Cheatography

# 1. Cell Structure - AS Level Biology 2021 Cheat Sheet by Eldunique

Cell Structure - AS Level Biology 2021

### Magnif­ication Calcul­ations

 I = Image size A = Actual size of image M = Magnif­­ic­ation 1m=1000mm 1mm=1000µm 1µm = 1000nm

### Eyepiece Graticules & Stage Microm­eters

 Number of Microm­­eters ÷ Number of Graticule Division = 1 Graticule Division Graticule Divisions x Magnif­ication Factor = Measur­­ement (µm)

### Magnif­ication

 How many times bigger the image of a specimen observed is in compared to the actual size of the specimen. A light microscope has two types of lens: An eyepiece lens. A series of objective lenses. Total Magnif­ica­tion: Eyepiece Lens Magnif­­ic­ation x Objective Lens Magnif­­ic­ation = Total Magnif­­ic­ation

### Resolution

 The ability to distin­­guish between two separate points. Resolution of a light microscope is limited by the wavelength of light. Electron micros­­copes have a higher resolution and magnif­­ic­ation as electrons have a much smaller wavelength than visible light.

### Electron Microscope VS Light Microscope

 Electron Microscope Light Microscope Large and instal­lations = Can't move. Small and easy to carry. Vacuum Needed. No Vacuum Needed. Compli­cated sample preparation. Easy sample prepar­ation. Over X 500 000 Magnification. Up to X 2000 Magnif­ica­tion. Resolution = 0.5nm Resolution = 200nm Specimens = Dead Specimens = Dead/L­iving

### Photom­icr­ographs

 Images obtained from a light micros­cope, these are used for specimens above 200 nm.

### Electron microg­raphs

 Images obtained from electron micros­copes, both scanning and transm­ission, these are used for specimens above 0.5 nm

### Cell Surface Membrane

 Controls exchange of material between the internal and external cell enviro­nment.

### Cell Wall (Plant Only)

 Used to enclos­e/p­rot­ect­/su­pport. Fully permeable = Lets anything through.

### Nucleus

 Gives instru­ction. Contains the cells DNA Contains nuclear envelope = separates nucleus from cytoplasm.

### Mitoch­ondrion

 Powerhouse of the cell. Site of aerobic respir­ation. Produces ATP. Has 70s Ribosomes & Circular DNA.

### Chloro­plast (Plant Only)

 Contain DNA. Can't live on their own. Where photos­ynt­hesis happens.

### Ribosome

 Built of 2 subunits. Do ont have a membrane. Ones found in cytosol = always attached to ER Ones found freely in cytoplasm or as part of the Rough endopl­asmic reticulum in Eukaryotic cells. Is a complex of ribosomal RNA & Proteins. Site of transl­ation.

### 80s Ribosomes

 60s & 40s subunits. Found in Eukaryotic Cells In cytoplasm

### 70s Ribosomes

 50s & 30s subunits. Ribosomes in Prokar­yotes. In Mitoch­ondria & Chloro­plast.

### Endopl­asmic Reticulum

 Has 2 Types Rough endopl­asmic reticulum (RER): Round sacs transport substa­nces. Processes proteins. Smooth endopl­asmic reticulum (ER): Involved in the produc­tio­n/p­roc­ess­ing­/st­orage of lipids­/ca­rbo­hyd­rat­es/­ste­roids. Site where substances needed by the cell are made. Has no ribosomes.

### Golgi body (Golgi appara­tus­/co­mplex)

 Synthe­sises specific functions: Hormones & enzymes. Modifies proteins and packages them into vesicles or lysosomes.

### Tonoplast (Plant Only)

 Controls exchange. Around vacuole in plants.

### Large Permanent Vacuole (Plant Only)

 Regulates osmotic proper­ties. Used to keep plants stiff. Where pigment (petal colour) is found.

### Lysosomes

 Cleaners of the cell. Single membrane. Contains concen­trated mixtures of digestive enzymes: Hydrolytic enzymes Attached to the vacuole of cells. Discha­rge­d/r­emoved from cell.

### Centrolie

 Involved in making the cilia. Not found in flowering plants & fungi.

### Microt­ubules

 Involved in movement of components within the cell. Guid & direct organe­lles.

### Plasmo­desmata

 Important for transp­ort­/co­mmu­nic­ati­on/­sig­nalling between cells. Controls movement & created paths between cells.

### The vital role of ATP

 Adenosine Tripho­sphate is a nucleo­tide. Provides energy to cells. It is produces in mitoch­ondria & chloro­plasts. This energyis required: In anabolic reactions. Active Transport. In animals. ATP from respir­ation = used to transfer energy in all energy­-re­quiring prosesses in the cells.

### Structural features of Typical Prokar­yotic Cells

 Bacteria are a type of prokar­yote. Unicel­lular 100s/1000s of times smaller than eukaryotic cells. Genetic material is not packaged within a membra­ne-­bound nucleus and is usually circular.

### Viruses

 Non-ce­llular struct­ures. They have: A protein coat called a ‘capsid’ A nucleic acid core (their genomes are either DNA or RNA, can be single or double­-st­randed)