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Biology 2.4

Cellular Life Processes

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Bio 2.4 Cell BitsBiological ideas, as they relate to each of the life processes at the cellular level, are

selected from:

• reasons for similarities and differences between cells such as cell size and shape,

•type and number of organelles present.

Limited to plant and animal cells

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Cell wallA rigid structure made of cellulose

surrounding plant cells. This provides shape and strength.

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Cell membranePlant cell

Animal cell

A layer that encloses the cell contents.

Controls what enters and exits the cell.

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Cell membraneIs made of two

layers of lipid (fat) molecules with proteins for cell identification, active transport and communication.

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Cytoplasmfills the interior of the cell. It

consists of a liquid (called the cytosol that contains water, proteins and dissolved ions) and cell organelles.

It is used to transport substances throughout the cell and create internal pressure and is where most chemical reactions occur.

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NucleusContains the

genetic material which controls the cells activities.

nucleoplasm

Nucleolus: round structure inside nucleus: produces the ribosomal RNA

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Nuclear membrane

Separates the contents of the nucleus from the cytoplasm. Perforated by pores and continuous with ER.

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ChromosomesStructures

made of DNA and protein containing genes for protein synthesis.

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MitochondriaOrganelles

within the cytoplasm for cell respiration - where food molecules are broken down to release energy.

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Chloroplast

Organelles in plant cells containing chlorophyll for photosynthesis.

Starch granule

StromaGrana

Membrane

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Centriole

Centrioles

Mostly present in animal cells for cell division.

Produces spindle fibres for separating chromosomes.

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Vacuole Liquid-filled

organelle in cytoplasm for creating pressure and storing water and dissolved substances.

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RibosomeOrganelle found

free in the cytoplasm or attached to ER.

Used for protein synthesis.

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Endoplasmic reticulumIs a system of membranes and

connecting tubes that provide a surface for chemical reactions and a pathway for moving material within the cell.

Rough ER

Smooth ER

RER vs SER• RER

– Produces proteins (both secreted & part of cell membrane)

• SER– Produces lipids, steroids– Metabolises carbohydrates– Regulates calcium levels

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LysosomeMembrane-bound sac containing

digestive enzymes.

Breaks down food and worn out cell parts.

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Golgi bodya series of membrane-bound sacs

for producing and releasing secretions.

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Plant Cellshave:

- rigid cell walls giving the plant cells a geometric shape;

- chloroplasts (usually);

- starch granules

- large central vacuole

They are usually larger than animal cells.

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Become specialised to perform support, absorption of water, conduct liquids, allow gases in and out, manufacture food, form protective surfaces and reproduction.

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Animal Cells

don’t have a cell wall and have centrioles and an irregular shape. Become specialised to perform specific tasks. Humans have over 200 different kinds of cells.

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Similarities and differences

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Cell size

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Cell size is limited by the rate at which essential nutrients and oxygen can diffuse into a cell and waste products can be removed.

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Cell shapeis determined by the role of the

cell.Nerve cells are long and thin to

conduct neural messages around the body.

Intestinal cells have frilly edges to increase surface area for rapid diffusion.

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Egg cells are spherical and large to contain organelles and nutrients for the zygote.

Sperm cells have a long flagellum and many mitochondria for fast movement.

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RBC’s are disc-shaped with rounded edges for easy passage through blood vessels.

Many cells are flat to increase the surface area, reduce travelling distance and increase diffusion rates

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Relative numbers of organelles present

Secretory cells (e.g. glands) have large numbers of golgi bodies.

Highly active cells (e.g. muscle) have larger numbers of mitochondria.

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Leaf cells contain large numbers of chloroplasts.

Root cells have a large surface area for efficient water absorption.