Biology: Topic 4 - cells

Standard unit of measurement for most cells?

micrometre

Micrometre symbol?

μm

How many micrometres in 1 millimetre?

1000μm in every mm

How many nanometres in a micrometre?

1000nm in ever μm

millimetre size in metres?

10⁻³m

micrometre size in metres?

10⁻⁶m

nanometre size in metres?

10⁻⁹m

Difference between electron and light microscope?

Electrons use electrons rather than light to produce images

Is resolution or magnification of a microscope more important?

Resolution

What is magnification?

Enlarging an image

What is resolution?

The ability to see two adjacent points as distinct entities following magnification

Advantages of light microscope?(4)

> can magnify up to x1500

> can see individual cells and some macrostructure

> live, coloured specimens can be viewed

> cheap + portable

Disadvantage of LM?

limited resolution

Advantages of electron microscope?(3)

> can magnify by x500,000

> can view ultrastructure (organelles)

> greater resolving power

Disadvantage of EM?(3)

> expensive + not portable

> only dead, thin specimens can be viewed

> preparation of specimens is complex and can introduce artefacts

Two types of electron microscopes?

> Transmission electron microscope(TEM)

> Scanning electron microscope(SEM)

Transmission electron microscope?

> passes electrons through a very thin specimen

> produces black and white image w/ very high resolution and mag

Scanning electron microscope?

> Electrons reflect off the surface of the image

> Resolution and mag not high

> useful for 3D coloured images of surface structures

Ultrastructure?

the detail of a cell when viewed through an electron microscope

Eukaryotic cells?

Cells which contain a membrane bound nucleus and membrane bound organelles

Where are Eukaryotic cells found?

plants, animals and fungi

Protoplasm?

Living contents of a cell surrounded by a plasma membrane

Animal cell diagram?

see page 10/ipad

What is the largest organelle?

nucleus

Function of nucleus?

controls the cell as it contains DNA which synthesises proteins

Components of the nucleus?

> Nuclear pore

> Nuclear membrane/envelope

> Ribosome

> Rough endoplasmic reticulum

> Euchromatin

> Heterochromatin

> nucleolus

How is DNA arranged in the nucleus?

chromosomes

Function of nuclear pore?

allows molecules in and out of the nucleus -> mRNA leaves through there

Structure of nuclear membrane/envelope?

Has a double membrane

What is encrusted on the outer membrane of the nuclear envelope

ribosomes

What are histones?

proteins which are found within the nucleus that package DNA

What is chromatin?

the complex DNA and proteins within the nucleus that forms chromosomes

Two types of chromatin?

Euchromatin and Heterochromatin

What is euchromatin?

consists of DNA that is active, meaning it will become a protein

Appearance of euchromatin in microscope?

Light

What is heterochromatin?

consists of mostly inactive DNA, meaning it will not become a protein

Appearance of heterochromatin in microscope?

darker

What is the nucleolus' function?

contains the DNA that codes for rRNA -> makes ribosomes

Appearance of nucleolus under microscope?

Darkest

What is the endoplasmic reticulum?

A series of tubes and sacs that run through the cytoplasm that modify and transport proteins

What are the sacs called that enclose the 3D membrane?

cisternae

What are ribosomes? (appearance and location)

Small, stud-like organelle attached to the outside of the reticulum

Where are proteins created?

Ribosomes

What reticulum do ribosomes attach to the outside of?

The rough endoplasmic reticulum

ER with no ribosomes on the outside?

Smooth endoplasmic reticulum

Function of rough endoplasmic reticulum?

> RER provides scaffolding for protein synthesis and the ER then allows for distribution of these proteins

What structure of the protein does the RER create?

secondary and tertiary structures of proteins

Where is RER often located?

Joined to the nuclear envelope

Why is the RER joined to the nuclear envelope?

RNA is carried out of the nucleus to the ribosomes

Role of smooth endoplasmic reticulum?

metabolises lipids and synthesises cholestrol

What are ribosomes?

small structures involved in protein synthesis

Where are ribosomes located?

can be free in the cytoplasm or attached to RER

What are ribosomes made of?

rRNA

Name for group of ribosomes?

