Cell structure

Eukaryotic vs prokaryotic cell

Eukaryotic cells contain membrane-bound organelles; prokaryotic cells do not

What are organelles

Structures found inside a cell

Nucleus size usually

5-10 μm

Draw a nucleus

What kind of cells is the nucleus in

All eukaryotic cells except red blood cells

What separates the nucleus from the cytoplasm

Nuclear envelope (double membrane)

Why does the nuclear envelope have pores

Allow mRNA and ribosomes out; allow enzymes in

What is chromatin

Material which chromosomes are made from; found in the nucleus

What is the nucleolus

Structure inside the nucleus where ribosomes are produced

What surrounds the nucleus

Rough endoplasmic reticulum + ribosomes

Size of mitochondria usually

0.5-1μm

Name features of the nucleus

Nucleolus, chromatin, nucleoplasm, nuclear envelope, nuclear pores

Function of a mitochondrion

Site of aerobic respiration in all eukaryotic cells

Describe structure of mitochondria

Surrounded by double membrane; inner membrane folds to form cristae

What are cristae

Structures formed by the inner membrane of a mitochondrion

What is the matrix

Inside cristae of mitochondria; contains enzymes needed for aerobic respiration

Where are mitochondria found

Eukaryotic cells; self replicating so abundant in cells where much metabolic activity takes place to provide energy

Chloroplast size usually

2-10μm

Where are chloroplasts found

Plant cells which photosynthesise

Chloroplast structure

Double membrane, then thylakoid membranes form grana joined together by lamellae

What are thylakoids

Membrane bound structures in chloroplasts containing chlorophyll; site of photosynthesis

What else do chloroplasts contain other then thylakoids

Small circular pieces of DNA, ribosomes, stroma (like cytoplasm)

Ribosome structure

No membrane

Where are ribosomes normally found in cells

Cytoplasm/RER

Describe the structure of a ribosome

Complex of ribosomal RNA (small subunit) and proteins (large subunit)

What kind of proteins do ribosomes bound to the exterior of RER synthesise

proteins to be exported outside the cell

What kind of proteins do ribosomes free in the cytoplasm synthesise

Proteins that will be used inside the cell

What part of protein synthesis happens on the ribosome

Translation

What kind of cells can the rough endoplasmic reticulum be found in

Plant and animal cells

What makes the rough endoplasmic reticulum “rough”

Surface covered in ribosomes

Describe the structure of the rough endoplasmic reticulum

Formed from folds of membrane continued from the nuclear envelope

What is the function of the rough endoplasmic reticulum

Folds and processes proteins that have been made at the ribosomes (once they have passed into cisternae)

What is a cisternae

Fluid-filled space (enclosed by membrane) found in endoplasmic reticulums and Golgi

What do the cisternae do

Form channels for transporting substances from one area of a cell to another

Why is the smooth endoplasmic reticulum “smooth”

No ribosomes on surface

What does the smooth endoplasmic reticulum do

Produce, process and involved in storage of lipids, carbohydrates and steroids

Describe the structure of the Golgi apparatus

Stack of flattened cisternae

Where is the SER found

Also next to the nucleus with the RER

Describe the function of the Golgi apparatus

Modifies proteins and lipids

Draw the structure of the Golgi apparatus

Where do transport vesicles come in to the Golgi apparatus

Cis face

Where do secretory vesicles leave the Golgi apparatus from

Trans face

What are lysosomes

Special form of vesicle containing hydrolytic enzymes

What do hydrolytic enzymes do

Break down biological molecules

What are lysosomes for

Breaking down waste material e.g. worn out organelles; used in immune system and apoptosis

Apoptosis meaning

Programmed cell death

Are lysosomes membrane bound

Yes

What are centrioles

Hollow fibres made of microtubules

What are microtubules

Polymers of the protein tubulin

What do a pair of centrioles (perpendicular to form an X) form

Centrosome

Role of centrioles in eukaryotic cells

Play a role in assembly of spindle fibres during cell division; key part of protein complex which form cilia/flagella

