OCR A LEVEL BIOLOGY - Cell Structure

What are cells?

Building blocks of life

What are the components of an animal cell?

• Nucleus

• Nuclear envelope

• Mitochondria

• Plasma membrane

• RER

• SER

• Golgi Apparatus

• Cytoplasm

• Ribosome

• Lysosome

What are 2 main groups that living organisms can be divided into?

• Eukaryotes - mostly multicellular organisms made up of eukaryotic cells, e.g. animals, plants, fungi, protists

• Prokaryotes - single-celled organisms made of prokaryotic cells, e.g. bacteria

Structure + function of the nucleus

Structure

• Nuclear envelope surrounding the nucleus containing pores

• Contains chromatin (DNA + histones) that condense to form chromosomes

• Contains nucleolus

Function

• Site of DNA replication and transcription

• Contains genetic info

• Site of ribosome synthesis

What is the structure + function of the nucleolus?

Structure

• Has proteins + RNA

Function

• Site of RNA production + synthesis of ribosomes

Structure + function of the nuclear envelope

Structure

• Double membrane with nuclear pores

Function

• Allows substances to move between the nucleus + the cytoplasm → e.g. mRNA leave the nucleus, steroid hormones enter

Structure + function of the RER?

Structure

• Network of membrane-bound flattened sacs (cisternae)

• Ribosomes on cisternae

Function

• Synthesises proteins (via ribosomes)

• Folds + processes proteins

• Transports proteins in vesicles to Golgi apparatus

Structure + function of SER

Structure

• Network of flattened membrane-bound sacs (cisternae)

• No ribosomes on surface

Function

• Synthesis + storage of lipids/carbs

• Involved in detoxifying drugs

• Stores calcium ions in some cells

Structure + function of Golgi Apparatus

Structure

• Network of flattened membrane bound sacs (cisternae)

• Vesicles bud off the edges

Functions

• Forms lysosomes

• Modifies, sorts + packages proteins + lipids

• Produces secretory vesicles for transport out of cell

• Adds carbs to proteins to form glycoproteins

Structure + function of ribosomes

Structure

• Free in cytoplasm/attached to RER

• Not surrounded by membrane

• Made of rRNA + proteins

• Small subunit + large subunit

Function

• Site of protein synthesis → involved in process of translation

Structure + function of mitochondria

Structure

• Surrounded by a double membrane

• Inner membrane folds to form cristae → provide large SA for enzyme action

• Inner fluid = matrix

• Contains circular DNA + 70S ribosomes

Function

• Site of aerobic respiration

• Produces ATP via oxidative phosphorylation

• Releases energy for cell activities

Structure + function of lysosome

Structure

• Small spherical vesicles surrounded by a single membrane

• Contains hydrolytic enzymes

Function

• Breaks down waste materials, pathogens + old organelles

• Recycles cell components

Structure + function of chloroplasts

Structure

• Double membrane

• Contains chlorophyll pigments

• Internal stacks of membranes (thylakoids) then stack to form grana

• Inner fluid = stroma (surrounds grana)

• Contains circular DNA + 70S ribosomes

Function

• Site of photosynthesis

• Light-dependent reactions occur at thylakoid membranes

• Light-independent - stroma

• Light → glucose

What is the membrane that surrounds the vacuole in plants cells referred to as?

Tonoplast

Structure + function of vacuole?

Structure + function of vesicle

Structure + function of cillia

Structure

• Short hair-like projections on the cell surface

• Made of microtubules (9+2) arrangement

Function

• Beat in a coordinated wave → moves substances across the cell surface (e.g. mucus moved in trachea to trap dust + bacteria)

Structure + function of cell wall

Structure + function of flagella