Year 11 Human Biology - Cells

Three main points of cell theory

1. all organisms are made of cells
2. cells are the basic units of life
3. cells arise from pre-exisitng cells

what does cell structure and activity allow

it allows the human body to function and have structure

what are the main cell components

membrane, cytoplasm, organelles, cytosol, cytoskeleton and inclusions

cytoplasm structure

semi fluid matrix, jelly like substance which includes organelles and cytosol

how much of cytosol is water

75 - 90%

what is cytosol

liquid in cell which has dissolved substances, is a place for metabolic reactions and assists is osmotic pressure and flow of chemical around the cell

what are organelles

membranous structures (usually) with specialised functions

nucleus structure

largest organelle, surrounded by double membrane with pores and filled with nuceloplasm

what is inside the nucleus

DNA and nucleolus

what does DNA do

codes for protein synthesis which gives cells their functions and structure

what does the nucleolus do

helps make proteins by assembling ribosomes

ribosomes structure

non membranous, small spheres

what do ribosomes do

construct amino acid chains

where are ribosomes found

in cytosol or on rough ER

endoplasmic reticulum structure

parallel membrane network spanning from cell membrane to nuclear membrane

endoplasmic reticulum function

stores, synthesises and transports aswell as being a surface for chemical reactions

rough ER function

holds ribosomes, protein transport and membrane lipid forming

smooth ER function

steroid synthesis and lipid metabolism

golgi body structure

flat stacked membranes near nucleus with vesicles forming at the edges

golgi body function

modify and package proteins for secretion

lysosomes strucutre

small membrnaous spheres (made by golgi) containing digestive enzymes

lysosome fucntion

break down big molecules, particles, dead organelles and the cell when it dies

mitochondria structure

double membranes spherical sausages. smooth outer membrane surround mitochondria and highly convoluted inner membrane (cristae)

mitochondria function

release energy from large molecules and store it as ATP, conducts aerboic stage of cellular respiration

why does the cristae have a large surface area

so that more reactions can take place on it

cilia and flagella structure

cytoplasmic projections on cell surface, cilia are short and exist in numbers, flagella are long and exist usually alone

cilia and flagella function

beat rythmically to move whole cell or move substances across cell surface

centrioles structure

rings of microtubules at 90\* to eachother

centrioles fucntion

form spindles during cell division

cytoskeleton structure

protein fibre framework made of microtubules (hollow rods) and microfilaments (solid rods)

cytoskeleton function

give cell shape, help cell move, support organelles and intracellular transport

inclusions

chemical substances which aren’t part of the cell structure

inclusions example

melanin and haemoglobin