biology

What is the cell wall of a prokaryotic cell made of?

peptidoglycan

What is the function of the bacterial chromosome?

Carries most of the bacterium's genetic information

Which cells can contain flagella?

animal and prokaryotic/bacterial cells

What is the function of a microscope?

To magnify the image of a biological specimen so that it appears larger

What is resolution?

. How clear an image is - the ability to distinguish between 2 points

. measured in nm

What are the 2 types of electron microscopes?

. transmission electron microscope (TEM)

. scanning electron microscope (SEM)

What is magnification?

. How much bigger an object is in an image compared to real life

. Has no units

State the properties of a light microscope

. beam of light

. low resolution

. low magnification

. 2D image

. Natural colour

. see inside of cell

State the properties of a TEM microscope

. beam of electrons

. high resolution

. high magnification

. 2D image

. B&W

. see inside of cell

State the properties of a SEM microscope

. beam of electrons

. high resolution

. high magnification

. 3D image

. B&W (or computer colouring)

. see outside of cell

Describe how to use a microscope to look at onion cells.

1) Place object on a microscope slide and place a cover slip on top

2) Use a low objective lens to view object at first - turn coarse focus knob to find the object and fine focus knob to see more clearly and draw and label any structure you can see

3) View at high magnification and draw and label any structure you can see

4) Label magnification - eyepiece lens x objective lens

What is cell division in mature animals?

. Mainly 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

What is a prokaryotic cell?

. Single-celled organisms

. Lack a nucleus and other membrane-bound organelles

. Bacteria are 1 type of prokaryotic cell

What is a eukaryotic cell?

. Genetic material enclosed in nucleus

. Contains a cell membrane and cytoplasm (also mitochondria and ribosomes)

. Plant and animal cells

What are some similarities between eukaryotic and prokaryotic cells?

. Both have cytoplasm, ribosomes, and cell membranes

. Both contain DNA

. Both can have a cell wall

What are some differences between eukaryotic and prokaryotic cells?

. E are larger than P

. P may have pilli/slime capsule/plasmids but E don't

. E have membrane bound organelles but P don't

. E contain DNA in a nucleus but P don't

. E can have cellulose cell walls, P have peptidoglycan cell walls

What is the function of the cell wall?

Strengthens the cell and gives it support.

What is the function of plasmids?

Small circular loops of DNA

Which cells have a nucleus?

Eukaryotic

Which cells have mitochondria?

Eukaryotic

Which cells have ribosomes?

all cells -

eukaryotic = larger ribosomes,

prokaryotic = smaller robosome

Which cells contain chloroplast?

plant cells

Which cells have a permanent vacuole?

plant cells

Which cells have cytoplasm?

all cells

Which cells can have plasmids?

Prokaryotic cells

What is the main difference between prokaryotes and eukaryotes?

size - prokaryotic cells are 1-2 orders of magnitude smaller

Why can't you see a prokaryotic cell with a microscope?

it's too small

What is the function of the nucleus?

. Controls cell activities

. contains genetic information

What are 3 organelles found in plant cells but not in animal cells?

. Cell wall

. Chloroplasts

. Permanent vacuole

What is the function of chloroplasts?

Site of photosynthesis (absorbs light energy to produce glucose/food)

Why are chloroplasts green?

They contain chlorophyll (green pigment that absorbs light energy for photosynthesis)

What is the function of cytoplasm?

Where chemical reactions take place

What is the function of the vacuole?

. Contains cell sap

. provides support

What is the function of the mitochondria?

Site of aerobic respiration which provides energy

What is the function of ribosomes?

Where protein synthesis occurs

How many mm in a cm?

10

How many micrometers are in a millimetre?

1,000

How many nanometres in a micrometre?

1,000

What are orders of magnitude?

. Used to make approximate comparisons between numbers or objects

. Shown using powers of 10

. If a number is 10x bigger than another, it's 1 order of magnitude bigger

How do you decide the order of magnitude of things?

. If bigger number/smaller number = less than 10, they're the same order of magnitude

. If it's around 10, the bigger number is 1 order of magnitude bigger

. Keep going with powers of 10 (so 100 = 2, 1000 = 3 etc.)

What is cell differentiation?

the process through which cells change to become specialised

What happens during cell differentiation?

. the genes for different cell types get turned on/off in the stem cell by chemical signals in/around the cell

. Causes cells to get different sub-cellular structures that help it to carry out a particular function

What is the function of a sperm cell?

Transfer of genetic material to an egg cell for fertilisation

What are some adaptations of a sperm cell?

. Flagellum (tail) enables sperm to swim

. Many mitochondria in mid-piece release energy for movement

. 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

. Haploid nucleus contains genetic material for fertilisation

. Produced in large numbers to increase the chance of fertilisation

What is the function of a nerve cell?

conduction of electrical impulses

What are some adaptations of nerve cells?

. Extended so that nerves can run to and from different parts of the body to the CNS (central nervous system)

. Extensions and branches (dendrites) to communicate with other nerve cells, muscles and glands

. Axon is covered with myelin sheath which insulates the axon and speeds up nerve impulse transmission

What is the function of a muscle cell?

contraction for movement

What are some adaptations of muscle cells?

. Contain protein filaments that slide over each other to cause muscle contraction

. Contain many well-developed mitochondria to release energy for muscle contraction

. In skeletal muscle, the cells merge so the muscle fibres contract in unison

What is the function of a root hair cell?