Polyribosomes - these create a 'hot spot' for protein synthesis

What is the Golgi apparatus? (components)

a series of curved flattened, single membrane sacs

What are the sacs called in the Golgi apparatus?

cisternae

Function of Golgi apparatus?

sorts, modifys and packages proteins and lipids

What type of structure does the Golgi apparatus create for proteins?

Quaternary structure

How may a protein be modified in the Golgi body?

> add carbohydrate or lipid

> prosthetic group or cofactor added

> different polypeptide chains joined together to create quaternary structure

example of protein modified by Golgi apparatus?

add a carbohydrate to the protein to make a glygoprotein

How are the proteins transported to the Golgi apparatus?

Vesicles

Path of vesicles bringing proteins to Golgi apparatus?

> Vesicles 'pinch off' the RER

> join the 'forming face' of Golgi apparatus

> vesicle containing the now modified protein will 'pinch off' the 'maturing face' of the Golgi apparatus

What happens to vesicles after they have gotten protein modified?

They either become secretory vesicles of lysosomes

What do secretory vesicles do?

they carry the modified protein within the cell or to the cell surface membrane to release its contents outside

What are lysosomes?

Tiny vesicles formed by the Golgi apparatus

What do lysosomes contain?

hydrolytic enzymes

Function of lysosomes?

Lysosomes fuse with other vesicles containing something that has to be destroyed

> this fusion forms secondary lysosomes

Where are lysosomes often found?

white blood cells - phagocytes

Parts of the mitochondria?

> Outer membrane

> Inner membrane

> Cristae

> Matrix

How is the inner membrane of the mitochondria adapted?

> encrusted with enzymes for aerobic respiration

> folded to create cristae which increase surface area

Shape of mitochondrial outer membrane?

Double membrane 'envelope'

Matrix in mitochondria?

fluid-like substance that fills the inner membrane

What is the mitochondria the site of?

ATP synthesis in aerobic respiration

What is the number of mitochondria in a cell dependant on?

The metabolic requirements of a cell e.g muscle cells have more

What other cells have many mitochondria?

Illeum walls because ATP is needed for active transport during adsorption

Mitochondria DNA?

they contain their own DNA and are able to grow and reproduce independently within the cell

What are microtubules?

hollow structures made up of the protein tubulin

Where are microtubules located?

cytoplasm, cilia, flagella and centriole

Function of microtubules?

form cytoskeleton, spindle fibres and the centriole

What is the cytoskeleton?

a network of fibres extending throughout the cytoplasm that maintains cell shape and keeps organelles in place

Function of spindle fibres?

important in the movement of chromosomes during cell division

What is the centriole made from?

Microtubules

Arrangement of microtubules in the centriole?

nine triplets of microtubules arranged in a circular formation

Function of centriole?

Involved with the separation of chromosomes during cell division

What organelles do plant cells not have?

> lysosomes

> centrioles

What do plant cells contain that animals cells do not?

> cell wall

> middle lamella

> plasmodesmata

> large vacuole

> chloroplasts

Where are chloroplasts found?

Mesophyll cells and green parts of plants

Components of chloroplast?

> Double membrane

> stroma

> lipid droplet

> grana

> thylakoid membrane

> starch grain

> intergranal lamellae

Function of chloroplasts?

produce glucose - site of photosynthesis

Where are chloroplasts found in high density?

palisade layer

What is the stroma?

fluid portion of the chloroplast (like cytoplasm)

What are the grana?

stacks of thylakoids

What are between grana?

inter-grana membrane

What do thylakoids contain?

chlorophyll

Intergranal lamellae?

Connect thylakoids within one granum to thylakoids within another granum

Purpose of lamellae?

keeps all sacs a safe distance to maximise efficiency

Why are there starch grains and small lipid droplets in chloroplasts?

made via photosynthesis

What is the plasmodesmata?

strands of cytoplasm that act as a link between neighbouring plant cells

Function of plasmodesmata?

> connect one cell to another

> communication between cells

What are plant cell walls made from?

polysaccharide cellulose in the form of microfibrils which cross-link