cells

• Meristems in plants

What are embryonic stem cells

• formed when an egg and cell fuse to Form zygote

• They can differentiate into cell in the body

What are adult stem cells

Found in bone marrow

What are meristems in plants

• found in root and shoot tips

• They can be used to form clones of the plant

What is therapeutic cloning

This is involves an embryo being produced with the same genes as the patient

What are the benefits of research with stem cells

• can be used to replace damaged and diseased cells

• Unwanted embryos from fertility clinics can be used instead of discarded

• Research into the process of differentiation

What are the problems with the research of stem cells

• removal of stem cells destroys embryos

• People may have religious or ethical objections as it is seen as an interference with reproduction

• Money and time can be spent on other parts of medicine

• If the growing stem cells are contaminated with virus the individual can be affected

What is diffusion

This is the moment of particles from an area of high concentration to an area of low concentration

What factors affect the rate of diffusion

• concentration gradient: steeper concentration gradient means diffusion occurs faster

• Temperature

• Surface area of the membrane

  all directly proportional to the rate of diffusion

Where is diffusion used

• in the lungs

• In the small intestine: cells have projections called villi where digested food is absorbed into the bloodstream

• The gills

• The roots

• In the leaves

What is osmosis

This is the movement of water from a region of low concentration to a region of high concentration through a semi permeable membrane

Describe different osmotic processes

• If the concentration of sugar in external solution is the same as the internal, there will be no movement and the solution is said to be isotonic to the cell

• If the concentration of sugar in external solution is higher than the internal, water moves out, and the solution is said to be hypertonic to the cell

• If the concentration of sugar in external solution is lower than the internal, water moves in, and the solution is said to be hypotonic to the cell

Describe osmosis in plants

• If the external solution is more dilute, water will move into the cell and into the vacuole, causing it to swell, resulting in pressure called turgor (essential in keeping the leaves and stems of plants rigid).

• If the external solution is less dilute, water will move out of the cell and they will become soft. Eventually the cell membrane will move away from the cell wall (called plasmolysis) and it will die.

Describe osmosis in animals

• the external solution is more dilute (higher water potential), it will move into animal cells causing them to burst.

• On the other hand, if the external solution is more concentrated (lower water potential), excess water will leave the cell causing it to become shrivelled.

What is active transport

This is the movement of particles from a region of lower concentration to a region of higher concentration against the concentration gradient with the use of energy

Where does active transport occur

• in the gut

• In root hairs

What is resolution

This is the ability to tell apart two or more objects that are close together

Experiment for light microscope

Difference between light microscope and electron

• light microsope uses light to form images while electron uses a beam of fast moving electrons

• Light microscope has lower resolving power (200nm) while electron has higher (0.2nm)

• Light electroscope can view live specimens while electron can only see dead specimens

• Light microscope forms colour image while electron forms black and white image

What are the parts of microscopes and their uses

• objective lens:to capture light from a specimen, focus it, and create the initial magnified image of the sample

• Cover slip: holds a specimen in place and prevents it from contamination

• Fine focus: making small, precise adjustments to the focus of the specimen.

• Coarse focus; bring the specimen into approximate or near focus

• Stain/dye: stain plant cells to make the internal structures more visible.

What stops someone from seeing through an objective lens

• no cells in the field of few

• Mirror not in correct position

• Objective lens dirty

• Slide not in correct position

• Microscope not focused

• Student is looking into air bubble

What are the different types of sport drinks

• Isotonic sports drinks contain similar concentrations of salt and sugar (glucose) as the human body and are primarily used for hydration and fluid replacement

• Hypertonic sports drinks contain concentrations of salt and sugar higher than typical blood levels

  • This provides high salt and sugar levels for absorption from the small intestine - these drinks are suitable for supplying glucose in particular during intense physical exercise (eg. during a marathon)

• Hypotonic sports drinks contain concentrations of salt and sugar lower than typical blood levels

  • Drinking this type of drink creates a concentration gradient between the bloodstream and small intestine with the water potential in the small intestine being higher - these drinks are suitable for rapid rehydration as water is drawn into the bloodstream by osmosis

Difference between sexual and asexual reproduction

Describe the function of muscles cells in the stomach

They contract to churn food

Explain how the human circulatory system is adapted to

• supply oxygen to tissues

• Remove waste products from tissues