2 cell structure, methods of studying cells qs

Structure of eukaryotic cells, structure of prokaryotic cells and viruses, microscopy

How big is the nucleus?

10-20 micrometres

What are the 5 parts of the nucleus?

Nuclear envelope, nuclear pores, nucleoplasm, chromosomes, nucleolus

What is the nuclear envelope? (3)

Double membrane surrounding nucleus, outer membrane continuous with ER, often ribosomes on surface

Function of nuclear envelope?

Entry + exit of materials

How big are nuclear pores + how many are there?

40-100 nanometres, 3000 pores

What is nucleoplasm?

Granular, jelly-like material

What are chromosomes?

Protein-bound, linear DNA

What does the nucleolus do? (2)

Manufactures ribosomal RNA, assembles ribosomes

What is the overall functions of a nucleus? (3)

Produces mRNA and tRNA (hence protein synthesis), retain genetic material of cell as DNA and chromosomes, manufactures ribosomal RNA and ribosomes

How big are mitochondria and what shape?

1-10 micrometres, rod-shaped

What is the double membrane in a mitochondrion? (2)

Controls entry and exit of material, inner of 2 folds form cristae = increases SA for respiration

What are cristae?

Extensions of inner membrane of a mitochondrion

Function of cristae?

Large SA for attachment of enzymes + other proteins involved in respiration

Function of matrix?

Proteins, lipids, ribosomes + DNA so mitochondria can make some of its own protein

Shape, length and diameter of chloroplasts?

Disc-shaped, 2-10 micrometres long, 1 micrometre diameter

What is a chloroplast envelope?

Double plasma membrane surrounding the organelle

What does the chloroplast envelope do + is it selective?

Controls entry and exit- very selective

What are grana in a chloroplast?

Stacks of up to 100 thylakoids

Function of grana?

Where light absorption takes place in photosynthesis

What shape are thylakoids?

Disc-like

What do thylakoids contain?

Chlorophyll-photosynthetic pigment

What are stroma and what does it contain?

Fluid-filled matrix, other structures e.g starch grains

Function of stroma?

Synthesis of sugars -2nd photosynthesis stage

3 overall functions of chloroplasts?

Grana membranes= large SA for ordered attachment of chlorophyll, electron carriers + enzymes, stroma fluid has all enzymes needed to make sugars, has DNA + ribosomes to quickly and easily manufacture some proteins for photosynthesis

Which ER has ribosomes?

ROUGH endoplasmic reticulum

2 functions of RER?

Provides large SA for synthesis of proteins + glycoproteins, provides pathway for material transport throughout cell (incl proteins)

Function of SER?

Synthesise, store and transport lipids and carbohydrates

Which cells have a extensive ER? (2)

Liver cells, secretory cells, e.g epithelial cells (line intestine)

Give 5 functions of golgi apparatus

Add carbohydrates to proteins to make glycoproteins, produce secretory enzymes, secrete carbohydrates(e.g in cell walls), transport, modify +store lipids, form lysosomes

What cells are golgi apparatus most developed in?

Secretory cells e.g epithelial cells

How big are lysosomes?

Up to 1 micrometre

4 functions of lysosomes?

Hydrolyse material ingested by phagocytic cells, exocytosis, digest worn-out organelles to re-use useful chemicals they’re made from, autolysis

Which 2 types of cells are lysosomes abundant?

Secretory cells, phagocytic cells

Where are 80S ribosomes found?

Eukaryotic cells

Where are 70S ribosomes found?

Prokaryotic cells, mitochondria, chloroplasts

How big are 80S ribosomes?

25 nanometres diameter

Are 70S ribosomes bigger or smaller than 80S?

Smaller

Structure of a ribosome? (2)

2 subunits- 1 large, 1 small, both contain ribosomal RNA + protein

Why are cell walls strong?

Consists of microfibrils of cellulose (a polysaccharide), which are very strong

2 functions of the middle lamella?

Marks boundary between adjacent walls, cements adjacent cell walls together (plant cell)

3 functions of cell wall?

Mechanical strength- prevents cell bursting due to pressure of osmotic water entry, mechanical strength to plant, allows water to pass through (transpiration)

What are algae cell walls made of?

Cellulose, glycoproteins or BOTH

What are fungi cell walls made of?

Chitin (polysaccharide)

What is a tonoplast in a vacuole?

Single membrane surrounding it

What 5 things can vacuoles contain (solution of)?

Mineral salts, amino acids, sugars, wastes, pigments (e.g anthocyanins)

3 functions of a vacuole?

