B1- cell level systems

what is the light microscope used for?

-viewing whole cells and large subcellular structures

explain process of using light microscope

• specimen placed on glass slide, covered with a cover slip and placed on the stage, eye piece and objective lens magnify the object and lamp illuminates from underneath

what is the light microscope used for?

-viewing whole cells and large subcellular structures

explain process of using light microscope

• specimen placed on glass slide, covered with a cover slip and placed on the stage, eye piece and objective lens magnify the object and lamp illuminates from underneath

what is the electron microscope used for?

• viewing cells in detail, use a beam of electrons.

explain how you use an electron microscope

• specimen is placed in a vacuum chamber/ electromagnets are used instead of lenses, picture is projected onto a TV screen

what is a stain?

• can be used to colour cells to make them easier to see.

what is resolution?

• ability to distinguish 2 or more objects

what is the equation for magnification?

magnification= size of image/ actual size

what are the subcellular structures found in animal cells?

nucleus, ribosomes, cytoplasm, cell membrane, mitochondria

what are the subcellular structures found in plants?

nucleus, cytoplasm, cell membrane, cell wall, ribosomes, mitochondria, vacuole, chloroplasts

nucleus?

controls cell and contains genetic material in form of chromosomes

cytoplasm?

most chemical reactions take place

cell membrane?

barrier that controls passage of substances going in and out of cells, contains receptor molecules

mitochondria?

contains enzymes for respiration and is the site of respiration

ribosomes?

make proteins for cell using protein synthesis

cell wall?

made from cellulose and for structural support

vacuole?

contains cell sap, provides structure

chloroplasts?

contain chlorophyll for photosynthesis

what is a prokaryotic cell?

• cell without a nucleus contains a loop of DNA instead (plasmid)

what other structures does a prokaryotic cell contain?

• flagellum- for movement

• ribosomes

• cell membrane + wall (some)

• cytoplasm

what is a eukaryotic cell?

• contain a nucleus eg. animal and plant cells

what is DNA?

• DNA is a polymer made up of repeating units called nucleotides in two strands from nucleic acid that join up to form a double helix structure.

what is the structure of a nucleotide?

what is an enzyme?

• it is a biological catalyst that speeds up chemical reactions

• it’s made from proteins and amino acids which can be folded for the substrate to fit into

what is the active site?

• part of enzyme where only a substrate with specific shape can fit into

what is the lock and key hypothesis?

• substrate joins onto active site of enzyme

• substrate fits into active site

• substrate is broken down into products and enzyme can be reused

what do high temperatures cause?

• increases activity of enzyme

• it will work best once it reaches the optimum temp- usually at 37 degrees

• if it gets any hotter, the active site will denature (change shape) and substrate can’t be catalysed

how does the pH affect enzymes?

• if it changes away from the optimum, it will cause the enzyme to denature

what does amylase do?

breaks down starch into maltose

what does protease do?

breaks down proteins into amino acids

what does lipase do?

turns lipids (fats) into glycerol and fatty acids

what does carbohydrase do?

turn carbohydrates into glucose

what is aerobic respiration?

• respiration containing oxygen

• an exothermic reaction, happens in all plants and animals, mostly in mitochondria

• glucose + oxygen = carbon dioxide +water

what is anaerobic respiration?

• respiration without oxygen, only happens in emergencies

• glucose = lactic acid

how does anaerobic respiration happen?

when your exercising and your body can’t supply enough oxygen to your muscles, so you start anaerobic respiration as there is an oxygen debt so it must be paid back to remove lactic acid in cells- causing heavy breathing

anaerobic respiration in plants

• glucose = ethanol + carbon dioxide

• happens in yeast cells called fermentation

• eg. used for bread

what is photosynthesis?

• coverts light energy into chemical energy and creates food for a plant

• endothermic reaction

where does photosynthesis occur?

in chloroplasts in cells as it contains chlorophyll which attracts sunlight

equation for photosynthesis?

carbon dioxide + water = oxygen + glucose

factors that affect photosynthesis?

• temperature- higher temperature (30 degrees) speeds up photosynthesis, if it’s too high it can damage enzymes

• light intensity- raised, increases photosynthesis

• carbon dioxide- increased rate increases photosynthesis

experiment for photosynthesis

test for starch?

• add iodine solution- brown colour to blue/black

test for carbs?

• add Benedict’s solution, heat sample, will go from blue to orange/red

test for proteins?

• add Biuret solution- light blue to pink/purple

test for lipids/fats?

• add ethanol and water, shake sample, turns cloudy from clear solution