Absorption of water and mineral ions from soil

What are some adaptations of root hair cells?

. Root 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

. Many mitochondria release energy for active transport of mineral ions

What is the function of xylem vessels?

Transport of water and dissolved mineral ions

What are some adaptations of xylem cells?

. 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

What is the function of phloem cells?

Transport of dissolved sugars and amino acids

What are some adaptations of phloem cells?

. 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 materials

. Companion cells, adjacent to the sieve tubes provide energy required to transport substances in the phloem

How do you calculate the magnification of a microscope?

magnification of eyepiece (usually 10) x magnification of objective lens

How big are animal cells?

0.01mm - 0.05mm

How big are plant cells?

0.01mm - 0.10mm

What is the function of epithelial tissue in the stomach?

covers the outside and inside of the stomach

What is the function of glandular tissue in the stomach?

Produces digestive juices

What is the function of muscular tissue in the stomach?

Allows food to be churned around the stomach

When do most types of animal cell differentiate?

at an early stage

When do most types of plant cell differentiate?

Most retain the ability to differentiate throughout life

What is the formula for magnification?

Magnification = image size / real size

What is a tissue?

a group of cells with a similar structure and function

What are organs?

Aggregations of tissues performing specific functions

What is an organ system?

. A group of organs working together to perform a particular function

. Work together to form organisms

What is the cell wall of plant and algal cells made of?

Cellulose

What is the function of the cell membrane?

Controls what goes in and out of the cell

What is the function of the flagellum?

Used to move around

Which cells have a cell wall?

plant cells (made of cellulose) and bacterial cells (made of peptidoglycan)

Still learning (60)

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Give 2 examples of diffusion in the body

. Oxygen and carbon dioxide in gas exchange

. The waste product urea diffusing from cells into the blood plasma for excretion in the kidney

How does diffusion happen in a single-celled organism?

. Has a relatively 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

How does diffusion happen in multicellular organisms?

. Have mechanisms to increase surface area proportionately, such as additional absorbing areas or adaptations of shape as diffusion across their surface is too slow

. Have transport systems and keep distances to a minimum for diffusion

Give an example of active transport in animals

. Allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration

. Sugar molecules are used for cell respiration

Which factors affect the rate of diffusion?

. Differences in concentrations (concentration gradient)

. Temperature

. Surface area of the membrane

What is the effectiveness of an exchange surface increased by?

. Large surface area

. Thin membrane

. Efficient blood supply (in animals) to provide a short diffusion path

. Being ventilated (in animals for gaseous exchange)

What is osmosis?

The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

What is active transport?

. Moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient)

. Requires energy from respiration

Give an example of active transport in plants

. Allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil

. Plants require ions for healthy growth

What is a solvent?

The substance that something else can dissolve in. (e.g water)

What is a solute?

The substance that dissolves (e.g squash)

What does hypertonic mean?

The concentration of solutes in the solution outside the cell is higher than the internal concentration so the solution is hypertonic to the cell

What does isotonic mean?

The concentration of solutes in the solution outside the cell is the same as the internal concentration so the solution is isotonic to the cell

What does hypotonic mean?

The concentration of solutes in the solution outside the cell is lower than the internal concentration so the solution is hypotonic to the cell

What happens to hypertonic animal cells?

If the water conc outside a cell falls, water will move out of the cell, by osmosis, down a conc gradient, through a partially permeable membrane, causing it to shrivel up.

What happens to isotonic animal cells?

Ideal concentration for animal cells to be in.

What is diffusion?

The spreading out of 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

What happens to hypotonic animal cells?

If the water conc outside a cell increases, water will move into the cell, by osmosis, down a conc gradient, through a partially permeable membrane, causing it to become lysed and burst.

What happens to hypertonic plant cells?

The cell becomes plasmolysed: Water moves out of the cell by osmosis, down a conc gradient, through a partially permeable membrane, causing the vacuole and cytoplasm to shrink which makes the cell membrane pull away from the cell wall.

What happens to isotonic plant cells?

They are flaccid: Water moves into and out of the cell by osmosis, down a conc gradient, through a partially permeable membrane, so the cells are no longer firm and swollen.

What happens to hypotonic plant cells?

They become turgid: Water moves into the cells by osmosis, down a conc gradient, through a partially permeable membrane, causing the vacuole to swell which presses the cytoplasm against the cell wall. The cell will not burst because of the cell wall. Fully turgid cells support the stems of non-woody plants.

Why does concentration gradient affect the rate of diffusion?

The greater the difference in concentration, the quicker the rate of diffusion.

Why does temperature affect the rate of diffusion?

The higher the temperature, the more kinetic energy the particles will have, so they will move and mix more quickly.

Why does the surface area of the cell membrane separating the different regions affect the rate of diffusion?

The greater the surface area, the faster the rate of diffusion.

How do you work out the surface area: volume ratio of a cube?

Surface area = length x length x 6

Volume = length x length x length

Simplify the ratio.

If one object has a higher surface area to volume ratio than another is it bigger or smaller?

Smaller (more surface area for each cm cubed of volume)

Why might organisms reduce their surface area? Give an example.

Organisms living in harsh environmental conditions may reduce their surface area, e.g cacti, to reduce loss of water.

How do you measure the rate of water uptake in an hour?

Water uptake in 1 hour = change in mass x (60 mins / period of time in mins)

How do you measure percentage change in mass?

(mass at the end - mass at the start/mass at the start) x 100