The Cell: Animal Cell Plant Cell

The Cell ANIMAL CELL

PLANT CELL

What Cells Do? Cells are the basic units of all living things. Cells make up bones, muscles, skin, and blood. Cells make up leaves, roots, stems, and flowers. As the organism grows, the cells must reproduce. Cell reproduction is called mitosis.

Cells: Prokaryote vs Eukaryote

Animal Cell Vs Plant Cell

Structure

Animal cells

Plant cells

cell membrane

Yes

yes

nucleus

Yes

yes

nucleolus

yes

yes

ribosomes

yes

yes

ER

yes

yes

Golgi

yes

yes

centrioles

yes

no

cell wall

no

yes

mitochondria

yes

yes

cholorplasts

no

yes

One big vacuole

no

yes

vacuole

Usually no

yes

• • • • • • •

cell membrane and cell wall Nucleus Mitochondria Endoplasmic reticulum Golgi body Chloroplast Lysosomes

Plant Cell wall

The nucleus is bounded by double membrane, the Nuclear Envelope, that is continuous with the ER (RER).

Nucleolus Structure -non-membraneous matrix of RNA (ribonucleic acid) and protein Function - instructions in DNA are copied here - works with ribosomes in the synthesis of protein

The openings in the Nuclear Envelope that allow the passage of material in and out of the nucleus are called Nuclear Pores

Small Molecules can diffuse freely through the Nuclear Pore, Larger molecules require active transport

lysosome

Arrows: red = anterograde transport steps blue = retrograde transport steps green = endocytic transport steps

Lysosomes are a specialized compartment of the secretory pathway that acts as a degradative organelle

A specific sugar acts as a sorting signal to target proteins to the lysosome

Mitochondrial structure • Two membranes • Inner membrane invaginated • Numbers of mitochondria per cell vary but usually 100s/cell

Matrix contains the TCA cycle (and other) soluble enzymes Inner membrane contains metabolite transporters and the electron transport chain

Overview of aerobic respiration

Mitochondria have their own DNA and Ribosomes Mitochondria have some of their own DNA, ribosomes, and can make many of their own proteins. The DNA is circular and lies in the matrix in structures called "nucleoids". Each nucleoid may contain 4-5 copies of the mitochondrial DNA (mtDNA).

mitochondrial DNA

Chloroplast structure

Chloroplasts • Chloroplasts are specialized organelles found in all higher plant cells containing chlorophyll, hence provide the green color. • A chloroplast is bounded by two membranes enclosing a fluidfilled stroma that contains enzymes. • Within the stroma are other membrane structures - the thylakoids and grana (singular = granum) where photosynthesis takes place. • Membranes inside the stroma are organized into thylakoids that house chlorophyll. • Chlorophyll absorbs solar energy and carbohydrates are made in the stroma.

Ribosom e

RuBisCO

Cytoc hrom e 6bf /

PhotosystemI

Stro ma

Ch loro p lats Photosystem I I

ATP sy nthase

Lu mne

Ribosom e

Matrix

Mitoch o nria d Com pl exI

Com pl ex II

Interm emran b eSp ace

Com pl ex III

Com pl ex VI

Com pl ex V

A vacuole is a membrane-bound sac. The membrane surrounding the plant cell vacuole is called the tonoplast. In animal cells, vacuoles are generally small.

A vacuole is a membrane organelle which is present in all plant cells. Vacuoles are essentially enclosed compartments which are filled with fluid such as water or various enzymes, though in certain cases they may contain solids which have been engulfed. The majority of vacuoles are formed through the fusion of multiple membrane vesicles. The organelle has no basic shape or size, instead varying its structure according to the needs of the cell – hence dynamic in shape. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Vacuoles tend to be large in plant cells and play a role in turgor pressure.

In general, vacuole functions include: •Isolating materials that might be harmful or a threat to the cell •Containing waste products •Containing small molecules •Maintaining internal hydrostatic pressure within the cell •Exporting unwanted substances from the cell •Vacuoles have the additional function of storing food Vacuoles of certain specialized cells contain such interesting products as rubber and opium. Other molecules stored in vacuoles are involved in the interactions of the plant with animals or with other plants. Eg. Pigment (colours) for insect attraction - flower petals. Defense chemicals - poisonous alkaloids, etc.

Centriole Structure - nine triplets of microtubules form one centriole - two centrioles form one centrosome The centrosome, also called the "microtubule organizing center", is an area in the cell where microtubles are produced. Function - forms spindle fibres to separate chromosomes during cell division

Within an animal cell centrosome there is a pair of small organelles, the centrioles. each made up of a ring of nine groups of microtubules. There are three fused microtubules in each group. The two centrioles are arranged such that one is perpendicular to the other. During animal cell division, the centrosome divides and the centrioles replicate. The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells.