Topic 1 - Cell biology (4.1) Paper 1 Flashcards by yash k

Plant and animal cells (eukaryotic cells) have a …

cell membrane, cytoplasm and genetic material enclosed in a nucleus.

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Bacterial cells (prokaryotic cells) are much … in comparison

smaller

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Prokaryotic cells have

cytoplasm and a cell membrane surrounded by a cell wall.

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Prokaryotic cells’s genetic material is

not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids.

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Plant and algal cells also have a cell wall made

cellulose, which strengthens the cell.

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Sperm cell

A tail moves them towards an egg cell.Many mitochondria
release energy for movement.Part of the tip of the head of the sperm, called the acrosome, releases enzymes to digest the egg membrane to allow fertilisation to take place.
Sperm are produced in large numbers to increase the chance of fertilisation.
ransfer of genetic material to an egg cell for fertilisation

Special features that aid function:
The mid-piece is packed with mitochondria to release energy (via respiration) for the tail
The tail rotates, propelling the sperm cell forward and allowing it to move
The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
The head contains a nucleus with half the normal number of chromosomes, allowing the sperm cell to fuse with an egg cell to restore the normal chromosome number

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nerve cells

Nerve cells are long, meaning that they can conduct nerve impulses between different areas of the body
Extensions of the cytoplasm known as dendrites allowing nerve cells to communicate with other nerve cells, muscles and glands
The axon is covered with a fatty sheath which speeds up nerve impulse transmission

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Muscle cells

Muscles cells are found in bundles which make up our muscles. These cells are able to contract and relax There are different types of muscle cell they also have lots of mitochondria to provide energy for contraction.
Contraction for movement

Special features that aid function:
Muscle cells have many mitochondria to release energy for contraction
All muscle cells contain protein filaments that can slide over each other to allow muscle contraction

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Root hair cells

The outside surface of roots are covered with root hair cells, which have tiny ‘hairs’ which poke into the soil. This massively increases the surface area for the root hair cell to absorb more water and mineralsRoot hairs increase surface area (SA) so the rate of water uptake by osmosis is greater

Thinner walls than other plant cells so that water can move through easily due to shorter diffusion distance

Mitochondria release energy for active transport of mineral ions

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XYLEM

Transport of water and dissolved ions

Special features that aid function:
No walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves.Cells contain no organelles or cytoplasm, allowing free passage of water.Outer walls are thickened with a substance called lignin, strengthening the tubes and providing support for the plant

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Phloem

Transport of dissolved sugars and amino acids

Special features that aid function:

Cells are joined end-to-end and contain holes in the end cell walls (sieve plates); this forms tubes which allow sugars and amino acids to flow easily

Cells have very few subcellular structures to aid the flow of material

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Most types of animal cell differentiate

at an early stage.

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Many types of plant cells differentiate

retain the ability to differentiate throughout life.

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In mature animals, cell division is mainly…
As a cell differentiates..

restricted to repair and replacement. As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell.

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magnification

imgae/object

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An electron microscope has a much higher …
This means that….
This has enabled biologists to see…

magnification and resolving power than a light microscope.
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.

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Bacteria multiply by simple cell division (binary fission) as often as …
if..
Bacteria can be grown in…
Uncontaminated cultures of microorganisms are required for…

every 20 minutes
…if they have enough nutrients and a suitable temperature.
..in a nutrient broth solution or as colonies on an agar gel plate.
…investigating the action of disinfectants and antibiotics.

Sterilization in the culturing microorganisms and aseptic techniques..

Wash…
growth media must be…
All work should be done…
inoculating loop…
lid of petri dish..
petri dish stored as..
The dish shoule be incubated at..

Wash your hands and work surfaces before beginning to prevent contamination.
Growth media must be heated before use to kill any bacteria living in it.
Growth media must be added to a sterile petri dish.
All work should be done in the presence of a Bunsen burner on a yellow flame to create a convection current above the bench and prevent contamination from the air.
The Bunsen burner can also be used to sterilise equipment such as the inoculating loop that is used to transfer bacteria.
Passing it through the flame will kill any bacteria.
The lid of the petri dish must be taped on and opened as little as possible to prevent contamination from microorganisms in the air.
The petri dish should be stored upside down to stop condensation falling on to the agar.
The dish should incubated at 25°C to restrict the growth of harmful pathogens.

Method for culturing microorganisms
pippete…
paper disks…

. Then use a sterile dropping pipette and spreader to evenly spread the bacteria (this step may have already been done for you before you started the experiment).Soak paper discs in different types or concentrations of antibiotics and antiseptics for the same length of time and place them, evenly distributed, on the agar plate with the bacterial covering. This allows the antibiotic or antiseptic to diffuse into the agar. Place a disc that has been soaked in sterile water onto the plate as a control.Tape the lid onto the petri dish and incubate upside down for 48 hours.

measuring zones of inhibition

Measure the diameter of zones of inhibition using a ruler.
Half the diameter to get the length of the radius.
Use
Area of a circle=πr
2
to find the area of the inhibition zone.

