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Question 1

Labelled Animal Cell diagram

Answer 1

insert pic

Question 2

Labelled Plant cell diagram

Answer 2

insert pic

Question 3

what’s the difference between Algal Cells and Plant cells

Answer 3

They both carry out photosynthesis, however they can be unicellular and multicellular. they contain the same organelles, however the chloroplasts in many algal cells are different shapes and sizes to plant chloroplasts.

Question 4

what’s the difference between Fungal Cells and Plant cells

Answer 4

Fungal cells can also be multicellular or unicellular, and they are very similar to plant cells, except their cell walls are made of CHITIN, not cellulose. Also, they don’t have chloroplasts as they don’t photosynthesise

Question 5

Cell surface membrane Organelle

Answer 5

Regulates movement of substances into and out of the cell. It has receptor molecules on it, which allow responses to chemicals, like hormones

Question 6

Nucleus Organelle

Answer 6

Contains Chromosomes, and controls the cells activities (Transcription) DNA also contains instructions for making proteins. The nuclear pores allow substances (mRNA) to move out of the nucleus and into the cytoplasm.

Question 7

Nucleolus Organelle

Answer 7

Makes Ribosomes

Question 8

Mitochondrion Organelle

Answer 8

Have a double membrane, the inner forms a structure called Cristae. Inside is the matrix where enzymes are involved in respiration. It is the site of aerobic respiration, to produce ATP - a common energy source in the cell.

Question 9

Chloroplast Organelle (Draw if can)

Answer 9

A small, flattened structure found in plant and Algal cells. They obtain Thylakoids, stacked into grand, connected by lamella. This is where photosynthesis takes place.

Question 10

Goligi Apparatus Organelle

Answer 10

A group of fluid-filled membrane bound flattened sacs. Vesicles are often seen at the edges of these sacs. It processes/Modifies (by adding carbohydrates to form glycoprotein/glycolipids) and packages new lipids and proteins. It also makes Lysosomes

Question 11

Golgi Vesicle Organelle

Answer 11

A small, fluid filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus. It stores lipids and proteins made by the Golgi apparatus and transports them out of the cell

Question 12

Lysosome Organelle

Answer 12

A round Organelle surrounded by a membrane with no clear internal structure. it contains digestive enzymes (Lysozyme’s) which are used to digest invading cells or to break down worn out components of the cell

Question 13

Ribosomes

Answer 13

A very small Organelle that floats free in the cytoplasm or its attached to the RER. it is made up of proteins and RNA. It is the site of protein synthesis

Question 14

Rough Endoplasmic Reticulum (RER) Organelle

Answer 14

A system of membranes closing fluid-filled space, covered in ribosomes. It folds and processes proteins that have been made by Ribosomes

Question 15

Smooth Endoplasmic Reticulum (SER) Organelle

Answer 15

Similar to RER but with no ribosomes, it synthesises and processes lipids.

Question 16

Cell wall

Answer 16

A rigid structure that surrounds cells in plants, algae and fungi. It supports the cells and prevents them from changing shape.

Question 17

Cell Vacuole Organelle

Answer 17

A membrane-bound Organelle found in the cytoplasm. it contains cell sap - a weak solution of sugar and salts. the surrounding membrane is called the TONOPLAST. It helps maintain pressure inside the cell and keeps them rigid, it stops them filtering and isolates unwanted chemicals inside the cell.

Question 18

Cell organisation

Answer 18

• Cells group together to form a tissue.
• A group os tissues work together to form organs.
• Organs work together to form an organ system

Question 19

What are Prokaryotes?

Answer 19

Single-celled organisms, which are smaller than eukaryotic cells, with no membrane bound organelles, like a nucleus, in their cytoplasm.

Question 20

Prokaryotic Cell Replication - Binary Fission

Answer 20

• The Circular DNA and plasmids replicate - circular DNA replicates once, but plasmids can be replicated many times
• The cell gets bigger and the DNA loops move to opposite ‘poles’
• The cytoplasm begins to split and a new cell wall begins to form
• The cytoplasm divides and two daughter cells are produced.

