B1 : Cell Biology

All of Cell Biology (Practicals Included)

What is a Prokaryotic Cell/Prokaryote?

A cell which does not have a nucleus (genetic material enclosed in a nucleus)

What is a Eukaryotic Cell/Eukaryote?

A cell which does have a nucleus (genetic material enclosed in a nucleus)

Give an example of a prokaryotic cell

Bacteria Cell

Give an example of eukaryotic cell (2)

• Animal Cell

• Plant Cell

Which type of cell is bigger

• Prokaryotic

• Eukaryotic

Eukaryotic cell

How many subcellular structures does a bacteria cell have?

6

Name all the subcellular structures in a bacteria cell

1. Cell membrane

2. Cell wall

3. Ribosomes

4. Cytoplasm

5. Singular strand of DNA (that floats freely)

6. Plasmids (small rings of DNA)

How many subcellular structures does a plant cell have?

8

Name all the subcellular structures in a plant cell

1. Cell membrane

2. Cell wall

3. Ribosomes

4. Mitochondria

5. Cytoplasm

6. Nucleus

7. Permanent Vacuole

8. Chloroplast

How many subcellular structures does an animal cell have?

5

Name all the subcellular structures in an animal cell

1. Cell membrane

2. Mitochondria

3. Ribosomes

4. Cytoplasm

5. Nucleus

What is the function of the cell membrane?

Controls what goes in and out of the cell

What is the function of the cell wall + what is it made out of?

It is rigid, made out of cellulose and supports and strengthens the cell

What is the function of the mitochondria?

Site of aerobic respiration, releases energy via glucose

What is the function of the cytoplasm?

Jelly like substance, contains enzymes, where all chemical reactions take place

What is the function of the permanent vacuole?

Contains cell sap, a weak solution of salts and sugars

What is the function of the chloroplast?

Site of photosynthesis, contains chlorophyll, a green pigment which absorbs light

What is the function of the nucleus?

Contains genetic material, controls the activities of the cell

What is the function of the ribosomes?

Site of protein synthesis

Light Microscopes : Pros + Cons (4)

• Relies on light to produce an image

• Easy to use

• Cheap

• Can see large subcellular structures (nuclei)

Electron Microscopes : Pros + Cons (6)

• Relies on electrons to produce an image

• Hard to use

• Expensive

• Can see smaller subcellular structures (ribosomes)

• Have higher resolution compared to a light microscope

• Have higher magnification compared to a light microscope

Define magnification

How many times bigger the image size is compared to the real size

Define resolution

The ability to distinguish between two points (higher resolution gives clearer image)

What is the function of the eye piece?

What you look through

What is the function of the stage

Where you place your slide

What is the function of the Coarse adjustment knob?

Moves the stage up or down + allows for rough focusing

What is the function of the fine adjustment knob?

Allows for precise focus when seeing smaller subcellular structures

What is the function of the high and low power objective lenses?

Magnification, start off with the lowest → wider field of view

What is the function of the light?

So you can see the slide

What is the equation for calculating magnification?

Magnification = image size/ real size

How do you prepare the microscope slide? (5)

1. Add a drop of water to the middle of a clean slide

2. Cut an onion and separate it into layers

3. Use tweezers to peel off the epidermal tissue and place it in the water

4. Add a drop of a stain (e.g. iodine solution) which is used to highlight objects by adding colour to them

5. Place a cover slip on top, make sure not to get any air bubbles as it will obstruct your view of the specimen

How do you prepare the light microscope to see the specimen? (6)

1. Clips the slide onto the stage

2. Select the lowest power objective lens (this will give you the widest field of view)

3. Look down the eyepiece and use the coarse adjustment knob to move the stage until the image is in rough focus (do not hit the objective lens)

4. Adjust focus with the fine adjustment knob until you get a clear image

5. Increase magnification and refocus to see different features

How do you draw your observations effectively? (8)

• Subcellular structures in proportion

• Label important features with straight, uncrossed lines

• drawn with clear, unbroken lines

• Include the magnification used

• Use sharp pencil

• Include the title of what you observed

• Drawing takes up at least half of the space

• No colouring/shading

What is cell differentiation?

When a cell changes to become specialised

What happens as cells change?

They gain different subcellular structures that help carry out specific functions

When do animal cells differentiate?

At an early stage, they lose the ability to differentiate after becoming specialised

When do plant cells differentiate?

Throughout their life span, plant cells do not lose the ability to differentiate

Why would mature animals differentiate?

For repair and replacement

What is the function of the sperm cell?

Reproduction → carry male DNA to the female DNA

How is the sperm cell adapted for its function? (3)

• Has a long tail and streamlined head for swimming to the egg

• Has many mitochondria to release energy for swimming

• Has enzymes in its heads to digest through the egg cell membrane

What is the function of the nerve cell?