Support herbaceous plants by making cells turgid, sugars + amino acids = temporary food store, pigments can colour petals- attracts pollenating insects

Are prokaryotic or eukaryotic cells larger?

eukaryotic

How big is a bacterial cell?

0.1-10 micrometres

What is the cell wall made of in bacterial cells?

murein

How do some bacteria protect themselves?

Secreting a capsule of malignous slime around the cell wall

In a bacterial cell, what is inside the cell wall?

Cell surface membrane

In a bacterial cell, what is in the cytoplasm?

70s ribosomes

What do bacteria store food reserves as?

Glycogen granules, oil droplets

In a bacterial cell, how is genetic material stored?

Circular strand of dna + plasmids

Bacteria can produce independently. What does this give them?

The ability to gain antibiotic resistance to harmful chemicals e.g antibiotics

What is the cell wall?

Physical barrier that excludes certain substances + protects against mechanical damage + osmotic lysis

Function of a cell capsule?

Protects bacteria from other cells + helps groups of bacteria to stick together

What is the cell-surface membrane?

Acts as a differentially permeable layer, which controls entry + exit of chemicals

What is circular DNA?

possesses genetic information for the replication of bacterial cells

What is a plasmid?

Possesses genes that may aid the survival of bacteria in adverse conditions e.g produces enzymes that break down antibiotics

What are the 3 domains?

Archea, eubacteria, eukaryota

What is archea + how many kindgoms?

Primitive forms of bacteria that can live in extreme conditions (extremophiles), contains 1 kingdom

What is eubacteria, give example +how many kingdoms?

true bacteria, cyanobacteria can photosynthesise, 1 kingdom

What is eukaryota + how many kingdoms, what are they?

organisms that have cells with a membrane bound nucleus, four kingdoms- protists, fungi, animals, plants

How big are viruses compared to a bacterial cell?

1000x smaller

Can viruses reproduce alone, and why?

No- need a host cell

4 steps to reproduce in a virus?

Virus particle attaches to host cell surface, virus enters host cell, virus uses host cells enzymes to produce copies of itself, virus leaves host cell to infect new host cells + continue reproducing

What is a capsid?

A protein structure which contains genetic material (DNA or RNA) of a virus

What is an attachment protein +where is it?

Allows virus to attach to + enter a host cell, lives on surface of virus

What is a lipid envelope + what are they formed from?

some capsules are surrounded by one, formed from the host cell membrane

Viruses are a-cellular- what does this mean?

Not cells

Why are viruses not living?

They can’t reproduce alone

3 Advantages of an electron microscope?

resolution is 0.1m- higher than light, detailed images + organelles e.g ribosomes, 3D images-shows contours (sem)

5 disadvantages of electron microscope?

Expensive, skill + training needed, can’t look at living things, vacuum needed as electron beams are deflected by air molecules, monochrome (unless colouring added)

Why do electron microscopes have better resolution than light microscopes?

Electrons have a much shorter wavelength than light

Why do electron microscopes need a vacuum?

If air is present, electrons would be absorbed by the air, not the sample

What is the radiation source of light microscopes?

Light

What is the wavelength of light microscopes?

400-700 nanometres

What is the lens of light microscopes?

Glass

What is the specimen for light microscopes?

Living or non-living, supported on a glass slide

What is the maximum resolution for light microscopes?

200 nanometres

What is the maximum magnification for light microscopes?

1000x

What stain is used for a light microscope?

Coloured dyes e.g methylene blue

What type of image is produced for a light microscope?

2D image, in colour

What does the T in tem stand for?

Transmission

What is the radiation source for scanning and transmission electron microscopes?

Electrons

What is the wavelength for both scanning and transmission microscopes?

0.005 nanometres

What is the lens for both scanning and transmission electron microscopes?

Electromagnetic

What is the specimen for TEM?

Non-living supported on a small copper grid, in a vacuum

What is the specimen for SEM?

Non-living supported on a metal disc, in a vacuum

What is the maximum resolution for TEM?

1 nanometre

What is the maximum magnification for TEM?

250,000x

What is the stain for TEM?

Impregnated with heavy metals

What is the type of image for TEM?

2D, monochrome

What is the maximum resolution for SEM?

10 nanometres

What is the maximum magnification for SEM?

100,000x

What is the stain for SEM?

Coated with carbon/gold

What is the image for SEM?

3D, monochrome

On 40x, how many divisions on an eyepiece graticule equals to 1mm/1000 micrometres?

40 divisions

On 100x, how many divisions on an eyepiece graticule equals to 1mm/1000 micrometres?

100 divisions