Question 21

What are viruses?

Answer 21

Viruses are ‘acellular’ - they’re not cells. They are just nucleic acids surrounded by protein. They invade and reproduce inside host cells of other organisms.

Question 22

Virus Structure

Answer 22

There is no Cell-surface membrane, no cytoplasm, and no ribosomes. They have a protein coat, called a capsid, with attachment proteins sticking out from them to help viruses cling to host cells. They are much smaller than bacteria cells. Some, For Example HIV, have lipid envelopes

Question 23

Virus Replication

Answer 23

Because they’re not alive, they don’t undergo cell division. Instead, they cling onto a host cell by their attachment proteins and inject their DNA or RNA into the host cell. They then uses the cells ‘machinery’ to replicate the virus. Some cells replicate the virus particles so much they burst

Question 24

What is Magnification?

Answer 24

How much bigger the image is than the specimen

Question 25

How is Magnification calculated (The formula)

Answer 25

Mag = Size of Image / Size of real Object IMO (top, left, right)

Question 26

Converting units

Answer 26

mm to micro (x1000) micro to mm (/ 1000) micro to nm (x1000) nm to micro (/1000)

Question 27

What is Resolution?

Answer 27

How detailed the image is - how well the microscope can distinguish between two points that are close together. if the microscope cannot distinguish between the objects, increasing the magnification won't help