Rapid signalling → send electrical signals from one part of the body to another

How is the nerve adapted for its function? (2)

• are long to cover more distance in the body

• have branches at the end of the cells to be able to join with other nerve cells and form a network throughout the body

What is the function of the muscle cell?

Contraction → to be able to contract quickly

How is the muscle cell adapted for its function? (3)

• are long which gives space for contraction

• contain many mitochondria to release energy for contraction

• contain protein fibres which allow it to change shape

What is the function of the root hair cell?

Absorbing water and minerals

How is the root hair cell adapted for its function? (2)

• Have long hairs which stick into the ground, these increase the surface are for maximum absorption

• Have no chloroplasts

What is the function of the phloem cell?

Transporting substances

How is the cell phloem adapted for its function? (2)

• Long tubes joined from end to end

• Has few subcellular structures which allows for maximum transportation

What is the function of the xylem cell?

Transporting substances

How is the cell xylem adapted for its function? (3)

• Thick walls made from lignin to strengthen and support the cell

• Long tubes joined end to end

• No subcellular structures (is a hollow tube) which allows for maximum transportation

What form of genetic material does the nucleus contain?

Chromosomes

What are chromosomes?

Coiled up lengths of DNA

How many chromosomes does a human body have?

46 chromosomes

23 from the mother + 23 from the father

What is mitosis a part of?

The cell cycle

Why does mitosis occur?

To repair or replace damaged cells

What are the stages of mitosis? (5) (do not mention the end result)

1. Cell grows and increases its subcellular structures (mitochondria and ribosomes)

2. DNA duplicates (each chromosomes replicates)

3. The chromosomes line up at the centre of the cell and each arm is pulled to opposite ends of the cell

4. The nucleus divides

5. The cytoplasm and cell membrane divide

What is produced via mitosis?

Two daughter cells that are genetically identical

How do prokaryotic cell divide?

Binary fission

What are the stages of binary fission? (3) (do not mention the end result)

1. The circular rings of DNA and plasmids replicate

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

3. The cytoplasm divides and a new cell wall begins to form

What is the product of binary fission?

Two new daughter cells are produced which have one strand of DNA but varying numbers of plasmids

What conditions are needed for bacteria to divide quickly via binary fission + what happens if this is not achieved?

The right nutrients and warm environment

However if the conditions become unfavourable, the cells will stop replicating and die

How often do bacteria divide?

Every 20 minutes

How do you achieve uncontaminated cultures? (4)

• Petri dish and culture medium must be sterilised → heating to kill any unwanted microorganisms

• Inoculating loop must be sterilised → passed through a flame to kill any unwanted microorganisms

• After transferring bacteria the petri dish should be taped lightly using 4 pieces of tape on the ‘corners’ to stop any microorganisms getting in

• The petri dish should be stored upside down to stop any condensation droplets falling onto the agar surface

What are bacteria grown on, give 2 examples + what temperature are the grown at + why?

1. Bacteria are grown on culture mediums

2. The culture medium can be used as a nutrient broth solution or solid agar jelly (Bacteria grown on agar plates will form visible colonies)

3. In school the temperature must be kept at below 25°C because any higher and harmful pathogens will grow

How do you investigate the effect of antibiotics on bacteria? (5)

1. Place paper discs soaked in different types/concentrations of antibiotics on the agar plate with even covering of bacteria

2. Antibiotics should diffuse into jelly. Anti-biotic resistant bacteria will grow on agar where bacteria have died - this is the inhibition zone

3. As a control use a paper disc soaked in distilled water so you can compare the effect of the antibiotics

4. Leave plate for 48h at 25°C

5. To compare effectiveness, calculate the area of the inhibition zones by using πr2

What are stem cells?

Undifferentiated cells that can differentiate into any cell by, depending on instructions given

What are the two types of stem cells found in humans + where are they found?

• Adult stem cells, found in the bone marrow of an adult

• Embryonic stem cells, found in embryos that have not yet developed into babies

What are the pros + cons of embryonic stem cells? (5)

• Can differentiate into any cell

• No wait time

• Produced in labs so the possibility of contamination whilst transferring is a risk and can cause disease in patients

• People have ethical and religious objections

• can cure diseases like type 1 diabetes and paralysis

What are the ethical reasons for and against embryonic stem cells?

For

• embryos used is research are unwanted from fertility clinics and if not used for medicine would’ve died anyway + those suffering from illness are more important than embryos

Against

• shouldn’t be used in experiments because they could be a potential human life

What are the pros + cons of adult stem cells? (4)

• An adult who has bone marrow gives consent for it to be used

• It can differentiate into a limited amount of cells

• Wait time as they might be rejected by the patient

• Can replace faulty blood cells

What is therapeutic cloning?

When an embryo could be made to have the same genetic information as the patient meaning the stem cell wouldn’t be rejected by the immune system

What is the stem cell found in plants called + where is it found?