The nucleus of a cell contains chromosomes made of…
Each chromosome carries a ..
chromosomes are found in..

DNA molecules. large number of genes.

In body cells the chromosomes are normally found in pairs.

The first portion of the cell cycle is the growth phase. EXplain this

The cell grows, then prepares for mitosis by replicating all of its subcellular structures like mitochondria and ribosomes.
The cell also duplicates all of its DNA so each new cell will have a copy of the DNA. When not dividing, the DNA is spread out in long strings but when copied ready for mitosis, it forms X-shaped chromosomes with both sides of the cross containing the same DNA.

The other part of the cell cycle is mitosis and is where the cell divides into 2 identical cells.Exaplain.

It begins with the nuclear membrane breaking down and the chromosomes lining up at the equator (centre) of the cell.
Fibres then pull the arms of the chromosome to opposite ends of the cell.
Membranes form around the chromosomes which creates the nuclei for the new cells.
Finally, the cytoplasm and cell membrane divide in a process called cytokinesis, producing 2 identical daughter cells that contain the same DNA as each other and the parent cell.

What happens during the full cell cyle

Cells divide in a series of stages called the cell cycle. Students should be able to describe the stages of the cell cycle, including mitosis.

During the cell cycle the genetic material is doubled and then divided into two identical cells.

Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria.

The DNA replicates to form two copies of each chromosome.

In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.

Finally the cytoplasm and cell membranes divide to form two identical cells.

Cell division by mitosis is important in the growth and development of multicellular organisms.

A stem cell is an...

undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.

Treatment with stem cells may be able to help conditions such as

diabetes and paralysis.

In therapeutic cloning an embryo is produced... Stem cells from the embryo are not rejected .. so....

with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.

The use of stem cells has potential risks ... Stem cells from meristems in plants can be used to.... Rare species can be... Crop plants with special features such as disease resistance can be ...

such as transfer of viral infection, and some people have ethical or religious objections. produce clones of plants quickly and economically. Rare species can be cloned to protect from extinction. Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.

Substances may move into and out of cells across the cell membranes via ...

....Diffusion which is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.

Some of the substances transported in and out of cells by diffusion

are oxygen and carbon dioxide in gas exchange, and of the waste product urea from cells into the blood plasma for excretion in the kidney.

Factors which affect the rate of diffusion are:

The difference in concentrations (concentration gradient) the temperature the surface area of the membrane.

single-celled organism has a relatively large .... this allows

large surface area to volume ratio. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.

large instestine is adapted for diffusion

Most absorption of digested food molecules into the bloodstream occurs across the wall of the small intestine. How it’s adapted to its role: It has a highly folded surface which is lined with specialised intestinal epithelial cells (which themselves have a highly folded cell membrane) – this increases SA Only one layer of epithelial cells covers the surface of each villus – this decreases diffusion distance Each villus has a good blood supply – this maintains a concentration gradient

lungs adapted for diffusion

Gas exchange between air in the alveoli and the blood, to supply cells with oxygen for aerobic respiration and to remove carbon dioxide Millions of alveoli (singular: alveolus) which collectively provide a huge surface area - this increases SA The wall of each alveolus is one cell thick, with a moist lining and excellent blood supply - this maintains a concentration gradient

gills adapted for diffusion

Gas exchange between water flowing through the gills and the blood, to supply cells with oxygen for aerobic respiration and to remove the waste product carbon dioxide How it’s adapted to its role: Each gill is made from lots of smaller plates called filaments, which themselves are covered in projections called lamellae – this increases SA Dense capillary network ensures a good blood supply which flows in the opposite direction to water passing through the gills – this maintains a concentration gradient

Root adaptations in diffusion

To absorb water and mineral ions (such as magnesium and nitrate ions) from the soil and anchor the plant How it’s adapted to its role: The root network is highly branched - this increases SA The surface of the roots are covered in root hair cells, which have a specialised structure with root hair projections – this increases SA

leave adapted for diffusion

The leaves contain most of a plant's photosynthetic cells Photosynthesis requires efficient gas exchange between air surrounding the leaf and the photosynthetic cells, whilst minimising water loss Stomata are tiny openings that predominantly cover the lower side of the leaf, allowing air to circulate inside the leaf – this decreases diffusion distance for carbon dioxide and oxygen The lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaft

In multicellular organisms, surfaces and organ systems are specialised for exchanging materials. This is to allow.... The effectiveness of an exchange surface is increased by...

This is to allow sufficient molecules to be transported into and out of cells for the organism’s needs. ..having a large surface area a membrane that is thin, to provide a short diffusion path (in animals) having an efficient blood supply (in animals, for gaseous exchange) being ventilated.

osmosis is

Water may move across cell membranes via osmosis. Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

Active transport is .... it requires...

Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.

Active transport allows mineral ions to be.. Plants require ions for... It also allows sugar molecules to be absorbed from... sugar molecules are used for...

absorbed into plant root hairs from very dilute solutions in the soil. ...Plants require ions for healthy growth ...lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.