Describe structure of cilia/flagella and how they move

9 pairs of microtubules in circle, 1 pair in the centre (9+2 structure); pairs move relative to adjacent pairs; creates bending motion

Proof that centrioles are not essential for spindle fibre assembly

Flowering plant cells form spindle fibres during cell division but do not have centrioles

Where are centrioles not found

Flowering plants; most fungi

What are cilia

Hair-like projections made from microtubules

What do cilia do

Allow movement of substances over cell surface (trachea) or sense chemicals around cell (nose)

What is a flagella

Projection like cilia made from longer microtubules

What do flagella do

Contract to provide cell movement e.g. sperm cells

Which organelles are involved in protein production?

Nucleus, ribosome, RER, Golgi, vesicles

Where are ribosomes manufactured

Nucleolus

Where is mRNA manufactured

Nucleus

Name the organelles of an animal cell

Plasma membrane; Nucleus; Rough/Smooth ER; mitochondrion; Golgi; ribosome; lysosome; cytoplasm

What do plant cells have that animal cells don’t?

Chloroplast; cell wall with plasmodesmata; vacuole

What is the membrane surrounding the vacuole called

Tonoplast

Which is further from nucleus: smooth or rough ER

Smooth

What is a plasmodesma / plasmodesmata (pl)

Channel in plant cell wall for exchanging substances with adjacent cells

What is contained in the vacuole

Cell sap

Describe the organelles in a prokaryotic bacteria cell

Cell wall (peptidoglycan); plasma membrane; chromosome; plasmid; ribosome; flagellum; mesosome

What is a mesosome

Site of aerobic respiration; at folds of membrane to increase SA to store more enzymes

3 reasons why the cytoskeleton is important

Provides mechanical strength to cells; aids transport within cells; enables cell movement

Are fungi eukaryotic

Yes

Describe how DNA is arranged in eukaryotic cells

Coiled around histone proteins in the nucleus; Linear

What is exocytosis (protein production)

Vesicles fusing with cell surface membrane to secrete proteins from cell

Where is mRNA manufactured

Nucleus (transcription)

Where are ribosomes manufactured for protein synthesis in the rER

Nucleolus

Which process proteins: RER or Golgi

Both

Draw a prokaryotic cell

Are bacteria prokaryotic

Yes

Which is larger: prokaryotic or eukaryotic cells

Eukaryotic cells are much larger

Describe the DNA in prokaryotic cells

Circular chromosome; not bound to histone proteins; in cytoplasm; sometimes plasmids

What are plasmids

Small circles of DNA; relatively small number of genes

What is important about plasmids in bacteria

Often contain genes which make bacteria resistant to antibiotics

Are there ribosomes in prokaryotic cells

Yes

What is different about the ribosomes in prokaryotic cells vs eukaryotic

Prokaryotic ribosomes are smaller (70S), eukaryotic cells are 80S

What is the s in 70s ribosome

Unit showing how quickly organelles move in a centrifuge

What is peptidoglycan

Polymer formed between peptides and polysaccharide molecules

Role of cell wall for prokaryotes

Maintain cell structure; stop cell from bursting

Are prokaryotic and eukaryotic flagella the same

No, different structures

What are pili

Fine protein strands

What are pili for

Help bacteria cell attach to surfaces or other bacteria

What are the nutrient stores in a bacterial cell

Lipid droplets and glycogen granules

When can you see mesosomes

Infoldings in cell membrane of prokaryotic cells; can see using electron microscope

What is the cytoskeleton

Extensive network of protein fibres

What are the 2 main protein fibres found in the cytoskeleton

Microtubules, microfilaments

How does cytoskeleton help intracellular movement

Acts as a track along which organelles can move e.g. vesicles/chromosomes

Is there a spindle involved in prokaryotic cell division

No - occurs by binary fission

What does the spindle do in cell division

Separate chromosomes

What are peptides

Amino acids