Question 28

Types of Microscopes

Answer 28

``` Optical (Light) Scanning Electron (SEM) Transmission Election (TEM) ```

Question 29

Optical microscopes

Answer 29

Use light to form an image. Max. Resolution of about 0.2 micrometers. Therefore organelles such as Ribosomes, Lysosomes snd ER can't be seen. Mitochondria can be seen however not in perfect detail. The Maximum magnification is x1500

Question 30

Electron Microscopes

Answer 30

Use Electrons to form an image. Higher resolution (around 0.0002 micrometers) than Optical microscopes, so more detailed image seen. Maximum magnification is x 1500000. They are black and white images, but coloured by a computer

Question 31

Transmission Electron Microscope (TEM)

Answer 31

Focus a beam of electrons through a specimen. Denser parts absorb more e- so they appear darker on the image. They Give high resolution, but the specimen must be dead, very thin, stained and in a vacuum with no artefacts to disrupt the image - a complex staining and preparation process.

Question 32

Scanning Electron Microscope (SER)

Answer 32

Scan a beam of electrons across the specimen. This knocks off electrons from the specimen, which are gathered by a Cathode rat tube to form an image. By the e- bouncing off, a 3D image is produced. They give lower resolution images than TEM's; however they can be used on thick specimens, but, the specimens need to be dead

Question 33

Plasma Membranes

Answer 33

All membranes around and within cells have the same basic structure, known as plasma membranes. The cell surface membrane is the plasma membrane which surrounds the cell. The Membranes are composed of phospholipids, proteins and carbohydrates, arranged in a fluid mosaic structure.

Question 34

Phospholipid Bilayer

Answer 34

Phospholipid molecules form a bilayer that gives the membrane its basic structure, with its hydrophobic tails and hydrophilic heads that prevent the passage of ions and water-soluble molecules, allow lipid-soluble substances to enter and leave the cell as well as making the membrane more flexible

Question 35

Proteins in the plasma membrane

Answer 35

They are embedded randomly in the phospholipid bilayer, with Extrinsic and Intrinsic proteins. - Extrinsic- on the surface or only partly embedded, that give mechanical support and when in conjunction with carbohydrates, they act as receptors to molecules such as hormones - Intrinsic - span the bilayer, some acting as carriers/channels to transport water-soluble material, whilst some allow active transport of ions across the membrane. Others are enzymes

Question 36

Carbohydrates in the plasma membrane

Answer 36

They are attached to lipids and proteins on the outside of the membrane forming glycolipids and Glycoproteins, which are important for cell recognition

Question 37

Fluid Mosaic Model described

Answer 37

- Fluid because the individual phospholipids can move in relation to one another, being flexible, allowing changes in shape and can be self sealing. - Mosaic because the proteins are embedded the same way tiles are in a mosaic.

Question 38

Specialised cells

Answer 38

A cells structure helps carry out its function, for example: - Root Hair Cell - absorbing water and mineral ions, so they have an increase surface area for uptake, many mitochondria to provide ATP for Active Transport and have thin cell walls for a short diffusion distance - Palisade cells needed for photosynthesis have large numbers of chloroplasts and are long and thin to absorb more sunlight

Question 39

Prokaryotic structure

Answer 39

They have cell walls (protection and maintaining shape, made from murein - a glycoprotein) - Cell surface membrane (controls entry and exit of substances) - Smaller ribosomes (70s) - No nucleus, just circular DNA (Not associated with proteins) which floats freely in the cytoplasm, as well as plasmids, small loops of DNA that aren't part of the main circular DNA, which contain genes for things like antibiotic resistance, that can be passed down generations. - Some have flagellum (for movement) - Slime capsules (for protection against attaching cells) They aerobically respire in a region of the cell surface membrane, as they don't have mitochondria

Question 40

Preparing Microscope Slides for Optical Microscopes

Answer 40

- Pipette a small drop of water onto the centre of the slide. - Use tweezers to place a thin section of the specimen on top of the water droplet. - Add a drop of dye to stain the specimen to highlight objects in a cell - Finally add the cover slip by carefully tilting and lowering it so it covers the specimen - try not to get any air bubbles in as they will obstruct the view of the specimen.

Question 41

What are Microscope Artefacts

Answer 41

Artefacts are things that can be seen down the microscope that aren't part of the specimen you're wanting to look at (Dust, air bubbles, fingerprints etc.) Artefacts are usually made during the preparation of the specimen and are common in Electron micrographs because there is a lot of preparation needed.

Question 42

What are the steps in Cell fractionation?

Answer 42

Homogenisation, Filtration and Ultracentrifugation

Question 43

Cell Fractionation - Homogenisation

Answer 43

Plasma membranes of cells are broken down to release organelles. This can be done by a microblender - which forces the cell surface membrane open, or by grinding up the cells. This should be down in COLD, ISOTONIC BUFFER SOLUTION! - Cold to inactivate the enzymes - Isotonic so the water potential is maintained so the organelles don't burst/shrivel up through osmosis - Buffer to keep the pH constant so enzymes and proteins are not damaged (Tertiary Structure not altered)

Question 44

Cell Fractionation - Filtration

Answer 44

The Homogenised cell solution is filtered through a gauze to separate large cell debris or tissue debris, like connective tissue, from the organelles. The organelles are much smaller so they pass through.

Question 45

Cell Fractionation - Ultracentrifugation

Answer 45

- The Filtrate is centrifuged at low speed so the densest organelles (Like nuclei) are separated first into a pellet (Dense material at the bottom of the test tube) The rest of the organelles stay suspended in the fluid - known as the supernatant - The Supernatant is removed and centrifuged again at a higher speed for a longer time. This process is repeated for higher and longer times until the organelles are separated according to their density Faster and longer centrifugation forces least dense organelles to be the pellet as it takes more force to pull the less dense organelles to the bottom

Question 46

Order of organelles which are separated out according to their density

Answer 46

``` Nuclei Chloroplasts - if plant cell Mitochondria Lysosomes Ribosomes ```

Question 47

The Cell cycle

Answer 47

- Consists of a period of the cells growing and new organelles and proteins being made = G1 - Then interphase, where the cell replicates its DNA, ready to divide = S (Synthesis) phase - Then a Gap Phase (G2) where the cell keeps growing and the proteins needed for cell division are made, ready for Mitosis to occur

Question 48

What happens during Interphase?

