Biology GCSE year 9 - Cell structure and Principles of Organisation

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 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 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 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 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

What is the function of the cell wall?

Strengthens the cell and gives it support.

What is the function of the cell membrane?

Controls what goes in and out of the cell

What is the function of plasmids?

Small circular loops of DNA

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)

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 contain flagella?

animal and prokaryotic/bacterial 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 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 are some adaptations of a sperm cell?

. Tail enables sperm to swim

. Many mitochondria release energy for movement

. Part of the tip of the head, called the acrosome, contains enzymes so the sperm can penetrate the egg

. Haploid nucleus contains genetic material for fertilisation

. Produced in large numbers to increase the chance of fertilisation

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 to communicate to other nerve cells, muscles and glands

. Have myelin sheath which insulates cell and speeds up nerve impulse

What are some adaptations of muscle cells?

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

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

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

What are some adaptations of root hair cells?

. Large surface area to provide contact with soil water

. Thin walls so as not to restrict the movement of water

What are some adaptations of xylem cells?

. no top and bottom walls between xylem vessels so there is a continuous column of water running through them

. Walls become thickened and woody to support the plant

What are some adaptations of phloem cells?

. Dissolved sugar and amino acids can be transported up and down the stem

. 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 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

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