Meristems, found on the growing tips of shoots and roots

What are the pros + uses for meristems? (4)

• Can differentiate into any type of cell throughout its entire life

• Can be used to produce clones of plants quickly and cheaply

• Can grow more rare species without worry of extinction

• Grow plants that have desired features for farmers like being disease resistant

What is diffusion?

The movement of particles from an area of higher concentration to an area of lower concentration across a partially permeable membrane

What states of matter does diffusion take place + why?

Liquids + gases because particles are free to move

What are the 3 factors that effect diffusion + how?

• Concentration gradient → the higher the concentration gradient the higher the rate of diffusion

• Temperature → the higher the temperature the higher the rate of diffusion

• Surface area → the larger the surface area the higher the rate of diffusion

What type of cell membrane lets small molecules diffuse through like oxygen and carbon dioxide?

A partially permeable membrane

What are the 2 examples of diffusion?

• Oxygen and carbon dioxide are transferred between cells and the environment during gas exchange

• In human, urea (a waste product) diffuses from cells into the blood plasma for removal from the body by the kidneys

What is osmosis?

The movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration

How would you investigate the effect of sugar solutions on potato chips? (3)

1. Cut potatoes into identical cylinders and measure their mass

2. Put them into beakers with different sugar solutions, one should be pure water and the other a very concentrated solution (1mol/dm³), also have other beakers with different concentrations (0.1mol/dm³,0.2mol/dm³)

3. Take cylinders out, dry them with tissue and measure their masses

What are the variables for the effect of sugar solutions?

DV: The mass of the potatoes

CV: volume of solution, temperature, type of potato, time kept in beaker

IV: The concentration of sugar solutions

What should happen to the cylinders if water has been drawn IN by osmosis?

Increase in mass

What should happen to the cylinders if water has been drawn OUT by osmosis?

Decrease in mass

What is active transport?

The movement of particles form an area of lower concentration to an area of higher concentration, against the concentration gradient across a partially permeable membrane

Where does active transport take place? (2)

• In root hair cells

• In the gut

Describe active transport in the root hair cell (3)

• Root hair cells need to take in minerals from the soil but the concentration of minerals is higher inside of the root hair cell than the soil so via active transport the root hair cell gains more minerals

• This is essential for growth.

• But a lot of energy from respiration is needed

Describe active transport in the gut (2)

• Active transport in the gut happens when there is a lower concentration of nutrients in the gut and a higher concentration of nutrients in the blood (nutrients: glucose + amino acids)

• It is then transported to the cell where it is used for respiration

Explain the surface area: volume ratio and the link to single-celled organisms and multicellular organisms (4)

• In single-celled organisms gases and dissolved substances can diffuse directly into and out of the cell

• This is because they have a large surface area compared to their volume

• However, with multicellular organisms, their surface area is too small for their volume and not enough substances can be supplied to accommodate their volumes

• This means that they need exchange surfaces for efficient diffusion

How have exchange surfaces adapted for the effective transport of substances? (4)

• Have thin membranes; short diffusion pathways

• Have large surface areas so lots of substances can diffuse at once

• Exchange surfaces in animals have lots of blood vessels; get stuff in and out of the blood quickly

• Gas exchange surfaces in animals are often ventilated; air moves in and out

What is the function of the lungs (2) and how are they adapted to do this? (4)

1. The job of the lungs is to transfer oxygen into the blood and remove carbon dioxide from it

2. To do this the lungs have millions of alveoli which are specialised to maximise diffusion of oxygen and carbon dioxide by

• An enormous surface area (as there are many of them)

• A moist lining for dissolving gases

• Very thin walls

• A good blood supply

What is the function of the small intestine (2) and how are they adapted to do this? (4)

1. They increase surface area so digested food is absorbed into the blood much quicker

2. Inside the small intestine which are long, there are millions of villi

3. They are

• One cell thick

• Have a good blood supply for quick absorption

• Many villi to increase the surface area

• Have many mitochondria for respiration

How are leaves adapted for efficient gas exchange? (5)

1. Carbon dioxide diffuses into the air spaces of the leaf, then it diffuses into the cells for photosynthesis

2. The underlayer of the leaf is the exchange surface and has loads of stomata which allows carbon dioxide to diffuse through

3. Oxygen and water vapour also diffuse out through the stomata

4. The size of stomata is controlled by guard cells; close stomata if water is being lost quicker than it is being replaced (without guard cells the plant would wilt)

5. Flattened shape of leaf increases surface area + many air spaces inside the leaf which act as exchange surfaces

How are fish adapted for efficient gas exchange? (6)

1. Gills are the exchange surface in fish

2. Water enters via the mouth and passes through gills; at the same time oxygen diffuses from water into blood and carbon dioxide diffuses from blood to water

3. Gills are made up of many gill filaments which increase surface area: gill filaments contain many lamellae which increase surface area even more

4. Lamellae have lots of blood capillaries to speed up diffusion

5. Have a thin surface layer to minimise distance gases have to diffuse

6. Blood flows one way and lamellae flow another to maintain a large concentration gradient