Answer 48

The cell carries out normal functions, but also prepares for division, as the DNA is unravelled and replicated, to double the genetic content. Organelles are also replicated and ATP content us increased.

Question 49

Why is Mitosis needed?

Answer 49

Mitosis is needed for multicellular organisms growth and repair of damaged tissues.

Question 50

The structure of chromosomes

Answer 50

The chromosomes are made of two strands, called chromatids, joined in the middle by a centromere. The two strands on the same chromosome are called sister chromatids. There are two strands as each chromosome has already made an identical copy of itself during interphase. Once mitosis is over, the chromatids end up as one-strand chromosomes (One chromatid, with a centromere) in the new daughter cells.

Question 51

Prophase (Pro = before)

Answer 51

The chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to the end of the cell, forming a network of protein called the spindle. The nuclear envelope begins to break down

Question 52

Metaphase (M= Middle)

Answer 52

The Chromosomes line up in the centre of the cell. The nuclear envelope has completely gone and the spindles attach to the centromeres

Question 53

Anaphase (A = Away)

Answer 53

The Spindle fibres contract, splitting the centromeres, pulling the chromosomes (Identical chromatids) apart

Question 54

Telophase

Answer 54

The chromatids reach the opposite poles on the spindle, they uncoils and become long and thin again. They are now called chromosomes again. The nuclear envelope forms around each group of chromosomes. The spindle fibres disappear/disintegrate

Question 55

Cytokinesis

Answer 55

The cytoplasm splits, splitting the two nuclei apart, producing two genetically identical daughter cells. Mitosis is finished and the daughter cells starts the interphase part of the cell cycle for the next round of mitosis

Question 56

Cancer and its treatment

Answer 56

Cancer is caused by a mutation of the genes that regulates mitosis and the cell cycle, leading to uncontrolled cell division, and eventually a tumour is formed. The treatment of cancer often involves disrupting the cell cycle so the cell division/cancer is prevented. - Some chemical drugs prevent the synthesis of enzymes needed for DNA replication during Interphase. If they aren't produced, it stops the cell from entering S phase - forcing the cell to kill itself - Radiation can damage DNA at several points, and if the cell detects this, it will kill itself - Inhibiting Metaphase by interfering with spindle formation

Question 57

Mitotic Index

Answer 57

Number of cells with visible chromosomes / Total number of cells

Question 58

Preparing a Root tip cell squash

Answer 58

- Add some 1M Hydrochloric acid to a boiling tube, and place it in a water bath at 60 degrees - Using a scalpel, cut 1cm of the tip from a growing root - Put the root tip into the boiling tube of acid and incubate for 5 mins. After this, remove the tip using tweezers and pipette water over the tip to wash it. Leave to dry. - Place the tip on a microscope slide and cut 2mm from the very tip of it. Break the tip open and spread the cells out thinly using a mounted needle, Then add a few drops of stain and leave for a few mins. - Place a cover slip over the cells and put a piece of folded filter paper on top. Squash the coverslip down to make the tissue thinner, allowing light to pass through it - don't smear the coverslip though, as this will damage the chromosomes

Question 59

Using an Optical microscope

Answer 59

- Start by clipping the slide onto the stage. - Select the lowest-powered Objective lens. - Use the Coarse adjustment knob to bring the stage up to just below the objective lens - Look down the eyepiece (which contains the ocular lens). -- Use the Coarse adjustment knob to try and move the stage downwards, to focus the image - Adjust the focus with the fine adjustment knob until a clear image is seen - If a greater magnification is needed, swap to a higher-powered objective lens and refocus

Question 60

Calculating the actual size of cells

Answer 60

An Eyepiece graticule is fitted onto the eyepiece. It is like a transparent ruler, but with no units. The Stage micrometer is placed on the stage - It is a microscope slide with an accurate scale (with units) and can be used to work out the value of each division on the eyepiece graticule at a particular magnification. This means if the stage micrometer is removed and a specimen is placed on the stage, using the eyepiece graticule (now with known units for that particular magnification) you can measure the size of the cells